# ATAR Notes: Forum

## VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Biology => Topic started by: alondouek on December 25, 2013, 11:04:46 am

Post by: alondouek on December 25, 2013, 11:04:46 am

If you have general questions about the VCE Biology course or how to improve in certain areas, this is the place to ask!

Everyone is welcome to contribute; even if you're unsure of yourself, providing different perspectives is incredibly valuable.

Please don't be dissuaded by the fact that you haven't finished Year 12, or didn't score as highly as others, or your advice contradicts something else you've seen on this thread, or whatever; none of this disqualifies you from helping others. And if you're worried you do have some sort of misconception, put it out there and someone else can clarify and modify your understanding!

There'll be a whole bunch of other high-scoring students with their own wealths of wisdom to share with you, including TuteSmart tutors! So you may even get multiple answers from different people offering their insights - very cool.

To ask a question or make a post, you will first need an ATAR Notes account. You probably already have one, but if you don't, it takes about four seconds to sign up - and completely free!

OTHER BIOLOGY RESOURCES

Original post.
Welcome all you budding biologists! On this board there are a lot of individual-question threads throughout the year. I've made this thread both to help get your VCE biology questions answered as quickly as possible, as well as to reduce clutter on this board where possible.

Happy studying!
Title: Re: VCE Biology Question Thread
Post by: alchemy on December 25, 2013, 11:15:29 am
Finally, a Biology question thread! Cheers alondouek. Would you recommend just deleting our individual question threads or transferring the content from those to over here?
Title: Re: VCE Biology Question Thread
Post by: alondouek on December 25, 2013, 11:17:33 am
Hey! Definitely don't delete any of your previous posts - I'm certainly not going to transfer any existing threads here. Let's keep this thread for whatever questions may arise from now :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on December 25, 2013, 09:33:58 pm
What is it meant by when enzymes lower their activation energy? What exactly is activation energy?
Title: Re: VCE Biology Question Thread
Post by: alondouek on December 25, 2013, 09:43:55 pm
What is it meant by when enzymes lower their activation energy? What exactly is activation energy?

Activation energy (Ea) is the minimum energy input needed for a chemical reaction to occur. All reactions need some energy input to facilitate their occurrence, but the Ea is often too high for biological systems, which are vulnerable to heat and other forms on high-energy situations.

Enzymes are biological catalysts. Catalysts lower the Ea of a chemical reaction system, which means the energy "currency" of the reaction is within more a more manageable range that the biological system (e.g. an organism) can manage without sustaining any damage. Biocatalysis is also important because organisms only have a certain amount of energy that they can devote to biological reaction systems, which means that by lowering the required energy input for vital biochemical reactions, the organism's energy input (such as food) can be reduced.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on December 25, 2013, 09:55:35 pm
What is it meant by when enzymes lower their activation energy? What exactly is activation energy?

I feel as if this wording is slightly misleading.

As alondouek has mentioned, activation energy is the input of energy required for a chemical reaction to take place. However, in the presence of an enzyme, this is lowered as enzymes are biological catalysts.
Title: Re: VCE Biology Question Thread
Post by: MM1 on December 25, 2013, 10:51:09 pm

Activation energy (Ea) is the minimum energy input needed for a chemical reaction to occur. All reactions need some energy input to facilitate their occurrence, but the Ea is often too high for biological systems, which are vulnerable to heat and other forms on high-energy situations.

Enzymes are biological catalysts. Catalysts lower the Ea of a chemical reaction system, which means the energy "currency" of the reaction is within more a more manageable range that the biological system (e.g. an organism) can manage without sustaining any damage. Biocatalysis is also important because organisms only have a certain amount of energy that they can devote to biological reaction systems, which means that by lowering the required energy input for vital biochemical reactions, the organism's energy input (such as food) can be reduced.

Thank you!
Title: Re: VCE Biology Question Thread
Post by: MM1 on December 25, 2013, 10:54:07 pm
I feel as if this wording is slightly misleading.

As alondouek has mentioned, activation energy is the input of energy required for a chemical reaction to take place. However, in the presence of an enzyme, this is lowered as enzymes are biological catalysts.

What is it meant by when enzymes lower their activation energy? What exactly is activation energy?
?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: alondouek on December 25, 2013, 10:56:46 pm

What is it meant by when enzymes lower their activation energy? What exactly is activation energy?
?

Thanks!

I think Oddly was referring to something else in the wording haha; enzymes don't lower their activation energy, they lower the activation energy of the reaction.
Title: Re: VCE Biology Question Thread
Post by: MM1 on December 26, 2013, 12:05:34 am
I think Oddly was referring to something else in the wording haha; enzymes don't lower their activation energy, they lower the activation energy of the reaction.

Oh, oops silly mistakes. Thanks for the clarification though. :)
Title: Re: VCE Biology Question Thread
Post by: DJA on December 26, 2013, 02:44:09 pm
What is the difference between carrier mediated protein channels and channel mediated protein channels in the phospholipid bilayer of the plasma membrane?? (i do know that they both do not require energy...but thats it)

And I am not referring to the active transport carrier protein where energy is required to carry substances through the plasma membrane.

Edit: The diagram I am pondering over and not understanding is on pg 44 of the Nature of Biology TB if anyone has that text.
(3 types of passive transport: Simple diffusion, Channel mediated, Carrier mediated: the last two I do not get the difference)

Title: Re: VCE Biology Question Thread
Post by: Yacoubb on December 26, 2013, 03:05:33 pm
What is the difference between carrier mediated protein channels and channel mediated protein channels in the phospholipid bilayer of the plasma membrane?? (i do know that they both do not require energy...but thats it)

And I am not referring to the active transport carrier protein where energy is required to carry substances through the plasma membrane.

Edit: The diagram I am pondering over and not understanding is on pg 44 of the Nature of Biology TB if anyone has that text.
(3 types of passive transport: Simple diffusion, Channel mediated, Carrier mediated: the last two I do not get the difference)

Carrier mediated transport involves a carrier protein. The carrier protein binds to the substance and undergoes a conformational change as it is bound to the substance. This molecule then possesses a specific shape that enables it to pass through a specific porous protein channel. Some substances do not require carrier proteins; channel mediated transport involves the substance travelling across the cell membrane via specific porous protein channels, into or out of the cell. And then as you already know, these are means of facilitated diffusion, and so are passive and require not ATP energy input in order to take place.

Hope this helped!

Title: Re: VCE Biology Question Thread
Post by: DJA on December 26, 2013, 03:11:23 pm
Carrier mediated transport involves a carrier protein. The carrier protein binds to the substance and undergoes a conformational change as it is bound to the substance. This molecule then possesses a specific shape that enables it to pass through a specific porous protein channel. Some substances do not require carrier proteins; channel mediated transport involves the substance travelling across the cell membrane via specific porous protein channels, into or out of the cell. And then as you already know, these are means of facilitated diffusion, and so are passive and require not ATP energy input in order to take place.

Hope this helped!

Thanks-a huge help! :)
Title: Re: VCE Biology Question Thread
Post by: DJA on December 26, 2013, 04:02:23 pm
What are the major biological processes that need to be known for VCE and more importantly how much detail is needed?
My current list so far is:
Protein synthesis
Photosynthesis
Let me know what I am missing in the way of processes.

Edited twice ::)
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on December 26, 2013, 04:25:06 pm
What are the major biological processes that need to be known for VCE and more importantly how much detail is needed?

My current list so far is:
Protein synthesis
Photosynthesis

Let me know what I am missing in the way of processes.

* Means of transport across the plasma membrane; osmosis, diffusion, facilitated diffusion, active transport and vesicular transport (including endocytosis and exocytosis).
* Protein Synthesis & Secretory Pathway - by time you finish the course, you must know transcription & translation in depth, and the pathway from the nucleus --> ribosome --> rough endoplasmic reticulum --> golgi complex --> secretory vesicle. At each stage, you must know what occurs.
* Enzyme activity: what is an enzyme, what is the role/importance of enzymes, factors affecting enzyme activity, including pH, temperature, enzyme/substrate/product concentration, inhibition and cofactor/coenzyme concentration.
* Photosynthesis: inputs and outputs, as well as location within the chloroplast of the light dependent & light independent stages of photosynthesis, as well as how photosynthetic rate is dependent on CO2 and light.
* Cellular respiration: the difference between aerobic and anaerobic respiration, including ATP energy yield per glucose molecules, inputs and outputs and location of each stage within the cell/within the mitochondrion (for Krebs Cycle and Electron Transport Chain in aerobic respiration).

That's Area of Study 1 :)
Title: Re: VCE Biology Question Thread
Post by: DJA on December 26, 2013, 04:35:02 pm
Thank you so much! Doing AOS 1 study atm and just consolidating the holes in my knowledge when I can't find the answers elsewhere. Cheers!

Question 1: Do lysosomes die in the process whereby they digest unwanted cell parts/damaged molecules/foreign molecules? (In essence, by digestion, do they self-destruct in the process or are they 're-usable' and can perform their processes multiple times?)

Question 2: Should we know the function of Peroxisomes and Endosomes for the VCE course?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on December 26, 2013, 04:40:05 pm
Thank you so much! Doing AOS 1 study atm and just consolidating the holes in my knowledge when I can't find the answers elsewhere. Cheers!

Question 1: Do lysosomes die in the process whereby they digest unwanted cell parts/damaged molecules/foreign molecules? (In essence, by digestion, do they self-destruct in the process or are they 're-usable' and can perform their processes multiple times?)

Question 2: Should we know the function of Peroxisomes and Endosomes for the VCE course?

(1.) Lysosomes are basically membrane-bound sacs that contain digestive enzymes called lysosymes. These lysozymes are secreted, the lysozymes break down the matter taken up by the cell, and the lysozyme, an enzyme, is neither used up nor consumed by this catabolic reaction. So essentially, no, the lysosomes are not destroyed in this instant.

2. You don't need to know much. I'd just remember that catalase, the enzyme that catalyses the breakdown of hydrogen peroxide, is contained in peroxisomes. Also, endosomes are just vesicles thar transport materials that enter the cell, to lysosomes, to undergo cellular digestion.
Title: Re: VCE Biology Question Thread
Post by: Stick on December 26, 2013, 05:12:34 pm
Thank you so much! Doing AOS 1 study atm and just consolidating the holes in my knowledge when I can't find the answers elsewhere. Cheers!

Question 1: Do lysosomes die in the process whereby they digest unwanted cell parts/damaged molecules/foreign molecules? (In essence, by digestion, do they self-destruct in the process or are they 're-usable' and can perform their processes multiple times?)

Question 2: Should we know the function of Peroxisomes and Endosomes for the VCE course?

Just making a big point of this. Do not say that non-living material (e.g. enzymes) die. This is a one way trip to getting zero marks for a short answer question, even if the other parts of your response are correct.
Title: Re: VCE Biology Question Thread
Post by: DJA on December 26, 2013, 05:35:26 pm
Just making a big point of this. Do not say that non-living material (e.g. enzymes) die. This is a one way trip to getting zero marks for a short answer question, even if the other parts of your response are correct.

Got it. Thanks for the heads up.

Are there any cells in the body that 'self-destruct' in order to consume/breakdown foreign material/invading antigens? (I'm thinking of phagocytes and lymphocytes here but I am really NOT sure.

If there are, would it be correct to say that these kinds of cells die in the process as these cells are living?
Title: Re: VCE Biology Question Thread
Post by: alondouek on December 26, 2013, 05:39:11 pm
Got it. Thanks for the heads up.

Are there any cells in the body that 'self-destruct' in order to consume/breakdown foreign material/invading antigens? (I'm thinking of phagocytes and lymphocytes here but I am really NOT sure.

If there are, would it be correct to say that these kinds of cells die in the process as these cells are living?

I'm not aware of any cells that specifically self-destruct to destroy foreign bodies, but all cells will trigger apoptosis as a mode of damage control. As these are regular cells, they definitely are living!
Title: Re: VCE Biology Question Thread
Post by: MM1 on December 27, 2013, 03:43:01 pm
Why are proteins not preferred energy sources whilst carbohydrates are? What are the reasons?
Title: Re: VCE Biology Question Thread
Post by: DJA on December 27, 2013, 04:26:06 pm
Why are proteins not preferred energy sources whilst carbohydrates are? What are the reasons?

My understanding of this is because carbohydrates (I'm thinking more specifically of glucose here which is the monosaccharide which comprises a lot of polysaccharides and disaccharides such as maltose, starch and glycogen) are used in aerobic cell respiration which is the primary mode for cells to create energy to allow it to function.

Cellular respiration is the process whereby living cells get their energy to function and this process requires glucose (C6H12O6) as a critical part of the equation
C6H12O6 + O2 ---> CO2 + H2O (+ Energy)
Thus carbohydrates are the preferred energy source.

Whereas proteins function primarily in structural roles (collagen and keratin), contractile roles (myosin and actin found in muscle tissue) and catalytic/regulartory roles etc. Note that amino acids are the basic subunits of proteins. While certain amino acids can aid energy productions, they are not directly part of any biological process to produce energy as far as I know.
Title: Re: VCE Biology Question Thread
Post by: DJA on December 27, 2013, 04:27:37 pm
My question is what is the difference between the 5' and 3' ends of a DNA strand and more importantly, is this knowledge required for the VCE course?

Title: Re: VCE Biology Question Thread
Post by: vox nihili on December 27, 2013, 04:31:38 pm
My question is what is the difference between the 5' and 3' ends of a DNA strand and more importantly, is this knowledge required for the VCE course?

The 3' is the -OH end and the 5' is the phosphate end. Yes this knowledge is required for the VCE course. You will have to know the direction of replication and transcription of DNA with respects to this configuration.
Title: Re: VCE Biology Question Thread
Post by: Stick on December 27, 2013, 04:46:42 pm
The 3' is the -OH end and the 5' is the phosphate end. Yes this knowledge is required for the VCE course. You will have to know the direction of replication and transcription of DNA with respects to this configuration.

Here's a good way to remember:

Five - Phosphate (same sound)
Three - Free (no phosphate) (similar word)
Title: Re: VCE Biology Question Thread
Post by: DJA on December 27, 2013, 05:12:25 pm
Thanks both of you!

I'm assuming that the way the nucleotides bond together to form long chains (DNA and RNA) is through a condensation reaction between the -phosphate group and the -OH group of two nucleotides?
Title: Re: VCE Biology Question Thread
Post by: alondouek on December 27, 2013, 05:19:33 pm
Thanks both of you!

I'm assuming that the way the nucleotides bond together to form long chains (DNA and RNA) is through a condensation reaction between the -phosphate group and the -OH group of two nucleotides?

DNA and RNA polymerise by connecting part of the phosphate group to one of the deoxyribose/ribose carbons (5' if I recall correctly). Here's a really good link that explain DNA polymerisation: http://www.chem.wisc.edu/deptfiles/genchem/netorial/modules/biomolecules/modules/dna1/dna13.htm
Title: Re: VCE Biology Question Thread
Post by: DJA on December 27, 2013, 05:51:26 pm
What is the point of the DNA strands found in chloroplasts?
Title: Re: VCE Biology Question Thread
Post by: alondouek on December 27, 2013, 05:56:42 pm
ctDNA has a number of purposes, for example protein production (as with many other types of DNA) for photosynthetic processes.
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on December 27, 2013, 06:06:54 pm
What is the point of the DNA strands found in chloroplasts?

For the purposes of VCE Biology, it would be sufficient to know 2 things:
~ ctDNA provides the set of genetic instructions required to synthesise specific proteins required for photosynthesis (e.g. the enzyme RuBisCO).
~ ctDNA provides evidence for the endosymbiotic theory of evolution (which you'll cover more in unit 4).
Title: Re: VCE Biology Question Thread
Post by: Stick on December 27, 2013, 06:07:23 pm
What is the point of the DNA strands found in chloroplasts?

The reactions that make up photosynthesis are all dependent on enzymes. As you should already know, enzymes are a type of protein. In some cases, we're going to need protein synthesis to occur rather rapidly in order to keep up normal function. If we relied on nuclear DNA, it'd be a rather inefficient pathway - the DNA would be transcribed in the nucleus, the messenger RNA would have to exit the nucleus and approach a ribosome somewhere in the cytoplasm to be translated and the new protein would then have to be transported through the endoplasmic reticulum to the chloroplast before it could be used to catalyse important photosynthetic reactions. As you can see, having the DNA (and ribosomes) where the resulting protein will be used is very handy - protein synthesis occurs in the chloroplast rather than somewhere else in the cell and it can be used as soon as translation has concluded.
Title: Re: VCE Biology Question Thread
Post by: DJA on December 27, 2013, 06:11:01 pm
Thanks for all the answers guys. Really consolidating my learning.

And on a side note congrats on your 2500th post stick :)
Title: Re: VCE Biology Question Thread
Post by: alchemy on December 27, 2013, 09:00:03 pm
A bit late to the party here, but I'll try ask some questions while I can.

Biocatalysis is also important because organisms only have a certain amount of energy that they can devote to biological reaction systems, which means that by lowering the required energy input for vital biochemical reactions, the organism's energy input (such as food) can be reduced.

Can you please explain this again? Lower input=lower input?

Lysosomes are basically membrane-bound sacs that contain digestive enzymes called lysosymes. These lysozymes are secreted, the lysozymes break down the matter taken up by the cell, and the lysozyme, an enzyme, is neither used up nor consumed by this catabolic reaction. So essentially, no, the lysosomes are not destroyed in this instant.

So when lysosomes ‘recycle’ mitochondria they aren’t destroyed in that process as well, right? What happens to these hydrolytic enzymes (lysozymes) once they’ve done their job of recycling? Also, why would an organelle, such as mitochondria, be recycled by these enzymes?

Title: Re: VCE Biology Question Thread
Post by: psyxwar on December 27, 2013, 09:03:32 pm
A bit late to the party here, but I'll try ask some questions while I can.

Can you please explain this again? Lower input=lower input?
needing less energy to drive metabolism = animal does not need to eat as much to survive
Title: Re: VCE Biology Question Thread
Post by: vox nihili on December 27, 2013, 09:25:52 pm
So when lysosomes ‘recycle’ mitochondria they aren’t destroyed in that process as well, right? What happens to these hydrolytic enzymes (lysozymes) once they’ve done their job of recycling? Also, why would an organelle, such as mitochondria, be recycled by these enzymes?

Whether or not the lysosomes are destroyed is irrelevant really. In some instances their membranes will be completely voided (so yes, destroyed), others not so much. Mitochondria are recycled because they get, for want of a better way to explain it, get tired and a bit buggered essentially. Like anything, there's wear and tear on the mitochondria, so they need to be replaced.
The enzymes themselves may very well be broken down, or go onto recycling more things. Quite often they will be broken down though, or can be degraded or deactivated by other cell processes. They're all very nitpicky questions, particular about what happens with the enzymes and I daresay there's are questions we don't really yet have definitive answers to.
Title: Re: VCE Biology Question Thread
Post by: Frozone on December 27, 2013, 10:29:58 pm
What is the difference between carrier mediated protein channels and channel mediated protein channels in the phospholipid bilayer of the plasma membrane?? (i do know that they both do not require energy...but thats it)

And I am not referring to the active transport carrier protein where energy is required to carry substances through the plasma membrane.

Edit: The diagram I am pondering over and not understanding is on pg 44 of the Nature of Biology TB if anyone has that text.
(3 types of passive transport: Simple diffusion, Channel mediated, Carrier mediated: the last two I do not get the difference)
My book says nothing about channel mediated and carrier mediated. Should I be worried. By the way I'm using heinenman biology 2.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on December 27, 2013, 10:44:01 pm
My book says nothing about channel mediated and carrier mediated. Should I be worried. By the way I'm using heinenman biology 2.

It may not use those exact terms. Mine (Nelson) just called them channel proteins and carrier proteins. yes you do need to know the difference.
Title: Re: VCE Biology Question Thread
Post by: DJA on December 27, 2013, 10:49:43 pm
Do we need to know about the induced fit model for enzymes? Or do we just need to know the lock and key model?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on December 27, 2013, 10:49:55 pm
I'm led to believe that carrier proteins, although used in diffusion, can also be used in active transport?
Title: Re: VCE Biology Question Thread
Post by: Stick on December 27, 2013, 10:52:54 pm
Do we need to know about the induced fit model for enzymes? Or do we just need to know the lock and key model?

It's not a bad idea to know both.

I'm led to believe that carrier proteins, although used in diffusion, can also be used in active transport?

Yep, you're correct! It's the only way active transport occurs. :)
Title: Re: VCE Biology Question Thread
Post by: grannysmith on December 27, 2013, 10:54:19 pm
Do we need to know about the induced fit model for enzymes? Or do we just need to know the lock and key model?

I think they're both models (theories if you like), and neither have been proven or disproved. One states that the active site is the exact complementary shape of the substrate, whereas the other one says that the enzyme "fits" itself around the substrate.

Edited
Title: Re: VCE Biology Question Thread
Post by: vox nihili on December 27, 2013, 10:56:31 pm
I think they're both models (theories if you like), and neither have been proven or disproved. One states that the active site is the exact shape of the substrate, whereas the other one says that the enzyme "fits" itself around the substrate.

Induced fit is supported by much more research than lock and key. Lock and key is presented as a way to introduce the theory, whereas induced fit is somewhat of an intellectual expansion on that, and is more correct. So technically, you learn the incorrect model first because it's easier, and then get corrected by induced fit. Nonetheless, lock and key does pop up often and is essentially right as a model.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on December 27, 2013, 10:58:58 pm
Induced fit is supported by much more research than lock and key. Lock and key is presented as a way to introduce the theory, whereas induced fit is somewhat of an intellectual expansion on that, and is more correct. So technically, you learn the incorrect model first because it's easier, and then get corrected by induced fit. Nonetheless, lock and key does pop up often and is essentially right as a model.

So I'm guessing for the purpose of VCE biology, both models are essentially correct?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on December 27, 2013, 10:59:50 pm
It's not a bad idea to know both.

Yep, you're correct! It's the only way active transport occurs. :)

Cool!
Title: Re: VCE Biology Question Thread
Post by: alchemy on December 27, 2013, 11:05:29 pm
I'm led to believe that carrier proteins, although used in diffusion, can also be used in active transport?

Just remember that active transport is for the movement of substances across the membrane, via carrier proteins and through protein channels, against the concentration gradient.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on December 27, 2013, 11:06:52 pm
Yep, thanks for the reminder
Title: Re: VCE Biology Question Thread
Post by: vox nihili on December 27, 2013, 11:11:46 pm
So I'm guessing for the purpose of VCE biology, both models are essentially correct?

In some respects, yes. I didn't explain it very well earlier to be honest!

Induced fit is what is right, but it's a bit cumbersome to explain and a bit of a conceptual pain in the arse.
Lock-and-key is wrong, but it's nearly good enough. In reality, a substrate does kind of fit into an active site like a key into a lock and that is why it works. It just misses that vital reshaping.

Conceptually, lock-and-key runs into road blocks when you start to look at inhibition and the effect of heat and high pH etc on proteins. So if you're asked really specifically how the action works, go with induced fit. Most often though you'll get questions that show an enzyme and a substrate and ask which goes with which; that's a clear exercise in lock-and-key.
Title: Re: VCE Biology Question Thread
Post by: MM1 on December 28, 2013, 12:21:41 am
How to plant cell membranes maintain fluidity if they lack cholesterol? I'm guessing they have some structure of similar function?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on December 28, 2013, 01:37:27 am
How to plant cell membranes maintain fluidity if they lack cholesterol? I'm guessing they have some structure of similar function?

The polyunsaturated fatty acid chains buried in the inside of the phosopholipid bi-layer retain fluidity of the membrane, even in the absence of cholestrol.
Title: Re: VCE Biology Question Thread
Post by: Stick on December 28, 2013, 10:21:32 am
How to plant cell membranes maintain fluidity if they lack cholesterol? I'm guessing they have some structure of similar function?

I'd just like to point out that this is something that's definitely beyond the scope of VCE Biology. While I do recommend reading beyond the course boundaries, it's still really important that you have an awareness for those boundaries nonetheless.
Title: Re: VCE Biology Question Thread
Post by: MM1 on December 28, 2013, 01:39:15 pm
The polyunsaturated fatty acid chains buried in the inside of the phosopholipid bi-layer retain fluidity of the membrane, even in the absence of cholestrol.

Thanks!!
Title: Re: VCE Biology Question Thread
Post by: MM1 on December 28, 2013, 01:41:24 pm
I'd just like to point out that this is something that's definitely beyond the scope of VCE Biology. While I do recommend reading beyond the course boundaries, it's still really important that you have an awareness for those boundaries nonetheless.

Oh okay, thanks for the heads up though!
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on December 28, 2013, 01:53:27 pm
I'd just like to point out that this is something that's definitely beyond the scope of VCE Biology. While I do recommend reading beyond the course boundaries, it's still really important that you have an awareness for those boundaries nonetheless.

So important! Don't deviate from the VCE Biology scope; I did and it didn't help me in any way. In fact, it probably affected my knowledge because I didn't focus on things required for VCE Biology because I was too busy learning the enzymes for the Calvin Cycle.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on December 28, 2013, 02:04:02 pm
Does the study design seem slightly vague in terms of what is expected of us to know, or is that just me?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on December 28, 2013, 02:05:23 pm
Don't deviate from the VCE Biology scope; I did and it didn't help me in any way.

Told you so ;) It will help you later on though. And in some respects is probably kept you interested.

Does the study design seem slightly vague in terms of what is expected of us to know, or is that just me?

All of them are vague.
Title: Re: VCE Biology Question Thread
Post by: MM1 on December 28, 2013, 02:23:30 pm
So important! Don't deviate from the VCE Biology scope; I did and it didn't help me in any way. In fact, it probably affected my knowledge because I didn't focus on things required for VCE Biology because I was too busy learning the enzymes for the Calvin Cycle.

Oh, it's just that I got this information from a TSFX booklet, so I'm assuming that it's all important information?
And also, apparently since the study design has been changed, it seems we aren't expected to know every intricate detail about photosynthesis and respiration... and I agree with @oddly, the study design is kinda vague in specifying these things.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on December 28, 2013, 02:26:55 pm
I'm contemplating on purchasing A+ Notes, but is it necessary if one already has the TSFX notes?
Briefly going through the A+ notes, they seem very concise. And as MM1 has brought up, the TSFX notes seem unnecessarily comprehensive?
Title: Re: VCE Biology Question Thread
Post by: Stick on December 28, 2013, 02:59:43 pm
Does the study design seem slightly vague in terms of what is expected of us to know, or is that just me?

The new study design isn't nearly as vague as the old one. You'll understand if you see the table summarising the changes made.

To be honest, there's a lot in VCE Biology that's incredibly vague - I'm talking about most extended response questions, actually. For most of the year I really had no idea where I was sitting and I still had no idea after the exam (one user here may recall a PM where I predicted I'd get 36-40 in Biology XD). You're going to see a lot of practice questions over the course of the year and go "What the hell is this asking?" or "What exactly does it want me to say?". My advice is to get as much exposure to past questions as you possibly can so that you start to develop some awareness for what the assessor is looking for. It does get a little bit better over time but it takes a lot of getting used to.

As someone who didn't do Units 1 & 2 either, I also found studying the subject in general a bit vague at times - I didn't exactly know what was necessary and what wasn't and didn't know which information to pick out from all the resources. Eventually I did find a methodical way to study through it all and this is the only thing I can put my 50 down to.

I'm contemplating on purchasing A+ Notes, but is it necessary if one already has the TSFX notes?
Briefly going through the A+ notes, they seem very concise. And as MM1 has brought up, the TSFX notes seem unnecessarily comprehensive?

I got so overwhelmed with all this information that I pretty much neglected all my other resources (Biozone and Biol Notes) and sourced nearly all of my content from Nature of Biology. However, my school booklist required me to purchase StudyOn, which is just an online resource that organises all the past VCAA questions by topic. This was how I revised all year and I think it was a massive help. You'll eventually see that each company has a slightly different style and approach in their questions so practicing only on VCAA questions was probably quite beneficial since I got a glimpse into what the assessors are actually looking for.
Title: Re: VCE Biology Question Thread
Post by: DJA on December 28, 2013, 03:03:50 pm
The new study design isn't nearly as vague as the old one. You'll understand if you see the table summarising the changes made.

To be honest, there's a lot in VCE Biology that's incredibly vague - I'm talking about most extended response questions, actually. For most of the year I really had no idea where I was sitting and I still had no idea after the exam (one user here may recall a PM where I predicted I'd get 36-40 in Biology XD). You're going to see a lot of practice questions over the course of the year and go "What the hell is this asking?" or "What exactly does it want me to say?". My advice is to get as much exposure to past questions as you possibly can so that you start to develop some awareness for what the assessor is looking for. It does get a little bit better over time but it takes a lot of getting used to.

As someone who didn't do Units 1 & 2 either, I also found studying the subject in general a bit vague at times - I didn't exactly know what was necessary and what wasn't and didn't know which information to pick out from all the resources. Eventually I did find a methodical way to study through it all and this is the only thing I can put my 50 down to.

I got so overwhelmed with all this information that I pretty much neglected all my other resources (Biozone and Biol Notes) and sourced nearly all of my content from Nature of Biology. However, my school booklist required me to purchase StudyOn, which is just an online resource that organises all the past VCAA questions by topic. This was how I revised all year and I think it was a massive help. You'll eventually see that each company has a slightly different style and approach in their questions so practicing only on VCAA questions was probably quite beneficial since I got a glimpse into what the assessors are actually looking for.

I fully endorse Studyon as well. Like Stick it was part of my booklist for 2014 and from what i have trialed it has been a huge help so far.

The combo of Nature of Biology, Biozone and Studyon has proved fantastic for me.
Title: Re: VCE Biology Question Thread
Post by: psyxwar on December 28, 2013, 04:47:21 pm
So I'm guessing for the purpose of VCE biology, both models are essentially correct?
just run with lock and key for VCE biology
Title: Re: VCE Biology Question Thread
Post by: millie96 on December 28, 2013, 07:00:45 pm
Can somebody explain to me the dipole nature of water?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on December 28, 2013, 07:11:32 pm
Can somebody explain to me the dipole nature of water?

A water molecule is dipole as it has two regions of opposite charge; the oxygen atom, due to its higher electronegativity, attracts the electrons that it shares in a covalent bond closer to itself. In turn, the oxygen atom is slightly (relatively) negative and the hydrogen atoms are made slightly (relatively) positive.

As a result of its dipole nature, it is said to be a universal solvent as it can dissolve other polar substances. It is important to note the notion of 'like dissolves like'.

Edited
Title: Re: VCE Biology Question Thread
Post by: psyxwar on December 28, 2013, 07:15:23 pm
Can somebody explain to me the dipole nature of water?
Water has an asymmetrical charge distribution; that is, though it is neutral overall, the molecule is not neutral throughout and some parts of the molecule are slightly positive, and others are slightly negative (indicated by a lower case delta (δ) (eg. δ+ refers to it being slightly positive)

This is due to the differences in electronegativity (electron-attracting ability) of its constituent elements, hydrogen and oxygen. Oxygen is a lot more electronegative than hydrogen and you can think of it as "hogging" the electrons shared in the bond. Thus, these electrons in the bonds between hydrogen and oxygen spend a lot more time around oxygen than hydrogen, and thus oxygen becomes slightly negative (due to having more than its fair share of electrons) and hydrogen becomes slightly positive.
Title: Re: VCE Biology Question Thread
Post by: alchemy on December 28, 2013, 10:30:14 pm
umm, does the light independent (carbon-reduction) stage provide energy for the Calvin cycle to occur?
NoB says that "plants do not build sugar simply by joining CO2 molecules together", so what then is the purpose of the carbon-reduction stage?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on December 28, 2013, 10:32:38 pm
umm, does the light independent (carbon-reduction) stage provide energy for the Calvin cycle to occur?
NoB says that "plants do not build sugar simply by joining CO2 molecules together", so what then is the purpose of the carbon-reduction stage?

The Calvin-Benson cycle takes place because carbon must be reduced from its highly oxidised state as carbon dioxide. However, you don't need to know this. For the purpose of VCE Biology, it is sufficient to say that in the stroma of chloroplasts, CO2 molecules react with H+ ions (provided by NADPH from the light-dependent phase), to produce glucose. ATP energy, produced during the light-dependent stage, provides the energy for the anabolic synthesis of glucose.
Title: Re: VCE Biology Question Thread
Post by: alondouek on December 28, 2013, 10:33:48 pm
umm, does the light independent (carbon-reduction) stage provide energy for the Calvin cycle to occur?
NoB says that "plants do not build sugar simply by joining CO2 molecules together", so what then is the purpose of the carbon-reduction stage?

The light-independent stage serves to produce glucose from CO2 and other compounds. NoB makes the point that it's a complex series of reactions, rather than just CO2+CO2+etc. I've attached a picture of the LIRs below, but you won't need to know any of the enzymes etc. until uni :)

(http://media1.shmoop.com/images/biology/biobook_photosyn_3.png)
Title: Re: VCE Biology Question Thread
Post by: alchemy on December 28, 2013, 10:56:35 pm
The light-independent stage serves to produce glucose from CO2 and other compounds. NoB makes the point that it's a complex series of reactions, rather than just CO2+CO2+etc. I've attached a picture of the LIRs below, but you won't need to know any of the enzymes etc. until uni :)

Thanks, but what provides energy for the Calvin cycle to occur?
Title: Re: VCE Biology Question Thread
Post by: alondouek on December 28, 2013, 10:58:10 pm
Thanks, but what provides energy for the Calvin cycle to occur?

Title: Re: VCE Biology Question Thread
Post by: alchemy on December 28, 2013, 11:30:27 pm

Oh right, I didn't see his post. My bad! Sorry Yacoubb.
Title: Re: VCE Biology Question Thread
Post by: Frozone on December 28, 2013, 11:47:10 pm
In the study guide I'm having trouble understanding what they mean by the packaging,transport, import of bio macromolecules. I'd like this clarified as I hope I'm not studying the wrong thing.  :-\
Title: Re: VCE Biology Question Thread
Post by: alondouek on December 28, 2013, 11:49:43 pm
In the study guide I'm having trouble understanding what they mean by the packaging,transport, import of bio macromolecules. I'd like this clarified as I hope I'm not studying the wrong thing.  :-\

Is there a specific concept you don't understand that I can help you with?
Title: Re: VCE Biology Question Thread
Post by: Frozone on December 28, 2013, 11:54:34 pm
Is there a specific concept you don't understand that I can help you with?
It's not the concepts that I'm struggling with(not yet at least), but the study design is vague and I'm not sure what I am supposed to be know for that specific part.
Title: Re: VCE Biology Question Thread
Post by: alondouek on December 28, 2013, 11:58:40 pm
There's nothing wrong with learning everything in your textbook/study guide about these concepts. That way, you can refine your knowledge later on when you have a better idea of the overall context of intra/extra-cellular transport!
Title: Re: VCE Biology Question Thread
Post by: sprakash97 on December 30, 2013, 10:21:23 am
Can someone please explain 3' and 5' in  DNA :)
Title: Re: VCE Biology Question Thread
Post by: alchemy on December 30, 2013, 10:55:26 am
Can someone please explain 3' and 5' in  DNA :)

It's been done before. Check page 2 of this thread.
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on December 30, 2013, 11:10:45 am
Can someone please explain 3' and 5' in  DNA :)

To be honest, all you need to know is that polynucleotide synthesis occurs 5' to 3', and that DNA is anti-parallel, meaning that one of the polynucleotide chains runs 5' to 3' in one direction, and the other polynucleotide chain (joined to the first by weak hydrogen bonding) runs 5' to 3' in the opposite direction.

But the part on knowing polynucleotide synthesis occurs 5' to 3' is important for many topics you'll cover in Unit 4 including the Polymerase Chain Reaction, Transcription, etc.
Title: Re: VCE Biology Question Thread
Post by: DJA on December 30, 2013, 11:43:13 am
I've read the threads outlining ATP synthesis, I've read Nature of Biology outlining it and I have studied the Biozone explanation but this biological process still eludes my understanding in how it all fits together. :-[
Could someone be kind enough to outline the whole process tracking the glucose molecule from the beginning right to the very end and how ATP is produced and consumed throughout the process as well as the meaning of each specific process at each stage (glycolysis, link reaction, krebs, electron transport).
I don't care if it goes outside the VCE course because I do not want to rote learn just the definitions for Krebs cycle etc. What I need to understand to learn it, is how it all fits together from beginning to end, because right now I am just confused as hell.

Title: Re: VCE Biology Question Thread
Post by: psyxwar on December 30, 2013, 12:42:20 pm
I've read the threads outlining ATP synthesis, I've read Nature of Biology outlining it and I have studied the Biozone explanation but this biological process still eludes my understanding in how it all fits together. :-[
Could someone be kind enough to outline the whole process tracking the glucose molecule from the beginning right to the very end and how ATP is produced and consumed throughout the process as well as the meaning of each specific process at each stage (glycolysis, link reaction, krebs, electron transport).
I don't care if it goes outside the VCE course because I do not want to rote learn just the definitions for Krebs cycle etc. What I need to understand to learn it, is how it all fits together from beginning to end, because right now I am just confused as hell.
I even had a freaking tutor session once off and he was completely useless and just scratched the surface.

Below is the depth I learnt it in (from my notes, actually). I'd like to stress that this is still just a simplification. However, this depth is still beyond the scope of 3/4 Bio.

There isn't much point learning more than what I put for Kreb's or Glycolysis, as at that point you're just rote learning enzymes and intermediate compounds.

Aerobic Cellular Respiration
•   Cellular respiration involves the breakdown of glucose into ATP (chemical energy in glucose is converted into immediately usable energy of ATP)
•   One of two types of respiration. It requires oxygen. The other type is anaerobic respiration, which does not require oxygen.
•   It is an exergonic, catabolic reaction (CATS EXPIRE: catabolic, exergonic, respire)
•   Balanced equation: C6H12O6 + 6O2     -->     6CO2 + 6H2O
•   Word equation: glucose + oxygen gas      -->    carbon dioxide + water
•   Occurs in the mitochondria:
•   It has two membranes - the outer membrane and the high folded inner membrane. A mitochondria can be easily recognised by this folded inner membrane. The infoldings in this inner membrane are known as the cristae.
•   The intracellular space bordered by the inner membrane is known as the mitochondrial matrix (or simply matrix).
•   The mitochondria has its own ribosomes and its own circular DNA (mtDNA), similar to prokaryotic DNA. This DNA is passed maternally.
•   This is evidence for the fact that they once existed as separated prokaryotic organisms (see the endosymbiotic theory)
•   It is slower than anaerobic respiration, but more efficient (more ATPs per glucose molecule generated)
•   It is a continuous, sustained reaction, whereas anaerobic respiration lasts for short bursts of time.
•   Occurs in three stages: Glycolysis, Krebs Cycle and Electron Transport. Only the last two are exclusive to aerobic respiration: glycolysis also occurs with anaerobic respiration

Glycolysis
•   Outputs: 2 pyruvate, 2 ATP, 2NADH
•   Where: cytosol
•   What happens: a glucose molecule is broken down into two pyruvate molecules via a series of intermediate reactions.
•   The process actually requires an input of 2 ATPs, but generates 4 ATPs, resulting in a net gain of 2 ATPs (probably not that relevant to the course). High energy electron carrier NADH is also produced.

Krebs Cycle/ Citric Acid Cycle
•   Outputs: NADH, FADH2,1 ATP, 3 CO2 (per pyruvate. Remember there are two pyruvates per glucose)
•   Where: mitrochondrial matrix
•   What happens: pyruvate is, via a series of intermediate reactions, converted into 3 carbon dioxide molecules, 2 ATP and high energy electron carriers for use in electron transport.
•   Pyruvate is first broken down into a two carbon compound (producing one CO2 molecule) which joins with coenzyme A to form Acetyl CoA (note that this is technically not part of the Krebs Cycle). Acetyl CoA enters the Krebs Cycle and undergoes a series of reactions, producing the high energy electron carriers NADH and FADH2 as well as ATP. This process produces 2 CO2 molecules (again, per pyruvate).
•   Why is it a cycle? This isn't too relevant to 3/4 Biology, but it is cyclic in nature because the Acetyl CoA joins with a 4 carbon compound known as oxaloacetate. The resulting substance undergoes the Krebs Cycle, which ends up regenerating oxaloacetate for future use (on top of the other products.)

Electron Transport Chain
•   Where: cristae of the mitochondria
•   What happens: the high energy electrons from the previous stages undergo a series of reactions, releasing the energy that drives ATP synthesis.
•   The high energy electron carriers, NADH and FADH2, carry the high energy electrons to the electron transport chain, a series of reactions that the electrons undergo (redox reactions), losing energy in each reaction. It (this electron transport chain) is facilitated by cytochrome protein complexes. The energy produced is used to drive the synthesis of ATP via the protein complex ATP Synthase (NB. this is a simplification. The following is for your interest only: the electron transport chain actually involves protons being pumped out into the intermembrane space between the cristae and the outer membrane. This causes a H+ buildup in the intermembrane space, meaning the H+ ions want to move back into the matrix (the H+ gradient is known as a proton-motive force). The only pathway for them to move back is ATP Synthase, and as they move back it drives the synthesis of ATP.)
•   The electrons are finally accepted by oxygen, which becomes reduced (remember reduction = gaining electrons) to water.
•   What causes the difference in ATP production in the electron transport chain? Some cells require the generation of more ATP, specifically liver and muscle cells because they are more energy intensive.
Title: Re: VCE Biology Question Thread
Post by: MM1 on December 30, 2013, 01:13:30 pm
Thanks psyxwar for that concise outline!

However, I'm still trying to fully understand the biochemical processes (photosynthesis & respiration); as in what's expected from VCAA. Apparently, we're only expected to know the inputs/outputs/location of reaction? What's the best way to go around learning this?

Thank you!!
Title: Re: VCE Biology Question Thread
Post by: DJA on December 30, 2013, 01:24:34 pm
Thanks psyxwar for that concise outline!

However, I'm still trying to fully understand the biochemical processes (photosynthesis & respiration); as in what's expected from VCAA. Apparently, we're only expected to know the inputs/outputs/location of reaction? What's the best way to go around learning this?

Thank you!!

Correct that is all you need to know for VCE. You can either choose to rote learn the input outputs etc or you can try and comprehend the full process. Personally I go with the latter because that's how I like to learn.

psyxwar thanks you legend.
Title: Re: VCE Biology Question Thread
Post by: alchemy on December 30, 2013, 01:32:45 pm
Do more enzymes collectively make the reaction rate faster, or mean less activation energy is required for the reaction to begin? My guess is not.
I know that enzyme concentration affects enzyme production. Net increase of enzyme = more product made per unit of time?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on December 30, 2013, 02:40:26 pm
Do more enzymes collectively make the reaction rate faster, or mean less activation energy is required for the reaction to begin? My guess is not.
I know that enzyme concentration affects enzyme production. Net increase of enzyme = more product made per unit of time?

Increase in reaction rate, provided that the enzyme concentration is the limiting factor and not the substrate concentration. You can't increase the concentration of enzymes indefinitely with the hope that the reaction rate will keep increasing, because you need substrate to fill those enzymes. That and other factors also complicate it as well.
Title: Re: VCE Biology Question Thread
Post by: sprakash97 on December 30, 2013, 07:32:08 pm
Thanks Yacoubb, also do you know any mnemonics for bio?
Title: Re: VCE Biology Question Thread
Post by: alondouek on December 30, 2013, 07:43:45 pm
For the nervous system aspect of the course, some people find it tough to remember which neurons are afferent and which are efferent;

SAME

Sensory - Afferent; Motor - Efferent
Title: Re: VCE Biology Question Thread
Post by: MM1 on December 30, 2013, 08:44:03 pm
Would you guys recommend making your own hand written notes? I feel it'd kinda be time consuming, considering already having TSFX, A+ notes and other reliable papers/resources? ...
Title: Re: VCE Biology Question Thread
Post by: alondouek on December 30, 2013, 08:55:52 pm
Would you guys recommend making your own hand written notes? I feel it'd kinda be time consuming, considering already having TSFX, A+ notes and other reliable papers/resources? ...

I made my own handwritten notes (see A Guide to Success in VCE Biology) even though I also had A+ Notes and various other stuff too, because I learn best by writing things out. This isn't the same for everyone - and time management is pretty important in VCE - so it's entirely up to you and how you think you will learn best :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on December 31, 2013, 06:21:57 pm
This question is most likely out of the scope of what's expected for VCE Biol, but what is 'choline' [found in phospholipids]?

Title: Re: VCE Biology Question Thread
Post by: psyxwar on December 31, 2013, 06:29:27 pm
Choline isn't necessarily apart of phospholipids; phospholipids have a variable group attached to the phosphate group, which can be choline. If you're interested in what it is exactly (which is completely irrelevant to the course), just read the wikipedia page.
Title: Re: VCE Biology Question Thread
Post by: DJA on January 04, 2014, 11:40:32 am
Increase in reaction rate, provided that the enzyme concentration is the limiting factor and not the substrate concentration. You can't increase the concentration of enzymes indefinitely with the hope that the reaction rate will keep increasing, because you need substrate to fill those enzymes. That and other factors also complicate it as well.
Regarding Enzymes:
So, IF you assume ample substrate and cofactors present, if you increase the concentration of enzymes, will the rate of the reaction similarly increase in a linear fashion?
I am assuming ideal conditions.

Does the rate of reaction eventually plateau or will the rate of reaction continue to increase assuming the said conditions?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 04, 2014, 11:48:36 am
Regarding Enzymes:
So, IF you assume ample substrate and cofactors present, if you increase the concentration of enzymes, will the rate of the reaction similarly increase in a linear fashion?
I am assuming ideal conditions.

Does the rate of reaction eventually plateau or will the rate of reaction continue to increase assuming the said conditions?

Answering your first question: if you increase substrate concentration as you increase enzyme concentration, the reaction rate of the enzyme will increase in a linear fashion, assuming all other variables are kept constant. However, you may see a plateau because of product concentration, which forms almost an obstacle that limits the time interval in which the enzyme & substrate combine & react together, thereby reducing the activity rate of the enzyme.
Title: Re: VCE Biology Question Thread
Post by: DJA on January 04, 2014, 11:56:43 am
Answering your first question: if you increase substrate concentration as you increase enzyme concentration, the reaction rate of the enzyme will increase in a linear fashion, assuming all other variables are kept constant. However, you may see a plateau because of product concentration, which forms almost an obstacle that limits the time interval in which the enzyme & substrate combine & react together, thereby reducing the activity rate of the enzyme.

So basically, the concentration of product surrounding the enzyme and substrate hinders the formation of the enzyme-substrate complexes-and this accounts for the plateau eventually?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 04, 2014, 11:58:07 am
So basically, the concentration of product surrounding the enzyme and substrate hinders the formation of the enzyme-substrate complexes-and this accounts for the plateau eventually?

Yes, think of it as "getting in the way" of the reactions
Title: Re: VCE Biology Question Thread
Post by: DJA on January 04, 2014, 12:03:46 pm
Yes, think of it as "getting in the way" of the reactions

Cheers!

Another question:
I was wondering regarding enzyme cofactors. I know that enzymes are entirely re-usable, but in the case of coenzymes which assist the catalytic function, (such as organic molecules, or ions) do these substances get 'used up' in the catalytic process (Do they bond to the substrate?

Or do the coenzymes merely play a role as a facilitator and don't actually COMBINE with the substrate and can thus be used repeatedly similar to the apoenzyme?
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 04, 2014, 12:53:21 pm
Cheers!

Another question:
I was wondering regarding enzyme cofactors. I know that enzymes are entirely re-usable, but in the case of coenzymes which assist the catalytic function, (such as organic molecules, or ions) do these substances get 'used up' in the catalytic process (Do they bond to the substrate?

Or do the coenzymes merely play a role as a facilitator and don't actually COMBINE with the substrate and can thus be used repeatedly similar to the apoenzyme?

As far as I know, coenzymes are organic molecules required by certain enzymes to carry out catalysis. They do bind to the active site of the enzyme and participate in catalysis, however, they are not considered 'substrates' of the reaction. Like regular enzymes they are not changed or "used up" in the reaction.
As for the relationship between a coenzyme and a cofactor, it is important to remember that a cofactor is a non-protein chemical compound whereas a coenzyme, as mentioned above, is an organic and loosely bound cofactor.

I probably missed out on a lot of other detail which you were after, as I only started studying this topic recently. Perhaps, someone else can expand on the above. Hope it helped though : )
Title: Re: VCE Biology Question Thread
Post by: DJA on January 04, 2014, 12:59:25 pm
As far as I know, coenzymes are organic molecules required by certain enzymes to carry out catalysis. They do bind to the active site of the enzyme and participate in catalysis, however, they are not considered 'substrates' of the reaction. Like regular enzymes they are not changed or "used up" in the reaction.
As for the relationship between a coenzyme and a cofactor, it is important to remember that a cofactor is a non-protein chemical compound whereas a coenzyme, as mentioned above, is an organic and loosely bound cofactor.

I probably missed out on a lot of other detail which you were after, as I only started studying this topic recently. Perhaps, someone else can expand on the above. Hope it helped though : )
Thanks for the help!

FYI Sheldon, I believe that:
A cofactor simply describes the additional chemical component which can be either organic molecules (vitamin) OR inorganic ions (e.g. Ca2+ ions). So a cofactor is like a big branching term to describe the two types: coenzymes and prosthetic groups. So you are correct on that.
A coenzyme merely describes a type of cofactor that it is temporarily attached to the apoenzyme part.
A prosthetic group describes a cofactor which is permanently bound to the apoenzyme part.

**EDIT: Although Coenzyme often refers to any organic cofactor (to make things more confusing) after I did some research!**
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 04, 2014, 01:07:37 pm

A coenzyme merely describes a type of cofactor that it is temporarily attached to the apoenzyme part.

Yep, that's what I meant by "loosely bound". Sorry for the confusion, if it caused any; I wasn't sure how to phrase that but I think you put it better ; )

Title: Re: VCE Biology Question Thread
Post by: DJA on January 04, 2014, 01:12:16 pm
Yep, that's what I meant by "loosely bound". Sorry for the confusion, if it caused any; I wasn't sure how to phrase that but I think you put it better ; )

**EDIT: Although Coenzyme often refers to any organic cofactor (to make things more confusing) after I did some research!**
Title: Re: VCE Biology Question Thread
Post by: psyxwar on January 04, 2014, 01:19:40 pm
For some reason in VCE biology there seems to be a dichotomy between coenzyme and cofactor, with the latter seemingly referring exclusively to inorganic substances and the former organic substances.
Title: Re: VCE Biology Question Thread
Post by: DJA on January 04, 2014, 01:25:34 pm
For some reason in VCE biology there seems to be a dichotomy between coenzyme and cofactor, with the latter seemingly referring exclusively to inorganic substances and the former organic substances.

wtf? just great..

Thanks VCE
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 04, 2014, 01:28:04 pm
**EDIT: Although Coenzyme often refers to any organic cofactor (to make things more confusing) after I did some research!**

...it is important to remember that a cofactor is a non-protein chemical compound whereas a coenzyme, as mentioned above, is an organic and loosely bound cofactor.

Umm, yeah I mentioned that lol :P
Title: Re: VCE Biology Question Thread
Post by: psyxwar on January 04, 2014, 01:29:14 pm
wtf? just great..

Thanks VCE
Don't quote me on that as I'm not sure if that's VCAA's opinion on it, but every VCE level text/ resource I read seemed to suggest that.
Title: Re: VCE Biology Question Thread
Post by: DJA on January 04, 2014, 01:46:00 pm
Don't quote me on that as I'm not sure if that's VCAA's opinion on it, but every VCE level text/ resource I read seemed to suggest that.

Yeah I've been noticing a similar trend. cheers for the headsup
Title: Re: VCE Biology Question Thread
Post by: SwagG on January 04, 2014, 07:52:19 pm
Hey Guys,
Do we need to know how to draw the molecular diagrams of etc. glucose? If so, is there any method of drawing it or remembering it?
Thanks
Title: Re: VCE Biology Question Thread
Post by: DJA on January 04, 2014, 08:04:08 pm
Hey Guys,
Do we need to know how to draw the molecular diagrams of etc. glucose? If so, is there any method of drawing it or remembering it?
Thanks

No. You do not need to be able to actually draw the carbon hexagonal ring structure of glucose in Bio.

You do need to know how some of the side groups interact in that a condensation reaction (and an emission of H2O) allows glucose monomers to bond to form adisaccharide - maltose through a glycosidic bond.
Title: Re: VCE Biology Question Thread
Post by: SwagG on January 04, 2014, 08:12:01 pm
No. You do not need to be able to actually draw the carbon hexagonal ring structure of glucose in Bio.

You do need to know how some of the side groups interact in that a condensation reaction (and an emission of H2O) allows glucose monomers to bond to form adisaccharide - maltose through a glycosidic bond.
Thanks :) :) :)
Title: Re: VCE Biology Question Thread
Post by: sammiegan on January 05, 2014, 03:43:45 pm
Hi, I was wondering if  the phospholipid bilayer was a polymer in itself, being made up of phospholipid molecules as its monomer?
And also is haemoglobin a polymer?
:)
thanks!
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 05, 2014, 04:05:46 pm
Hi, I was wondering if  the phospholipid bilayer was a polymer in itself, being made up of phospholipid molecules as its monomer?
And also is haemoglobin a polymer?
:)
thanks!

Nope on both counts! The phospholipid bilayer is not a polymer, but is is stabilised and given rigidity by membrane molecules such as cholesterol.

Haemoglobin is a quaternary protein with inorganic prosthetic groups inside it, but it isn't a polymer
Title: Re: VCE Biology Question Thread
Post by: DJA on January 05, 2014, 04:07:38 pm
Hi, I was wondering if  the phospholipid bilayer was a polymer in itself, being made up of phospholipid molecules as its monomer?
And also is haemoglobin a polymer?
:)
thanks!

1) No the phosoplipid bilayer is not a polymer. A polymer is a substance which has a molecular structure composed of a lot of similar units (monomers) bonded together. The phospholipid bilayer while being composed of many many individual phospholipids is not bonded together strongly in the way polymerisation does.
For example with condensation polymerization between a hydroxy and carboxyl group, a covalent bond is formed which is very strong. In comparison, all that holds phospholipids together is fairly weak in comparison van der waals and hydrogen bonding (you don't need to know the specifics for bio). Such weaker forces allow the membrane to be flexible, semi-permeable and definitely not fixed in any way. If it was polymerized, it would be far more fixed. Think of a protein amino chain-completely different story.

2)  Haemoglobin is not a polymer in itself. It is a globular conjugated protein containing 4 polypeptides, 2 identical beta chains and two identical alpha chains which forms around a haem group which binds to oxygen. Note that the polypeptide chains THEMSELVES are polymers as they are composed of amino acid monomers. However the haemoglobin molecule itself is simply a product of a protein's quatenary structure.

Please post if you need further clarification! Hope this helped :)

beaten by alondoeuk but ill post anyway :)
Title: Re: VCE Biology Question Thread
Post by: sammiegan on January 05, 2014, 09:09:34 pm
Nope on both counts! The phospholipid bilayer is not a polymer, but is is stabilised and given rigidity by membrane molecules such as cholesterol.

Haemoglobin is a quaternary protein with inorganic prosthetic groups inside it, but it isn't a polymer

Oh okay! :) Thankyou so much for the explanation!!:)
From, Sammie
Title: Re: VCE Biology Question Thread
Post by: DJA on January 07, 2014, 04:40:27 pm
Following psyxwar's very helpful explanation of Cellular Respiration, I have drawn up in color my own diagrammatic representation of Cellular Respiration.
Note that the info goes beyond VCE Biology on many counts. The reason why I personally have decided to learn further than the course is simply because I find you understand more holistically if you go a bit further and hence are more likely to remember it. If you just rote learn facts without understanding I find it personally much harder to learn.

I hope this helps visual learners understand cellular respiration.
Enjoy!

(http://s29.postimg.org/etndt3y5z/DSC03685_A.jpg)
(http://s29.postimg.org/zf25l0fqv/DSC03686_B.jpg)

Cheers for the info and fix alondouek!
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 07, 2014, 05:09:25 pm
Can someone clarify what it is meant by the 5' to 3' of a DNA molecule?

Also, are coenzymes a 'category' of cofactors?

Cheers! :)
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 07, 2014, 05:12:31 pm
Can someone clarify what it is meant by the 5' to 3' of a DNA molecule?

Also, are coenzymes a 'category' of cofactors?

Cheers! :)

So a phosphate group is attached to the number 5 carbon of deoxyribose, so the end of the DNA where the phosphate is the last thing, that's 5' (the end that the phosphates are pointing to per se). A hydroxyl group (OH) is attached to the number 3 carbon of deoxyribose, so that end is called 3'.

Essentially, yep. The VCAA are just painful with this and we have no idea why they even make the distinction...
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 07, 2014, 05:50:59 pm
So a phosphate group is attached to the number 5 carbon of deoxyribose, so the end of the DNA where the phosphate is the last thing, that's 5' (the end that the phosphates are pointing to per se). A hydroxyl group (OH) is attached to the number 3 carbon of deoxyribose, so that end is called 3'.

Essentially, yep. The VCAA are just painful with this and we have no idea why they even make the distinction...

Thanks! :)

Yeah I've had the same problem with understanding chromatids; is the chromosome holistically considered a chromatid or is it the separate strands held together by the centromere called chromatids. A little confusing. My teacher said both is correct...
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 07, 2014, 05:53:48 pm
Thanks! :)

Yeah I've had the same problem with understanding chromatids; is the chromosome holistically considered a chromatid or is it the separate strands held together by the centromere called chromatids. A little confusing. My teacher said both is correct...

Best way to look at it is that a chromatid is one strand of DNA with histones. Therefore when the chromosomes replicate, you get two chromatids in one chromosome.
Title: Re: VCE Biology Question Thread
Post by: DJA on January 08, 2014, 10:09:17 am
Is ATPase a protein complex embedded in the cristae of the mitochondrion or is it simply an enzyme that floats around?
Title: Re: VCE Biology Question Thread
Post by: Shenz0r on January 08, 2014, 10:50:30 am
Yup, ATPase is a transmembrane enzyme so it's found on cristae. When the other proteins involved in the electron transport chain receive electrons, they pump protons into the intermembrane space. This creates a proton gradient, and the protons then diffuse through ATPase back into the matrix in order to generate ATP. This is why ATPase cannot be an enzyme that floats around.

This is outside of the course's scope but it should help to understand it nevertheless.

Title: Re: VCE Biology Question Thread
Post by: DJA on January 08, 2014, 11:10:39 am
Yup, ATPase is a transmembrane enzyme so it's found on cristae. When the other proteins involved in the electron transport chain receive electrons, they pump protons into the intermembrane space. This creates a proton gradient, and the protons then diffuse through ATPase back into the matrix in order to generate ATP. This is why ATPase cannot be an enzyme that floats around.

Thanks for that.
And similarly what about cytochrome complexes. Are they also embedded in the cristae, or are they just enzymes?
Title: Re: VCE Biology Question Thread
Post by: DJA on January 08, 2014, 02:07:08 pm
Also could someone please post a concise explanation if possible of photosynthesis according to what needs to be actually known in the scope of the VCE course?

I would be greatly appreciative.
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 08, 2014, 10:56:12 pm
Also could someone please post a concise explanation if possible of photosynthesis according to what needs to be actually known in the scope of the VCE course?

I would be greatly appreciative.

Photosynthesis occurs in two stages:

Light-dependent stage:
1.) This stage takes place in the thylakoid membranes of chloroplasts.
2.) Light energy is absorbed by chlorophyll molecules; electrons within chloroplasts become energised.
3.) Water is split to form H+ ions and oxygen gas.
4.) NADPH and ATP is formed.

Light-independent stage:
1.) This stage takes place in the stroma of chloroplasts.
2.) Carbon dioxide reacts with H+ ions (provided by NADPH) to produce glucose.
3.) ATP provides the energy for the synthesis of glucose.
4.) Excess H+ ions react with O2- ions to produce water (a by-product).
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 10, 2014, 12:12:39 am
Hi, can someone please explain the relationship between the structure and function of the extracellular matrix?

Because I understand its structure, that it consists of long flexible fibres embedded in a glycoprotein and glycolipid matrix but I am unsure of how this relates to its function?

Thankyou  :)
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 10, 2014, 12:20:15 am
Hi, can someone please explain the relationship between the structure and function of the extracellular matrix?

Because I understand its structure, that it consists of long flexible fibres embedded in a glycoprotein and glycolipid matrix but I am unsure of how this relates to its function?

Thankyou  :)

The extracellular matrix (let's call it the ECM for brevity) is composed of a multitude of components so it stands to reason that there are many associated functions, including:

- structural support for the cell
- regulation of intracellular communication
- tissue barriers

among others. The ECM also has a role in the regulation of growth and in wound healing.
Title: Re: VCE Biology Question Thread
Post by: That Other Guy on January 10, 2014, 04:58:15 pm
I'm unsure of whether or not the specifics of this are extraneous to the study design, but how exactly does pH denature a protein? Does it pertain to the release of hydrogen ions and their subsequent bonding with certain amino acids? I could only see this as a feasible deduction if amino acids were polar...
Furthermore, if this is the case, then do some amino acids only exist within certain environments? For example, enzymes produced in the stomach would surely be resilient to denaturation in low pH levels, and yet others would not. Hence, would it be plausible to suggest that only non-polar amino acids form the polypeptides of proteins existing in highly acidic environments?
Are any amino acids polar?

I am theorizing here, but I would appreciate some clarity!

Title: Re: VCE Biology Question Thread
Post by: masonruc on January 10, 2014, 05:17:44 pm
I'm unsure of whether or not the specifics of this are extraneous to the study design, but how exactly does pH denature a protein? Does it pertain to the release of hydrogen ions and their subsequent bonding with certain amino acids? I could only see this as a feasible deduction if amino acids were polar...
Furthermore, if this is the case, then do some amino acids only exist within certain environments? For example, enzymes produced in the stomach would surely be resilient to denaturation in low pH levels, and yet others would not. Hence, would it be plausible to suggest that only non-polar amino acids form the polypeptides of proteins existing in highly acidic environments?
Are any amino acids polar?

I am theorizing here, but I would appreciate some clarity!

Omg slow down way to in depth for bio. All you need to know is that enzymes (proteins) work in an optimal pH enviro anything outside that optimal will have an effect on the structure of the protein. Hence the shape will alter and it will no longer be able to perform it's function.
Title: Re: VCE Biology Question Thread
Post by: That Other Guy on January 10, 2014, 05:43:15 pm
Omg slow down way to in depth for bio. All you need to know is that enzymes (proteins) work in an optimal pH enviro anything outside that optimal will have an effect on the structure of the protein. Hence the shape will alter and it will no longer be able to perform it's function.

Hahaha, I know that I probably jumped in the deep end... but I hate learning something without having a holistic explanation or model to at least satisfy my temporarily. :P I don't even know if my question was realistic or not. But thanks anyway!
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 10, 2014, 05:55:34 pm
I'm unsure of whether or not the specifics of this are extraneous to the study design, but how exactly does pH denature a protein? Does it pertain to the release of hydrogen ions and their subsequent bonding with certain amino acids? I could only see this as a feasible deduction if amino acids were polar...
Furthermore, if this is the case, then do some amino acids only exist within certain environments? For example, enzymes produced in the stomach would surely be resilient to denaturation in low pH levels, and yet others would not. Hence, would it be plausible to suggest that only non-polar amino acids form the polypeptides of proteins existing in highly acidic environments?
Are any amino acids polar?

I am theorizing here, but I would appreciate some clarity!

Denaturation itself is a result of a change in the protein from a stable conformation to an unstable one. Different proteins have different preferred pH ranges, and when they are subjected to a pH that is not within their preferred range they reflect the change in their environment and alter in some way. Because tertiary and quaternary proteins are folded in a very specific way (so as to allow for specificity to a substrate), changes to the protein structure through denaturation ultimately affect or negate the function of that protein.

For example, if I were to place an enzyme in a lower-than-preferred pH, there are more H+ ions available. Some of the amino acids that make up this protein are polar (i.e. having a clear separation of electrical charge in the molecule); therefore the negative areas of the polar amino acids attract H+ ions, which then has an effect on the ability of the enzyme to hold its regular state (that is, it is unstable). The enzyme is said to be denatured, as it can no longer perform its regular function, being interaction with its specific substrate.

Hope that helped! :)
Title: Re: VCE Biology Question Thread
Post by: That Other Guy on January 10, 2014, 05:59:58 pm
Denaturation itself is a result of a change in the protein from a stable conformation to an unstable one. Different proteins have different preferred pH ranges, and when they are subjected to a pH that is not within their preferred range they reflect the change in their environment and alter in some way. Because tertiary and quaternary proteins are folded in a very specific way (so as to allow for specificity to a substrate), changes to the protein structure through denaturation ultimately affect or negate the function of that protein.

For example, if I were to place an enzyme in a lower-than-preferred pH, there are more H+ ions available. Some of the amino acids that make up this protein are polar (i.e. having a clear separation of electrical charge in the molecule); therefore the negative areas of the polar amino acids attract H+ ions, which then has an effect on the ability of the enzyme to hold its regular state (that is, it is unstable). The enzyme is said to be denatured, as it can no longer perform its regular function, being interaction with its specific substrate.

Hope that helped! :)

Yes, this was a major help! Logically, I assumed that some amino acids were polar, but I wasn't sure. In regards to enzymes in, for instance, the stomach, does the sequencing/composition of the protein allow for more resilience? Would it therefore be non-polar?
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 10, 2014, 06:12:18 pm
In regards to enzymes in, for instance, the stomach, does the sequencing/composition of the protein allow for more resilience? Would it therefore be non-polar?

In short, yes. This is also beyond the VCE biology course, but some enzymes have inactive precursors called zymogens. In the stomach, our main proteolytic (breaks down proteins) enzyme is pepsin, but it is not synthesised by the body as pepsin. Instead, certain cells in the stomach (called 'chief cells') synthesize an inactive form of pepsin called pepsinogen. Pepsinogen is activated by the HCl in the stomach, thereby converting it into pepsin which can then fulfil its proteolytic role. How enzymes - in this example pepsin and pepsinogen - act in an environment is always at heart due to their amino-acid sequence.

How enzymes behave is a lot more complicated than a simple question of polarity; there are many, many factors that allow for them to act as they do as part of a biological system.
Title: Re: VCE Biology Question Thread
Post by: That Other Guy on January 10, 2014, 06:15:28 pm
In short, yes. This is also beyond the VCE biology course, but some enzymes have inactive precursors called zymogens. In the stomach, our main proteolytic (breaks down proteins) enzyme is pepsin, but it is not synthesised by the body as pepsin. Instead, certain cells in the stomach (called 'chief cells') synthesize an inactive form of pepsin called pepsinogen. Pepsinogen is activated by the HCl in the stomach, thereby converting it into pepsin which can then fulfil its proteolytic role. How enzymes - in this example pepsin and pepsinogen - act in an environment is always at heart due to their amino-acid sequence.

How enzymes behave is a lot more complicated than a simple question of polarity; there are many, many factors that allow for them to act as they do as part of a biological system.

I have heard about inactive protein and their activation, but never understood their application. Although this is all very interesting, I'll try not to think about it too much; I'll probably end up referencing it in some way and lose marks. :P
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 10, 2014, 06:20:24 pm
I'll probably end up referencing it in some way and lose marks. :P

Wait, are marks deducted if we reference information out of the scope of VCE Biol?!
Title: Re: VCE Biology Question Thread
Post by: psyxwar on January 10, 2014, 06:24:46 pm
Wait, are marks deducted if we reference information out of the scope of VCE Biol?!
nope, but if you reference information that is incorrect you will be penalised. It's good to learn stuff beyond the course, but don't do it for the sake of improving your biology mark; do it for the sake of learning (because honestly, there are better ways to invest time than reading about content irrelevant to the course if all you want to do is succeed in the subject)
Title: Re: VCE Biology Question Thread
Post by: That Other Guy on January 10, 2014, 06:25:53 pm
Wait, are marks deducted if we reference information out of the scope of VCE Biol?!

I'm not sure... but in the case of my protein question, if I explained all of that in an answer that required the simple answer of 'Proteins become denatured when the pH is beyond or below its optimum range.' Then surely I would lose marks... right? I haven't done a 3/4 subject before, so I have no idea.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 10, 2014, 06:27:46 pm
I'm not certain on this, but I think they may take off marks if it seems you're trying to further justify a correct response?
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 10, 2014, 06:29:06 pm
Wait, are marks deducted if we reference information out of the scope of VCE Biol?!

No haha, you'll never be deducted for knowing more than necessary.

However, markers do like to take off marks for waffling and for not answering the question. One of the main techniques my teacher taught me and I teach those I tutor is to answer the question 1) efficiently, 2) briefly and 3) correctly :P
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 10, 2014, 07:09:38 pm
Wait, are marks deducted if we reference information out of the scope of VCE Biol?!

You won't be deducted. But if you give an answer that's out of the scope, without referencing the answer that is in the scope of the course, you will lose marks.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 10, 2014, 07:11:53 pm
Would it be correct/sufficient to say that cholesterol helps maintain the fluid mosaic model of the cell membrane?
Title: Re: VCE Biology Question Thread
Post by: datfatcat on January 10, 2014, 07:13:52 pm
Wait, are marks deducted if we reference information out of the scope of VCE Biol?!
No but you need to make sure the information is correct (and relevant to the question). Furthermore, like what others mentioned, you need to actually answer the question with the knowledge under the vce course
Title: Re: VCE Biology Question Thread
Post by: psyxwar on January 10, 2014, 07:14:35 pm
Would it be correct/sufficient to say that cholesterol helps maintain the fluid mosaic model of the cell membrane?
that doesn't really make any sense
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 10, 2014, 07:17:59 pm
that doesn't really make any sense

Hmm.. I guess not. Perhaps the fluidity/rigidity of the cell membrane?
Title: Re: VCE Biology Question Thread
Post by: That Other Guy on January 10, 2014, 07:18:27 pm
Would it be correct/sufficient to say that cholesterol helps maintain the fluid mosaic model of the cell membrane?

What do you mean by that?
If no cholesterol is present in the membrane, the cell contents will spill out into the extracellular environment. Cholesterol maintains the cell membrane's rigidity, enables it to be fluid and minimises permeability to water-soluble molecules.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 10, 2014, 07:20:38 pm
Hmm.. I guess not. Perhaps the fluidity/rigidity of the cell membrane?

Fluidity.

EDIT: see what Alon says below :)
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 10, 2014, 07:22:39 pm
Would it be correct/sufficient to say that cholesterol helps maintain the fluid mosaic model of the cell membrane?

Essentially, cholesterol's role in the cell membrane is to maintain fluidity and flexibility of the cell membrane. In cold climates, cholesterol increases the fluidity of the cell membrane to hinder the solidification of the membrane, and reduces its fluidity in normal range temps to maintain the stability of the membrane.
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 10, 2014, 07:25:03 pm
Fluidity.

Also rigidity! Membrane cholesterol is interesting as it serves both of these purposes as needed, in different environments :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 10, 2014, 07:28:57 pm
Would it be correct/sufficient to say that cholesterol helps maintain the fluid mosaic model of the cell membrane?

Cholesterol reduces membrane fluidity by reducing phospholipid movement at moderate temperatures, but it also hinders solidification at low temperatures. [from TSFX].
It's somewhat correct but I wouldn't say sufficient if you're explaining the fluid mosaic model and how cholesterol contributes to it. I think that statement wouldn't be 100% correct because what if we consider plant cells that lack cholesterol (I think)?
It's not exactly correct and it's not sufficient, but you're on the right track. Just expound on it more. Hope this helps :)
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 10, 2014, 07:29:53 pm
Is there a disadvantage to not organising notes according to the study design?
Title: Re: VCE Biology Question Thread
Post by: psyxwar on January 10, 2014, 07:30:34 pm
Function of cholesterol: cholesterol makes the cell membrane more:
o   more flexible
o   more stable
o   more fluid in colder temperatures

This is according to past assessment reports.
Title: Re: VCE Biology Question Thread
Post by: Stick on January 10, 2014, 08:20:34 pm
Is there a disadvantage to not organising notes according to the study design?

Not necessarily.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 10, 2014, 10:15:36 pm
Is this a good summary of the different levels of protein structure?

Primary- refers to the sequence of amino acids in a polypeptide
Secondary- refers to the coiling and folding of a polypeptide due to hydrogen bonds, in the form of alpha helices, beta pleated sheets and random coils
Tertiary- refers to the conformational shape of the polypeptide, which determines its function
Quaternary- refers to the overall structure of a protein as a result of a linkage of polypeptides

Is it necessary to know the various bonds which contribute to the tertiary structure etc?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 10, 2014, 10:22:06 pm
Is this a good summary of the different levels of protein structure?

Primary- refers to the sequence of amino acids in a polypeptide
Secondary- refers to the coiling and folding of a polypeptide due to hydrogen bonds, in the form of alpha helices, beta pleated sheets and random coils
Tertiary- refers to the conformational shape of the polypeptide, which determines its function
Quaternary- refers to the overall structure of a protein as a result of a linkage of polypeptides

Is it necessary to know the various bonds which contribute to the tertiary structure etc?

That's a good summary :)

Its actually been stated in the FAQs that you don't have to know about bonding. But I reckon you should; when a protein denatures, weak inter particle bonds (H bonds) are broken, but strong covalent peptide bonds are not, so just be wary of that.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 10, 2014, 10:44:22 pm
But I reckon you should; when a protein denatures, weak inter particle bonds (H bonds) are broken, but strong covalent peptide bonds are not, so just be wary of that.

I'm going to be a real pedant here!

It's not "weak interparticle bonds" and H bonds aren't the only ones. In essence, you're correct and without Chem you'd probably never have known. And because you're doing Chem, so for your benefit here, hydrogen bonds are by no means "weak" intermolecular interactions. They're the strong intermolecular ones. They're just weaker than covalent bonds.

The bonds that are broken up denaturation are:

Hydrogen bonds, dipole-dipole interactions, ionic bonds and Van der Waal's forces.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 10, 2014, 10:51:55 pm
I'm going to be a real pedant here!

It's not "weak interparticle bonds" and H bonds aren't the only ones. In essence, you're correct and without Chem you'd probably never have known. And because you're doing Chem, so for your benefit here, hydrogen bonds are by no means "weak" intermolecular interactions. They're the strong intermolecular ones. They're just weaker than covalent bonds.

The bonds that are broken up denaturation are:

Hydrogen bonds, dipole-dipole interactions, ionic bonds and Van der Waal's forces.

Would I need to know this for the purpose of VCE Biology?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 10, 2014, 11:02:03 pm
Would I need to know this for the purpose of VCE Biology?

Not at all :)
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 10, 2014, 11:05:52 pm
Hi,

Can transport membrane proteins (carrier and channel proteins) be embedded within the membranes of organelles as well? Not just in the plasma membrane?

Thanks  :)
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 10, 2014, 11:08:11 pm
Hi,

Can transport membrane proteins (carrier and channel proteins) be embedded within the membranes of organelles as well? Not just in the plasma membrane?

Thanks  :)

They absolutely can. Mitochondria and chloroplasts both have them. Don't think any others do though I'm happy to be corrected.
Title: Re: VCE Biology Question Thread
Post by: psyxwar on January 10, 2014, 11:08:29 pm
I'm going to be a real pedant here!

It's not "weak interparticle bonds" and H bonds aren't the only ones. In essence, you're correct and without Chem you'd probably never have known. And because you're doing Chem, so for your benefit here, hydrogen bonds are by no means "weak" intermolecular interactions. They're the strong intermolecular ones. They're just weaker than covalent bonds.

The bonds that are broken up denaturation are:

Hydrogen bonds, dipole-dipole interactions, ionic bonds and Van der Waal's forces.
Depends on what the adjective is referring to; h-bonds are still weak bonds. "Weak intermolecular" bonds vs. "weak" intermolecular bonds :P
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 10, 2014, 11:16:03 pm
They absolutely can. Mitochondria and chloroplasts both have them. Don't think any others do though I'm happy to be corrected.

thankyou :) !
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 10, 2014, 11:17:01 pm
Depends on what the adjective is referring to; h-bonds are still weak bonds. "Weak intermolecular" bonds vs. "weak" intermolecular bonds :P

If I wanted to be a real arse, if he were saying "weak and intermolecular bonds", there should be a comma "weak, intermolecular bonds". If not, intermolecular bonds could be described as a noun in and of itself. But I don't want to be a complete arse, because you and yacoubb are fantastic, so I see your point. The clarification was just worthwhile to address any confusion and it may not have been wrong :)
Title: Re: VCE Biology Question Thread
Post by: psyxwar on January 10, 2014, 11:26:50 pm

If I wanted to be a real arse, if he were saying "weak and intermolecular bonds", there should be a comma "weak, intermolecular bonds". If not, intermolecular bonds could be described as a noun in and of itself. But I don't want to be a complete arse, because you and yacoubb are fantastic, so I see your point. The clarification was just worthwhile to address any confusion and it may not have been wrong :)
#englang
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 10, 2014, 11:33:16 pm
#englang

I almost busted out some (because I knew you were pretty good at it!) but then thought "shit, I've got nothing to bust out anymore...".

But moral of the story everyone (and so I don't get in trouble for not staying on topic).
Intermolecular bonds are weak in the scheme of things. H-bonds are not a type of weak intermolecular bond, they're a strong intermolecular bond...so they're a strong, weak bond (Y) #mindfuck
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 10, 2014, 11:49:30 pm
I almost busted out some (because I knew you were pretty good at it!) but then thought "shit, I've got nothing to bust out anymore...".

But moral of the story everyone (and so I don't get in trouble for not staying on topic).
Intermolecular bonds are weak in the scheme of things. H-bonds are not a type of weak intermolecular bond, they're a strong intermolecular bond...so they're a strong, weak bond (Y) #mindfuck

Biology teachers state that they're weak, whilst Chem teachers state that they're strong. We can never win :P
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 10, 2014, 11:51:07 pm
When talking about endocytosis and exocytosis, what are the names of the vesicles formed?

I seem to remember the term endocytotic vesicle and exocytotic vesicle from my unit 1&2 textbook, however the 3&4 book says " endocytic vesicle".

Which one is the correct term? Or are there multiple?

Thanks  :)
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 10, 2014, 11:52:18 pm
Biology teachers state that they're weak, whilst Chem teachers state that they're strong. We can never win :P

haha we really can't my friend!

When talking about endocytosis and exocytosis, what are the names of the vesicles formed?

I seem to remember the term endocytotic vesicle and exocytotic vesicle from my unit 1&2 textbook, however the 3&4 book says " endocytic vesicle".

Which one is the correct term? Or are there multiple?

Thanks  :)

If they go out, exocytotic vesicle, if they're coming in, endocytotic. That seems reasonable to me, but I wouldn't split hairs over it. "Vesicle" is fine by itself.
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 10, 2014, 11:54:08 pm
Biology teachers state that they're weak, whilst Chem teachers state that they're strong. We can never win :P

Well I think it depends upon the context. When you say that hydrogen bonds are weak, the inference is that they are weak relative to intramolecular forces (i.e. Compared to covalent bonds, for instance).

In chemistry, inter particle forces include dispersion forces, dipole-dipole forces and hydrogen bonding. Out of all the intermolecular forces, hydrogen bonds are the strongest; that is, they are the stronger of the weak.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 10, 2014, 11:59:19 pm
Well I think it depends upon the context. When you say that hydrogen bonds are weak, the inference is that they are weak relative to intramolecular forces (i.e. Compared to covalent bonds, for instance).

In chemistry, inter particle forces include dispersion forces, dipole-dipole forces and hydrogen bonding. Out of all the intermolecular forces, hydrogen bonds are the strongest; that is, they are the stronger of the weak.

Totally makes sense now! As always, thanks for the great explanation :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 11, 2014, 05:41:19 pm
So for the new study design, a lot of information has been removed when it comes to AO2 - Detecting & Responding. What are some of the topics that have been removed that don't need focusing on? Can someone please give me a rundown on it? Would be much appreciated and beneficial for everyone. Cheers.
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 11, 2014, 07:52:29 pm
So for the new study design, a lot of information has been removed when it comes to AO2 - Detecting & Responding. What are some of the topics that have been removed that don't need focusing on? Can someone please give me a rundown on it? Would be much appreciated and beneficial for everyone. Cheers.

Endocrine system:
All you need to know:
- Different types of hormones (peptide/protein, lipid-based and amino acid derivative).
- Signal transduction
- Signal transduction and the action of hormones at the cellular level (e.g. Instead of looking at insulin acting as a hormone to reduce blood glucose levels, you'd look at insulin as acting on specific target cells, and the response it initiates being an increase in the permeability of the cell membrane to glucose, to increase absorbption of glucose from the blood, and in the long run, lower blood sugar levels during hyperglycaemia).

Nervous System:
All that has been taken out is the generation of action potentials.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 11, 2014, 11:01:26 pm
Does any one else have this problem? When doing exam questions, usually I tend to write underneath the lines (in the space below) because I need more space. The information is relevant though. Do examiners mind this kind of thing? Just wondering.
Title: Re: VCE Biology Question Thread
Post by: Scooby on January 11, 2014, 11:03:17 pm
Does any one else have this problem? When doing exam questions, usually I tend to write underneath the lines (in the space below) because I need more space. The information is relevant though. Do examiners mind this kind of thing? Just wondering.

No problems as long as it's clearly indicated
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 11, 2014, 11:03:50 pm
Does any one else have this problem? When doing exam questions, usually I tend to write underneath the lines (in the space below) because I need more space. The information is relevant though. Do examiners mind this kind of thing? Just wondering.

No, that's fine so long as it's neat and the examiner can read it. Keep in mind though that the space given is generally an indication of the expected length of the answer, so you might consider working on shortening your answers where possible.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 11, 2014, 11:04:19 pm
Does any one else have this problem? When doing exam questions, usually I tend to write underneath the lines (in the space below) because I need more space. The information is relevant though. Do examiners mind this kind of thing? Just wondering.

As long as it's directly under the question and not in the exclusion zone, you'll be fine. You can't use an arrow for example to point to space down the bottom if you need more space to write for a question at the top of the page (eg. if you need more space for question 2a, so you write it in the free space below the lines for question 2b and use an arrow to point to it—can't do that!)
Title: Re: VCE Biology Question Thread
Post by: Scooby on January 11, 2014, 11:22:02 pm
As long as it's directly under the question and not in the exclusion zone, you'll be fine. You can't use an arrow for example to point to space down the bottom if you need more space to write for a question at the top of the page (eg. if you need more space for question 2a, so you write it in the free space below the lines for question 2b and use an arrow to point to it—can't do that!)

Ahhhhh I did stuff like that on pretty much every page of my Bio exam. Maybe I had patient examiners  :P
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 11, 2014, 11:25:13 pm
Ahhhhh I did stuff like that on pretty much every page of my Bio exam. Maybe I had patient examiners  :P

It's technically banned under the assessment, but as I think we can now safely say based on your brilliant 50, it's only taken with a grain of salt by examiners...
Title: Re: VCE Biology Question Thread
Post by: Scooby on January 11, 2014, 11:33:29 pm
It's technically banned under the assessment, but as I think we can now safely say based on your brilliant 50, it's only taken with a grain of salt by examiners...

But yeah, definitely try not to do it either way. Best not to annoy the people marking your exam if you can avoid it
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 11, 2014, 11:38:56 pm

But yeah, definitely try not to do it either way. Best not to annoy the people marking your exam if you can avoid it

Yeah, I don't know why but I feel as if they might get so irritated by convolutedly written answers that they might subconsciously be more harsh in marking the paper :P Gotta be on the safe side.

Also, congratz on an amazing SS. May I ask, what was your usual study routine for Bio; what was it that really contributed to getting a 50? Cheers! :)
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 12, 2014, 12:06:08 am

But yeah, definitely try not to do it either way. Best not to annoy the people marking your exam if you can avoid it

I could be wrong. I heard it from a psychology teacher who'd spoken to the head assessor for that, and she said it was standard practice. That said, you got a 50 in Psychology too, so even that still applies... hahah
Title: Re: VCE Biology Question Thread
Post by: Scooby on January 12, 2014, 12:11:50 am
I could be wrong. I heard it from a psychology teacher who'd spoken to the head assessor for that, and she said it was standard practice. That said, you got a 50 in Psychology too, so even that still applies... hahah

Yeah, I definitely wasn't as bad in Psych though (extra space for responses section really helps ahahaha)
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 12, 2014, 01:15:37 am
Can someone give me a concise description of the fluid mosaic model? Cheers.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 12, 2014, 01:22:56 am
Can someone give me a concise description of the fluid mosaic model? Cheers.

Membranes are not solid structures. The various elements in the membrane aren't static, they move around in it. So by fluid mosaic, it means that the membrane itself behaves somewhat like a fluid, and in particular, embedded proteins and structures are able to move around that fluid. Membranes themselves can maintain a shape (though can also change it), just the elements in it don't stay in their places, they're free to move around.
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 12, 2014, 06:56:40 am
Can someone give me a concise description of the fluid mosaic model? Cheers.

•   Not rigid – “fluid”
•   Irregular protein pattern – “mosaic”
Title: Re: VCE Biology Question Thread
Post by: Stick on January 12, 2014, 11:05:23 am
Does any one else have this problem? When doing exam questions, usually I tend to write underneath the lines (in the space below) because I need more space. The information is relevant though. Do examiners mind this kind of thing? Just wondering.

My exam looked like a dog's breakfast. Provided it's still legible, you should be fine. :)
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 12, 2014, 11:26:22 am
My exam looked like a dog's breakfast. Provided it's still legible, you should be fine. :)

Same with mine. There was a question on the bottleneck effect and genetic drift which I thought I'd lose marks for because it was really messy (we had boxes and no lines). Got full marks for the question. Considering its legible, as Stick has mentioned, it'll be accepted! However, its completely natural for us to feel that the assessors are waiting for us to stuff something up, but in fact, in the majority of cases, they want us to do well!
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 12, 2014, 12:57:58 pm
...its completely natural for us to feel that the assessors are waiting for us to stuff something up, but in fact, in the majority of cases, they want us to do well!

That's awesome. Never knew that.
Title: Re: VCE Biology Question Thread
Post by: Stick on January 12, 2014, 02:05:16 pm
Yeah, assessors are instructed to try and reward students for what they HAVE done, not penalise them for what wasn't done or what should have been done.
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 12, 2014, 04:54:48 pm
Yeah, assessors are instructed to try and reward students for what they HAVE done, not penalise them for what wasn't done or what should have been done.

That's how some people get 10/10 in English exam scripts even if you haven't finished! Its quite solacing to know that though!
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 12, 2014, 09:33:47 pm
Hi :)
Does anyone know why the internal membrane of mitochondria, have stalked particles on them?
Thanks ! and also why are there holes in the folds of the inner membranes of mitochondria?

Thankyou!
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 12, 2014, 09:42:34 pm
Hi :)
Does anyone know why the internal membrane of mitochondria, have stalked particles on them?
Thanks ! and also why are there holes in the folds of the inner membranes of mitochondria?

Thankyou!

I believe the stalked particles increase the surface area to therefore increase the rate of reactions occurring so more production of ATP. The holes probably are spaces in which molecules can pass through to the electron transport chain.

Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 12, 2014, 09:54:56 pm
I believe the stalked particles increase the surface area to therefore increase the rate of reactions occurring so more production of ATP. The holes probably are spaces in which molecules can pass through to the electron transport chain.

Thankyou very much for your explanation!  :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 13, 2014, 01:29:35 am
Why is it recommended to start VCAA past exam papers 2-4 weeks prior to the exam? I get why it's left till the end, but shouldn't they be practiced throughout the year to obtain a better grasp of VCAA styled questions; or does doing other exam papers from companies such as Neap suffice? Just want to know other peoples opinions on this.

Also, does anyone have any exam tactics? What would you recommend doing during reading time? Cheers!
Title: Re: VCE Biology Question Thread
Post by: MagicGecko on January 13, 2014, 02:30:06 am
Why is it recommended to start VCAA past exam papers 2-4 weeks prior to the exam? I get why it's left till the end, but shouldn't they be practiced throughout the year to obtain a better grasp of VCAA styled questions; or does doing other exam papers from companies such as Neap suffice? Just want to know other peoples opinions on this.

Also, does anyone have any exam tactics? What would you recommend doing during reading time? Cheers!
I'm not sure where you read that from, but I agree with you, biology exams should be practiced throughout the year so you can get used to VCAA's style. But I guess it all comes down to the individual (it always does), some find it better to learn as much material as they can and in the last 2-4 week they tackle as many exams as possible, others would rather do them throughout the year.

During reading time..hmmm...well I would suggest not looking at SA unless you really know your stuff, I say this because I know people that looked at the SA during reading time and were shocked to see a particular question he/she did not know much about but then again there were others that knew there stuff and looking at the SA motivated them. It acts like a double edged sword actually.
Anyway the obvious advice would be to do MC first, as there will probably be some MC questions that might help you to answer some SA questions.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 13, 2014, 02:40:33 am

Hope that helps,
Rod

Thanks Rod, that was very helpful. Either way, a SS of 38 is really good and not easy to achieve. I guess it comes down to really knowing your stuff and being able to formulate a good response on the spot. I'll definitely create a log book to help me with that. Also, having 20 mins spare is amazing; I've heard a lot of students don't even get to complete the paper. Anyway cheers!
Title: Re: VCE Biology Question Thread
Post by: psyxwar on January 13, 2014, 08:03:20 am
Why is it recommended to start VCAA past exam papers 2-4 weeks prior to the exam? I get why it's left till the end, but shouldn't they be practiced throughout the year to obtain a better grasp of VCAA styled questions; or does doing other exam papers from companies such as Neap suffice? Just want to know other peoples opinions on this.

Also, does anyone have any exam tactics? What would you recommend doing during reading time? Cheers!
I don't agree with this either tbh, definitely have a shot of doing some vcaa papers beforehand.

I personally read SA in reading time, did MC first in writing time, then did SAl
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 13, 2014, 09:34:44 am
I don't agree with this either tbh, definitely have a shot of doing some vcaa papers beforehand.

I personally read SA in reading time, did MC first in writing time, then did SAl

Seconded! :)
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 13, 2014, 10:43:55 am
So when should we start practise questions? At the moment, would it be sufficient to have covered unit 3 AOS1?
I'm a bit worried tbh. So much information
Title: Re: VCE Biology Question Thread
Post by: Russ on January 13, 2014, 10:44:50 am
So when should be start practise questions? At the moment, would it be sufficient to have covered unit 3 AOS1?
I'm a bit worried tbh. So much information

It's still the summer holidays, it would be sufficient to have not done any of this yet :P
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 13, 2014, 10:53:33 am
Fair enough :)
I just hope I have enough time in the end to be able to complete and review my practice exams.
Title: Re: VCE Biology Question Thread
Post by: Russ on January 13, 2014, 11:01:03 am
Don't get me wrong, you can work ahead if you want and if you have time/motivation, but you don't need to have done half the course before you start in Feb.
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 13, 2014, 11:22:21 am
Fair enough :)
I just hope I have enough time in the end to be able to complete and review my practice exams.

By the time you're finalising your practice exam regime, you're going to be so over practice papers lol! You'll be praying for the exam day to come so you can just finish the bloody exam! :) Don't worry! You have plenty of time!
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 13, 2014, 11:26:38 am
By the time you're finalising your practice exam regime, you're going to be so over practice papers lol! You'll be praying for the exam day to come so you can just finish the bloody exam! :) Don't worry! You have plenty of time!

Thanks Yacoubb :)
I'm already praying for the year to finish :P

Also, would it be better to make summaries or notes that are in-depth?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 13, 2014, 11:28:23 am
Thanks Yacoubb :)
I'm already praying for the year to finish :P

Also, would it be better to make summaries or notes that are in-depth?

Both! You need to remember that when you sit a SAC or the exam, your knowledge of the course for that topic must be really in depth. However, you must tailor it to fit the question. Summaries are great to read just before your assessment, or even just quickly before you go to bed :)
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 13, 2014, 11:29:10 am
Don't get me wrong, you can work ahead if you want and if you have time/motivation, but you don't need to have done half the course before you start in Feb.

I understand :) Just needed to clarify since there's so many different views as to when practice exams should be approached, etc.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 13, 2014, 11:30:54 am
Both! You need to remember that when you sit a SAC or the exam, your knowledge of the course for that topic must be really in depth. However, you must tailor it to fit the question. Summaries are great to read just before your assessment, or even just quickly before you go to bed :)

Makes sense now :) Thank-you :)
I might continue writing my notes and perhaps make summaries whilst revising..
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 13, 2014, 11:35:42 am
Hi in chemistry we have learnt about exothermic reactions giving off energy and endothermic reactions absorbing energy, and in our biology book we are learning about endergonic reactions absorbing energy and exergonic reactiong giving off energy,

What is the difference between exothermic and exergonic and the difference between endothermic and endergonic reactions?
If there is one that is, :)

Thanks

Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 13, 2014, 11:40:52 am
i'm really confused..my chem teacher said that in a chemical reaction when you are breaking bonds, it takes more energy, thus the reaction absorbs energy (endothermic reaction) and that when you are making bonds, it does not require alot of energy and so instead energy is released (exothermic reaction). However, in my bio book it suggests the total opposite by saying that catabolic reactions are exergonic reactions (They give off energy).

Thanks :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 13, 2014, 11:41:18 am
Hi in chemistry we have learnt about exothermic reactions giving off energy and endothermic reactions absorbing energy, and in our biology book we are learning about endergonic reactions absorbing energy and exergonic reactiong giving off energy,

What is the difference between exothermic and exergonic and the difference between endothermic and endergonic reactions?
If there is one that is, :)

Thanks

Generally, they mean the same thing. But I think there is a slight difference, I wouldn't know as I just started chem sorry. But in biology we use exergonic and endergonic though and your definitions for them are correct.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 13, 2014, 11:44:16 am
Generally, they mean the same thing. But I think there is a slight difference, I wouldn't know as I just started chem sorry. But in biology we use exergonic and endergonic though and your definitions for them are correct.

Title: Re: VCE Biology Question Thread
Post by: Shenz0r on January 13, 2014, 11:46:19 am
Hi in chemistry we have learnt about exothermic reactions giving off energy and endothermic reactions absorbing energy, and in our biology book we are learning about endergonic reactions absorbing energy and exergonic reactiong giving off energy,

What is the difference between exothermic and exergonic and the difference between endothermic and endergonic reactions?
If there is one that is, :)

Thanks
There is a difference, but for the purpose of VCE biology, endergonic/exergonic should be used instead of endothermic/exothermic.

Endothermic/exothermic relate to a change in heat, whereas endergonic/exergonic relate to Gibbs Free Energy (you don't need to know this)
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 13, 2014, 11:56:19 am
There is a difference, but for the purpose of VCE biology, endergonic/exergonic should be used instead of endothermic/exothermic.

Endothermic/exothermic relate to a change in heat, whereas endergonic/exergonic relate to Gibbs Free Energy (you don't need to know this)

Thanks heaps! That helps me to understand it better!
Oh okay :)
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 13, 2014, 01:24:04 pm
Which organelles would be required to produce neurotransmitter molecule within a neuron?
Would it be enough to say ribosomes, or would I have be more specific and mention ribosomes on the rough endoplasmic reticulum?

How do neurotransmitter molecules exit the axon terminal to reach the synaptic cleft?
Golgi apparatus package neurotransmitters into secretory vesicles which exit via exocytosis. Or would it be enough to say that they exit via exocytosis?

Edit: I'm trying to be as brief as possible if you haven't already noticed :p
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 13, 2014, 02:19:45 pm
Which organelles would be required to produce neurotransmitter molecule within a neuron?
Would it be enough to say ribosomes, or would I have be more specific and mention ribosomes on the rough endoplasmic reticulum?

How do neurotransmitter molecules exit the axon terminal to reach the synaptic cleft?
Golgi apparatus package neurotransmitters into secretory vesicles which exit via exocytosis. Or would it be enough to say that they exit via exocytosis?

Edit: I'm trying to be as brief as possible if you haven't already noticed :p

I'd say the ribosomes on the rough endoplasmic reticulum. Any polypeptide that is synthesised by a cell, and carry out their biological function outside the cell of production, are synthesised in the ribosomes studded on the endoplasmic reticulum organelle.

When an action potential arrives at the axon terminal, this triggers an influx of Ca2+ ions. As a result, this triggers the exocytosis of neurotransmitter molecules (which are found in small, synaptic vesicles). Once they are secreted by exocytosis (an endergonic process), they diffuse across the synaptic cleft, bind to post-synaptic receptors and carry out their excitatory or inhibitory function.

Hope this helps :)
PS its good to be as succinct as possible. Assessors love punchy, succint answers that are very clear! :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 13, 2014, 02:41:52 pm
Are we required to know about the divisions of the PNS?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 13, 2014, 02:59:27 pm
Are we required to know about the divisions of the PNS?

All you need to know about the peripheral nervous system is that it includes all the nerves that connect the central nervous system to the rest of the body. You don't need to do about sympathetic/parasympathetic and all those divisions of the PNS.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 13, 2014, 08:07:30 pm
What is the purpose of excitatory & inhibitory neurotransmitters? Thanks in advance.
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 13, 2014, 08:19:44 pm
What is the purpose of excitatory & inhibitory neurotransmitters? Thanks in advance.

Well, consider the words 'excite' and 'inhibit'. They're opposites, right? It follows that excitatory and inhibitory neurotransmitters have opposite functions - that is to say, they both activate receptors (as is the function of any neurotransmitter) but the effect that follows can be unique. Excitatory neurotransmitters elicit an increased chance of the firing of an action potential by a receiving neuron (I'm assuming you know what this is, let me know if you need me to elaborate), while an inhibitory neurotransmitter does the opposite: it reduces the chance of a neuron firing an AP.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 13, 2014, 08:30:54 pm
Well, consider the words 'excite' and 'inhibit'. They're opposites, right? It follows that excitatory and inhibitory neurotransmitters have opposite functions - that is to say, they both activate receptors (as is the function of any neurotransmitter) but the effect that follows can be unique. Excitatory neurotransmitters elicit an increased chance of the firing of an action potential by a receiving neuron (I'm assuming you know what this is, let me know if you need me to elaborate), while an inhibitory neurotransmitter does the opposite: it reduces the chance of a neuron firing an AP.

Why would an inhibitory neurotransmitter reduce the chance of a neuron firing an AP?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 13, 2014, 08:40:15 pm
Why would an inhibitory neurotransmitter reduce the chance of a neuron firing an AP?

I believe inhibitory neurotransmitters bind to receptors in the post synaptic cell which make either chloride ions flood into the cell, or potassium ions move out of the cell. That is, chloride/potassium protein channels are opened.
Either way, the neuron becomes hyperpolarised and its membrane potential is made even more negative than the resting threshold.
In effect, the chance of generating an action potential (impulse) is decreased.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 13, 2014, 08:45:47 pm
I believe inhibitory neurotransmitters bind to receptors in the post synaptic cell which make either chloride ions flood into the cell, or potassium ions move out of the cell. That is, chloride/potassium protein channels are opened.
Either way, the neuron becomes hyperpolarised and its membrane potential is made even more negative than the resting threshold.
In effect, the chance of generating an action potential (impulse) is decreased.

I totally get what you mean, but I'm wondering what's the biological purpose/significance of having inhibitory neurotransmitters? Or maybe I shouldn't delve that far into it. Thanks though!
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 13, 2014, 08:48:05 pm
I totally get what you mean, but I'm wondering what's the biological purpose/significance of having inhibitory neurotransmitters? Or maybe I shouldn't delve that far into it. Thanks though!

They're circuit breakers of sorts. Otherwise the action potential would start in one corner of the brain and spread to all corners of the brain, creating a flurry of activity. Inhibitory neurones make it more controlled, they give the brain its finesse I guess.
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 13, 2014, 08:48:53 pm
I totally get what you mean, but I'm wondering what's the biological purpose/significance of having inhibitory neurotransmitters? Or maybe I shouldn't delve that far into it. Thanks though!

We can't have every neuron firing at once! That would overwhelm our system pretty badly - in fact, that what happens when epileptics have a seizure; their neurons are firing uncontrollably and they therefore can't consciously control their actions.

As such, inhibitory neurotransmitters "dampen" neurons so they can't fire all the time.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 13, 2014, 08:57:42 pm
We can't have every neuron firing at once! That would overwhelm our system pretty badly - in fact, that what happens when epileptics have a seizure; their neurons are firing uncontrollably and they therefore can't consciously control their actions.

As such, inhibitory neurotransmitters "dampen" neurons so they can't fire all the time.

Oh :P Now I get it haha! Cheers! So, would it be true to say that messages sent my these inhibitory neurotransmitters are of less importance; not that urgent?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 13, 2014, 09:00:36 pm
Oh :P Now I get it haha! Cheers! So, would it be true to say that messages sent my these inhibitory neurotransmitters are of less importance; not that urgent?

Not at all. Brain activity is determined by circuits of neurones, not just individual neurones. So inhibitory neurones, very importantly, control the circuits. Failures in inhibitory neurones play a role in most mental illnesses and a number of neuronal diseases (as already mentioned by alon)
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on January 13, 2014, 10:13:00 pm
heyy, just wondering if anyone knew if we need to know the specific types of bonds like peptide bonds. Because VCAA says this " The names for the specific types of bonds (for example, glycosidic, peptide) or bonding (for example hydrogen, covalent, disulfide) in carbohydrates, lipids, proteins and nucleic acids are not required." But during the 2014 unit 3 Biology summer lecture Mr Mac said we needed to know peptide bonds and some others also in the notes they provided us. So just confused if i need to know them or not. if you know???
thanks.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 13, 2014, 10:31:01 pm
heyy, just wondering if anyone knew if we need to know the specific types of bonds like peptide bonds. Because VCAA says this " The names for the specific types of bonds (for example, glycosidic, peptide) or bonding (for example hydrogen, covalent, disulfide) in carbohydrates, lipids, proteins and nucleic acids are not required." But during the 2014 unit 3 Biology summer lecture Mr Mac said we needed to know peptide bonds and some others also in the notes they provided us. So just confused if i need to know them or not. if you know???
thanks.

Despite TSFX's grandstanding, the VCAA do know their course better than them. Trust the VCAA :)
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 14, 2014, 09:22:41 am
Hey guys,

Sorry I am not really sure in which thread this question belong, but I guess it relates to biology as well :)
This might sound silly, but when you have SAC's in your school, does the content on them have to relate to the content outlined in the area of studies?
Or is that only in the end-of-year exam?

thanks!
Title: Re: VCE Biology Question Thread
Post by: eagles on January 14, 2014, 09:53:38 am
School sacs vary from school to school and the degree of relevance to the VCAA study design is also different. While one school may go into more detail into photosynthesis than required by VCAA or test on irrelevant textbook material, you just need to follow what your school does to perform well on the SACs while throughout the year, concentrate on the checkpoints required by the VCAA study design for biology to ace the exam.

(On a note of certainty, the end-of-year exam relates is strictly limited to the official study design requirements. )
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 14, 2014, 10:31:08 am
School sacs vary from school to school and the degree of relevance to the VCAA study design is also different. While one school may go into more detail into photosynthesis than required by VCAA or test on irrelevant textbook material, you just need to follow what your school does to perform well on the SACs while throughout the year, concentrate on the checkpoints required by the VCAA study design for biology to ace the exam.

(On a note of certainty, the end-of-year exam relates is strictly limited to the official study design requirements. )

Oh okay thanks :)
I understand it now,!
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 14, 2014, 11:11:30 am
Hi, I was wondering why does the rate of photorespiration in C3 plants increase at a higher temperature?
Is it because there is more light energy, so more ATP molecules and NADPH molecules are being formed in the light-dependent stage of photosynthesis, but in the Calvin-Benson cycle there is not enough carbon-dioxide molecules for them to 'fix' so once the carbon dioxide molecules run out, Rubisco starts to fix oxygen instead?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: eagles on January 14, 2014, 11:24:47 am
"C3 plants cannot grow in hot areas because RuBisCO incorporates more oxygen into RuBP as temperatures increase. This leads to photorespiration, which leads to a net loss of carbon and nitrogen from the plant and can, therefore, limit growth. In dry areas, C3 plants shut their stomata to reduce water loss, but this stops CO2 from entering the leaves and, therefore, reduces the concentration of CO2 in the leaves. This lowers the CO2:O2 ratio and, therefore, also increases photorespiration. "
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 14, 2014, 11:34:45 am
"C3 plants cannot grow in hot areas because RuBisCO incorporates more oxygen into RuBP as temperatures increase. This leads to photorespiration, which leads to a net loss of carbon and nitrogen from the plant and can, therefore, limit growth. In dry areas, C3 plants shut their stomata to reduce water loss, but this stops CO2 from entering the leaves and, therefore, reduces the concentration of CO2 in the leaves. This lowers the CO2:O2 ratio and, therefore, also increases photorespiration. "

Thanks a ton! :)
Title: Re: VCE Biology Question Thread
Post by: Stick on January 14, 2014, 11:48:15 am
Hi, I was wondering why does the rate of photorespiration in C3 plants increase at a higher temperature?
Is it because there is more light energy, so more ATP molecules and NADPH molecules are being formed in the light-dependent stage of photosynthesis, but in the Calvin-Benson cycle there is not enough carbon-dioxide molecules for them to 'fix' so once the carbon dioxide molecules run out, Rubisco starts to fix oxygen instead?

Thanks!

This is beyond the scope of the VCE Biology course.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 16, 2014, 01:19:30 am
This is beyond the scope of the VCE Biology course.

oh okay thanks for letting me know! :)
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 16, 2014, 01:20:58 am
Hi is the inner membrane of the chloroplasts what makes up the thylakoid membrane?
Or is the thylakoid membrane a third membrane of itself?
Because I read two different pieces of information from two different sources and so I was confused!
Thanks :)
Title: Re: VCE Biology Question Thread
Post by: Scooby on January 16, 2014, 02:19:26 am
Hi is the inner membrane of the chloroplasts what makes up the thylakoid membrane?
Or is the thylakoid membrane a third membrane of itself?
Because I read two different pieces of information from two different sources and so I was confused!
Thanks :)

(http://image.tutorvista.com/content/feed/tvcs/chloroplastCartoon.gif)

A chloroplast has an inner and outer membrane. The space within the inner membrane is referred to as the lumen of the chlorplast and is filled with a fluid called stroma. Within this lumen there are grana, which are stacks of these membrane-bound structures called thylakoids. The membranes of these thylakoids are called the thylakoid membranes (which makes sense :P). Thylakoids are hollow, and that hollow space within them is called the thylakoid lumen

The light-dependent stage of photosynthesis occurs on the thylakoid membranes

Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on January 16, 2014, 09:25:57 am
(http://image.tutorvista.com/content/feed/tvcs/chloroplastCartoon.gif)

A chloroplast has an inner and outer membrane. The space within the inner membrane is referred to as the lumen of the chlorplast and is filled with a fluid called stroma. Within this lumen there are grana, which are stacks of these membrane-bound structures called thylakoids. The membranes of these thylakoids are called the thylakoid membranes (which makes sense :P). Thylakoids are hollow, and that hollow space within them is called the thylakoid lumen

The light-dependent stage of photosynthesis occurs on the thylakoid membranes

That makes alot of sense now! Thanks for including the diagram as well, I was able to visualise it better!

:)
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 16, 2014, 11:20:10 am
With regards to the reactants of photosynthesis, is it more correct to say that there are 12 molecules of H20 as opposed to 6 (considering both equations are balanced)?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 16, 2014, 11:23:33 am
With regards to the reactants of photosynthesis, is it more correct to say that there are 12 molecules of H20 as opposed to 6 (considering both equations are balanced)?

You can use either! I personally opted for the 12 H2Os
Title: Re: VCE Biology Question Thread
Post by: Scooby on January 16, 2014, 11:50:04 am
With regards to the reactants of photosynthesis, is it more correct to say that there are 12 molecules of H20 as opposed to 6 (considering both equations are balanced)?

If they ask for the net input per glucose molecule I'd say six
Title: Re: VCE Biology Question Thread
Post by: Stick on January 16, 2014, 11:54:56 am
With regards to the reactants of photosynthesis, is it more correct to say that there are 12 molecules of H20 as opposed to 6 (considering both equations are balanced)?

I always got told to put 12 on the left hand side and 6 on the right hand side, due to the fact that two separate stages are occurring in which 12 water molecules do react and 6 are produced per glucose molecule.
Title: Re: VCE Biology Question Thread
Post by: vella97 on January 16, 2014, 03:52:37 pm
In reference to pages 29 & 185 of Cambridge checkpoints 2013:

Q: In fibrous proteins, the polypeptide chains are arranged in parallel to form long fibres or sheets. In globular proteins, the polypeptide chains are folded into compact spherical or globular shapes. Describe a distinctive property of a fibrous protein and explain how this property is due to the arrangement of its polypeptides?

The answer says that one of the properties is its elasticity. But I'm confused because silk is an example of a fibrous protein and I know that silk does NOT stretch due its tightly constructed beta pleats secondary structure.

Could someone please explain this to me??

Thanks!
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 16, 2014, 04:38:20 pm
What type of proteins do 'free' ribosomes in the cytosol manufacture? I know ribosomes studded on the Rough E.R manufacture tertiary level proteins?
Also, does the E.R secrete its contents for the cell or for external cells? Can someone clarify this please? Thanks!
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 16, 2014, 04:45:29 pm
What type of proteins do 'free' ribosomes in the cytosol manufacture? I know ribosomes studded on the Rough E.R manufacture tertiary level proteins?
Also, does the E.R secrete its contents for the cell or for external cells? Can someone clarify this please? Thanks!

Both free ribosomes and ribosomes on the rough ER synthesis tertiary level proteins. The only difference is that proteins synthesised by the ribosomes on the Rough ER are packaged into vesicles and sent to the Golgi for further modification before being released via exocytosis.
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 16, 2014, 05:26:52 pm
What type of proteins do 'free' ribosomes in the cytosol manufacture? I know ribosomes studded on the Rough E.R manufacture tertiary level proteins?
Also, does the E.R secrete its contents for the cell or for external cells? Can someone clarify this please? Thanks!

Free ribosomes are the site of protein synthesis, for proteins that carry out their biological function within the cells they are produced. Ribosomes studded on the endoplasmic reticulum, which forms the rough endoplasmic reticulum organelle, synthesise proteins that carry out their biological function outside the cell in which they are produced.

The endoplasmic reticulum is an organelle made up of a network of membranous sacs, transporting substances within the cell and also partially modify the substances transported within the cell. It is the golgi apparatus that packages synthesised materials into vesicles that bud off the golgi body, and transport the synthesised materials out of the cell by exocytosis.

Title: Re: VCE Biology Question Thread
Post by: MM1 on January 16, 2014, 05:38:47 pm
Free ribosomes are the site of protein synthesis, for proteins that carry out their biological function within the cells they are produced. Ribosomes studded on the endoplasmic reticulum, which forms the rough endoplasmic reticulum organelle, synthesise proteins that carry out their biological function outside the cell in which they are produced.

The endoplasmic reticulum is an organelle made up of a network of membranous sacs, transporting substances within the cell and also partially modify the substances transported within the cell. It is the golgi apparatus that packages synthesised materials into vesicles that bud off the golgi body, and transport the synthesised materials out of the cell by exocytosis.

Thanks! Can the smooth and rough E.R interact; does it always have to follow the sequential steps of E.R > Golgi complex > vesicle?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 16, 2014, 05:45:02 pm
Thanks! Can the smooth and rough E.R interact; does it always have to follow the sequential steps of E.R > Golgi complex > vesicle?

The smooth endoplasmic reticulum synthesises lipids and transports them within cells, whereas the rough endoplasmic reticulum synthesises proteins and transports them within cells. So no, they don't react.

Yes, the step is rough endoplasmic reticulum --> golgi complex --> vesicle!
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 16, 2014, 07:36:22 pm
In reference to pages 29 & 185 of Cambridge checkpoints 2013:

Q: In fibrous proteins, the polypeptide chains are arranged in parallel to form long fibres or sheets. In globular proteins, the polypeptide chains are folded into compact spherical or globular shapes. Describe a distinctive property of a fibrous protein and explain how this property is due to the arrangement of its polypeptides?

The answer says that one of the properties is its elasticity. But I'm confused because silk is an example of a fibrous protein and I know that silk does NOT stretch due its tightly constructed beta pleats secondary structure.

Could someone please explain this to me??

Thanks!

Notice that the actual answer addresses two points, which I have summarized below:

1) The parallel arrangement of polypeptides means that they form long fibers or sheets. This refers to the beta pleated sheets as a secondary structure. Silk is well known for this property.
2) Some, but not all, fibrous proteins can be stretched and then return to their original shape. This refers to a protein's alpha helices.

You've only quoted one of them in your question.
You may have reached the correct conclusion if you payed attention to when the question asked "explain how this property as due to the arrangement of polypeptides". Fibrous proteins can have either an alpha helix or a beta pleated sheet. Recall that alpha helices can be twisted or stretched and return to their original shape. Beta pleated sheets, on the other hand, do the opposite. They are rigid and cannot be stretched. I would negate the comparison to a globular protein. That's not exactly what the question asks for. Anyway, hopefully I answered your question ( :
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 16, 2014, 07:53:28 pm
In reference to pages 29 & 185 of Cambridge checkpoints 2013:

Q: In fibrous proteins, the polypeptide chains are arranged in parallel to form long fibres or sheets. In globular proteins, the polypeptide chains are folded into compact spherical or globular shapes. Describe a distinctive property of a fibrous protein and explain how this property is due to the arrangement of its polypeptides?

The answer says that one of the properties is its elasticity. But I'm confused because silk is an example of a fibrous protein and I know that silk does NOT stretch due its tightly constructed beta pleats secondary structure.

Could someone please explain this to me??

Thanks!

Elasticity is only one property, and silk is only one form of fibrous protein.
The reason silk is relatively rigid is due to its beta pleated sheets, so you're correct. But this doesn't mean it's elastic. Rather, it isn't.

Basically, the arrangement (secondary structure) of a polypeptide determines its property.
Title: Re: VCE Biology Question Thread
Post by: millie96 on January 16, 2014, 09:47:53 pm
In the study design it says 'polysaccharides and their glucose monomers' --> are the glucose monomers like starch,cellulose etc?
Title: Re: VCE Biology Question Thread
Post by: datfatcat on January 16, 2014, 09:52:38 pm
In the study design it says 'polysaccharides and their glucose monomers' --> are the glucose monomers like starch,cellulose etc?
Glucose, fructose and galactose are examples of monomers. Starch and cellulose are polysaccharide. (Starch consists of a large number of glucose units joined by glycosidic bonds)
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 16, 2014, 10:27:51 pm
Basically, the arrangement (secondary structure) of a polypeptide determines its property.

I'm not sure this is correct. Each level of structure plays a part in the role of a protein.

The primary structure determines the sequence of amino acid residues in the polypeptide, which in turn determines the basic folding patterns of the secondary structure, which then in turn determine the overall folding pattern of the tertiary structure, which can then influence the ability of a polypeptide to associate with other polypeptides in a quaternary structure.
It would be folly to say that the secondary structure is the most important. The tertiary/quaternary structure is what allows the protein to carry out its functions. Any changes to that are what researches are normally concerned with. Many of those changes involve a change in the primary structure (base sequence of the DNA essentially), which alter everything thereafter.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 16, 2014, 10:34:55 pm
I'm not sure this is correct. Each level of structure plays a part in the role of a protein.

The primary structure determines the sequence of amino acid residues in the polypeptide, which in turn determines the basic folding patterns of the secondary structure, which then in turn determine the overall folding pattern of the tertiary structure, which can then influence the ability of a polypeptide to associate with other polypeptides in a quaternary structure.
It would be folly to say that the secondary structure is the most important. The tertiary/quaternary structure is what allows the protein to carry out its functions. Any changes to that are what researches are normally concerned with. Many of those changes involve a change in the primary structure (base sequence of the DNA essentially), which alter everything thereafter.

My bad. I was referring to the way the quantity of alpha helices/beta pleats generally determines whether the fibrous protein is more elastic or rigid. But I may be wrong :/ Sorry for that
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 16, 2014, 10:54:14 pm
My bad. I was referring to the way the quantity of alpha helices/beta pleats generally determines whether the fibrous protein is more elastic or rigid. But I may be wrong :/ Sorry for that

In that case, sure that's a reasonable assumption to make, it's just not one that you want to generalise, because I think the course really tries to stress the interrelationship between the various levels of protein structure. It's an important consideration to make, so I wanted to clear that up.

Don't be sorry! That's exactly what everyone's here for, for that back and forth. Plus, only the completely stupid are always right :)
Title: Re: VCE Biology Question Thread
Post by: vella97 on January 16, 2014, 11:02:57 pm
Notice that the actual answer addresses two points, which I have summarized below:

1) The parallel arrangement of polypeptides means that they form long fibers or sheets. This refers to the beta pleated sheets as a secondary structure. Silk is well known for this property.
2) Some, but not all, fibrous proteins can be stretched and then return to their original shape. This refers to a protein's alpha helices.

You've only quoted one of them in your question.
You may have reached the correct conclusion if you payed attention to when the question asked "explain how this property as due to the arrangement of polypeptides". Fibrous proteins can have either an alpha helix or a beta pleated sheet. Recall that alpha helices can be twisted or stretched and return to their original shape. Beta pleated sheets, on the other hand, do the opposite. They are rigid and cannot be stretched. I would negate the comparison to a globular protein. That's not exactly what the question asks for. Anyway, hopefully I answered your question ( :

I've only quoted one in the question because that is how the question appeared in the Checkpoints, which confused me because I knew that beta pleats structures could not stretch. Should it have been made clearer in the question or is this supposed to be assumed knowledge? And if it's supposed to be assumed knowledge, then what was the point of stating the first type of structure of a fibrous protein in the first place?

Title: Re: VCE Biology Question Thread
Post by: alchemy on January 17, 2014, 08:26:51 am
I've only quoted one in the question because that is how the question appeared in the Checkpoints, which confused me because I knew that beta pleats structures could not stretch. Should it have been made clearer in the question or is this supposed to be assumed knowledge? And if it's supposed to be assumed knowledge, then what was the point of stating the first type of structure of a fibrous protein in the first place?

Like I said before, the question asks for you to refer to the "arrangement of polypeptides" in your answer. This, in other words, means something to do with the proteins structure (Primary, Secondary, Tertiary or Quaternary). We only have to really consider the secondary structure as the question states the type of structure as a fibrous protein, as you correctly recalled. So it's not exactly "assumed knowledge" in this case, but rather knowing how to interpret the question.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 17, 2014, 02:53:20 pm
How is non-competitive inhibition reversed?
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 17, 2014, 05:45:17 pm
Can someone please provide a concise definition of 'denaturation'? One that possibly encompasses the following points:
• It's irreversible
• Loss of 3-dimensional shape.
• Results from an altercation of bonds.
• Rendering the protein non-functional
• Is caused by a variety of factors

Cheers!
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 17, 2014, 06:03:53 pm
Can someone please provide a concise definition of 'denaturation'? One that possibly encompasses the following points:
• It's irreversible
• Loss of 3-dimensional shape.
• Results from an altercation of bonds.
• Rendering the protein non-functional
• Is caused by a variety of factors

Cheers!

You're pretty much already done! haha

"Denaturation is the irreversible loss of 3-dimensional protein shape due to the alteration of intra-molecular bonds. This is due to environmental factors such as heat or pH, and renders the denatured protein non-functional".

:)
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 17, 2014, 06:22:55 pm
You're pretty much already done! haha

"Denaturation is the irreversible loss of 3-dimensional protein shape due to the alteration of intra-molecular bonds. This is due to environmental factors such as heat or pH, and renders the denatured protein non-functional".

:)

Thanks alondouek for that condensed definition :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 19, 2014, 06:47:23 pm
Can someone please distinguish between a primary host and an intermediate host? Cheers!
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 19, 2014, 07:07:11 pm
Can someone please distinguish between a primary host and an intermediate host? Cheers!

Primary host --> Host that the adult parasite lives in/on

Intermediate host --> Host that the larval parasite lives in/on
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 19, 2014, 07:23:07 pm
Can someone please distinguish between a primary host and an intermediate host? Cheers!

Primary host: site of sexual reproduction
Secondary host: site of asexual reproduction
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on January 20, 2014, 05:57:42 pm
How does a coenzyme affect the rate of a reaction?
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 20, 2014, 06:01:05 pm
How does a coenzyme affect the rate of a reaction?

This may or may not be beyond the VCE course but, simply speaking, coenzymes facilitate electron transfer between the enzyme and the substrates.
Title: Re: VCE Biology Question Thread
Post by: Jason12 on January 20, 2014, 06:20:39 pm
If an amino acid is involved in the formation of a sulfur bond, what can you conclude about the molecular formula of that amino acid?
Title: Re: VCE Biology Question Thread
Post by: MagicGecko on January 20, 2014, 06:23:59 pm
If an amino acid is involved in the formation of a sulfur bond, what can you conclude about the molecular formula of that amino acid?
In this case out of the 20 amino acids only two contain sulfur atoms: cysteine or methionine
However only cysteine is able to form sulfur bonds so the molecular formula for cysteine is your answer.
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 20, 2014, 06:25:11 pm
If an amino acid is involved in the formation of a sulfur bond, what can you conclude about the molecular formula of that amino acid?

Well, amino acids are the monomer units of proteins, which are biomacromolecules. All biomacromolecules have carbon, hydrogen and oxygen. We also know that amino acids will always have nitrogen (due to the amino group (NH2) on one side of the amino acid). Because this statement says that a sulfur bond in apparent, we also know that the amino acid contains sulfur.

So, the likely molecular formula of that amino acid is, generally speaking, CHONS.
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on January 20, 2014, 06:26:24 pm
This may or may not be beyond the VCE course but, simply speaking, coenzymes facilitate electron transfer between the enzyme and the substrates.
Also, would a coenzyme have any effect on the amount of product produced?
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 20, 2014, 06:27:43 pm
Also, would a coenzyme have any effect on the amount of product produced?

If an enzyme requires a coenzyme to interact with a specific substrate, then the presence of that coenzyme would definitely have an effect on the amount of product produced in a given time.
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 20, 2014, 06:28:45 pm
If an amino acid is involved in the formation of a sulfur bond, what can you conclude about the molecular formula of that amino acid?

Well, amino acids are the monomer units of proteins, which are biomacromolecules. All biomacromolecules have carbon, hydrogen and oxygen. We also know that amino acids will always have nitrogen (due to the amino group (NH2) on one side of the amino acid). Because this statement says that a sulfur bond in apparent, we also know that the amino acid contains sulfur.

So, the likely molecular formula of that amino acid is, generally speaking, CHONS.

So Sulfur would be present in the Amino Acids R-variable group, right?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 20, 2014, 06:30:17 pm
So Sulfur would be present in the Amino Acids R-variable group, right?

Yes, as the variable group is what varies between the different amino acids :p
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 20, 2014, 06:34:09 pm
(http://1.bp.blogspot.com/_5DLPaUqdg2g/TBEF_WSQU2I/AAAAAAAAAG0/ox5jOkyE4Lk/s1600/Alpha-amino-acid-2D-flat.png)

All the magic happens in the R-variable group! :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 20, 2014, 08:24:20 pm
What resources/stationery would you guys recommend for Biol haha?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 20, 2014, 08:35:09 pm
What resources/stationery would you guys recommend for Biol haha?

I just had a notebook where I wrote up all my notes and looseleaf to record whatever we did in class. It meant I was writing my own notes. Probably a pretty shit way to learn to be honest, but it worked I guess.
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 20, 2014, 10:03:44 pm
I just had a notebook where I wrote up all my notes and looseleaf to record whatever we did in class. It meant I was writing my own notes. Probably a pretty shit way to learn to be honest, but it worked I guess.

Yep, that's me too. I'm not really big on stationary, I guess
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on January 21, 2014, 09:52:03 am
What aspects of Calvin cycle do we need to know? Is it that the ATP and NADPH produced in the light independent reactions are used to convert carbon dioxide into glucose during the process?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 21, 2014, 10:45:04 am
What aspects of Calvin cycle do we need to know? Is it that the ATP and NADPH produced in the light independent reactions are used to convert carbon dioxide into glucose during the process?

All you need to know is that in the light-independent stage, CO2 reacts with H+ ions (provided by NADPH) to produce glucose. ATP produced in the light-dependent stage provides the energy for synthesis of glucose, an endergonic process.

Don't learn intracicies that aren't assessed on the study design. :)
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on January 21, 2014, 03:53:46 pm
What is the difference to active immunity and acquired immunity, or are they exactly the same thing?
Thanks.
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 21, 2014, 11:51:15 pm
What is the difference to active immunity and acquired immunity, or are they exactly the same thing?
Thanks.

Acquired immunity means that you've become immune to a particular allergen; applies to both passive and active.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on January 23, 2014, 03:56:49 pm
Thanks Yacoubb.
i was wondering with the different pathogens, how much do we need to know about protists and worms (all do we just need to know in general how worms cause diseases and not need to know about each of them).
Thanks.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 23, 2014, 04:50:45 pm
Thanks Yacoubb.
i was wondering with the different pathogens, how much do we need to know about protists and worms (all do we just need to know in general how worms cause diseases and not need to know about each of them).
Thanks.

No need to know about individual species. Nobody has time for that.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on January 23, 2014, 05:26:41 pm
okay then, thanks.
and yup that makes sense, cause so much to learn.
So i just need to know about worms in general. thanks.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on January 23, 2014, 05:54:38 pm
Just out of curiosity when i went reading over chapter 1 of biology, i came upon water being a universal solvent.
I know that it is the universal solvent because it can dissolve most other molecules (given that it is polar like water). So i was wondering then isn't it true that other polar molecules (not water) can also be called a universal solvent (as it is still polar like water is)? Correct me please, i'm probably wrong- but i just wanted to clarify why water is a universal solvent?
Thanks.
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on January 23, 2014, 06:03:58 pm
Just out of curiosity when i went reading over chapter 1 of biology, i came upon water being a universal solvent.
I know that it is the universal solvent because it can dissolve most other molecules (given that it is polar like water). So i was wondering then isn't it true that other polar molecules (not water) can also be called a universal solvent (as it is still polar like water is)? Correct me please, i'm probably wrong- but i just wanted to clarify why water is a universal solvent?
Thanks.
I'm just guessing but another fact that makes water a universal solvent is that almost everything is made up from 50% of water, the world is made up from 70%, our body about 70% (sorry I can't remember the exact number). Whilst other substances can also dissolve things, they do not present as much as water does in our daily life.
Just my assumption though, hope this helps
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 23, 2014, 06:04:02 pm
Just out of curiosity when i went reading over chapter 1 of biology, i came upon water being a universal solvent.
I know that it is the universal solvent because it can dissolve most other molecules (given that it is polar like water). So i was wondering then isn't it true that other polar molecules (not water) can also be called a universal solvent (as it is still polar like water is)? Correct me please, i'm probably wrong- but i just wanted to clarify why water is a universal solvent?
Thanks.

If I'm not mistaken, water is considered to be a universal solvent as all the chemical reactions in our body occur in a watery environment which is suitable due to its polarity. This does not mean that all polar molecules are universal solvents. For example, ammonia (NH3) is a polar molecule and is a good solvent for organic molecules. Despite this, it is inferior to water. Furthermore, water dissolves more substances better than any other solvent therefore it is a universal solvent.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 23, 2014, 06:05:40 pm
It's not actually a universal solvent, though it's considered the universal solvent because there is no known chemical that can dissolve as many things as water.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 23, 2014, 06:06:20 pm
I also just wanted to know, to what extent do we need to know about the Krebs Cycle? It's by far the most confusing concept.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on January 23, 2014, 06:29:14 pm
Thank you so much everyone for your help, much appreciated.
And i think for the krebs cycle we just need to know the inputs, outputs, where it occurs (being the cristae)? (but i'm not to sure) and yup i agree it is really confusing- i think the extent its present in textbooks maybe getting to uni level bio. hope i could help.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 23, 2014, 06:45:31 pm
Thank you so much everyone for your help, much appreciated.
And i think for the krebs cycle we just need to know the inputs, outputs, where it occurs (being the cristae)? (but i'm not to sure) and yup i agree it is really confusing- i think the extent its present in textbooks maybe getting to uni level bio. hope i could help.

Cheers :) You might be right!
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 23, 2014, 07:59:05 pm
i think the extent its present in textbooks maybe getting to uni level bio.

I use the NoB textbook and I don't think it explains it quite at that level. However, do a quick internet search and there's uni level stuff regarding the Kreb's cycle everywhere!
Title: Re: VCE Biology Question Thread
Post by: Stick on January 23, 2014, 08:49:52 pm
The way Nature of Biology explains aerobic respiration is perfect, in my opinion. As always, it's a great idea to read beyond the course out of pure interest, but for assessment purposes I certainly wouldn't delve into the mechanics of aerobic respiration in short answer/extended response questions.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 24, 2014, 08:14:48 pm
Why do enzymes breakdown neurotransmitters after they've performed their function at the synapse?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 24, 2014, 08:17:10 pm
Why do enzymes breakdown neurotransmitters after they've performed their function at the synapse?
So that you stop feeling the pain (as an example)!

Alternatively, so as to prevent any further excitatory or inhibitory signaling.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 24, 2014, 08:22:06 pm
So that you stop feeling the pain (as an example)!

True. Why can't they be reused though? Just a thought.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 24, 2014, 08:33:03 pm
True. Why can't they be reused though? Just a thought.
I believe they can be reused; they are returned to the axon terminal (via active transport?).
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 24, 2014, 08:37:35 pm
I believe they can be reused; they are returned to the axon terminal (via active transport?).

Really, I thought they were all broken down by enzymes... Cheers anyway.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 24, 2014, 08:56:19 pm
Is the following definition of a cytoplasm accurate?

'a jelly-like substance that contains the contents of a cell (except the nucleus) such as the ions, enzymes, organelles and is more than 90% water'

Why doesn't the cytoplasm enclose the nucleus?

Thanks :)

Also, I know that the cytosol is the fluid component of the cytoplasm but is it correct to say that the cytoplasm also contains cytosol since it encloses the organelles? What is the significance of the cytosol's fluidity?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 24, 2014, 09:06:39 pm
Is the following definition of a cytoplasm accurate?

'a jelly-like substance that contains the contents of a cell (except the nucleus) such as the ions, enzymes, organelles and is more than 90% water'

Why doesn't the cytoplasm enclose the nucleus?

Thanks :)

Also, I know that the cytosol is the fluid component of the cytoplasm but is it correct to say that the cytoplasm also contains cytosol since it encloses the organelles? What is the significance of the cytosol's fluidity?
Cytoplasm: the fluid within a cell which includes all cell organelles apart from the nucleus. I see it as a collective term (composed of cell organelles + cytosol minus nucleus)
Apparently, the nucleus isn't part of the cytoplasm as it contains its own fluid called nucleoplasm.

Yes, cytosol is a constituent of cytoplasm. Its fluidity is significant in that it suspends the organelles that are part of the cytoplasm. Edit: should also mention that because it is mostly made of water, many cellular reactions occur within it.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 24, 2014, 09:09:17 pm
Cytoplasm: the fluid within a cell which includes all cell organelles apart from the nucleus. I see it as a collective term (composed of cell organelles + cytosol minus nucleus)
Apparently, the nucleus isn't part of the cytoplasm as it contains its own fluid called nucleoplasm.

Yes, cytosol is a constituent of cytoplasm. Its fluidity is significant in that it suspends the organelles that are part of the cytoplasm.

Thank-you!!

Also wanted to clarify, can the smooth ER and rough ER be considered two different organelles since they possess different functions?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 24, 2014, 09:11:08 pm
Thank-you!!

Also wanted to clarify, can the smooth ER and rough ER be considered two different organelles since they possess different functions?

Two variants of an organelle. But I guess saying they're two separate organelles is fine.
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 24, 2014, 09:11:19 pm
Thank-you!!

Also wanted to clarify, can the smooth ER and rough ER be considered two different organelles since they possess different functions?

Yes, it's broadly defined as a 'type of organelle' from the texts I've read.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 24, 2014, 09:22:30 pm
Is the following definition of a cytoplasm accurate?

'a jelly-like substance that contains the contents of a cell (except the nucleus) such as the ions, enzymes, organelles and is more than 90% water'

Why doesn't the cytoplasm enclose the nucleus?

Thanks :)

Also, I know that the cytosol is the fluid component of the cytoplasm but is it correct to say that the cytoplasm also contains cytosol since it encloses the organelles? What is the significance of the cytosol's fluidity?

Relating to the significance of the cytosol's fluidity; I believe its fluidity is vital for overall cell functions. Can you image if it was not fluid?
From what I've read, the aspect of fluidity in the cytoplasm(which consists of cytosol) creates cytoplasmic reorganisation during cell reproduction and in some protists it provides the mechanism for cell locomotion (movement); it aids in the delivery of nutrients, cell products, and genetic information to all parts of a cell, allowing cell components to flow to all parts of the cell. So basically it's important for all intracellular functions. Hope that helps.

Edit: Think of it in terms of osmosis as well (I suppose).
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 24, 2014, 09:24:58 pm
Relating to the significance of the cytosol's fluidity; I believe its fluidity is vital for overall cell functions. Can you image if it was not fluid?
From what I've read, the aspect of fluidity in the cytoplasm(which consists of cytosol) creates cytoplasmic reorganisation during cell reproduction and in some protists it provides the mechanism for cell locomotion (movement); it aids in the delivery of nutrients, cell products, and genetic information to all parts of a cell, allowing cell components to flow to all parts of the cell. So basically it's important for all intracellular functions. Hope that helps.

Thank-you! That makes much more sense now :)
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 24, 2014, 09:31:16 pm

Basically I was told that organelles do not necessarily require membranes. (e.g. ribosomes are not membrane-bound) Is this true?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 24, 2014, 09:36:57 pm

Basically I was told that organelles do not necessarily require membranes. (e.g. ribosomes are not membrane-bound) Is this true?

This is true. Some organelles (i.e. ALL those found in prokaryotic cells and SOME found in eukaryotic cells) are not membrane bound. The best example of this is the ribosome.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 24, 2014, 09:40:51 pm
This is true. Some organelles (i.e. ALL those found in prokaryotic cells and SOME found in eukaryotic cells) are not membrane bound. The best example of this is the ribosome.

Thank-you!
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 25, 2014, 05:36:37 pm
Referring to osmosis, what's correct to say: a higher water concentration or higher solute con. when taking about hypo/hypertonic solutions? Or is both correct?
Title: Re: VCE Biology Question Thread
Post by: Stick on January 25, 2014, 05:39:15 pm
The terms "high water potential" and "low water potential" are probably more favourable. Water is the solvent, not the solute, and hence using the term "concentration" isn't really viable. Alternatively, you can refer to the concentration of the solute in question.
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 25, 2014, 05:54:45 pm
Referring to osmosis, what's correct to say: a higher water concentration or higher solute con. when taking about hypo/hypertonic solutions? Or is both correct?

When describing or referring to osmosis, it's good to mention relate to the water concentration instead of solute concentration, just like how Stick described it above. However, really both are fine.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 25, 2014, 05:57:38 pm
The terms "high water potential" and "low water potential" are probably more favourable. Water is the solvent, not the solute, and hence using the term "concentration" isn't really viable. Alternatively, you can refer to the concentration of the solute in question.
So it would be: osmosis is the net movement of water molecules from a region of low water potential to a region of high water potential, across a semi permeable membrane. Is it necessary to mention the expenditure of energy?
Title: Re: VCE Biology Question Thread
Post by: Stick on January 25, 2014, 05:58:53 pm
You can include it if you'd like. :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 25, 2014, 06:01:19 pm
So it would be: osmosis is the net movement of water molecules from a region of low water potential to a region of high water potential, across a semi permeable membrane. Is it necessary to mention the expenditure of energy?

It's probably not necessary but you could refer to it as the passive net movement of ... etc.

Also, I think it would be a good idea to mention the solute concentration perhaps? So 'a region of low water potential (high solute concentration) to a region of high water potential (low solute con.). That's if your comparing solutions.

Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 25, 2014, 06:13:28 pm
So it would be: osmosis is the net movement of water molecules from a region of low water potential to a region of high water potential, across a semi permeable membrane. Is it necessary to mention the expenditure of energy?

My definition:

Osmosis is the passive, net movement of free water molecules across the semi-permeable plasma membrane, from an area of low solute concentration, to an area of high solute concentration, along the osmotic gradient.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 25, 2014, 06:13:58 pm
When describing or referring to osmosis, it's good to mention relate to the water concentration instead of solute concentration, just like how Stick described it above. However, really both are fine.

Thanks alchemy! (+1 is not working for some reason)
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 25, 2014, 06:24:10 pm
I had a question regarding DNA.
I know that hair and nails do not contain DNA. But can someone please tell me why. Is it because they do not require DNA and the roots are responsible for their growth?

Also, it is somehow related to the fact that both hair and nails are made of keratin? Thank-you :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 25, 2014, 06:39:24 pm
I had a question regarding DNA.
I know that hair and nails do not contain DNA. But can someone please tell me why. Is it because they do not require DNA and the roots are responsible for their growth?

Also, it is somehow related to the fact that both hair and nails are made of keratin? Thank-you :)

The hair strand and nail are made of proteins which were created by the cells lining the hair strand (the follicle) and the nail (the nail bed). I'm guessing they don't exactly require DNA because they aren't performing a function that necessitates 'directions' from DNA. A red blood cell would be a good example of this.
Also I believe, since keratin is a globular protein it's quite large and needs space to occupy. Hair and nails degenerate like RBC so there is no point of having DNA in the actual hair strand or nail.

Someone please correct me if I'm wrong. Cheers.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 25, 2014, 06:43:01 pm

The hair strand and nail are made of proteins which were created by the cells lining the hair strand (the follicle) and the nail (the nail bed). I'm guessing they don't exactly require DNA because they aren't performing a function that necessitates 'directions' from DNA. A red blood cell would be a good example of this.
Also I believe, since keratin is a globular protein it's quite large and needs space to occupy. Hair and nails degenerate like RBC so there is no point of having DNA in the actual hair strand or nail.

Someone please correct me if I'm wrong. Cheers.

Thanks! So would it be true to say that hair and nails are composed of dead cells that carry no function and thus have no DNA?
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 25, 2014, 06:44:32 pm
I had a question regarding DNA.
I know that hair and nails do not contain DNA. But can someone please tell me why. Is it because they do not require DNA and the roots are responsible for their growth?
Also, it is somehow related to the fact that both hair and nails are made of keratin? Thank-you :)

This is an interesting question that I somehow stumbled upon while doing a research task sometime ago.
Firstly, recall that DNA is contained in the nucleus. Hair, skin and nail cells destroy their nuclei as part of their developmental process. They do this in order to maximize the space in the cell filled with the structural protein keratin. This means that the cell nucleus and other internal parts of the cell are destroyed and their space is filled by keratin. MM1 said pretty much the same, I think.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 25, 2014, 06:49:59 pm
Thanks! So would it be true to say that hair and nails are composed of dead cells that carry no function and thus have no DNA?

I don't think so. They do carry out a function. I'm thinking of red blood cells here but I'm not 100% sure. I wouldn't term them 'dead cells' because they do contain protein which is an organic molecule that is functioning. In a sense, they are dead but I wouldn't bet on it.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 25, 2014, 06:50:44 pm
This is an interesting question that I somehow stumbled upon while doing a research task sometime ago.
Firstly, recall that DNA is contained in the nucleus. Hair, skin and nail cells destroy their nuclei as part of their developmental process. They do this in order to maximize the space in the cell filled with the structural protein keratin. This means that the cell nucleus and other internal parts of the cell are destroyed and their space is filled by keratin. MM1 said pretty much the same, I think.

Thank-you!
Title: Re: VCE Biology Question Thread
Post by: Stick on January 25, 2014, 10:11:23 pm
I'm sorry, this might deviate the thread from its intended purpose for a moment, but this is something I've been wondering for a while now.

How come when you straighten curly hair with a hair straightener, the hair regains its curl when it gets wet? The heat should cause the permanent denaturation of the keratin (and other proteins) present in hair, so I'm not 100% sure as to how it goes back. I guess the reverse also applies regarding curling straight hair with curling irons.

Lol whenever my sister straightens her hair I always start thinking of this. XD
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 25, 2014, 10:16:30 pm
I'm sorry, this might deviate the thread from its intended purpose for a moment, but this is something I've been wondering for a while now.

How come when you straighten curly hair with a hair straightener, the hair regains its curl when it gets wet? The heat should cause the permanent denaturation of the keratin (and other proteins) present in hair, so I'm not 100% sure as to how it goes back. I guess the reverse also applies regarding curling straight hair with curling irons.

Lol whenever my sister straightens her hair I always start thinking of this. XD

I'd have to hazard a guess (because I no naught about hair-straightening), but I'd say it was because the exposure of the hair to heat is quick and short-lasting enough to only break the disulfide bonds in the hair (which cause the curling) without sufficiently denaturing the keratin structures.

Hence, exposure to water changes the regular environment of the hair, inducing it to return to its original state (as no permanent change by denaturation has occurred).
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 25, 2014, 10:27:13 pm
I'm sorry, this might deviate the thread from its intended purpose for a moment, but this is something I've been wondering for a while now.

How come when you straighten curly hair with a hair straightener, the hair regains its curl when it gets wet? The heat should cause the permanent denaturation of the keratin (and other proteins) present in hair, so I'm not 100% sure as to how it goes back. I guess the reverse also applies regarding curling straight hair with curling irons.

Lol whenever my sister straightens her hair I always start thinking of this. XD

Funnily enough, I got this question as part of my holiday homework. I'm not sure if this is correct but this is what I wrote:
"Hair is composed of the protein Keratin which is an alpha helix. It is able to stretch and its hydrogen bonds can be broken when heat is applied, but it eventually returns to its original shape as hydrogen bonds form over time."
Would water (H2O) help in these hydrogen bonds in forming?
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 25, 2014, 10:33:54 pm
Funnily enough, I got this question as part of my holiday homework. I'm not sure if this is correct but this is what I wrote:
"Hair is composed of the protein Keratin which is an alpha helix. It is able to stretch and its hydrogen bonds can be broken when heat is applied, but it eventually returns to its original shape as hydrogen bonds form over time."
Would water (H2O) help in these hydrogen bonds in forming?

I'm probably incorrect here, but doesn't water, when added, break bonds?
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 25, 2014, 10:36:44 pm
I'm probably incorrect here, but doesn't water, when added, break bonds?

It can act as a solvent by breaking bonds, but it can also induce formation of new bonds depending on the gaseous H2O saturation of the environment that the hair is in. (That's an answer to your question too, alchemy!)
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on January 25, 2014, 10:57:17 pm
Funnily enough, I got this question as part of my holiday homework. I'm not sure if this is correct but this is what I wrote:
"Hair is composed of the protein Keratin which is an alpha helix. It is able to stretch and its hydrogen bonds can be broken when heat is applied, but it eventually returns to its original shape as hydrogen bonds form over time."
Would water (H2O) help in these hydrogen bonds in forming?
In biology, Hydrogen bond is considered to be a quite weak bond, it can easily break and reform (that's why water is cohesive). Hydrogen bond is made from when an H+ attracts an N,O, or F. Hence,  in water, when H+ attracts to OH-, it will create a water molecule. In Keratin, if you look at the alpha helix structure, it's quite flexible, easily stretch since H-bond is weak but easily rejoin since the H+ and O- will try to attract to each other, making the bond cohesive.
Another reason is, keratin contains cysteine amino acids, these amino acid contains Sulfur element. if 2 cysteines meet, they can build a disulphide link between them. Imo, if you add water, then these H+ and O- along the chain will not attract to each other anymore ( or less attract) since there are more H+ and OH- from the added water molecules, therefore, it will break the bond.
These are just my knowledge and might contain some errors :(, still, hope this makes sense.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 26, 2014, 12:18:08 am
I know this varies for every school, but how many SACS are there in Biol generally?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 26, 2014, 12:32:04 am
I know this varies for every school, but how many SACS are there in Biol generally?

Title: Re: VCE Biology Question Thread
Post by: alchemy on January 26, 2014, 10:30:34 am
I know this varies for every school, but how many SACS are there in Biol generally?

Stuff have been taken out of the study design, so the word is we will have 6 sacs over the course of this year. However, in class, the teacher said we'll be having 10  :'(
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 26, 2014, 10:39:47 am
• Movement across the membrane
• Enzymes
• Photosynthesis/Cellular Respiration
• Detecting and Responding
• Immunity
• Mitosis/Meiosis
• Monohybrid/Dihybrid crosses
• DNA manipulation
• Evolutionary relationships
• Human Intervention in Evolution
Title: Re: VCE Biology Question Thread
Post by: Jazza12396 on January 26, 2014, 01:48:47 pm
I'm a bit confused with the wording of the stages of Photosynthesis in the textbook. Could someone please explain the stages to me!
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 26, 2014, 02:28:41 pm
I'm a bit confused with the wording of the stages of Photosynthesis in the textbook. Could someone please explain the stages to me!

Light-Dependent Stage:
- Chlorophyll molecules absorb light energy.
- Electrons in the chlorophyll molecules become excited; as a result, the excited electrons enter the electron transport chain.
- To replenish the electrons lost from chlorophyll molecules, water is split to form H+ ions and oxygen gas (a by-product).
- ATP is formed from ADP + Pi (i.e. Adenosine Di-phosphate + Inorganic phosphate).

Light-Independent Stage:
- Carbon dioxide reacts with H+ ions (provided by NADPH) to form glucose. ATP provides the energy needed to synthesise glucose.
- After the electrons travel through the electron transport chain, they are collected by oxygen atoms, which then become O2- ions. O2- ions then react with excess H+ to form water (a by-product).

Title: Re: VCE Biology Question Thread
Post by: Jazza12396 on January 26, 2014, 03:00:47 pm
Thank you
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 26, 2014, 03:49:50 pm
Is it possible for a monosaccharide to have one carbon atom --> CH20
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 26, 2014, 03:51:28 pm
Is it possible for a monosaccharide to have one carbon atom --> CH20

CH2O is formaldehyde (an aldehyde), which is definitely not a monosaccharide :)
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 26, 2014, 03:56:43 pm
CH2O is formaldehyde (an aldehyde), which is definitely not a monosaccharide :)

Thanks alondouek!
So even if a carbon-hydrogen-oxygen compound is proportional to that of a carbohydrate, it's not always a sugar?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 26, 2014, 04:00:31 pm
Thanks alondouek!
So even if a carbon-hydrogen-oxygen compound is proportional to that of a carbohydrate, it's not always a sugar?

It depends on which definition you look at. Carbohydrates are often actually given the formula Cx(H2O)y, where x≥3. Though some chemists disagree with this definition and let x be equal to 2, making a diose the smallest kind of which only one, glycoaldehyde, exists.
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 26, 2014, 04:04:06 pm
Thanks alondouek!
So even if a carbon-hydrogen-oxygen compound is proportional to that of a carbohydrate, it's not always a sugar?

What T-Rav said^

Keep in mind that the ubiquitous components of most - if not all - biomacromolecules and their monomeric components are carbon, hydrogen and oxygen. Given this, a lot of compounds will have a general formula derivative of CnHnOn, but they can be wildly different in grouping, structure and function!
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 26, 2014, 04:08:00 pm
Thank-you! That makes much more sense now! :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 26, 2014, 06:01:31 pm
Do plants have specific immunity? If yes, can someone please explain the concept? Thanks!
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 26, 2014, 06:28:29 pm
Do plants have specific immunity? If yes, can someone please explain the concept? Thanks!

No. Plants only have physical and chemical barriers to stop pathogenic agents from entering the internal environment of the plant organism. This includes things like the formation of galls to trap and prevent the spread of a pathogen, etc. No specific attacks are made against specific strains of pathogens, and no memory is involved.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 26, 2014, 06:36:48 pm
No. Plants only have physical and chemical barriers to stop pathogenic agents from entering the internal environment of the plant organism. This includes things like the formation of galls to trap and prevent the spread of a pathogen, etc. No specific attacks are made against specific strains of pathogens, and no memory is involved.

Thanks Yacoubb! So if a pathogen does manage to enter into the internal environment, does the plant have no other choice but to essentially die? Do plants possess anything similar to the mechanisms of a white blood cell?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 26, 2014, 06:52:24 pm
Thanks Yacoubb! So if a pathogen does manage to enter into the internal environment, does the plant have no other choice but to essentially die? Do plants possess anything similar to the mechanisms of a white blood cell?

There are different means by which the plant can try to protect itself. For instance, the formation of a gall. This gall is just a mass of tissue that forms around the site where the pathogen enters, which traps the pathogen, and prevents it from spreading to other parts of the plant.

However, its more than likely the plant will die if it is infected by a pathogen, because of its limited immunity to pathogenic agents.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 26, 2014, 08:25:51 pm
I just wanted to clarify, glucose is found in the form of glycogen in animals and as starch in plants.
I know that excess glycogen is stored as fat in animals but is it possible for a plant to have 'excess' starch? If so, in what form does it exist?
Thanks!
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on January 26, 2014, 08:32:43 pm
I just wanted to clarify, glucose is found in the form of glycogen in animals and as starch in plants.
I know that excess glycogen is stored as fat in animals but is it possible for a plant to have 'excess' starch? If so, in what form does it exist?
Thanks!

Starch is found as starch granules within plant cells. The starch molecules are hydrolysed when required, to provide a source of glucose.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on January 26, 2014, 08:46:57 pm
I was just reading the nature of biology and Nelson of biology unit 4 genes, genomics, genetic code, cell division and stuff, an have noticed quite a lot of stuff that is only said in nature of biology. So I was just wondering if we needed to know the below stuff: downstream/upstream flanking region, hybridization, dissociation, re-association, chargaff's rule, gene duplication, horizontal gene transfer. Finding it hard to tell what relevant here cause its all over the place. Thanks.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 26, 2014, 09:05:22 pm
I just wanted to clarify, glucose is found in the form of glycogen in animals and as starch in plants.
I know that excess glycogen is stored as fat in animals but is it possible for a plant to have 'excess' starch? If so, in what form does it exist?
Thanks!

I wouldn't say that glucose is stored as glycogen. It's nitpicking, but it's not really. It's more or less the major complex carbohydrate is glycogen.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 27, 2014, 01:57:27 pm
This question has actually been on my mind for a long time...
Why do we refer to chemical reactions in the body as cellular reactions?
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 27, 2014, 01:58:45 pm
This question has actually been on my mind for a long time...
Why do we refer to chemical reactions in the body as cellular reactions?

Because the cells are where the vast majority of biochemical processes are carried out
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 27, 2014, 02:05:13 pm
Because the cells are where the vast majority of biochemical processes are carried out

Thanks alondouek!
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 27, 2014, 07:40:17 pm
I was a bit confused about the function of enzymes. According to my textbook, enzymes reduce activation energy however have no effect on the rest of the reaction. Is this true? If so, when people say that enzymes catalyse a reaction, do they actually mean that enzymes catalyse the beginning of a reaction?

Thank-you and sorry about the confusion!
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 27, 2014, 07:49:13 pm
I was a bit confused about the function of enzymes. According to my textbook, enzymes reduce activation energy however have no effect on the rest of the reaction. Is this true? If so, when people say that enzymes catalyse a reaction, do they actually mean that enzymes catalyse the beginning of a reaction?

Thank-you and sorry about the confusion!

It depends on the type of enzyme really. It's hard to explain, because it's kind of true and kind of not. Some enzymes just orient things better, and that reduces the activation energy, whereas others actually press and hold substrates together, and thereby participate in the whole reaction. Just presume that reactions are instantaneous (each individual step that is).
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 27, 2014, 09:36:46 pm
What do we need to know about rational drug design?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 27, 2014, 09:41:47 pm
What do we need to know about rational drug design?

What it is.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 27, 2014, 09:45:28 pm
To what extent do we need to know about thermophilic bacteria?
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 27, 2014, 09:53:07 pm
To what extent do we need to know about thermophilic bacteria?

Probably nothing beyond the fact that they are bacteria that thrive in higher temperatures.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 27, 2014, 10:20:54 pm
Why is it that competitive chemical inhibitors will stop binding to an enzyme if there is a build-up of substrates?
Why don't non-competitive inhibitors also stop binding?
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on January 27, 2014, 10:35:56 pm
Can digestive enzymes also be called hydrolytic enzymes? (Or is it best just to refer them as the former?)
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 27, 2014, 10:55:05 pm
Why is it that competitive chemical inhibitors will stop binding to an enzyme if there is a build-up of substrates?
Why don't non-competitive inhibitors also stop binding?

A competitive inhibitor binds to the enzyme's active site. We can reverse this inhibition by increasing substrate concentration, as the substrate can essentially "overpower" the effect of the inhibitor by occupying the active site instead, in a way 'forcing' the inhibitor out of the active site (remember that the enzyme in this scenario is specific to both the substrate and the competitive inhibitor).

Non-competitive inhibitors do also stop binding (I think you may have made a small error in the question :) ), but this form of inhibition is not considered reversible (within the bounds of the VCE curriculum) because the inhibitor binds to a site OTHER than the active site. This distorts the shape of the enzyme's active site, which means that increasing substrate concentration will have no effect because the substrate cannot bind to the active site.

Can digestive enzymes also be called hydrolytic enzymes? (Or is it best just to refer them as the former?)

All digestive enzymes are hydrolytic (the belong to the class of enzymes known as hydrolases), so that's fine!
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 28, 2014, 01:49:57 pm
Where does the energy to make ATP from ADP+Pi come from? Since it's an anabolic reaction.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 28, 2014, 05:54:05 pm
Where does the energy to make ATP from ADP+Pi come from? Since it's an anabolic reaction.

Breaking down sugars, fats etc. Because they release energy, the break down of them is used to fuel the reaction between ADP and inorganic phosphate.
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 28, 2014, 05:56:50 pm
Where does the energy to make ATP from ADP+Pi come from? Since it's an anabolic reaction.

Oxidative phosphorylation, which is the formal term for what T-Rav mentioned above.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 28, 2014, 06:55:40 pm
According to my textbook, useful molecules diffuse back into the cytoplasm from the lysosome. How is this possible?

Also, how do the hydrolytic enzymes in the lysosomes break down foreign debris when the enzyme and substrate are meant to be specific?

Thanks :)
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on January 28, 2014, 07:26:10 pm
For the first part- i think its because the lysosome brakes down all the complex molecules so the simpler ones can then be used by the cell again to build other different more complex molecules (that require the same sub-units). just guessing from my limited knowledge, otherwise no idea. and for the second part not too sure either.
I was just wondering for the disease chapter, what are we required to know about each different agent/ pathogen- (eg there name, function)? thanks.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 28, 2014, 07:47:11 pm
According to my textbook, useful molecules diffuse back into the cytoplasm from the lysosome. How is this possible?

Also, how do the hydrolytic enzymes in the lysosomes break down foreign debris when the enzyme and substrate are meant to be specific?

Thanks :)

Basically what Chang Feng said, some of these molecules, when broken down, can be used again by the cell so therefore they are retained. Perhaps by exocytosis if you mean how.

As for your second question, I believe the enzyme is able to slightly change its shape as the substrate binds on to it. Even though they aren't the same structurally they are similar. Think of the Induced Fit theory here, where the enzyme locks onto the substrate at its active site by slightly changing shape.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 28, 2014, 07:51:23 pm
I was just wondering for the disease chapter, what are we required to know about each different agent/ pathogen- (eg there name, function)? thanks.

According to the SD, we're required to know about cellular and non-cellular agents such as viruses and prions. I think we just need to know what they are and their function and features and what effect they might impose if having affected someone. Knowing a few diseases isn't required but I think it would be good to know.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on January 28, 2014, 08:00:37 pm
so if enzymes can change as represented by the induced fit model, does that mean technically all substrates are similar to the enzyme since their would be a variety of different complex molecules with different binding sites which need to be broken down by enzymes. wait, or is it there are many different enzymes in the lysosome with various active sites?
and thanks too.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 28, 2014, 08:06:14 pm
so if enzymes can change as represented by the induced fit model, does that mean technically all substrates are similar to the enzyme since their would be a variety of different complex molecules with different binding sites which need to be broken down by enzymes. wait, or is it there are many different enzymes in the lysosome with various active sites?
and thanks too.

There are different ways in which an enzyme binds to a substrate. As MM1 mentioned, the induced fit model is an example in which coenzymes enable the enzyme to fit the substrate. The lock and key model is another method in which the enzyme accurately fits the substrate.
In the case of lysosomes, I'm guessing most of the binding between enzyme and substrate is similar to the induced fit model since the hydrolytic enzymes break down foreign and unwanted debris therefore if the binding were specific, then the enzyme may not be able to break down other unwanted substances.
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 28, 2014, 08:12:26 pm
so if enzymes can change as represented by the induced fit model, does that mean technically all substrates are similar to the enzyme since their would be a variety of different complex molecules with different binding sites which need to be broken down by enzymes. wait, or is it there are many different enzymes in the lysosome with various active sites?
and thanks too.

I wouldn't say all substrates are similar to the enzyme - it's their active site which is similar in structure.
Maybe there are many different enzymes in the lysosome with various active sites however I think the fact that the enzymes can alter their shape (induced fit theory) is what metabolises the reactions.

Title: Re: VCE Biology Question Thread
Post by: scribble on January 28, 2014, 08:20:42 pm
hydrolytic enzymes are a broad term used to describe enzymes that break biomolecules down into smaller components by hydrolysis.
there are many, many different types of hydrolytic enzymes contained within a lysosome . proteases for example break hydrolyse the peptide bond that links individual amino acids together in proteins, and nucleases break the phosphodiester bond between nucleotides in dna.
and then under those categories, there are specifics as well. Some proteases may only cleave the protein at a specific amino acid for example. (you needn't worry about this at vce level)
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 28, 2014, 08:44:38 pm
so if enzymes can change as represented by the induced fit model, does that mean technically all substrates are similar to the enzyme since their would be a variety of different complex molecules with different binding sites which need to be broken down by enzymes. wait, or is it there are many different enzymes in the lysosome with various active sites?
and thanks too.

Acid hydrolases (the type of enzyme in lysosomes) come in many different forms. As with all of biology, form leads to function and therefore differences in form lead to differences in function. Acid hydrolases of varying form can be proteases, glycosidases, lipases etc (i.e. they can break down a wide range of molecules because they have a wide range of structures)
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on January 29, 2014, 01:35:19 pm
Hi guys, wondering if you could help me out with a few questions I have!

1)Are conjugated proteins counted as a part of the protein’s quaternary structure?
2)Are lipids made up of chains of glycogen and fatty acids? Or are fatty acids and glycerols arranged in some other form?
3)Are proteins in the plasma membrane only of the quaternary structure?
4)Does tRNA only have three bases in its sequence? The photo attached is the concerned question from my textbook
Thank you! :)
Title: Re: VCE Biology Question Thread
Post by: elsalouise123 on January 29, 2014, 03:10:48 pm
Just wondering what the best way to study for this subject ( in particular all you 40 and > scores!!)

Is it viable to type notes in class and then go home and write notes out with other sources as per study design???

Your knowledge would be greatly appreciated. thanks
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 29, 2014, 07:11:46 pm
Hi guys, wondering if you could help me out with a few questions I have!

1)Are conjugated proteins counted as apart of the protein’s quaternary structure?
2)Are lipids made up of chains of glycogen and fatty acids? Or are fatty acids and glycerols arranged in some other form?
3)Are proteins in the plasma membrane only of the quaternary structure?
4)Does tRNA only have three bases in its sequence? The photo attached is the concerned question from my textbook
Thank you! :)

1) Do you mean "as a part*" instead of "as apart"? If you do, you should know that not all conjugated proteins are considered to have quarternary structure. Collagen is an example of a conjugated protein that does have a quarternary structure. Conjugated proteins have a prosthetic group (non-protein part) attached to them, meaning upon hydrolysis they would yield another chemical component other than amino acids.
2) Lipids aren't linked together to form 'chains of glycogen and fatty acids'. Proteins are examples of long chains of amino acids as evident in their primary structure. Lipids have smaller molecules that aren't exactly structured in the form of repetitive chains.
3) I think you mean "do proteins in the plasma membrane have a quarternary structure?", as proteins cannot only have a quarternary structure! So, not all membrane proteins have a quarternary structure. I believe most of them have tertiary structures.
4) RNA has 4 bases in general. It's just that Thymine from DNA is replaced by Uracil in RNA. So RNA would have Adenine, Uracil, Guanine and Cytosine.
As for the photo, it won't be possible to tell what type of RNA it is, unless we know its function. Hope that helps, and as always, someone please correct me if I was incorrect on any of the above.
Title: Re: VCE Biology Question Thread
Post by: MagicGecko on January 29, 2014, 07:27:40 pm
Just wondering what the best way to study for this subject ( in particular all you 40 and > scores!!)

Is it viable to type notes in class and then go home and write notes out with other sources as per study design???

Your knowledge would be greatly appreciated. thanks

Everyone has their own techniques in studying biology. I never really liked typing out notes, too troublesome, especially with diagrams. I had a lecture pad which I would copy down the notes in class. I would then go home and re write those notes in my biology notebook. I found writing down the info twice helped me remember it better. Also drawing a lot of pictures helped me :P
It may also help if you have access to two textbooks, because some textbook are more detailed than others. Listening to Douchy's biology podcast's was quite good if I remember correctly, sure did help in the immunity part.
Title: Re: VCE Biology Question Thread
Post by: MagicGecko on January 29, 2014, 07:40:07 pm
Hi guys, wondering if you could help me out with a few questions I have!

1)Are conjugated proteins counted as apart of the protein’s quaternary structure?
2)Are lipids made up of chains of glycogen and fatty acids? Or are fatty acids and glycerols arranged in some other form?
3)Are proteins in the plasma membrane only of the quaternary structure?
4)Does tRNA only have three bases in its sequence? The photo attached is the concerned question from my textbook
Thank you! :)

Branching off on what alchemy said about 2)
If lipids were made up of 'chains' of glycogen and fatty acids, this would make them the monomer of lipids, however lipids don't have a monomer. Instead you refer to them as sub-units and no, they don't make 'chains'.
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on January 29, 2014, 09:07:54 pm
1) Do you mean "as a part*" instead of "as apart"? If you do, you should know that not all conjugated proteins are considered to have quarternary structure. Collagen is an example of a conjugated protein that does have a quarternary structure. Conjugated proteins have a prosthetic group (non-protein part) attached to them, meaning upon hydrolysis they would yield another chemical component other than amino acids.
2) Lipids aren't linked together to form 'chains of glycogen and fatty acids'. Proteins are examples of long chains of amino acids as evident in their primary structure. Lipids have smaller molecules that aren't exactly structured in the form of repetitive chains.
3) I think you mean "do proteins in the plasma membrane have a quarternary structure?", as proteins cannot only have a quarternary structure! So, not all membrane proteins have a quarternary structure. I believe most of them have tertiary structures.
4) RNA has 4 bases in general. It's just that Thymine from DNA is replaced by Uracil in RNA. So RNA would have Adenine, Uracil, Guanine and Cytosine.
As for the photo, it won't be possible to tell what type of RNA it is, unless we know its function. Hope that helps, and as always, someone please correct me if I was incorrect on any of the above.

Thanks so much!
So building on question 2), what kind of forces hold lipids together?
For question 3), I meant what I said. I had encountered a question earlier asking if membrane proteins were only of a quaternary structure  :P I think I've just presumed that quaternary structured proteins are more common than their tertiary counterparts.
With question 4), I'm still confused as to why all RNA looks the same. I know that RNA has four different nitrogenous bases, but isn't the RNA sequence in each tRNA just 3 bases? Concerning the picture, why is it impossible to differentiate between RNA types when tRNA has a base sequence of 3 nitrogenous bases? I'm missing something about the structure of tRNA! :-\
Title: Re: VCE Biology Question Thread
Post by: MagicGecko on January 29, 2014, 09:44:12 pm
The hydrophobic tails are held together by 'Van der Waals' forces whereas 'hydrogen bonds' is the force that holds hydrophilic heads together as well as interact with water, therefore helping to stabilize the phospholipid bilayer structure.

Concerning the picture, why is it impossible to differentiate between RNA types when tRNA has a base sequence of 3 nitrogenous bases?

(http://www.snider.fwcs.k12.in.us/apbiology/homework/Unit%2006/16-92.gif)

This picture might help. Basically tRNA doesn't have just 3 nitrogen bases, in actual fact it has many, its just that the 3 you assumed it only had are the only anti-codons (hence why some diagrams normally just display those three bases since those are the only 'important' ones).
The only way you would be able to distinguish what type of RNA it is would be if the question added something like 'this RNA also codes for 6 amino acids', in which case it would be mRNA, because mRNA is the only one out of the three which is translated into a polypeptide.
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 29, 2014, 09:48:57 pm
You can stipulate the size of the image by using [img width=insert number here (e.g. 500)]insert image URL here[/img]
Title: Re: VCE Biology Question Thread
Post by: MagicGecko on January 29, 2014, 09:54:02 pm
You can stipulate the size of the image by using [img width=insert number here (e.g. 500)]insert image URL here[/img]

Really? Lemme just check that out :P

*EDIT*  It worked! I set it to 400, thanks!
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 29, 2014, 10:02:42 pm
So building on question 2), what kind of forces hold lipids together?
For question 3), I meant what I said. I had encountered a question earlier asking if membrane proteins were only of a quaternary structure  :P I think I've just presumed that quaternary structured proteins are more common than their tertiary counterparts.
With question 4), I'm still confused as to why all RNA looks the same. I know that RNA has four different nitrogenous bases, but isn't the RNA sequence in each tRNA just 3 bases? Concerning the picture, why is it impossible to differentiate between RNA types when tRNA has a base sequence of 3 nitrogenous bases? I'm missing something about the structure of tRNA! :-\

As a general rule: All proteins have primary, secondary and tertiary structures; but not all proteins have quartenary structures. The primary structure refers to the sequence of amino acids in the polypeptide chain. The secondary structure refers to the characteristic 3D shape of a protein, given rise to by different R groups and their arrangement on either side of the peptide bonds. The tertiary structure of a protein is it's overall geometric shape, a modified secondary structure really, and is what allows a protein to carry out its function. A quarternery structure refers to proteins made of more than one polypeptide chain. For example, hemoglobin is made up of 4 polypeptide chains, and is globular (one of the two main classes of quarternery structured proteins). However, realise that not all proteins can have more than one polypeptide chain. Therefore, not all proteins can have a quarternery structure.
Regarding your question on RNA, I think you are referring to codons. A codon is the initial nucleotide from which translation starts. Codons are sets of 3 adjacent nucleotides that t-RNA transfers from mRNA in the process of synthesising amino acids. All RNA still have the 4 bases (AUGC), but they read only in groups of 3 when being translated into an amino acid. RNA have the same structure but different function? I'll let someone else answer that.
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on January 29, 2014, 10:04:15 pm
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 29, 2014, 10:07:13 pm

What I used to do was to write a preliminary answer in dot points, then formulate it into a brief, cogent (and hopefully correct) answer. By the time the exam comes around, you should be able to do the dot-pointing in your head so you can get your answer onto the page quickly!
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 30, 2014, 05:36:25 pm
Why aren't lipid based molecules repelled by the hydrophilic phosphate when they diffuse through the bilayer? How are they able to overcome this?

Also, when would you guys recommend starting VCAA past exam papers? Should I do them now (advised by my teacher) or leave them till the last month or so?
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 30, 2014, 06:10:02 pm
Another question... hope you guys don't mind.

So lipids are known to have a higher energy yield compared to carbohydrates; How come? Do they have a general formula like monosaccharides (CH2O)n ?

Thanks aplenty!
Title: Re: VCE Biology Question Thread
Post by: vox nihili on January 30, 2014, 06:21:31 pm
Another question... hope you guys don't mind.

So lipids are known to have a higher energy yield compared to carbohydrates; How come? Do they have a general formula like monosaccharides (CH2O)n ?

Thanks aplenty!

The bonds are stronger, more energy pent up in the bonds and the configurations they break down too are lower energy configurations.
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 30, 2014, 07:03:06 pm
Also, when would you guys recommend starting VCAA past exam papers? Should I do them now (advised by my teacher) or leave them till the last month or so?

Didn't your school just start? I go to a selective school, and even the freakishly smart people I know haven't touched any practice papers yet.
It's up to you though, do what you think you are capable of doing, and I'm sure that'll be best :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on January 30, 2014, 07:20:53 pm
Didn't your school just start? I go to a selective school, and even the freakishly smart people I know haven't touched any practice papers yet.
It's up to you though, do what you think you are capable of doing, and I'm sure that'll be best :)

Yes; I guess by 'now' I meant end of February for general exam papers :P. My teacher said it's okay to use VCAA past exam papers as you would use commercial ones; but then I've heard that it's better to leave VCAA for last so that's why I'm asking. I'll probably go with the latter.
Thanks anyway! :)
Title: Re: VCE Biology Question Thread
Post by: alchemy on January 30, 2014, 09:55:10 pm
... I've heard that it's better to leave VCAA for last so that's why I'm asking.

Yup, I'd probably leave them for last as well (:
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 30, 2014, 09:56:40 pm
same here! personally, I think now's the best time to solidify your understanding of the concepts :)

But anyways Good luck to all Bio students!
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on January 30, 2014, 10:21:41 pm

Simple sugars have the general formula of (CH2O)n. . If disaccharides are classified as a simple sugar, and sucrose is an example of a disaccharide, then why does it have a formula of C12H22O11 ?

This question has been bugging me for the last few days :(
Title: Re: VCE Biology Question Thread
Post by: grannysmith on January 30, 2014, 10:26:36 pm

Simple sugars have the general formula of (CH2O)n. . If disaccharides are classified as a simple sugar, and sucrose is an example of a disaccharide, then why does it have a formula of C12H22O11 ?

This question has been bugging me for the last few days :(

Disaccharides are formed when two monosaccharides covalently bond together (glycosodic bond) through condensation polymerisation. Because of this, a H and OH is lost, forming water. Therefore disaccharides have 2 less hydrogens and 1 less oxygen.
Title: Re: VCE Biology Question Thread
Post by: Stick on January 30, 2014, 10:28:51 pm
Do you remember what happens when two monosaccharides bond together to form a disaccharide? This process occurs through a condensation reaction, in which a water molecule (H2O) is produced. So, the molecular formula of the disaccharide will be the addition of two monosaccharides (C6H12O6 + C6H12O6 = C12H24O12) minus the water molecule (C12H24O12 - H2O = C12H22O11).

The number of water molecules condensed out of the monosaccharides during a condensation polymerisation reaction is always one less than the number of monosaccharides present. :)
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on January 31, 2014, 04:22:00 pm
Oh that makes much more sense. Thanks heaps Stick and Oddly  :D
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 31, 2014, 06:47:50 pm
I actually had a few questions related to the law of thermodynamics -
can someone please explain it and how its relevant to the unit 3 course?
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 31, 2014, 06:55:24 pm
I actually had a few questions related to the law of thermodynamics -
can someone please explain it and how its relevant to the unit 3 course?

Well, a couple of things should be established before I (attempt to) give an answer :P

>There are 4 Laws of Thermodynamics
>You probably (read: Almost certainly) don't need to know them for the biology course (if you're doing physics on the other hand...)

The only application I can think of for any of the laws of thermodynamics is the 0th Law, which states that "If two systems are in thermal equilibrium with a third system, they must be in thermal equilibrium with each other" and the 1st Law: "Heat is a form of energy" (as per wiki). Unless some crazy changes have happened to the bio course in the past year, you don't need to know anything about entropy (so don't worry about laws 2 and 3).

Aside from 'heat is energy', which is pretty fundamental, the zeroth law has some applications in cellular transport mechanisms and biosynthesis of molecules ----> but again, this sort of thing is definitely beyond the course.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 31, 2014, 07:01:07 pm
Thank-you alondouek!
I also had another question --- can free energy also be referred to as potential energy?

Also, how is heat given off? It obviously isn't tangible so does the giving off of heat also involve it passing any membranes?

Thanks :)
Title: Re: VCE Biology Question Thread
Post by: alondouek on January 31, 2014, 07:17:45 pm
I also had another question --- can free energy also be referred to as potential energy?

Gibbs Free Energy $\Delta G$  is kinda/sorta a quantity of potential energy (called a thermodynamic potential). Potential energy itself is a measure of the stored energy of a system, and the $\Delta G$ is pretty much that (i.e. it's a measure of the "usable" energy of a thermodynamic system).

N.B. The only time I ever studied physics was for a first-year biophysics unit, so my knowledge may be a bit (understatement of the century) iffy. Anyone: Feel free to correct me where I'm wrong!

Also, how is heat given off? It obviously isn't tangible so does the giving off of heat also involve it passing any membranes?

The question "how is heat given off" is a little too general to answer directly. If you're talking about giving off heat on the individual person scale, then you'd be thinking about things like radiation, convection and evaporation (essentially, how our physical environment allows us to lose heat when needed).
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 31, 2014, 07:19:54 pm
Thanks alondouek!
I only just realised how stupid my question was :P
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on January 31, 2014, 08:30:38 pm

But can someone please explain the krebs cycle and the electron transport?
I understand glycolysis and fermentation but I'm confused about what happens in the aerobic pathway..
Title: Re: VCE Biology Question Thread
Post by: DJA on February 01, 2014, 06:01:38 pm

But can someone please explain the krebs cycle and the electron transport?
I understand glycolysis and fermentation but I'm confused about what happens in the aerobic pathway..

You could check out my visual representation on my post to this thread. Link below:
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 01, 2014, 06:16:48 pm
You could check out my visual representation on my post to this thread. Link below:

DJALogical is back!  :D
Yeah, that diagram really helped me before. It depicts all you need to know.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 01, 2014, 06:55:54 pm
You could check out my visual representation on my post to this thread. Link below:

A chemist would probably want to kill you for it, but that diagram is top notch. I may even use it this year!
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 01, 2014, 10:36:20 pm
Suggest why many globular proteins, in contrast to fibrous proteins, have a catalytic or regulatory role.

- I answered that since globular proteins are easily water soluble and most biochemical reactions occur in a watery medium, this quality (solubility) makes it ideal; in contrast to fibrous proteins.

Is this also a correct answer?; the other answer is that they have a catalytic/regulatory role because their structure (spherical tertiary shape) allows for an active site hence enabling it as ideal for a catalytic and regulatory role (such as in enzymes and hormones).

Is my first answer correct/acceptable for full marks or is the second one 'more' correct?

Cheers!!

Title: Re: VCE Biology Question Thread
Post by: psyxwar on February 01, 2014, 10:52:27 pm
Suggest why many globular proteins, in contrast to fibrous proteins, have a catalytic or regulatory role.

- I answered that since globular proteins are easily water soluble and most biochemical reactions occur in a watery medium, this quality (solubility) makes it ideal; in contrast to fibrous proteins.

Is this also a correct answer?; the other answer is that they have a catalytic/regulatory role because their structure (spherical tertiary shape) allows for an active site hence enabling it as ideal for a catalytic and regulatory role (such as in enzymes and hormones).

Is my first answer correct/acceptable for full marks or is the second one 'more' correct?

Cheers!!
I'm not sure if being water soluble is enough to justify their catalytic/ regulatory roles. You should definitely talk about structure (remember that proteins' function are dictated by their structure) and how it comes into play. The shape of globular proteins allows them to better interact with ligands, helping to facilliate a role in catalysis and regulation.

Just an FYI though, you don't need to know about fibrous/globular proteins anymore.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 01, 2014, 10:54:24 pm
Suggest why many globular proteins, in contrast to fibrous proteins, have a catalytic or regulatory role.

- I answered that since globular proteins are easily water soluble and most biochemical reactions occur in a watery medium, this quality (solubility) makes it ideal; in contrast to fibrous proteins.

Is this also a correct answer?; the other answer is that they have a catalytic/regulatory role because their structure (spherical tertiary shape) allows for an active site hence enabling it as ideal for a catalytic and regulatory role (such as in enzymes and hormones).

Is my first answer correct/acceptable for full marks or is the second one 'more' correct?

Cheers!!

This seems a bit full on for the Biology course.

I'm with psyxwar though. The most obvious answer is that for a protein to act as a catalyst it must have an active site. Fibrous proteins are flat and long, they're filamentary and therefore can't fulfill this requirement, whereas globular proteins are, well globular, and therefore can.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 01, 2014, 11:22:58 pm
I'm not sure if being water soluble is enough to justify their catalytic/ regulatory roles. You should definitely talk about structure (remember that proteins' function are dictated by their structure) and how it comes into play. The shape of globular proteins allows them to better interact with ligands, helping to facilliate a role in catalysis and regulation.

Just an FYI though, you don't need to know about fibrous/globular proteins anymore.

Thanks psyxwar! I just noticed I should've primarily referred to proteins specifically since enzymes and hormones are protein-based. Cheers!

This seems a bit full on for the Biology course.

I'm with psyxwar though. The most obvious answer is that for a protein to act as a catalyst it must have an active site. Fibrous proteins are flat and long, they're filamentary and therefore can't fulfill this requirement, whereas globular proteins are, well globular, and therefore can.

Cheers Mr. T-Rav!; yeah it was from a Biozone workbook - full of redundant material.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 02, 2014, 12:10:19 am
Cheers Mr. T-Rav!; yeah it was from a Biozone workbook - full of redundant material.

This is very true. Though, I must say that the question probably wasn't too unreasonable. It was along the lines of the thinking that the Biol course likes you to do. The key point to take home from it was that for a protein to be a hormone or an enzyme, it must have a specific and unique shape. Something that can't really be achieved by fibrous proteins :)
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 02, 2014, 09:45:24 am
For the various plant hormones eg auxin. Are we only meant to know a basic one sentence function of what it does??
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on February 02, 2014, 10:05:43 am
For the various plant hormones eg auxin. Are we only meant to know a basic one sentence function of what it does??

Yeah learn what the function of the plant hormone is. Questions on the exam will provide you with information of whether they are water/lipid-soluble, so you don't have to learn it in too much detail. The five plant hormones you need to know are:
• Auxins
• Gibberellins
• Cytokinins
• Ethylene
• Abscisic Acid
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 02, 2014, 10:26:04 am
alright, sure thanks. And one other thing looking at the TSFX Summer lecture notes they seem to have quite a few pages on plant hormones. Some of the ones i question we need to know are as follows- labeling the plant leaf, the opening and closing of stomata- talks about K+ ions moving across guard cells depending if day or night time, apical dominance, photoperiodism, seed dormancy, human uses of plant hormones. Are we required to know all of this stuff too. And also are we required to know about the various signalling and pheromones in animals eg visual signalling, sexual pheromones. thank you so much. - cause textbooks seem to make it brief, but TSFX goes on about 10 pages talking about it. Thanks again.
Title: Re: VCE Biology Question Thread
Post by: Stick on February 02, 2014, 11:02:57 am
* Labelling the plant leaf - it's a good idea to know its basic structure but it'd be unlikely that you'd have to label it during an assessment
* The opening and closing of stomata - not required
* Apical dominance - required
* Photoperiodism - required
* Seed dormancy - required
* Human uses of plant hormones - briefly required (mainly agricultural applications)
* Visual signalling - not required
* Sexual pheromones - required

However, you don't need to go into that much detail for all of this.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 02, 2014, 11:24:34 am
Okay thank you so much. So I just really need to like a 1 sentence of what are these things, and a 1 sentence of what they do/ purpose.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 02, 2014, 04:11:34 pm
According to my textbook, cell death and cell reproduction are balanced. Does this mean that cell's degenerate at the same rate as they reproduce?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 02, 2014, 05:52:37 pm
With regards to the Calvin cycle, do we need to know the comparison between C3 and C4 plants? What about PGAL?

NoB is such a comprehensive text is it not?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on February 02, 2014, 05:58:46 pm
With regards to the Calvin cycle, do we need to know the comparison between C3 and C4 plants? What about PGAL?

NoB is such a comprehensive text is it not?

You don't need to know the comparison between C3 and C4 Plants. You don't need to know about PGAL either. All you need to know (and you probably don't even need to know this), is that the Calvin Cycle takes place so that carbon can be reduced from its highly oxidised state as carbon dioxide, and the carbon skeleton then reacts with H+ ions (and oxygen), to synthesise glucose.

You really only need to know the inputs/outputs of the light-independent stage, and acknowledge that the Calvin Cycle takes place.
Title: Re: VCE Biology Question Thread
Post by: Stick on February 02, 2014, 06:07:08 pm
According to my textbook, cell death and cell reproduction are balanced. Does this mean that cell's degenerate at the same rate as they reproduce?

In a healthy organism, yes.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 02, 2014, 06:17:46 pm
Do we need to know anything on Chapter 4 of NoB? Most of it seems irrelevant.

I'll stop asking questions now :p
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 02, 2014, 06:19:30 pm
Do we need to know anything on Chapter 4 of NoB? Most of it seems irrelevant.

I'll stop asking questions now :p

If I'm not mistaken, Yacoubb had mentioned that the only thing you need to know from Ch4 is rational drug design.
Title: Re: VCE Biology Question Thread
Post by: Stick on February 02, 2014, 06:19:36 pm
I think the textbook puts enzyme inhibition in that chapter lol. You need to know that.

Rational drug design is no longer part of the course.
Title: Re: VCE Biology Question Thread
Post by: soli on February 02, 2014, 06:20:01 pm
can someone please give me a more detailed explanation as to why membranes are permeable to lipid-soluble molecules, but impermeable to water-soluble molecules?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 02, 2014, 06:26:54 pm
can someone please give me a more detailed explanation as to why membranes are permeable to lipid-soluble molecules, but impermeable to water-soluble molecules?

Membranes are composed of phospholipids which contain a glycerol attached to a phosphate head and two fatty acid tails. These fatty acid tails are hydrophobic non polar molecules that repel water as water is polar. Lipophilic substances can easily diffuse through the membrane however ions and polar substances require protein channels that are embedded in the membrane.
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on February 02, 2014, 06:29:36 pm
If I'm not mistaken, Yacoubb had mentioned that the only thing you need to know from Ch4 is rational drug design.

I said you didn't need to know anything from chapter 4 :)

can someone please give me a more detailed explanation as to why membranes are permeable to lipid-soluble molecules, but impermeable to water-soluble molecules?

The plasma membrane is made up primarily of a phospholipid bi-layer. The fatty acid tails are hydrophobic. Because of the like-nature of the bi-layer and the lipid-soluble molecules, the molecules are able to rapidly dissolve across the plasma membrane without the need of protein trans-membrane receptors. Because of the hydrophilic nature of water-soluble molecules, they are repelled by the membrane, and so cannot dissolve readily across the cell membrane, and need receptor proteins and secondary-messenger molecules to relay the message during signal transduction.

Title: Re: VCE Biology Question Thread
Post by: MM1 on February 02, 2014, 06:39:50 pm
The plasma membrane is made up primarily of a phospholipid bi-layer. The fatty acid tails are hydrophobic. Because of the like-nature of the bi-layer and the lipid-soluble molecules, the molecules are able to rapidly dissolve across the plasma membrane without the need of protein trans-membrane receptors. Because of the hydrophilic nature of water-soluble molecules, they are repelled by the membrane, and so cannot dissolve readily across the cell membrane, and need receptor proteins and secondary-messenger molecules to relay the message during signal transduction.

Just a quick [burning] question- Why aren't lipid molecules repelled by the hydrophilic phosphate head? How are they able to overcome this and readily diffuse through the bi-layer?? I'm guessing this has something to do with the uneven proportion of phosphate vs. fatty-tails :\ ??
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on February 02, 2014, 07:30:16 pm
Just a quick [burning] question- Why aren't lipid molecules repelled by the hydrophilic phosphate head? How are they able to overcome this and readily diffuse through the bi-layer?? I'm guessing this has something to do with the uneven proportion of phosphate vs. fatty-tails :\ ??
In the plasma membrane, phospholipid molecules do not actually "stay close" together, there are gaps between each molecule, therefore, substances that are SMALL and lipid-soluble should be able to move through those gaps and diffuse inside the cell.
Hope this helps!
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 02, 2014, 07:33:03 pm
In the plasma membrane, phospholipid molecules do not actually "stay close" together, there are gaps between each molecule, therefore, substances that are SMALL and lipid-soluble should be able to move through those gaps and diffuse inside the cell.
Hope this helps!

Ah YES! Finally it all makes sense; should've remembered about small substances! Thanks a million nhmn0301!! :D
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 03, 2014, 05:56:34 pm
Enzymes are also called 'organic cataylsts.' What is the meaning of this term?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 03, 2014, 06:03:46 pm
Enzymes are also called 'organic cataylsts.' What is the meaning of this term?
Basically, they speed up chemical reactions by lowering its activation energy (initial amount of energy required to kick start the reaction). ' Organic catalyst' is the same as 'biological catalyst', essentially.

I've got a question of my own:
Are active sites the same as bonding sites when referring to globular proteins (catalytic/regulatory) in general?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 03, 2014, 06:31:08 pm
Basically, they speed up chemical reactions by lowering its activation energy (initial amount of energy required to kick start the reaction). ' Organic catalyst' is the same as 'biological catalyst', essentially.

I've got a question of my own:
Are active sites the same as bonding sites when referring to globular proteins (catalytic/regulatory) in general?

Do you mean binding sites?
Active sites refer to the structure of the enzyme that fits the binding site of the substrate.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 03, 2014, 06:40:56 pm
Do you mean binding sites?
Active sites refer to the structure of the enzyme that fits the binding site of the substrate.
Yeah, okay.
What about receptor proteins which bind to hormones (for example). Could you say the hormone binds to the active site of the receptor protein, or is the term active site restricted to enzymes?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 03, 2014, 06:50:51 pm
Yeah, okay.
What about receptor proteins which bind to hormones (for example). Could you say the hormone binds to the active site of the receptor protein, or is the term active site restricted to enzymes?

I'm pretty sure active sites are applicable to receptor proteins however from my understanding, receptor proteins can detect hormones in two ways:
(i) The receptor protein binds to the hormone
(ii) The protein channel opens to allowing incoming signals such as neurotransmitters to come through

Someone please correct me if I'm wrong.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 03, 2014, 07:00:51 pm
What about receptor proteins which bind to hormones (for example). Could you say the hormone binds to the active site of the receptor protein, or is the term active site restricted to enzymes?

I'm pretty sure active sites are applicable to receptor proteins however from my understanding, receptor proteins can detect hormones in two ways:
(i) The receptor protein binds to the hormone
(ii) The protein channel opens to allowing incoming signals such as neurotransmitters to come through

Someone please correct me if I'm wrong.

I think nerdmmb is correct. The term active site is definitely not restricted to enzymes. Because of secondary and tertiary structures, proteins adopt specific shapes. The spot at which two molecules with specific shapes fit together to interact is called the active site. Also, an enzyme is a protein itself.

EDIT: Thanks for the correction psyxway.
Title: Re: VCE Biology Question Thread
Post by: psyxwar on February 03, 2014, 07:08:34 pm
I think nerdmmb is correct. And btw the term active site is definitely not restricted to enzymes. Because of secondary and tertiary structures, proteins adopt specific shapes. The spot at which two molecules with specific shapes fit together to interact is called the active site. Also, an enzyme is a protein itself.
I'm pretty sure the term "active site" is exclusive to enzymes.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 03, 2014, 08:08:23 pm
Does anyone have any notes regarding transcription and translation?
It would be awesome if someone could explain them to me  :D
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on February 03, 2014, 08:25:47 pm
I'm pretty sure active sites are applicable to receptor proteins however from my understanding, receptor proteins can detect hormones in two ways:
(i) The receptor protein binds to the hormone
(ii) The protein channel opens to allowing incoming signals such as neurotransmitters to come through

Someone please correct me if I'm wrong.

Say reception site, not active site!
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 03, 2014, 08:28:49 pm
Does anyone have any notes regarding transcription and translation?
It would be awesome if someone could explain them to me  :D

ATARnotes has a whole section dedicated to notes. It'll be worth checking this out: http://www.atarnotes.com/?p=notes
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on February 03, 2014, 08:39:07 pm
What part of the course are all of you up to so far? I think I should be studying ahead a bit more :/...
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 03, 2014, 08:43:54 pm
What part of the course are all of you up to so far? I think I should be studying ahead a bit more :/...

Still AOS1 :)
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 03, 2014, 09:12:05 pm
We have started protein synthesis- translation, transcription etc
But studying ahead is a great idea.  Go for it  ;)
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 03, 2014, 09:32:11 pm
Still AOS1 :)
Same here :)
I don't see much point in tackling AOS2 right at this time. I'd rather just consolidate what I already know and probably teach myself how to explain stuff better lol
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 03, 2014, 09:45:38 pm
Is the NEAP Biology Units 3&4 Questions Guide & Exam Guide worth it? I've heard it's erroneous in some areas?

Also, how are you guys collating your notes? Briefly or comprehensive?

Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 03, 2014, 09:53:20 pm
Well, my notes are often brief but informative. Pick out the main points (VCAA study guide should help) and revise it as much as you can till you get to the point where even one small word can trigger your memory.
I tried this for my Chemistry NEAP test and trust me... IT WORKS
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 03, 2014, 10:21:26 pm
I on the other hand did a shit tonne of notes and still do now. I know it's not an effective study technique, so if you can do something else, do it. For some reason, it's the only thing I can do consistently so if it works, it works. Importantly, you need to experiment with what you like and decide from there. No matter what suggestion you get, that'll never decide for you.
Title: Re: VCE Biology Question Thread
Post by: popoy111 on February 03, 2014, 10:27:30 pm
Why do cells such as those on the surface of a root expend energy to take up some substances?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 03, 2014, 10:33:39 pm
Why do cells such as those on the surface of a root expend energy to take up some substances?

I think you mean the protein receptors that are embedded in the cellular membranes.
They only expend energy when an ion needs to be taken against the concentration gradient.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 03, 2014, 10:37:38 pm
Why do cells such as those on the surface of a root expend energy to take up some substances?
Sometimes, a cell needs more of a substance than diffusion is capable of supplying. To overcome this, a cell may use active transport, which is against the concentration gradient and hence requires the input of energy.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 03, 2014, 11:06:56 pm
I think you mean the protein receptors that are embedded in the cellular membranes.
They only expend energy when an ion needs to be taken against the concentration gradient.

Not completely correct, but in the ball park.

The cellular environment is designed so that it can be different to the external environment. That's why the membrane is there; to create that difference. If diffusion alone set the cellular environment, it would be almost identical to its external environment and therefore having a cell would be redundant. Active transport is a way of setting up differences between the cell and external environment. This can be for a huge number of reasons, but normally it is used for what oddly suggested: because the cell needs extra stuff.
Title: Re: VCE Biology Question Thread
Post by: TimewaveZero on February 04, 2014, 08:33:32 pm
Just a question about cellular respiration...

During the Krebs Cycle, what acceptor molecules are produced?

I know FADH2 is produced, but I have two bio textbooks (Nature of Biology and Worlds within Worlds) the latter being from the 70's, but goes into a lot more detail than NoB. Now, Worlds within worlds suggests that 4 molecules of NADH2 is produced whereas nature of biology suggests 4 molecules of NADH is produced. What is correct?
Title: Re: VCE Biology Question Thread
Post by: alondouek on February 04, 2014, 08:39:55 pm
I would advise that you don't use any science textbook from the 70s; we've come a long way since then :P

The Kreb's Cycle outputs include:
- either 1x ATP or 1x GTP (depending on cell type)

I think you (or the authors) may have gotten confused between FADH2 (which is correct) and NADH2, which is a less common name for the output NADH/H+. We tend not to group the NADH and H+ together by calling them NADH2 because that would imply that the output is an NADH2 molecule, which isn't the case.
Title: Re: VCE Biology Question Thread
Post by: TimewaveZero on February 04, 2014, 08:44:24 pm
I would advise that you don't use any science textbook from the 70s; we've come a long way since then :P

The Kreb's Cycle outputs include:
- either 1x ATP or 1x GTP (depending on cell type)

I think you (or the authors) may have gotten confused between FADH2 (which is correct) and NADH2, which is a less common name for the output NADH/H+. We tend not to group the NADH and H+ together by calling them NADH2 because that would imply that the output is an NADH2 molecule, which isn't the case.

Ah I see, thankyou.

And yes, I am definitely not relying on my 70's textbook, I only use it to read over what I've read from my textbook, as it goes into more detail.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 04, 2014, 09:01:00 pm
Why aren't interleukins hormones?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 04, 2014, 09:10:47 pm
Why aren't interleukins hormones?

Hormones are long distance, interleukins aren't.
Title: Re: VCE Biology Question Thread
Post by: alondouek on February 04, 2014, 09:12:58 pm
Why aren't interleukins hormones?

Interleukins are a type of cytokine. Cytokines differ from hormones in that cytokines are secreted by a wide range of cellular origins, while true hormones are only secreted from specific glands. Truth be told though, the distinction is often tough to make as there is a strong overlap between the definitions of hormones and cytokines in relation to immune function.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 04, 2014, 09:32:05 pm
Interleukins are a type of cytokine. Cytokines differ from hormones in that cytokines are secreted by a wide range of cellular origins, while true hormones are only secreted from specific glands. Truth be told though, the distinction is often tough to make as there is a strong overlap between the definitions of hormones and cytokines in relation to immune function.

Biology is full of rubbish like that, hey? Because it's such an old science and has generated so much interest, so many of the different names for things overlap. Biologists spend half of their time arguing about what's what to be honest... hahah
Title: Re: VCE Biology Question Thread
Post by: alondouek on February 04, 2014, 09:36:17 pm
Biology is full of rubbish like that, hey? Because it's such an old science and has generated so much interest, so many of the different names for things overlap. Biologists spend half of their time arguing about what's what to be honest... hahah

It is a bit tedious (wait till you need to write a literature review and you're trying to figure out why different authors have like 10 different names for the same thing), but in the interests of the scientific method it's probably for the best. If different scientists have different ideas on a topic, then it opens door for better critical evaluation of that topic :)
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 04, 2014, 10:06:40 pm
...but I have two bio textbooks (Nature of Biology and Worlds within Worlds) the latter being from the 70's, but goes into a lot more detail than NoB.

Why would you use a 70's textbook in the first place? You do realise that the VCE Biology course has been toned down over the years, and even NoB probably has more detail than what's required according to the opinion of many on this forum.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 04, 2014, 10:08:08 pm
It is a bit tedious (wait till you need to write a literature review and you're trying to figure out why different authors have like 10 different names for the same thing), but in the interests of the scientific method it's probably for the best. If different scientists have different ideas on a topic, then it opens door for better critical evaluation of that topic :)

Different ideas yes, but when they have so much overlap and so many various systems and names for the same thing. It makes it quite a pain in the arse!
Yeah, not looking forward to literature reviews!
Title: Re: VCE Biology Question Thread
Post by: alondouek on February 04, 2014, 10:35:45 pm
Different ideas yes, but when they have so much overlap and so many various systems and names for the same thing. It makes it quite a pain in the arse!
Yeah, not looking forward to literature reviews!

Totally agree, this is why empiricism is so important (but dreadfully neglected). As for lit reviews, they're fine until you're going to publish one and then it's all redraft and redraft et cetera ad nauseum
Title: Re: VCE Biology Question Thread
Post by: TimewaveZero on February 05, 2014, 08:24:18 am
Why would you use a 70's textbook in the first place? You do realise that the VCE Biology course has been toned down over the years, and even NoB probably has more detail than what's required according to the opinion of many on this forum.

Because I'm the kind of person who A) Likes reading B) Feel like I need to know as much as I can about something regardless whether I have to or not C) the book was just sitting on the shelf so I thought I'd pick it up, and it actually does help clarify a few things, as it is set out like a book rather than a textbook
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 05, 2014, 12:33:24 pm
Totally agree, this is why empiricism is so important (but dreadfully neglected). As for lit reviews, they're fine until you're going to publish one and then it's all redraft and redraft et cetera ad nauseum

Biology is quite unique among the sciences for this. Well perhaps not unique, but when compared to Physics and Chemistry where at least what is known and established is referred to in the same way. It's a pain in the neck, they need to standardise!

Because I'm the kind of person who A) Likes reading B) Feel like I need to know as much as I can about something regardless whether I have to or not C) the book was just sitting on the shelf so I thought I'd pick it up, and it actually does help clarify a few things, as it is set out like a book rather than a textbook

These are all good reasons to look at it, though I wouldn't be using it to clarify imo. The book will be very largely incorrect as most of the biol course content is actually relatively new.
Title: Re: VCE Biology Question Thread
Post by: smile+energy on February 05, 2014, 04:16:16 pm
Hi, everyone
I am learning 3/4 this yr but I didn't do the 1/2. Now, I am struggling bio a bit, can anyone tell me what should I do to? And what I really to focus on? things like key terms, do I need to remember all of them back to the front? Thanks in advance :)
Title: Re: VCE Biology Question Thread
Post by: popoy111 on February 05, 2014, 08:02:05 pm
3. Explain why a functioning cell membrane is essential to maintain the integrity and survival of cells showing your understanding of the structure of the cell membrane.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 05, 2014, 08:45:20 pm
3. Explain why a functioning cell membrane is essential to maintain the integrity and survival of cells showing your understanding of the structure of the cell membrane.
The cell membrane is selectively permeable allowing it to import and export substances needed by the cell as necessary. The cell is compartmentalized by the cell membrane making it possible for membrane bound organelles to have different compositions and achieve metabolic efficiency. These compartments are important in making sure energy is conserved and used most efficiently inside the cell by preventing interference between different reaction pathways and enabling radically different reaction environments to be accommodated in organelles.
The cell membrane is composed of phospholipids with a hydrophilic phosphate head and hydrophobic lipid tails. This means the phosphate heads point into the cytosol and the lipid tails point towards each other (diagram might help in visualizing this). The steroid cholestrol is wedged between the phospholipid molecules of animal cells and is a fluidity buffer for the membrane by resisting changes in membrane fluidity that can result from changing temperature. This is fundamental in how some animals have evolved to cope with extreme temperatures. For example, Arctic Fish have a high proportion of unsaturated hydrocarbon (kinked) tails in their membrane enabling their membranes to stay fluid. If they had saturated hydrocarbon tails packed together, the membrane would be highly viscous and would solidify in the low temperatures of its habitat, meaning the cell would lack its functionality too.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 05, 2014, 09:42:08 pm
Can anyone explain transcription and translation in easy words?
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 05, 2014, 10:16:44 pm
Can anyone explain transcription and translation in easy words?
Transcription is the RNA production from a DNA template. It can occur in the nucleus, mitochondria or chloroplast in Eukaryotes. Base sequences in DNA (triplet codes) are copied onto an m-RNA molecule as codons.
Translation is when the base sequence in mRNA are used to produce an amino acid sequence of a polypeptide chain, which folds to become a protein.

Title: Re: VCE Biology Question Thread
Post by: alchemy on February 05, 2014, 11:06:37 pm
So I did a prac to identify how much water was taken up/lost by potato tuber cells. There were 5 test tubes with different concentrations of sucrose (0M,0.25M,0.5M,0.75M,1M); a small slice of potato was placed in each of them and left for 25 mins. When placed initially, all pieces of potato were at the bottom of the test tube. At around 8 mins, I noticed that the potato cell in the 0.75M and 1M solution begun to float. I'm assuming this is because water had left the cell from regions of low solute concentration to regions of high solute concentration and the density of the potato tuber cells in both these solutions became less than the density of water (lower mass to volume ratio).  However, at around 22 minutes, the cell in the 0.75M sucrose solution sunk to the bottom of the test tube. The only reason I can think of to explain this is that water flowed back into the now hypertonic cell, causing it to increase in mass and density. However, comparing the size of the potato tuber piece (1cm) and the volume of the test tube (20mL), this doesn't make sense. Can someone explain what would have really happened and also why the cell in the 1M solution did not ultimately sink as well?
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 05, 2014, 11:18:29 pm
Is StudyOn worth it? Does the online code come with the purchased book? Thanks.
Title: Re: VCE Biology Question Thread
Post by: alondouek on February 05, 2014, 11:56:41 pm
[snip] at around 22 minutes, the cell in the 0.75M sucrose solution sunk to the bottom of the test tube. The only reason I can think of to explain this is that water flowed back into the now hypertonic cell, causing it to increase in mass and density. However, comparing the size of the potato tuber piece (1cm) and the volume of the test tube (20mL), this doesn't make sense. Can someone explain what would have really happened and also why the cell in the 1M solution did not ultimately sink as well?

The best explanation that I can come up with - aside from experimental error, which is something you should seriously consider - is that there was an eventual net movement of H2O back into the plant cell sample. Let's try to rationalise this:

• Plant cell is placed in 0.75M solution.
• The solution is hypertonic to the cell, causing net movement of water OUT of the cell into the solution. The solution is now hypotonic to the cell.
• The net flow of water into the solution has diluted the solution to an extent that it is sufficiently hypotonic relative to the cell's tonicity that there is now net H2O movement back into the cell.

The issue here is that the plant cell and the solution did not reach an equilibrium, which would occur after a while unless the solute concentration of the solution is extremely high.

The fact that this net back-flow of H2O didn't happen with the 1M sample somewhat supports this theory, because even with the dilution of the solution by the cell's water content, the solution may still have been to hypertonic relative to the cells that no net H2O flow back into the cells can occur.

N.B. This is all conjecture given that I did not observe your lab practice and cannot readily reproduce the experiment (at home haha). As I mentioned above, consider how experimental error may have played a part here; perhaps the 0.75M solution was prepared incorrectly and was not, in fact, 0.75M?
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 06, 2014, 10:07:58 am
Hi, I was confused as to whether radioisotopes and radioactive isotopes are the same thing?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: alondouek on February 06, 2014, 10:10:19 am
Hi, I was confused as to whether radioisotopes and radioactive isotopes are the same thing?

Thanks!

Yep, they're the same! Scientists like to shorten, truncate and abbreviate wherever possible :P
Title: Re: VCE Biology Question Thread
Post by: aqple on February 06, 2014, 07:17:14 pm
Is StudyOn worth it? Does the online code come with the purchased book? Thanks.

Online code comes with the purchased book. It's just another resource of a lot of practice exam questions that are easily accessible, it's pretty convenient.
Title: Re: VCE Biology Question Thread
Post by: aqple on February 06, 2014, 07:21:29 pm
Hi, everyone
I am learning 3/4 this yr but I didn't do the 1/2. Now, I am struggling bio a bit, can anyone tell me what should I do to? And what I really to focus on? things like key terms, do I need to remember all of them back to the front? Thanks in advance :)

You don't need 1 & 2 to do well, just focus on what you are doing now in class. I'd recommend doing extra study outside of class, try to grasp the concepts in every chapter and definitely memorise key terms, write detailed summaries and if you are stuck on something, just ask your teacher or on this thread. Good luck :)
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 06, 2014, 09:08:25 pm
Online code comes with the purchased book. It's just another resource of a lot of practice exam questions that are easily accessible, it's pretty convenient.

StudyOn sounds like a gimmick at first, but I think it's quite worth it. I make sure to complete StudyOn questions before class as they tend to be easier than BioZone and Checkpoints.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 06, 2014, 09:22:31 pm
StudyOn sounds like a gimmick at first, but I think it's quite worth it. I make sure to complete StudyOn questions before class as they tend to be easier than BioZone and Checkpoints.
^
When I compare my answers to Biozone's it's just like gg
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 06, 2014, 09:28:41 pm
^
When I compare my answers to Biozone's it's just like gg

gg?

Title: Re: VCE Biology Question Thread
Post by: alchemy on February 06, 2014, 09:37:21 pm
^
When I compare my answers to Biozone's it's just like gg

OMG, I thought I was the only one. BioZone answers $>$ my answers, anyday.

gg?

Good Game.
Title: Re: VCE Biology Question Thread
Post by: Stick on February 06, 2014, 09:41:21 pm
I hated my Biozone. I barely even used it in Year 12. My resource of worship was in fact StudyOn. :P
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 06, 2014, 10:01:18 pm
Yep, they're the same! Scientists like to shorten, truncate and abbreviate wherever possible :P

Thanks!! :)
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 06, 2014, 10:58:18 pm
I hated my Biozone. I barely even used it in Year 12. My resource of worship was in fact StudyOn. :P

Are the majority of questions their own, or are there a lot of questions from VCAA?
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 06, 2014, 11:13:24 pm
Are the majority of questions their own, or are there a lot of questions from VCAA?
Majority are their own made questions, but there are a lot of VCAA ones as well.
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on February 07, 2014, 10:42:56 am
Do competitive inhibitors alter an enzyme's conformational structure?
Can non-competitive inhibitors be said to only affect the formation of enzyme-product complexes?
Is an understanding of enzyme kinetics necessary for VCE bio?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 07, 2014, 11:00:59 am
Do competitive inhibitors alter an enzyme's conformational structure?
Can non-competitive inhibitors be said to only affect the formation of enzyme-product complexes?
Is an understanding of enzyme kinetics necessary for VCE bio?

Yes
Hmmm not really. They alter the shape of the enzyme so yeah.
No
Title: Re: VCE Biology Question Thread
Post by: Stick on February 07, 2014, 11:01:53 am
Majority are their own made questions, but there are a lot of VCAA ones as well.

Are you sure? Most of the questions I did were VCAA questions, with only a handful being Jacaranda questions (and these questions were always of lower quality).
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 07, 2014, 11:35:16 am
How do cells maintain a constant pH?

The answer in my checkpoints book says it is because the cytosol of the cell acts as a buffer.
I was wondering if this was because of amino acids in the cytosol, that allowed the cytosol to act as a buffer?
Because I learnt that amino acids can act as buffers :)

Thanks!
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on February 07, 2014, 12:14:18 pm
Yes
Hmmm not really. They alter the shape of the enzyme so yeah.
No

How do competitive inhibitors affect enzyme shape? Something about the bonding I suppose? Please be as detailed as possible!
So, non-competitive inhibitors affect both enzyme-substrate complexes and enzyme-product complexes?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 07, 2014, 01:20:55 pm
How do competitive inhibitors affect enzyme shape? Something about the bonding I suppose? Please be as detailed as possible!
So, non-competitive inhibitors affect both enzyme-substrate complexes and enzyme-product complexes?
Competitive inhibitors bind themselves to the active site of an enzyme. They do not alter the shape as such, but more so block the substrate from binding to the enzyme.

Non competitive inhibitors alter the shape of the enzyme, effectively preventing enzyme-substrate complexes from forming.

Are you getting confused between the two terms?
Basically, competitive inhibitors 'compete' with the substrate for the active site, whereas non competitive inhibitors do not as they alter the conformational shape of the enzyme by attaching themselves to a region other than the active site.

Title: Re: VCE Biology Question Thread
Post by: MM1 on February 07, 2014, 05:59:05 pm
How are aggregates of triglycerides bonded to form a macromolecule? And how are they decomposed?
Also, can someone please explain the enzyme activation energy graph?
And can someone differentiate between acquired and induced immunity?

AND, in the event of a fever [in response to a parasite]; doesn't the increased temperature denature the proteins and enzymes?
Cheers :)
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 07, 2014, 06:28:46 pm
The enzyme activation energy graph suggests how with an enzyme much less energy is required to start up a metabolic reaction in comparison to without enzyme much more energy is required to initiate a chemical reaction.
Acquired immunity is the body itself producing antibodies on exposure to a particular antigen, but induced immunity is getting given antigens put into body via eg vaccination to make body produced antibodies. Correct me please.
And could someone explain if we need to know about the Brian, spinal cord, the different Neurohormones, and to want extent if so. Thanks
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 07, 2014, 07:01:06 pm
The enzyme activation energy graph suggests how with an enzyme much less energy is required to start up a metabolic reaction in comparison to without enzyme much more energy is required to initiate a chemical reaction.
Acquired immunity is the body itself producing antibodies on exposure to a particular antigen, but induced immunity is getting given antigens put into body via eg vaccination to make body produced antibodies. Correct me please.
And could someone explain if we need to know about the Brian, spinal cord, the different Neurohormones, and to want extent if so. Thanks

Thanks Chang!

I'm not sure. but I think we need to know:
The Brain (it's neurons{types), glands [pituitary] and their role.
The spinal cord in terms of it's neurons, role, [reflexes].
I think we need to know the general meaning of the term neurohormones and how they differ to general hormone and their role.

The Study Design doesn't really stipulate much about those topics; so again,I'm not sure.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 08, 2014, 12:14:11 am
Thanks.
Another question, does DNA ligase bind the phosphodiester of DNA when they are split into fragments. Do they bind any two strands of DNA that have complementary exposes nucleotides by establishing hydrogen binds. Or? Please explain, textbooks slightly confusing me saying slightly different things. Thanks.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 08, 2014, 12:59:38 am
Thanks.
Another question, does DNA ligase bind the phosphodiester of DNA when they are split into fragments. Do they bind any two strands of DNA that have complementary exposes nucleotides by establishing hydrogen binds. Or? Please explain, textbooks slightly confusing me saying slightly different things. Thanks.

First part is definitely right. What a DNA ligase does is catalyse the condensation reaction that forms the ester. So in that manner, they do, as you've rightly pointed out, join up fragments of DNA.
They don't however have anything to do with establishing hydrogen bonds. As it happens, intermolecular interactions don't need enzymes to function. So, those hydrogen bonds just restore themselves because it's the most stable configuration.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 08, 2014, 12:26:29 pm
why is the regulation of ions important for the normal function of muscle and nerve cells?
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 08, 2014, 12:38:49 pm
why is the regulation of ions important for the normal function of muscle and nerve cells?

Ions are important in regulating a concentration gradient to ensure normal functioning of muscle and nerve cells; Ions allow for muscle contraction and ions in nerve cells enable for an action potential to occur [nerve signal] to get the message across.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 08, 2014, 12:42:14 pm
How is an autoimmune disease allayed?
How does mRNA travel through the cytosol?

Thanks!!
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 08, 2014, 01:02:55 pm
How does mRNA travel through the cytosol?

Pretty sure you don't need to know this.
But if you're wondering how do mRNA travel to the ribosomes (part of their main role) , that's probably a nice thing to know but, again, not necessary. Well, the mRNA are floating in the cytoplasm and diffusing in all directions; the ribosomes are doing this too. When a mRNA and ribosome contact each other they interact and carry out their function. It's also good to know that everything in the cell that is not attached to something is floating around through diffusion.
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on February 08, 2014, 01:10:40 pm
Can competitive inhibitors and non-competitive inhibitors be both reversible and irreversible?
Do we need to differentiate between non-competitive and mixed inhibitors?

Any suggestions for additional resources on enzymes? My textbook is very lacking!

Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 08, 2014, 02:04:48 pm
Just like to clarify a few things pertaining to homeostasis.
Multicellular organisms maintain a relatively stable internal environment as they are stimulus-response mechanisms.

There are two types of stimulus-response mechanisms; negative feedback system and positive feedback system.

The negative feedback system includes the on/off mechanism and proportional control system.

I had a question, is the on/off mechanism and proportional control system only applicable to hormones?
My textbook is quite vague in explaining this.

Thank-you!
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 08, 2014, 02:32:03 pm
Can competitive inhibitors and non-competitive inhibitors be both reversible and irreversible?
Do we need to differentiate between non-competitive and mixed inhibitors?

Any suggestions for additional resources on enzymes? My textbook is very lacking!

What are competitive and non-competitive inhibitors? Answering this will bring you closer to the answer of your question. For all intents and purposes though, they are different axes (as illustrated in my really shitty diagram). I can draw/provide a diagram of the actual inhibitions of an enzyme if you think that'll help.

(http://i.imgur.com/vOE0hG9.png)

Once again apologies for my shitty drawing. I can't answer your second question, check the study design. As for resources, just have a good google around, there are many youtube videos on the subject. Perhaps check our the Khan academy youtube videos about biology.
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 08, 2014, 02:38:35 pm
Multicellular organisms maintain a relatively stable internal environment as they are stimulus-response mechanisms.

Organisms aren't stimulus response mechanisms :p. Not sure what you mean here.

I had a question, is the on/off mechanism and proportional control system only applicable to hormones?

Hormones contrasted against what? Drugs? Neural Signals? I think we need this before we can answer it. Neurons are obviously on or off, your arm is either moving or it isn't for instance, you either sense pain in your thigh or you don't. Could we get a definition of proportional control? Pending that, what i think you mean is that it isn't simply on or off/ it isn't black or white, it comes in shades. Hormones aren't the only things that operate in "shades". Neural impulses can be "graded" to do things like this but im not sure if its relevant to VCE, so can drugs.
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 08, 2014, 03:04:11 pm
I wound up drawing those diagrams. An inhibitor is competitive if it competes for the active site with another molecule. It's non-competitive if its action is at another site, in this diagram i drew an allosteric site (fairly sure you dont need to know what it is for VCE purposes).

(http://i.imgur.com/WUrDJNB.png)

(http://i.imgur.com/TgboNxM.png)

(http://i.imgur.com/rahqD9K.png)

(http://i.imgur.com/avMmsYa.png)
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 08, 2014, 03:47:44 pm
Can non-competitive inhibition be reversed? If so, by what means?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 08, 2014, 03:51:32 pm
I wound up drawing those diagrams. An inhibitor is competitive if it competes for the active site with another molecule. It's non-competitive if its action is at another site, in this diagram i drew an allosteric site (fairly sure you dont need to know what it is for VCE purposes).

(http://i.imgur.com/WUrDJNB.png)

(http://i.imgur.com/TgboNxM.png)

(http://i.imgur.com/rahqD9K.png)

(http://i.imgur.com/avMmsYa.png)

These diagrams want to make me cry, perfect  :'(
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 08, 2014, 03:53:06 pm
Can non-competitive inhibition be reversed? If so, by what means?

Would you like to perhaps share some of your own reasoning or thoughts first? They don't need to be right at all but its worth a shot!
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 08, 2014, 04:04:42 pm
Do all cells respond to neurotransmitters?

Also, can someone please explain whether neurotransmitters control the release of hormones?

I'm confused..
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 08, 2014, 04:18:14 pm
Would you like to perhaps share some of your own reasoning or thoughts first? They don't need to be right at all but its worth a shot!

Well from what I've read, both competitive and non-competitive inhibition is reversible. I know that competitive inhibition can be reversed by increasing the substrate concentration to eventually 'force' the competitive inhibitor to release it self from the active site. [Does it lose its avidity for the enzyme?]

However, I'm not sure how non-competitive inhibition is reversed? And even though it somehow may be reversed, does the enzyme retain it's conformation shape since it alters?

Title: Re: VCE Biology Question Thread
Post by: anon9884 on February 08, 2014, 04:22:46 pm
Is it important to know the structural differences between various types of lipids, carbohydrates and other biomolecules? For example, the structural differences between cellulose and starch?
I have a sac coming up and i'm unsure whether I should spend time on this area!  :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 08, 2014, 04:24:15 pm
Do all cells respond to neurotransmitters?

Also, can someone please explain whether neurotransmitters control the release of hormones?

I'm confused..

Neurotransmitters are only released by neurons. Therefore, only neurons respond to them.

Glands in the brain such as the hypothalamus and pituitary control the release of hormones.
The function of a neurotransmitter is to transmit signals from a neuron to a target cell across a synapse. From my understanding, they don't have anything to do with hormones.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 08, 2014, 04:33:44 pm
Is it important to know the structural differences between various types of lipids, carbohydrates and other biomolecules? For example, the structural differences between cellulose and starch?
I have a sac coming up and i'm unsure whether I should spend time on this area!  :)

Probably not that important, but I think it would be good to know. For example, take lipids. They take many forms - triglycerides, phospholipids, steroids, cholesterol. They all have a different composition which largely affects their function.
Some carbohydrates may be soluble (inulin) and others insoluble (cellulose and starch).

I think it would be beneficial to know how their different structure is related to their specific function.

Good-luck with your SAC- I'd recommend you encompass all areas of study to have a fuller understanding. :)
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 08, 2014, 04:36:02 pm
Do all cells respond to neurotransmitters?

Also, can someone please explain whether neurotransmitters control the release of hormones?

I'm confused..

What would make a cell respond to a neurotransmitter? What makes a cell respond to any signal (hormone, etc)?

Well from what I've read, both competitive and non-competitive inhibition is reversible. I know that competitive inhibition can be reversed by increasing the substrate concentration to eventually 'force' the competitive inhibitor to release it self from the active site. [Does it lose it's avidity for the enzyme?]

However, I'm not sure how non-competitive inhibition is reversed? And even though it somehow may be reversed, does the enzyme retain it's conformation shape since it alters?

You answered the question correctly there (at least in concepts, i wont judge it on it's execution). It still has affinity for the enzyme, it's just that theres so much substrate that its overwhelming the inhibitor. It makes more sense in terms of university level understanding of enzyme kinetics, it definitely becomes more intuitive but your understanding is basically correct there. If you're doing VCE Chemistry, they might briefly touch upon this kind of thing.

Non-competitive inhibition can be reversed via the same mechanism, i believe (i could be wrong, been awhile since ive done biochemistry). I'm not sure if this level of knowledge is required for VCE, it certainly wasn't required when i did it. The conformational shape may or may not change depending on several factors which are beyond the scope of VCE.

Neurotransmitters are only released by neurons. Therefore, only neurons respond to them.

Glands in the brain such as the hypothalamus and pituitary control the release of hormones.
The function of a neurotransmitter is to transmit signals from a neuron to a target cell across a synapse. From my understanding, they don't have anything to do with hormones.

This isn't 100% correct but i'm not sure what you need to know for this regarding VCE. The wording is a bit misleading as well. Whilst only neurons respond to neurotransmitters (true for VCE anyway), it's not that only neurons are doing things. The neurons attached to your leg muscle will be stimulated but as a result of that, your leg muscle responds to the signal and twitches.

Neurotransmitters and hormones are connected in a way that is probably beyond VCE. Neurotransmitters and hormones are similar in that they are both signalling mechanisms, they allow one part of the body or one cell to do another part of the body or another cell to do something.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 08, 2014, 04:48:21 pm
Neurotransmitters are only released by neurons. Therefore, only neurons respond to them.

Glands in the brain such as the hypothalamus and pituitary control the release of hormones.
The function of a neurotransmitter is to transmit signals from a neuron to a target cell across a synapse. From my understanding, they don't have anything to do with hormones.

Muscle cells can also respond to neurotransmitters. Some neurotransmitters function as hormones as well. I would assume that you do need to know this for year twelve as well I think.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 08, 2014, 05:11:35 pm
Thank-you :)
I was also wondering, do we need to know about diabetes?
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on February 08, 2014, 05:19:04 pm
Thank-you :)
I was also wondering, do we need to know about diabetes?

You don't need to know about diabetes. :)
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 08, 2014, 05:53:03 pm
Are all hormones made of proteins?
Title: Re: VCE Biology Question Thread
Post by: anon9884 on February 08, 2014, 05:53:41 pm
Probably not that important, but I think it would be good to know. For example, take lipids. They take many forms - triglycerides, phospholipids, steroids, cholesterol. They all have a different composition which largely affects their function.
Some carbohydrates may be soluble (inulin) and others insoluble (cellulose and starch).

I think it would be beneficial to know how their different structure is related to their specific function.

Good-luck with your SAC- I'd recommend you encompass all areas of study to have a fuller understanding. :)

Thank you so much for your help! I really appreciated it!  :)
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 08, 2014, 06:19:25 pm
Are all hormones made of proteins?

No. Some are steroid based: corticosteroids for example.
Some are amino acids: thyroxine for example.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 08, 2014, 09:59:01 pm
Do we have to know about the different types of microtubules/filaments and cell junctions?
Title: Re: VCE Biology Question Thread
Post by: popoy111 on February 08, 2014, 10:01:10 pm
List and explain the factors that affect the rate of diffusion of substances across membranes.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 08, 2014, 10:10:56 pm
Do we have to know about the different types of microtubules/filaments and cell junctions?
Apparently not MM1...

List and explain the factors that affect the rate of diffusion of substances across membranes.
Temperature - A greater temperature increases the kinetic energy of molecules allowing them to diffuse across the membrane faster.
Concentration gradient - A greater concentration gradient would mean solutes are naturally more inclined to travel from regions of their high concentration to regions of their low concentration
Surface Area - Membranes with more surface area allow more molecules to diffuse per unit of time.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 09, 2014, 12:51:02 am
Temperature - A greater temperature increases the kinetic energy of molecules allowing them to diffuse across the membrane faster.
Concentration gradient - A greater concentration gradient would mean solutes are naturally more inclined to travel from regions of their high concentration to regions of their low concentration
Surface Area - Membranes with more surface area allow more molecules to diffuse per unit of time.

Not to forget the nature of the substance itself, such as size and polarity as well as characteristics of the membrane as well.

Those very largely are what people want you to remember though, so you've definitely hit the right ones there.
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 09, 2014, 09:11:03 am
Do we have to know about the different types of microtubules/filaments and cell junctions?

I don't anticipate that'll come up in a VCE level, it's more of a second year uni thing.
Title: Re: VCE Biology Question Thread
Post by: Reus on February 09, 2014, 11:30:41 am
Brief points that need to be known (main components), before doing the membrane PRAC/SAC?
Thanks!
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on February 09, 2014, 11:40:14 am
What should we write to describe the process leading up and including the denaturation of an enzyme? Are there any particular terms that we should use?
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 09, 2014, 11:47:35 am
What should we write to describe the process leading up and including the denaturation of an enzyme? Are there any particular terms that we should use?

Have a go first and i'll tell you if you're correct.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 09, 2014, 11:56:54 am
How would you define a glycoprotein?

I always get glycolipids and glycoproteins confused :S
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 09, 2014, 12:03:56 pm
How would you define a glycoprotein?

I always get glycolipids and glycoproteins confused :S

Break down the words - glycolipids and glycoproteins

Hell, even remove the glyco bit for now. What do we wind up with? lipids and proteins. You probably know what those are, so, it wouldn't be too hard to tell the difference between a glycoprotein and a glycolipid. A definition can be found on the net or in the appendix of your book(s).
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 09, 2014, 03:59:24 pm
How would you define a glycoprotein?

I always get glycolipids and glycoproteins confused :S

For examples: Glycolipids can be found on the top or extracellular side of the plasma membrane. They are the least common of membrane proteins (~2%). Many integral proteins can be glycoproteins that span through the membrane.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 09, 2014, 04:10:28 pm
Break down the words - glycolipids and glycoproteins

Hell, even remove the glyco bit for now. What do we wind up with? lipids and proteins. You probably know what those are, so, it wouldn't be too hard to tell the difference between a glycoprotein and a glycolipid. A definition can be found on the net or in the appendix of your book(s).

Thanks! :)
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 09, 2014, 04:11:15 pm
For examples: Glycolipids can be found on the top or extracellular side of the plasma membrane. They are the least common of membrane proteins (~2%). Many integral proteins can be glycoproteins that span through the membrane.

Thankyou! :)
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 09, 2014, 04:21:03 pm
So how are bio sacs anyways.
Are they like normal tests?
Title: Re: VCE Biology Question Thread
Post by: Sup on February 09, 2014, 04:35:46 pm
So how are bio sacs anyways.
Are they like normal tests?
They differ from school to school. Some SACs may be prac based, where you have to perform a prac, then use your prac results to answer questions.
You may have to do a prac report for a SAC. Other SACs may be just tests which include interpreting info given to you, and other forms of SACs may pop up.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 09, 2014, 05:25:37 pm
What does the term 'systems biology' mean?
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 09, 2014, 07:07:58 pm
Can it be said that a membrane is an aggregate of lipids? Since lipids don't form polymers, rather they form aggregates, what are examples of these aggregates formed?
Thanks!
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on February 09, 2014, 07:12:17 pm
Can it be said that a membrane is an aggregate of lipids? Since lipids don't form polymers, rather they form aggregates, what are examples of these aggregates formed?
Thanks!

Yeah. The phospholipid bi-layer component of the plasma membrane is an aggregation of phospholipids (in a bi-layer form), with proteins and carbohydrates embedded into this aggregate.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 09, 2014, 09:47:41 pm
Sorry. Was reading through textbooks and there were some major differences between textbooks so not sure what we need to know. Help please.
How much do we need to know about vectors, and do we need to know the different ones for transferring genes. Which types of identification of genes do we need to know and how much, eg STRs, VNTRs, HVRs. And we are not required to know the different applications of biotechnology right?? Eg gene therapy. Thanks.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 09, 2014, 09:50:40 pm
Sorry. Was reading through textbooks and there were some major differences between textbooks so not sure what we need to know. Help please.
How much do we need to know about vectors, and do we need to know the different ones for transferring genes. Which types of identification of genes do we need to know and how much, eg STRs, VNTRs, HVRs. And we are not required to know the different applications of biotechnology right?? Eg gene therapy. Thanks.

Was wondering this too. I thought this got taken out of the study design  ???
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on February 09, 2014, 11:32:14 pm
Sorry. Was reading through textbooks and there were some major differences between textbooks so not sure what we need to know. Help please.
How much do we need to know about vectors, and do we need to know the different ones for transferring genes. Which types of identification of genes do we need to know and how much, eg STRs, VNTRs, HVRs. And we are not required to know the different applications of biotechnology right?? Eg gene therapy. Thanks.

All you need to know is:
- Plasmids are used in gene cloning as vectors
- Vectors (i.e. organisms that transfers disease from one organism to another without being infected).
- Retroviruses and Adenoviruses used in gene therapy
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 10, 2014, 09:52:29 am
What does the term 'systems biology' mean?

Not sure if thats in the course, where did you get that from? It might be because i'm getting old (ripe old age of 21) and they changed the study design significantly though.

Can it be said that a membrane is an aggregate of lipids? Since lipids don't form polymers, rather they form aggregates, what are examples of these aggregates formed?
Thanks!

Yes, they're just basically just collected there in one place. It's quite amazing how they spontaneously assemble, it's still one of the most miraculous things in biology for me. Sort of imagine a bunch of individual people forming a queue, it's a bit like that, they just happen to line up and collect due to their chemical properties. Also notice there's a lot going on, atoms never really stay still, they're always moving. It's the same with the lipid bilayer and parts of the cell as well.

Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 10, 2014, 05:04:01 pm
Okay then thanks. For vectors- I meant in the transferring of genes, like how we use bacteria to transfer genes upon building it for human.
I used Nelson biology and nature of biology for these information.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 10, 2014, 05:21:16 pm
Not sure if thats in the course, where did you get that from? It might be because i'm getting old (ripe old age of 21) and they changed the study design significantly though.

Yes, they're just basically just collected there in one place. It's quite amazing how they spontaneously assemble, it's still one of the most miraculous things in biology for me. Sort of imagine a bunch of individual people forming a queue, it's a bit like that, they just happen to line up and collect due to their chemical properties. Also notice there's a lot going on, atoms never really stay still, they're always moving. It's the same with the lipid bilayer and parts of the cell as well.

oh oops :S

Maybe it isnt in the study design, I was just confused because there was a question in my Nelson 3/4 Textbook asking what it means!

The paragraph in my book said: "The movement of molecules across membranes, the movement of molecules within
cells and cell interactions show how cells are systems. They represent systems biology
on a molecular scale."

:)

Title: Re: VCE Biology Question Thread
Post by: MM1 on February 10, 2014, 05:37:00 pm

oh oops :S

Maybe it isnt in the study design, I was just confused because there was a question in my Nelson 3/4 Textbook asking what it means!

The paragraph in my book said: "The movement of molecules across membranes, the movement of molecules within
cells and cell interactions show how cells are systems. They represent systems biology
on a molecular scale."

:)

Do you mean this:
Cells form tissues; tissues form organs; and organs work together to form systems (such as circulatory, digestive, etc) ?
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 10, 2014, 07:23:48 pm
Sorry. How do you differentiate and define exactly what glycoprotein and glycolipid are??
Also for those questions when there ask how does the structure relate to functions eg how does the structure of starch relate to its function? How much knowledge are we expected to know about it, and are we expected to know the structure of the different types of polymers for starch, glycogen, chitin, cellulose. Thanks.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 10, 2014, 07:30:24 pm
Sorry. How do you differentiate and define exactly what glycoprotein and glycolipid are??
Also for those questions when there ask how does the structure relate to functions eg how does the structure of starch relate to its function? How much knowledge are we expected to know about it, and are we expected to know the structure of the different types of polymers for starch, glycogen, chitin, cellulose. Thanks.

Glycoprotein
Glycolipid

A glycoprotein is a protein with a carbohydrate attached. A glycolipid is a lipid with a carbohydrate attached.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 10, 2014, 07:32:54 pm
Sorry. How do you differentiate and define exactly what glycoprotein and glycolipid are??
Also for those questions when there ask how does the structure relate to functions eg how does the structure of starch relate to its function? How much knowledge are we expected to know about it, and are we expected to know the structure of the different types of polymers for starch, glycogen, chitin, cellulose. Thanks.

Think of it this way. Glycolipid: is a carbohydrate attached to a phosphate head.

In contrast glycoprotein: is a carbohydrate attached to a protein channel embedded in the membrane.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 10, 2014, 07:59:14 pm
Sorry. How do you differentiate and define exactly what glycoprotein and glycolipid are??
Also for those questions when there ask how does the structure relate to functions eg how does the structure of starch relate to its function? How much knowledge are we expected to know about it, and are we expected to know the structure of the different types of polymers for starch, glycogen, chitin, cellulose. Thanks.

Glycoproteins are examples of conjugated proteins where a protein molecule is attached to a carbohydrate. Glyco refers to 'producing sugar' so that means carbohydrates.

I'm not entirely sure as to what we need know about structure (in terms of the alpha-1,6 bonds or etc) but in the case of starch I think they fact that it's made of highly branched monosaccharides makes it a good source of energy( it's function). [There are many glycosidic bonds which once broken exert energy for cell use].
Hope that somewhat helped!

Think of it this way. Glycolipid: is a carbohydrate attached to a phosphate head.

Do you mean: a glycolipid is a lipid molecule attached to a carbohydrate :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 10, 2014, 08:06:29 pm
I've also got another question - Facilitated diffusion: the diffusion of substances that occur through protein channels/carriers; does not expend energy.

In regards to protein carriers, [such as the Na+ K+ pump which is an example of facilitated diffusion?] how come this process is terms 'passive'? Doesn't it require energy in the form of ATP to alter the shape of the protein carrier? Or is it active transport?
Basically how does a carrier protein function and why is it classified under facilitated diffusion?

Thanks!!

Also can someone please explain dispersion forces and Van der waals interactions? Cheers!
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 10, 2014, 09:07:13 pm
I've also got another question - Facilitated diffusion: the diffusion of substances that occur through protein channels/carriers; does not expend energy.

In regards to protein carriers, [such as the Na+ K+ pump which is an example of facilitated diffusion?] how come this process is terms 'passive'? Doesn't it require energy in the form of ATP to alter the shape of the protein carrier? Or is it active transport?
Basically how does a carrier protein function and why is it classified under facilitated diffusion?

Thanks!!

Also can someone please explain dispersion forces and Van der waals interactions? Cheers!

Sodium/potassium pumps are active :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 10, 2014, 10:11:43 pm
Sodium/potassium pumps are active :)

So are carrier proteins used only in active transport? From what I know (which may be wrong), a carrier molecule to change its shape (to allow for another molecule to pass), it needs ATP to induce that change. So ...
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 10, 2014, 10:17:02 pm
So are carrier proteins used only in active transport? From what I know (which may be wrong), a carrier molecule to change its shape (to allow for another molecule to pass), it needs ATP to induce that change. So ...

You use carrier proteins in facilitated diffusion as well. They're a little bit different though. When something bumps into them, they kind of just suck it in, kind of like quick sand. Whereas ones that require ATP are more like a vacuum, they force stuff through even if there's no gradient.

So carrier proteins in facilitated diffusion use the gradient to get stuff through.
Carrier proteins in active transport use the gradient AND force stuff through.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 10, 2014, 11:11:20 pm
Does temperature affect how much CO2 is taken in and how much water is lost in photosynthesis?
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 10, 2014, 11:38:21 pm
Does temperature affect how much CO2 is taken in and how much water is lost in photosynthesis?

For water, I'm assuming yes because of transpiration??
Title: Re: VCE Biology Question Thread
Post by: eagles on February 11, 2014, 07:50:36 am
Just as carrier proteins change shape to accomadate the transport of substances in and out of the cell, can channel proteins also change shape? If so, can you specify in what instances?

Cheers!
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 11, 2014, 09:12:34 am
Just as carrier proteins change shape to accomadate the transport of substances in and out of the cell, can channel proteins also change shape? If so, can you specify in what instances?

Cheers!

In some respects. But not really. They're kind of like a real channel, fixed shape, but some have gates.
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 11, 2014, 12:05:53 pm
I'd think of channel proteins more as pipes really (yes the hard plastic ones under your sink). In-fact, the property that they rarely change shape is actually very important in their function in a way. You want channels only letting in what they are "designed" to let in and not everything.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 11, 2014, 06:31:23 pm
With regards to the inputs and outputs of cellular respiration/photosynthesis, are we required to know the specific number of each one (e.g. 2 x NAD)?
Title: Re: VCE Biology Question Thread
Post by: Stick on February 11, 2014, 06:54:27 pm
No, only the main reactants and products.
Title: Re: VCE Biology Question Thread
Post by: EFPBH on February 11, 2014, 07:23:27 pm
hello

whats a brief description of the two main pathways of signals that initiate apoptosis:

signals from inside the cell a cell- mitochondrial pathway
signals from outside the a cell- the death receptor pathway

thanks :)
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 11, 2014, 08:31:27 pm
hii,
Whats an accurate definition for enzyme denature that would be awarded full marks on the exam??
The image one is a definition to a question in the insight exam about denature exam. it seemed my own definition lack a bit of information to it and had more of other stuff, so i was just wondering what would be an specific one to answer on VCAA exams?
thanks.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 11, 2014, 09:18:30 pm
hii,
Whats an accurate definition for enzyme denature that would be awarded full marks on the exam??

The image you attached gives a sufficient explanation doesn't it? What exactly are you looking to incorporate in your definition?
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 11, 2014, 09:24:22 pm
hii,
Whats an accurate definition for enzyme denature that would be awarded full marks on the exam??
The image one is a definition to a question in the insight exam about denature exam. it seemed my own definition lack a bit of information to it and had more of other stuff, so i was just wondering what would be an specific one to answer on VCAA exams?
thanks.

Enzyme denaturing occurs when the enzymes is exposed to high temperature, more that it's optimum range which then cause the active site of the enzyme to change shape. This restricts the enzyme from performing any more reactions as no substrates can bind to it anymore. Someone pls correct me if I'm wrong. Just saying this from the top of my head. :)
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 11, 2014, 10:23:23 pm
My definition was something like enzyme denature is an organic catalyst which has its specific tertiary structure conformation shape altered, hence loses its ability to accommodate previous substrates and thus loses its function (guessing I need to also talk about hydrogen bonds braking due to heating, anything else) thanks
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 11, 2014, 11:11:12 pm
Enzyme denaturing occurs when the enzymes is exposed to high temperature, more that it's optimum range which then cause the active site of the enzyme to change shape. This restricts the enzyme from performing any more reactions as no substrates can bind to it anymore. Someone pls correct me if I'm wrong. Just saying this from the top of my head. :)

This sounds good, but I think you should mention how an enzyme denatures at high temperatures (H bonds breaking) as well somewhere in your response.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 11, 2014, 11:16:11 pm
Denaturation is when temperature or pH deviates from a predefined optimum level such that intermolecular bonding in the protein is disrupted, changing the 3-dimensional conformation of the protein. It is an irreversible process and results in a loss of function.

Important points that have been missed

-irreversible
-pH can do it as well
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 12, 2014, 01:10:36 pm
The things you need to know for VCE is that it's irreversible. When you scramble an egg, you denature the protein. You can't "unscramble" an egg, it is permanently like that. It's a great example to remember. That's the key concept they actually want you to remember in my humble opinion. AS T-Rav said, both heat and pH (less sensitive to this though) can do it. If you look at in terms of the lock and key model, you're essentially changing the shape of the lock. Imagine if i came to your house and changed every lock or the shape of your power points, nothing would work, the keys wouldn't go in and your plugs wouldn't go in, things just fall apart and fail to function.

Spoiler
Recent research has suggested denaturation might not be permanent in some cases and enzymes can partially "refold" and regain some functionality, in particular smaller ones. Not relevant for VCE though.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 12, 2014, 03:18:11 pm
This sounds good, but I think you should mention how an enzyme denatures at high temperatures (H bonds breaking) as well somewhere in your response.

Yeah, forgot to mention that. Thanks for correcting me before I made that mistake on any of my sacs, or worse on the exam  :D
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 12, 2014, 05:36:39 pm
Yeah, forgot to mention that. Thanks for correcting me before I made that mistake on any of my sacs, or worse on the exam  :D

No worries; I think that's what we're all here for. But I think you should use this:

Denaturation is when temperature or pH deviates from a predefined optimum level such that intermolecular bonding in the protein is disrupted, changing the 3-dimensional conformation of the protein. It is an irreversible process and results in a loss of function.

^That's really well defined :O If only I could define like that  :'(
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 12, 2014, 06:02:16 pm
Would endocytosis reduce the size of the plasma membrane of a cell?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: alondouek on February 12, 2014, 06:52:12 pm
Would endocytosis reduce the size of the plasma membrane of a cell?

Thanks!

Not by any measurable amount - vesicles from the plasma membrane are very small relative to the size of the cell
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 12, 2014, 07:54:43 pm
Sorry. What is the difference between condensation reaction and polymerisation? According to insight past paper the answer to question what is the name given to the process where monomers join to become macromolecules?? Thanks
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 12, 2014, 07:55:02 pm
Is polymerisation.
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on February 12, 2014, 08:05:37 pm
Sorry. What is the difference between condensation reaction and polymerisation? According to insight past paper the answer to question what is the name given to the process where monomers join to become macromolecules?? Thanks
A condensation reaction is one in which reactants combine real easing water with the product.
A polymerisation reaction is one in which monomers combine to form a polymer. ( I think this is the answer that you are looking for )
However, note that fats does not have a monomer, hence, polymerisation does not occur for this case, you have to read the question carefully.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 12, 2014, 08:14:08 pm
Not by any measurable amount - vesicles from the plasma membrane are very small relative to the size of the cell

Thankyou! :)
Title: Re: VCE Biology Question Thread
Post by: Frozone on February 12, 2014, 09:07:42 pm
What is an easier way or remembering the difference between endergonic and exogernic?
I really hope there is because I mix them up a lot.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 12, 2014, 09:13:48 pm
What is an easier way or remembering the difference between endergonic and exogernic?
I really hope there is because I mix them up a lot.

Personally whenever I think of exergonic I think of exert because energy is being 'exerted' or released. Hope this may help :P

Title: Re: VCE Biology Question Thread
Post by: alchemy on February 12, 2014, 09:15:21 pm
Sorry. What is the difference between condensation reaction and polymerisation? According to insight past paper the answer to question what is the name given to the process where monomers join to become macromolecules?? Thanks

Why you apologize?  :'(
A condensation reaction is a type of polymerization reaction. The two types of polymerization are 'addition' and 'condensation'. In addition polymerization monomers bond together without the loss of any atom or molecule. In condensation polymerization monomers bond together as well but a molecule, usually water, is lost during the process.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 12, 2014, 09:17:01 pm
What is an easier way or remembering the difference between endergonic and exogernic?
I really hope there is because I mix them up a lot.

I just link meanings of endergonic with anabolic and exergonic with catabolic. Apparently that can be more confusing though...  :-\
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 12, 2014, 09:58:34 pm
Okay. So condensation reaction is just molecules forming together to make a larger molecule realising water during the process. Polymerisation is specifically the joining of monomers together to form a polymer. And a condensation polymerisation is when specially monomers are joined together to form a polymer, but realising water too.
Then for hydrolysis reactions, is it just that. Or is there also hydrolysis polymerisation???
Thanks you so much
Title: Re: VCE Biology Question Thread
Post by: Stick on February 12, 2014, 10:37:17 pm
Hydrolysis involves the breaking of subunits, so no, you cannot build a polymer from monomers through hydrolysis (you can release monomers from a polymer though).
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 12, 2014, 10:38:07 pm
Okay. So condensation reaction is just molecules forming together to make a larger molecule realising water during the process. Polymerisation is specifically the joining of monomers together to form a polymer. And a condensation polymerisation is when specially monomers are joined together to form a polymer, but realising water too.
Then for hydrolysis reactions, is it just that. Or is there also hydrolysis polymerisation???
Thanks you so much

Condensation and condensation polymerisation are the same thing.
Title: Re: VCE Biology Question Thread
Post by: Stick on February 12, 2014, 10:42:08 pm
Not always, the formation of a triglyceride and the formation of a nucleotide from their respective subunits are not condensation polymerisation reactions - we aren't forming polymers from monomers.
Title: Re: VCE Biology Question Thread
Post by: Tyleralp1 on February 13, 2014, 06:07:26 pm
Hey all,

Just wondering, I was reading a practice Biology sac and came across a question which seemed to have had me in a knot. I don't recall what it said exactly, but essentially, a freshwater frog, is placed into salt water. It said the sodium ions move in the frog, and then the they are pumped out. It asks for us to explain how they get in and out?

Therefore, could someone please give me detailed answer to that? Also, I thought that solutes don't move into cells, only the water, so why in this case are the ions moving in? Doesn't the polar nature of the protein channels repel charged particles?

Is this a trick question.

Thanks :)
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 13, 2014, 06:17:16 pm
Perhaps the sodium ions are actively transported into the frog's cells o.o
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 13, 2014, 06:18:49 pm
Hey all,

Just wondering, I was reading a practice Biology sac and came across a question which seemed to have had me in a knot. I don't recall what it said exactly, but essentially, a freshwater frog, is placed into salt water. It said the sodium ions move in the frog, and then the they are pumped out. It asks for us to explain how they get in and out?

Therefore, could someone please give me detailed answer to that? Also, I thought that solutes don't move into cells, only the water, so why in this case are the ions moving in? Doesn't the polar nature of the protein channels repel charged particles?

Is this a trick question.

Thanks :)

So I might not be 100% correct here, but I've learnt that the protein pumps are actually part hydrophilic and part hydrophobic (so the area which is next to the phosphate heads is hydrophilic and the middle region is hydrophobic). Which therefore allows for transmission of charged particles such as ions through this pump. Hope this somewhat may help.

Some one please correct me if I'm wrong; cheers!
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 13, 2014, 06:54:56 pm
1. Do we need to know about trace elements?
2. Is it correct to say that animal cells, which lack cell walls, undergo lysis when placed in an aqueous solution due to the osmotic pressure that accumulates within the cell to enable the two mediums (cytoplasm and aqueous solution) to reach equilibrium?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on February 13, 2014, 07:35:14 pm
I'm not quite sure how to answer this question for H/W :/ :

When mountain climbers reach high altitudes the concentration of gas particles decreases. What affect would this have on the diffusion of carbon dioxide?

I'm assuming that the concentration of carbon dioxide expelled from the mountain climbers is high and therefore, the rate of diffusion of carbon dioxide will be rapid?
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 13, 2014, 07:44:05 pm
I'm not quite sure how to answer this question for H/W :/ :

When mountain climbers reach high altitudes the concentration of gas particles decreases. What affect would this have on the diffusion of carbon dioxide?

I'm assuming that the concentration of carbon dioxide expelled from the mountain climbers is high and therefore, the rate of diffusion of carbon dioxide will be rapid?

I think your answer is correct because since there is a large concentration gradient, diffusion will occur at a faster rate.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 13, 2014, 07:50:30 pm
1. Do we need to know about trace elements?
2. Is it correct to say that animal cells, which lack cell walls, undergo lysis when placed in an aqueous solution due to the osmotic pressure that accumulates within the cell to enable the two mediums (cytoplasm and aqueous solution) to reach equilibrium?

Thanks!
2. Animal cells generally undergo lysis (that is, they burst) when placed in a hypotonic solution as there is a net movement of water molecules from the region of higher water concentration - outside the cell - to the region of lower water concentration - inside the cell. This causes the cell to swell and eventually, if no regulatory mechanisms are in play, causes it to burst. I think it's important to note that osmosis will occur regardless of whether the cell is about to burst or not; so long as equilibrium has not been reached, water will continue to move into the cell. So you could probably deduce that the cell will burst before equilibrium is reached.

Edit: forgot to mention, animal cells lack both a cell wall and a large vacuole
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 13, 2014, 07:54:45 pm
2. Animal cells generally undergo lysis (that is, they burst) when placed in a hypotonic solution as there is a net movement of water molecules from the region of higher water concentration - outside the cell - to the region of lower water concentration - inside the cell. This causes the cell to swell and eventually, if no regulatory mechanisms are in play, causes it to burst. I think it's important to note that osmosis will occur regardless of whether the cell is about to burst or not; so long as equilibrium has not been reached, water will continue to move into the cell. So you could probably deduce that the cell will burst before equilibrium is reached.

Edit: forgot to mention, animal cells lack both a cell wall and a large vacuole
Thanks! Can you please explain what kinds of regulatory mechanisms prevent lysis? I never actually knew that..
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 13, 2014, 07:57:30 pm
Thanks! Can you please explain what regulatory mechanisms prevent lysis? I never actually knew that..

For example, most cells are packed closely together; they exert pressure on one another which prevents them from bursting.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 13, 2014, 08:03:46 pm
I was also wondering, does bipolar refer to chemical substances that possess both polar and non-polar properties such as alcohol?
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 13, 2014, 08:06:32 pm
I was also wondering, does bipolar refer to chemical substances that possess both polar and non-polar properties such as alcohol?

No and alcohol is polar.

Title: Re: VCE Biology Question Thread
Post by: MM1 on February 13, 2014, 08:09:09 pm
How do substances like detergent disrupt the bilayer?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 13, 2014, 08:19:22 pm
How do substances like detergent disrupt the bilayer?

Please quote me if I'm wrong but the phospholipid bilayer is primarily composed of phospholipids however it has large amounts of protein embedded in it. If you've washed dishes before, you may have noticed that once you add the detergent, the oils suddenly begin to evacuate as far as possible. Similarly, the polarity of detergents puts huge amounts of pressure onto the bilayer causing it to disintegrate - I'm guessing this happens because the phospholipids try to get away from the detergent and in the process, separate from one another. (especially since the bilayer has LOTS of protein channels/pumps which makes the job easier) it's also important to note that the phospholipids aren't actually stuck to together and are instead flexible.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 13, 2014, 08:27:06 pm
How is a breathalyser able to give an accurate indication of blood alcohol concentration?

Also, since blood cells don't have a nucleus, does this mean that they don't produce proteins?

And, can blood cells absorb the molecules that any other cell in the body can absorb such as alcohol?
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on February 13, 2014, 08:31:12 pm
Quote
Also, since blood cells don't have a nucleus, does this mean that they don't produce proteins?

Blood cells do actually have a nucleus at some point in lifetime - so I assume that they do produce proteins then, but because of the blood cells' function (to predominately carry oxygen ) they get rid of their nucleus as they become mature, in order to increase surface area which allows them to hold more haemolglobin (therefore carry more oxygen), and improve flexibility when passing through thin diameters such as capillaries.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 13, 2014, 08:34:29 pm
Please quote me if I'm wrong but the phospholipid bilayer is primarily composed of phospholipids however it has large amounts of protein embedded in it. If you've washed dishes before, you may have noticed that once you add the detergent, the oils suddenly begin to evacuate as far as possible. Similarly, the polarity of detergents puts huge amounts of pressure onto the bilayer causing it to disintegrate - I'm guessing this happens because the phospholipids try to get away from the detergent and in the process, separate from one another. (especially since the bilayer has LOTS of protein channels/pumps which makes the job easier) it's also important to note that the phospholipids aren't actually stuck to together and are instead flexible.

That's pretttttty much it, but not quite.

Detergent disrupts the phospholipid bilayer because it's made of lipids. So it's kind of like mixing coke with water, you'd expect them to just mix around. So it actually has the effect of diluting the bilayer. Because it doesn't have the same structural properties as bilayers, this means that wherever the detergent has mixed in (essentially) the bilayer won't be a layer anymore, instead, just free, happy phospholipids.
Title: Re: VCE Biology Question Thread
Post by: Tyleralp1 on February 13, 2014, 08:45:40 pm
If a fresh water frog is placed in salt water:

Is it right to say that sodium ions move via facilitated diffusion into the cell, causing the concentration of ions to increase in the cell. Then, in an attempt to combat this, the frog will actively pump out the ions.

OR

Due to the new hypertonic environment, the frog will loose water via osmoisis. As it does, the concentration of ions within it increases, causing a need to expel the ions, which is done via active transport?

If neither of these are correct, what would be correct in terms of what occurs via osmosis and with the sodium ions. THANKS :D
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on February 13, 2014, 08:57:06 pm
If a fresh water frog is placed in salt water:

Is it right to say that sodium ions move via facilitated diffusion into the cell, causing the concentration of ions to increase in the cell. Then, in an attempt to combat this, the frog will actively pump out the ions.

OR

Due to the new hypertonic environment, the frog will loose water via osmoisis. As it does, the concentration of ions within it increases, causing a need to expel the ions, which is done via active transport?

If neither of these are correct, what would be correct in terms of what occurs via osmosis and with the sodium ions. THANKS :D
If the frog is placed in salt water, the environment outside has a lower water concentration than the evironment inside the frog's cells. Hence, due to osmosis, the water will move from a high concentration of water, the frog's cells, to a region of low water concentration, salt water, to create an equilibrium effect. However, this would cause too much water leaving the cell and the frog will shrink/dehydrate and die.
Hope this helps.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 13, 2014, 08:59:10 pm
If a fresh water frog is placed in salt water:

Is it right to say that sodium ions move via facilitated diffusion into the cell, causing the concentration of ions to increase in the cell. Then, in an attempt to combat this, the frog will actively pump out the ions.

OR

Due to the new hypertonic environment, the frog will loose water via osmoisis. As it does, the concentration of ions within it increases, causing a need to expel the ions, which is done via active transport?

If neither of these are correct, what would be correct in terms of what occurs via osmosis and with the sodium ions. THANKS :D

If I'm not wrong, there will be a net movement of water molecules out of the frog since it is hypertonic to the surrounding medium. Cell's don't lose ions in a hypertonic solution, instead, they shrivel because water diffuses out of the cell via osmosis to enable the two solutions to reach equilibrium. If this is not regulated, the frog may die.

Title: Re: VCE Biology Question Thread
Post by: alchemy on February 13, 2014, 08:59:49 pm
If a fresh water frog is placed in salt water:

Is it right to say that sodium ions move via facilitated diffusion into the cell, causing the concentration of ions to increase in the cell. Then, in an attempt to combat this, the frog will actively pump out the ions.

OR

Due to the new hypertonic environment, the frog will loose water via osmoisis. As it does, the concentration of ions within it increases, causing a need to expel the ions, which is done via active transport?

If neither of these are correct, what would be correct in terms of what occurs via osmosis and with the sodium ions. THANKS :D

The net movement of fresh water will be going outside the cell. Some salt water does move inside, but this is minimal and I don't think active transport comes into play here; even if it did, the frog wouldn't survive for long. The frog would eventually dehydrate and die in these conditions. If it was a plant cell, however, it would develop a contractile vacuole in order to expel excess salt water.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 13, 2014, 09:02:35 pm
Also, I think you meant hypotonic :)

He means hypertonic, doesn't he?

Due to the new hypertonic environment, the frog will lose water via osmoisis...
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 13, 2014, 09:05:54 pm
He means hypertonic, doesn't he?

woops!! I'm SO sorry! lol
Title: Re: VCE Biology Question Thread
Post by: aqple on February 13, 2014, 09:10:09 pm
He means hypertonic, doesn't he?

Hypertonic environment as in the intracellular environment contains more solvent than solute relative to the salt water, the frog loses water and dies :(
Title: Re: VCE Biology Question Thread
Post by: Tyleralp1 on February 13, 2014, 10:25:41 pm
How do non-polar substances pass through the plasma membrane? I knot it's via diffusion, but does it occur as they are attracted to the phosphate head as they are non-polar, or are small enough to pass through the pores, and aren't repelled by the fatty acids as they too are non-polar?

Essentialy, how does non-polar substances get passed a negatively charged phosphate head?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 13, 2014, 10:27:07 pm
How do non-polar substances pass through the plasma membrane? I knot it's via diffusion, but does it occur as they are attracted to the phosphate head as they are non-polar, or are small enough to pass through the pores, and aren't repelled by the fatty acids as they too are non-polar?

Essentialy, how does non-polar substances get passed a negatively charged phosphate head?

You're right- there are pores in between the phospholipids so they can get through :)
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 13, 2014, 10:29:49 pm
How do non-polar substances pass through the plasma membrane? I knot it's via diffusion, but does it occur as they are attracted to the phosphate head as they are non-polar, or are small enough to pass through the pores, and aren't repelled by the fatty acids as they too are non-polar?

Essentialy, how does non-polar substances get passed a negatively charged phosphate head?

It moves around and breaks a bit, so they just slide through like it's water. Non-polar substances don't go through the gaps though, it's incorrect to say this :)
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 13, 2014, 10:39:41 pm
Essentialy, how does non-polar substances get passed a negatively charged phosphate head?

The only substances that can move across the membrane via 'simple diffusion' are lipid-soluble molecules such as steroids, or very small molecules, such as H2O, O2 and CO2. Larger molecules and lipid-insoluble molecules require the aid of a protein channel to move across the membrane.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 13, 2014, 10:59:50 pm
Just to make a few things clear for everyone (and if anybody does see some problems jump on them please, because it's been a little while).

As alchemy has mentioned, simple diffusion will involve small molecules or lipid soluble molecules. It's really important that you all understand this, but also understand why this is occurring. The plasma membrane is made of a phospholipid. Yes, this is an amphipathic molecule, but it probably is important to note that the major component is that lipid. The polar region is certainly much smaller. So, lipids can pass through by simple diffusion as well because it only needs to get past a pretty week polar barrier to make it into that nice, lipid environment.

Small molecules can get through because they're just that, they're small. The phospholipid bilayer can't pack in perfectly, and by virtue of the fact that the cell is at 37°C and not -273°C, the phospholipids will constantly move and jiggle around. For small molecules, they can just weave through, even if they are slightly charged. The effect of polarity isn't enough to knock them away either.

So the key points there:

-the effect of the phosphate heads' polarity will not be sufficient to deflect a lipid molecule; a phospholipid is a mainly non-polar molecule. The lipid will just barge through that tiny deflection.
-small molecules can get through for two reasons: there are tiny gaps because the packaging of phospholipids next to each other isn't perfect, and because the effect of polarity, likewise, isn't strong enough to knock them back.

Compare this last point with charged molecules. Whilst small, they bare a full charge, which would respond too much to the charge difference between itself and the phospholipid. The charge difference between an ion and a polar molecule is greater than the charge difference between two polar molecules. In this case, the difference will be great enough to keep the ions out.

The membrane is one of the most incredible things in Biology. Its design is absolutely perfect and its chemistry astounding. These systems that you're learning about, various types of transport across the membrane, reflect the complexity of its chemistry. That's why there's so much to learn, because you really are learning about an incredible structure.
Title: Re: VCE Biology Question Thread
Post by: Tyleralp1 on February 13, 2014, 11:17:47 pm
IS the polymer of monosaccharides: Polysaccharides or Carbohydrates.
Is the polymer of glcuose: polysachharides or Carbohydrates
Title: Re: VCE Biology Question Thread
Post by: alondouek on February 13, 2014, 11:20:23 pm
IS the polymer of monosaccharides: Polysaccharides or Carbohydrates.
Is the polymer of glcuose: polysachharides or Carbohydrates

1. Polysaccharides
2. Complex Carbohydrates/polysaccharides

Would you like me to explain why? :)
Title: Re: VCE Biology Question Thread
Post by: Tyleralp1 on February 13, 2014, 11:22:28 pm
That would be very helpful if you did :)

Btw,  thank you to all who helped answer my frantic pre sac questions Really apappreciate it :D
Title: Re: VCE Biology Question Thread
Post by: alondouek on February 13, 2014, 11:34:37 pm
That would be very helpful if you did :)

Btw,  thank you to all who helped answer my frantic pre sac questions Really apappreciate it :D

Monosaccharides are monomer saccharides units, such as glucose. The plural of 'mono' is 'poly', and polysaccharides are a general term for many monosaccharides joined together by glycosidic bonds. (Between the levels of 'monosaccharide' and 'polysaccharide', there is a stage called 'oligossccharides'. You probably don't need to know this for VCE, so heads up).

Using glucose as our model carbohydrate monomer unit:

- monosaccharide --> one glucose unit
- (oligosaccharide --> between 2-10 joined glucose units)
- polysaccharides --> more than 10 joined glucose units

Glucose is a specific monosaccharide; polysaccharides are the polymer units of monosaccharides, so the best definition of a polymer of glucose is a complex carbohydrate (such as starch), i.e. A polysaccharide.
Title: Re: VCE Biology Question Thread
Post by: Paulrus on February 14, 2014, 08:44:44 am
ok bear with me for a second cos this is probably a stupid question, but i'm not sure why my teacher marked this as wrong.
my reasoning was that the solution the cell has been placed in has a higher concentration of the solute (5%) than the inside of the cell (2%), making it a hypertonic solution. because the outside solution has a higher concentration of solute, i thought there would be net movement of water coming out of the cell in order to reach equilibrium. my teacher corrected it and drew an arrow going inwards and i'm not sure why.
what am i missing here? i have a sac on this later today and i'm feeling kinda panicked cos of this  :-\
Title: Re: VCE Biology Question Thread
Post by: MagicGecko on February 14, 2014, 10:40:49 am
mmhm osmosis is the net movement of water molecules across a semi-permeable membrane from a region of low concentration (high water concentration) to a region of high solute concentration (low water concentration). Knowing that, the water molecules would like you said, move out of the cell. So you're actually not missing anything, I'd say your teacher is wrong. Maybe he'she did this at midnight and wasn't thinking straight? Have you tried asking your teacher why he/she marked it as wrong?
Title: Re: VCE Biology Question Thread
Post by: popoy111 on February 14, 2014, 12:13:55 pm
I have both tsfx and neap notes from the summer school lectures which one should i use primarily and which one is better and why?
Title: Re: VCE Biology Question Thread
Post by: masonruc on February 14, 2014, 02:59:14 pm
I have both tsfx and neap notes from the summer school lectures which one should i use primarily and which one is better and why?

TSFX hands down!

-Notes reflect study design with tsfx, past experiences with neap is that they go way outside what is needed.
Title: Re: VCE Biology Question Thread
Post by: Paulrus on February 14, 2014, 05:58:42 pm
mmhm osmosis is the net movement of water molecules across a semi-permeable membrane from a region of low concentration (high water concentration) to a region of high solute concentration (low water concentration). Knowing that, the water molecules would like you said, move out of the cell. So you're actually not missing anything, I'd say your teacher is wrong. Maybe he'she did this at midnight and wasn't thinking straight? Have you tried asking your teacher why he/she marked it as wrong?

i asked her earlier today and she apologised and said she was half asleep while marking haha
i'm glad i wasn't wrong, but man that confused me  :P
Title: Re: VCE Biology Question Thread
Post by: KanMan on February 14, 2014, 09:33:33 pm
Hi everyone, I'm new to forum so I do apologise if I've accidentally responded in the wrong section.  :D
I was wondering if anyone could clarify to me  two questions.
1) What is the difference between proteoglycans and glycoproteins?
2) Are there amino acids which have roles other than in the formation of proteins?

Title: Re: VCE Biology Question Thread
Post by: alchemy on February 14, 2014, 10:00:23 pm
Hi everyone, I'm new to forum so I do apologise if I've accidentally responded in the wrong section.  :D
I was wondering if anyone could clarify to me  two questions.
1) What is the difference between proteoglycans and glycoproteins?
2) Are there amino acids which have roles other than in the formation of proteins?

1) Firstly, you don't have to know this. I don't think you ever would have in the past. Even if you did, VCAA have toned down their study design so much over the years that there's no point in hoping this will show up on your exam. But if you are inquiring from interest, that's cool. From wider reading, I recall proteoglycans to be a special class of glycoprotein. Also, glycoproteins are referred to as a type of protein but proteoglycans are more often referred to as a type of carbohydrate as they consist mostly of polysaccharide (~95%) in comparison to glycoproteins.
2) I had this question before but forgot to ask it here. Amino acids tend to stabilise pH by removing excess H+ or OH- ions. They can act as neurotransmitters, and are also available as dietary supplements.
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 15, 2014, 10:47:08 am
As alchemy said, both those are outside the study design and far outside VCE. They're more 2nd year biochemistry. Not sure where you got them but i'd use that less as a source in the future.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 15, 2014, 11:08:29 am
Can someone pleeease help me with this..

I get confused between independent and dependent variables.

Say in an osmosis experiment involving potato pieces in a salt water concentration,
what is the independent variable and what is the dependent variable?
Is it true to say that a controlled experiment can have many dependent variables but only one independent variable?

If I were to observe what would happen to potato pieces in three beakers (A, B and C). (Note beaker A contains dilute water, beaker B contains 2.5% salt and beaker C contains 5% salt), what would be a good hypothesis for this?

Thanks!!  ;D
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on February 15, 2014, 12:27:01 pm
Can someone pleeease help me with this..

I get confused between independent and dependent variables.

Say in an osmosis experiment involving potato pieces in a salt water concentration,
what is the independent variable and what is the dependent variable?
Is it true to say that a controlled experiment can have many dependent variables but only one independent variable?

If I were to observe what would happen to potato pieces in three beakers (A, B and C). (Note beaker A contains dilute water, beaker B contains 2.5% salt and beaker C contains 5% salt), what would be a good hypothesis for this?

Thanks!!  ;D
In an experiment, for eg the potato experiment, in order to get the diluted and concentrated solution, you must add salt to each beaker, hence, you can change the concentration of salt whatever you want, you can add more, you can add less, it's all up to you. Hence, we call the concentration of salt the INDEPENDENT VARIABLE. Since the external environment will determine the net movement of wAter in or out of the potatoes cells, we call the net movement of water the DEPENDENT VARIABLE since it is caused by the concentration of substrate outside. In practice, it is actually really hard to make sure that all the other variables constant and ONLY the independent and dependent variables that change,hence, we have to minimize as much as possible the changes in all other variables except independent and dependent variables.
A good hypothesis is all about making a measurable and observable hypothesis, you have to be specific about your quantities. Hypothesis is usually an " If....then..." statement.  Hence, my possible hypothesis for this is, " If the concentration of salt on the external environment changes in an addition of 2.5% then, there will be a net movement of water from the potato cells to the external environment (a hypertonic environment) by osmosis effect, hence, there will be a decrease in mass of the potato due to the loss of water content"
Hope this helps.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 15, 2014, 12:32:40 pm
Can someone pleeease help me with this..

I get confused between independent and dependent variables.

Say in an osmosis experiment involving potato pieces in a salt water concentration,
what is the independent variable and what is the dependent variable?
Is it true to say that a controlled experiment can have many dependent variables but only one independent variable?

If I were to observe what would happen to potato pieces in three beakers (A, B and C). (Note beaker A contains dilute water, beaker B contains 2.5% salt and beaker C contains 5% salt), what would be a good hypothesis for this?

Thanks!!  ;D

Hey, I had the same prac  :D

I mentioned that the independent variable was the salt concentration and the dependent variable was the mass of the potato tuber cells (if you used the 'weighing method'). Yes, there can be more than 1 dependent variable in an experiment but, for this experiment, you should only be investigating one DV. For example, in another experiment, if you were investigating the effect of catalase on hydrogen peroxide, the dependent variable could be the height of oxygen bubbles and/or the number of oxygen bubbles that formed when catalase was reacted with hydrogen peroxide. However, you will most likely only measure and compare the height of oxygen bubbles as it's much more difficult to count the number that form. So, my point is: even though there may be more than one DV, you only mention how many you tested (mostly likely 1 or 2). Also, it's important to know that the whole purpose of control variables is to know that your independent variables don't act in isolation (so you know that there isn't any other factor affecting them during the experiment).
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 15, 2014, 12:38:28 pm
Thanks heaps nhmn0301 and alchemy!

And do you know roughly how long schools give for students to write up their experimental reports? I have a sac coming up this week :(
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 15, 2014, 01:00:34 pm
Thanks heaps nhmn0301 and alchemy!

And do you know roughly how long schools give for students to write up their experimental reports? I have a sac coming up this week :(

We didn't have to write up a prac report; only answer questions regarding the prac. It was 45 mins for us.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 15, 2014, 05:10:35 pm
Just curious why does ADP have to add another free phosphate molecule before it can brake of the terminal phosphate to release energy. Why isn't ADP capable of also breaking of its terminal phosphate??
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 15, 2014, 05:18:56 pm
Just curious why does ADP have to add another free phosphate molecule before it can brake of the terminal phosphate to release energy. Why isn't ADP capable of also breaking of its terminal phosphate??

It technically could, and in some reactions it does. It's just that ATP is better set up to do it. I can't exactly explain why, because it'd require higher level chemistry than I'll ever know, but it'll have to do with ATP—>ADP just being an easier pathway to cycle through, and give the biggest energy yield as well. It's also probably because AMP is also a nucleotide, so ADP—>AMP levels wouldn't be able to regulated as well as ATP/ADP :)
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 15, 2014, 06:32:07 pm
Thanks. Sorry another question. Isn't it that only carrier protein can be used in active transport and not channel protein??  And for endocytosis can large, non-lipid soluble molecules pass through and why (cause isn't it still repelled by the lipid membrane of plasma membrane. Thanks- got confused with my knowledge when had a question regarding this.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 15, 2014, 06:36:35 pm
Thanks. Sorry another question. Isn't it that only carrier protein can be used in active transport and not channel protein??  And for endocytosis can large, non-lipid soluble molecules pass through and why (cause isn't it still repelled by the lipid membrane of plasma membrane. Thanks- got confused with my knowledge when had a question regarding this.

Yep, only carriers.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 15, 2014, 06:42:11 pm
Yep, only carriers.

Can carrier proteins also be used for passive carrier mediated transport for specific molecules?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 15, 2014, 06:54:12 pm
Can carrier proteins also be used for passive carrier mediated transport for specific molecules?

Carrier proteins play a role in facilitated diffusion, yep.
Title: Re: VCE Biology Question Thread
Post by: madhatter117 on February 15, 2014, 08:55:34 pm
Hey I was wondering if someone could answer my questions?
I was wondering if anyone could explain a simplified version of protein synthesis? The way my teacher has taught it really confused me...
Also is anyone able to explain/define signal transduction??
Thanks heaps! :)
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 15, 2014, 09:07:20 pm
Hey I was wondering if someone could answer my questions?
I was wondering if anyone could explain a simplified version of protein synthesis? The way my teacher has taught it really confused me...
Also is anyone able to explain/define signal transduction??
Thanks heaps! :)

RNA polymerase transcribes the template strand of a DNA molecule in the nucleus. mRNA takes this strand from the nucleus to the ribosome for translation. tRNA transports amino acids that corresponds with each 3 nitrogen bases on the mRNA strand. Once another tRNA approaches the ribosome, a peptide bond is formed between the amino acids. Once all the amino acids have been assembled (in other words, once the nitrogen bases have been translated), a stop codon is attached to stop any more amino acids from being assembled.
The ribosome then frees the mRNA stand which is broken down in the cytoplasm.
Ta-da you have a polypeptide chain :)

Note: the amino acids are found in the cytosol.

Please correct me if I'm wrong.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 15, 2014, 10:44:52 pm
RNA polymerase transcribes the template strand of a DNA molecule in the nucleus. mRNA takes this strand from the nucleus to the ribosome for translation. tRNA transports amino acids that corresponds with each 3 nitrogen bases on the mRNA strand. Once another tRNA approaches the ribosome, a peptide bond is formed between the amino acids. Once all the amino acids have been assembled (in other words, once the nitrogen bases have been translated), a stop codon is attached to stop any more amino acids from being assembled.
The ribosome then frees the mRNA stand which is broken down in the cytoplasm.
Ta-da you have a polypeptide chain :)

Note: the amino acids are found in the cytosol.

Please correct me if I'm wrong.

For someone in Unit 3, this is very good  :D
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 15, 2014, 11:42:29 pm
For someone in Unit 3, this is very good  :D

Thank-you :D
Title: Re: VCE Biology Question Thread
Post by: madhatter117 on February 16, 2014, 12:08:25 pm
RNA polymerase transcribes the template strand of a DNA molecule in the nucleus. mRNA takes this strand from the nucleus to the ribosome for translation. tRNA transports amino acids that corresponds with each 3 nitrogen bases on the mRNA strand. Once another tRNA approaches the ribosome, a peptide bond is formed between the amino acids. Once all the amino acids have been assembled (in other words, once the nitrogen bases have been translated), a stop codon is attached to stop any more amino acids from being assembled.
The ribosome then frees the mRNA stand which is broken down in the cytoplasm.
Ta-da you have a polypeptide chain :)

Note: the amino acids are found in the cytosol.

Please correct me if I'm wrong.

Thanks heaps!!  ;D
was also still wondering about a simplified term for signal transduction?
and what it is we have to know on the proteome and proteomics and conjugated proteins??  :P
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 16, 2014, 12:12:25 pm
Thanks heaps!!  ;D
was also still wondering about a simplified term for signal transduction?
and what it is we have to know on the proteome and proteomics and conjugated proteins??  :P

Not too sure about that, sorry :(
but you can watch this video http://www.youtube.com/watch?v=FtVb7r8aHco
Title: Re: VCE Biology Question Thread
Post by: Azula on February 16, 2014, 02:08:37 pm
Through which part, in particular, does water travel through the phospholipid bilayer? Simply in between the phospholipds?
Thanks
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 16, 2014, 02:28:58 pm
Through which part, in particular, does water travel through the phospholipid bilayer? Simply in between the phospholipds?
Thanks

Yes :) a cell membrane is porous allowing certain small polar molecules such as water to diffuse through. This is also known as simple diffusion.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 16, 2014, 02:48:06 pm
Can a hypothesis encompass more than 1 point? I have a SAC on movement across membranes [osmosis]; can my hypothesis be broad like: 'Water will diffuse from an area of low conc. to high. conc.' or should I also mention tonicity [hyper,hypo,iso] ?
Also for aim, do we have to talk about the effect of osmosis on X  or just investigating osmosis in X ?
And can a potato piece be referred to as a plant cell or should I refer to it as a piece of potato?

That depends entirely on your Prac. Be specific, but not overly specific. Also, don't mention too many points in your aim or hypothesis. I referred to the pieces of potato as potato tuber cells and plant cells at times (depends on the Prac though).

and what it is we have to know on the proteome and proteomics and conjugated proteins??

You need to know their definitions and worldly importance, I guess. The proteome refers to the entire array of proteins expressed by an organism. Proteomics is the study of the proteome and is important for a number of reasons; the mains ones being that proteins are interlinked and don't act in isolation. Proteomics is promising because it can tell us whether or not drugs tested in humans will have the same effect on animals. Conjugated proteins have a non-protein (prosthetic or non-amino) component in them. For example, haemoglobin contains the heme prosthetic group that contains iron. Other well known examples of conjugated proteins are lipoproteins, glycoproteins and phosphoproteins.
Title: Re: VCE Biology Question Thread
Post by: alondouek on February 16, 2014, 03:02:28 pm
Through which part, in particular, does water travel through the phospholipid bilayer? Simply in between the phospholipds?
Thanks

I don't know if this is part of the course, but the majority of water movement into and out of the cell is facilitated by specific membrane channels called aquaporins.

Some water does diffuse through the membrane, but it is incorrect with the current understanding of cell membrane structure to attribute water movement solely to simple diffusion.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 16, 2014, 03:30:51 pm
Q. If a leaf cell was placed in a solution of strong detergent which of the following would be observed?
A- Green colour would escape from the leaf.

Why is this?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 16, 2014, 03:38:40 pm
Q. If a leaf cell was placed in a solution of strong detergent which of the following would be observed?
A- Green colour would escape from the leaf.

Why is this?

Since detergent distintegrates the phospholipid membrane, the contents of the cell including the chloroplasts would escape.
Chloroplast is green therefore the solution would appear green.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 16, 2014, 03:39:57 pm
Q. If a leaf cell was placed in a solution of strong detergent which of the following would be observed?
A- Green colour would escape from the leaf.

Why is this?
It's probably because detergents are emulsifiers, in that they basically disrupt the structure of the plasma membrane (essentially allows the lipids and water to mix). Consequently, the chloroplast (green) would come out

Edit: beaten by nerdmmb
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 16, 2014, 03:44:20 pm
Yes, however not all plant cells contain chloroplasts? Or am I being over analytical here :P
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 16, 2014, 03:47:20 pm
Yes, however not all plant cells contain chloroplasts? Or am I being over analytical here :P

It's a leaf cell, which contains chloroplasts.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 16, 2014, 07:42:16 pm
Hey, just wondering when they ask relate the structure to the function of the specific thing eg relate the structure of glycogen to its specific function- how much are we required to know. Is simply saying its a branched polysaccharide that provide a carbohydrate energy storage sufficient??
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 16, 2014, 07:43:27 pm
And are we required to know specific examples of fibrous and globules protein eg keratin and their specific function
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 16, 2014, 07:47:09 pm
And are we required to know specific examples of fibrous and globules protein eg keratin and their specific function

Apparently it's been taken out of the study design [globular and fibrous proteins], but I think it'll be good to know a few examples :)
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 16, 2014, 08:13:17 pm
wait, so has the study design from last year changed?
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 16, 2014, 08:16:12 pm
wait, so has the study design from last year changed?

No, the current SD is from 2013-2016.
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on February 16, 2014, 08:42:14 pm
Hydrochloric acid denatures amylase due to it's high pH. This pH change therefore permanently distorts amylase's conformational shape due to the breaking of ionic bonds in the enzyme's tertiary structure. Amylase's active site is consequently destroyed and enzyme-substrate complexes will fail to form.

Does this cover Hydrochloric acid's effect on amylase entirely?
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 16, 2014, 08:54:48 pm
Hydrochloric acid denatures amylase due to it's high pH. This pH change therefore permanently distorts amylase's conformational shape due to the breaking of ionic bonds in the enzyme's tertiary structure. Amylase's active site is consequently destroyed and enzyme-substrate complexes will fail to form.

Does this cover Hydrochloric acid's effect on amylase entirely?

Yes, but it's not only the ionic bonds that break in the protein's (enzyme's) tertiary structure. When an enzyme is denatured, all its bonds are broken; this includes the hydrophobic interactions, that hold a protein's tertiary structure, and the covalent bonds that form between cysteine residues (disulphide bridges).  You don't have to mention all of this, obviously, but just don't restrict your explanation to the breakage of ionic bonds only.

EDIT: Thanks again T-Rav!
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 16, 2014, 08:56:56 pm
Apparently it's been taken out of the study design [globular and fibrous proteins], but I think it'll be good to know a few examples :)

I thought they were taken out too, but they cropped up on Checkpoints 2013... I'm still not sure why :C
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 16, 2014, 09:04:14 pm
Yes, but it's not only the ionic bonds that break in the protein's (enzyme's) tertiary structure. When an enzyme is denatured, all its bonds are broken; this includes the hydrophobic interactions, that hold a protein's tertiary structure, and the covalent bonds that form between cysteine residues (disulphide bridges).  You don't have to mention all of this, obviously, but just don't restrict your explanation to the breakage of ionic bonds only.

This is not always true, but in the ballpark. In most cases, disulphide bridges probably won't actually break. They're a covalent bond just like the peptide bonds, so they're actually quite strong.

Otherwise, you're actually right and the gist of what you're saying is completely correct.
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on February 16, 2014, 09:06:00 pm
Yes, but it's not only the ionic bonds that break in the protein's (enzyme's) tertiary structure. When an enzyme is denatured, all its bonds are broken; this includes the hydrophobic interactions, that hold a protein's tertiary structure, and the covalent bonds that form between cysteine residues (disulphide bridges).  You don't have to mention all of this, obviously, but just don't restrict your explanation to the breakage of ionic bonds only.

Thank you! It's just that my checkpoints book only specified that ionic bonds break in pH denaturing. So to clarify, when an enzyme becomes denatured, which bonds break? Checkpoints also wrote that only hydrogen bonds and Van Der Waals forces break in high temperature denaturation...is this right? Also, is pH denaturation reversible?
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 16, 2014, 09:12:43 pm
Thank you! It's just that my checkpoints book only specified that ionic bonds break in pH denaturing. So to clarify, when an enzyme becomes denatured, which bonds break? Checkpoints also wrote that only hydrogen bonds and Van Der Waals forces break in high temperature denaturation...is this right? Also, is pH denaturation reversible?

Yeah, Checkpoints answers are like that sometimes which goes to show that you probably won't lose marks for mentioning that.
Yes, only Hydrogen bonds and Van Der Waals forces break in high temp denaturation. As Mr.T-Rav mentioned above, covalent bonds aren't likely to break even at high temps or extreme pH levels.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 16, 2014, 09:32:36 pm
Thank you! It's just that my checkpoints book only specified that ionic bonds break in pH denaturing. So to clarify, when an enzyme becomes denatured, which bonds break? Checkpoints also wrote that only hydrogen bonds and Van Der Waals forces break in high temperature denaturation...is this right? Also, is pH denaturation reversible?
Thank you! It's just that my checkpoints book only specified that ionic bonds break in pH denaturing. So to clarify, when an enzyme becomes denatured, which bonds break? Checkpoints also wrote that only hydrogen bonds and Van Der Waals forces break in high temperature denaturation...is this right? Also, is pH denaturation reversible?

I'd love for someone to confirm, because perhaps I'm missing something, but I think Checkpoints is quite wrong here...
Title: Re: VCE Biology Question Thread
Post by: rery on February 16, 2014, 09:36:52 pm
I'd love for someone to confirm, because perhaps I'm missing something, but I think Checkpoints is quite wrong here...

From memory biology 3/4 resources often refer to ionic interactions as bonds
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 16, 2014, 09:44:27 pm
Thank you! It's just that my checkpoints book only specified that ionic bonds break in pH denaturing. So to clarify, when an enzyme becomes denatured, which bonds break? Checkpoints also wrote that only hydrogen bonds and Van Der Waals forces break in high temperature denaturation...is this right? Also, is pH denaturation reversible?

What CP edition and page is this question on?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 16, 2014, 09:48:39 pm
Is it actually necessary to mention the breaking of bonds when defining denaturation? Is it enough to say: denaturation is the process by which a protein permanently loses its conformational shape and hence its function, through a change in temperature or pH beyond that of its optimum level.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 16, 2014, 09:52:02 pm
Is it actually necessary to mention the breaking of bonds when defining denaturation? Is it enough to say: denaturation is the process by which a protein permanently loses its conformational shape and hence its function, through a change in temperature or pH beyond that of its optimum level.

I think you should mention the breakage of bonds because you've got to explain how it loses its conformational shape.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 16, 2014, 10:12:35 pm
Also about this. I just thought  then when enzymes are raised below or above temperatures (but not to the extent that it will denature), do bonds still break??? And if so how did they reform when temperate/ other deviation is returned to optimal temperature. If bonds don't break then how do enzymes lose their functions??  Thanks
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 16, 2014, 10:36:23 pm
Also about this. I just thought  then when enzymes are raised below or above temperatures (but not to the extent that it will denature), do bonds still break??? And if so how did they reform when temperate/ other deviation is returned to optimal temperature. If bonds don't break then how do enzymes lose their functions??  Thanks

Firstly, at low temperatures bonds don't break and the enzyme doesn't denature. Once an enzyme has denatured, it cannot return to its original shape. Bonds do break at high temperatures and at extreme pH's, and therefore the enzyme loses it's original function.
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on February 16, 2014, 10:47:45 pm
What CP edition and page is this question on?

2014 checkpoints page 177, question 2-22
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 16, 2014, 11:14:51 pm
2014 checkpoints page 177, question 2-22

Damn, I don't have that one.... But since they provided such a definition, all we can do is assume that it will be acceptable.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 16, 2014, 11:49:57 pm
Also about this. I just thought  then when enzymes are raised below or above temperatures (but not to the extent that it will denature), do bonds still break??? And if so how did they reform when temperate/ other deviation is returned to optimal temperature. If bonds don't break then how do enzymes lose their functions??  Thanks
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 17, 2014, 12:00:15 am
Also about this. I just thought  then when enzymes are raised below or above temperatures (but not to the extent that it will denature), do bonds still break??? And if so how did they reform when temperate/ other deviation is returned to optimal temperature. If bonds don't break then how do enzymes lose their functions??  Thanks

Enzymes only lose their conformational shape once they reach the critical temperature - the temperature above optimal temperature whereby bonds are broken and the enzyme therefore is unable to carry out its functions. Unless an enzyme is present to reverse the denatured enzyme's loss of tertiary structure, then the enzyme has been denatured permanently.

Enzymes can also be affected by fluctuating pH levels and chemical inhibition.
ln low temperatures, enzymes are not denatured however the speed at which they catalyse reactions are slowed down and when the temperature begins to increase so does the speed at which the enzyme catalyses the reaction.
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on February 17, 2014, 12:01:16 am
Also about this. I just thought  then when enzymes are raised below or above temperatures (but not to the extent that it will denature), do bonds still break??? And if so how did they reform when temperate/ other deviation is returned to optimal temperature. If bonds don't break then how do enzymes lose their functions??  Thanks

When enzymes are exposed to temperatures that are below their optimum, they become less effective and their reaction rate drops due to a loss of kinetic energy. This effect is completely reversible if heat is added. So no, bonds do not break when temperatures get cooler and thus enzyme structure does not change.

When temperatures surpass the optimum, the critical point is reached and enzyme's begin to denature due to bonds breaking (Van der Waal forces and hydrogen bonds<---according to Checkpoints 2014). Denaturing enzymes cannot be resurrected (without enzyme assistance); their conformational shape is permanently distorted due to changes made to their tertiary and quaternary structures. So just say that you heated up a solution of amylase and starch to 80 degrees celsius and then returned it to 37 degrees celsius. No catabolic reaction will be observed because the intense heat would have denatured the enzyme.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 17, 2014, 12:20:54 am
It's worthwhile noting that an enzyme does not denature the second it goes above its optimal temperature. It just means that the substrate(s) have too much kinetic energy sometimes and therefore they can't associate as well with the active site of the enzyme.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 17, 2014, 04:16:32 pm
Enzymes only lose their conformational shape once they reach the critical temperature - the temperature above optimal temperature whereby bonds are broken and the enzyme therefore is unable to carry out its functions.

When temperatures surpass the optimum, the critical point is reached and enzyme's begin to denature...

So just to confirm, these two statements aren't exactly accurate, right? The critical temperature and the point just after the optimal temperature peak are two different things? What about the effect of pH; are enzymes denatured right after the optimum peak?

Unless an enzyme is present to reverse the denatured enzyme's loss of tertiary structure, then the enzyme has been denatured permanently.

Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on February 17, 2014, 05:18:43 pm
Strictly speaking, how come other enzymes come and reverse the denaturation process? Even though it seems like the only solution, however, if an enzyme reaches its critical temperature, others enzymes will get denatured as well. Hence, there's no way we can reverse the process. Please correct me if I'm wrong.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 17, 2014, 05:38:28 pm
Just wondering what exactly starts an inflammation. I know that serotonin stimulates vasodilation so more blood comes to infected site, hence phagocytes. But what causes serotonin to do this? Thanks
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 17, 2014, 06:52:39 pm
Has anybody done the osmosis sac?
If yes, what did it involve?
Our school is doing the osmosis prac on potatoes being placed in different solutions, so anyone done that?
Title: Re: VCE Biology Question Thread
Post by: masonruc on February 17, 2014, 08:00:38 pm
Has anybody done the osmosis sac?
If yes, what did it involve?
Our school is doing the osmosis prac on potatoes being placed in different solutions, so anyone done that?

Did that last year, from my memory you place the potatoes in different concentrated solutions so depending on what beaker the potato chunks are placed in they will either weigh less or more than prior to being placed in the solution. I think I used water for my control rather than the solutions (varied concentrations of salt) my teacher had made up.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 17, 2014, 08:05:34 pm
What's a really good hypothesis for the potato sac? In just one line preferably? Cheers.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 17, 2014, 08:06:57 pm
Did that last year, from my memory you place the potatoes in different concentrated solutions so depending on what beaker the potato chunks are placed in they will either weigh less or more than prior to being placed in the solution. I think I used water for my control rather than the solutions (varied concentrations of salt) my teacher had made up.

Thanks. Did u have to do a write up part of the sac as well?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 17, 2014, 08:20:01 pm
What's a really good hypothesis for the potato sac? In just one line preferably? Cheers.

Mine will probably be along the lines of: The potato cylinders placed in the NaCl solutions will lose water and hence mass by osmosis, as they are hypotonic to the solutions. The potato cylinders placed in water will gain water and hence mass by osmosis, as they are hypertonic to the water.

Someone please correct me if I'm wrong.
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on February 17, 2014, 08:21:54 pm
What's a really good hypothesis for the potato sac? In just one line preferably? Cheers.
You can find more information on page 42 of this thread, others have previously discussed it as well.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 17, 2014, 09:07:40 pm
Also were do observations go in a scientific write up? In the discussion or results? Or do the results only contain graphs, etc?

Usually you'd present it as a graph/table in the results, and then you'd explain the underlying concepts pertaining to your results in the discussion.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 17, 2014, 09:12:01 pm
Usually you'd present it as a graph/table in the results, and then you'd explain the underlying concepts pertaining to your results in the discussion.

Do you mean as in explain the results obtained in more detail?

Does anyone know if there's a word limit to the discussion or conclusion ?
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on February 17, 2014, 09:20:03 pm
Does anyone know if there's a word limit to the discussion or conclusion ?
I'm pretty sure that there would not be, but conclusions are generally concise as they basically answer the aim of the experiment.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 17, 2014, 09:20:48 pm
Do you mean as in explain the results obtained in more detail?

Does anyone know if there's a word limit to the discussion or conclusion ?

Yes.

Haha, no word limit unless the teacher specifies one :p
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 17, 2014, 10:35:03 pm
How can consuming too much protein affect the body? I trying googling this but it only came up with fitness links -_-
Title: Re: VCE Biology Question Thread
Post by: Frozone on February 17, 2014, 10:50:13 pm
What is the role of the cell membrane?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 17, 2014, 10:59:35 pm
What is the role of the cell membrane?

The plasma membrane plays an integral role in the regulation of inputs and outputs in the cell, is involved in intercellular recognition and communication, encloses the contents within a cell and also protects a cell from its immediate environment.
Title: Re: VCE Biology Question Thread
Post by: Scooby on February 17, 2014, 11:23:38 pm
How can consuming too much protein affect the body? I trying googling this but it only came up with fitness links -_-

Quote
When a high dietary protein intake is consumed, there is an increase in urea excretion, which suggests that amino acid oxidation is increased. High levels of protein intake increase the activity of branched-chain ketoacid dehydrogenase. As a result, oxidation is facilitated, and the amino group of the amino acid is excreted to the liver. This process suggests that excess protein consumption results in protein oxidation and that the protein is excreted. The body is unable to store excess protein. Protein is digested into amino acids, which enter the bloodstream. Excess amino acids are converted to other usable molecules by the liver in a process called deamination. Deamination converts nitrogen from the amino acid into ammonia, which is converted by the liver into urea in the urea cycle. Excretion of urea is performed by the kidneys. These organs can normally cope with any extra workload, but, if kidney disease occurs, a decrease in protein will often be prescribed. When there is excess protein intake, amino acids can be converted to glucose or ketones, in addition to being oxidized for fuel. When food protein intake is periodically high or low, the body tries to keep protein levels at an equilibrium by using the "labile protein reserve", which serves as a short-term protein store to be used for emergencies or daily variations in protein intake. However, that reserve is not utilized as longer-term storage for future needs.
Many researchers have also found that excessive intake of protein increases calcium excretion in urine. It has been thought that this occurs to maintain the pH imbalance from the oxidation of sulfur amino acids. Also, it is inconclusive whether bone resorption contributes to bone loss and osteoporosis. However, it is also found that a regular intake of calcium would be able to stabilize this loss.
Another issue arising from over-consumption of protein is a higher risk of kidney stone formation from calcium in the renal circulatory system. It has been found that high animal protein intake in healthy individuals increases the probability of forming kidney stones by 250 percent.
An epidemiological study from 2006 has found no relationship between total protein intake and blood pressure; it did, however, find an inverse relationship between vegetable protein intake and blood pressure.

Definitely not something you need to know  :P
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 18, 2014, 06:57:05 pm

If an experimental report asks us to write a variable in the experiment but doesn't specify whether we should write independent or dependent variable, then what should we write?

Also, if we repeat the experiment, do we mention it in the discussion? If so, how? is it acceptable to say that the experiment was repeated?
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 18, 2014, 07:14:16 pm

If an experimental report asks us to write a variable in the experiment but doesn't specify whether we should write independent or dependent variable, then what should we write?

Also, if we repeat the experiment, do we mention it in the discussion? If so, how? is it acceptable to say that the experiment was repeated?

I would mention both the independent and dependent variables, but usually reports aren't that vague to not specify the variable they wanted you to describe...
Yes, you would mention if you repeated the experiment in the discussion. You must also say why the experiment was repeated. The most obvious reason is to reduce experimental error.
Title: Re: VCE Biology Question Thread
Post by: eagles on February 18, 2014, 07:15:47 pm
Do both DNA and RNA contain the elements, carbon, hydrogen, oxygen, nitrogen and phosphorus?

Thanks.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 18, 2014, 07:33:20 pm
Do both DNA and RNA contain the elements, carbon, hydrogen, oxygen, nitrogen and phosphorus?

Thanks.

Yes :) They're both nucleic acids and all nucleic acids contain carbon, hydrogen, oxygen, nitrogen and phosphorus.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 18, 2014, 09:07:16 pm
Can liquid brought out of a cell by exocytosis also be referred to as pinocytosis or is this term only restricted to endocytosis?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 18, 2014, 09:11:41 pm
I think it's restricted to endocytosis.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 18, 2014, 09:23:28 pm
So what would we refer to liquid that's brought out of a cell?
Simply exocytosis?
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 18, 2014, 09:27:51 pm
Do both DNA and RNA contain the elements, carbon, hydrogen, oxygen, nitrogen and phosphorus?

Yes :) They're both nucleic acids and all nucleic acids contain carbon, hydrogen, oxygen, nitrogen and phosphorus.

They don't *always* contain phosphorous.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 18, 2014, 09:32:35 pm
They don't *always* contain phosphorous.

What makes you say that?
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 18, 2014, 09:43:20 pm
What makes you say that?

OH, SORRY! I thought you guys were referring to proteins! LOL.
Ignore what I said :-X
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 18, 2014, 09:44:31 pm
OH, SORRY! I thought you guys were referring to proteins! LOL.
Ignore what I said :-X

Lol That's okay :)
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on February 19, 2014, 12:23:15 am
Which cells in a plant leaf don't photosynthesise? I remember coming across this question in a Neap practice exam.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 19, 2014, 12:49:15 am
Which cells in a plant leaf don't photosynthesise? I remember coming across this question in a Neap practice exam.

Not something that you need to know at all.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 20, 2014, 12:05:39 am
How are people going about memorising all the specific definitions and terminology, not sure if I'm using way too much time to memorise it and only getting a short amount memorised in a long time. Tips please?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 20, 2014, 12:11:57 am
How are people going about memorising all the specific definitions and terminology, not sure if I'm using way too much time to memorise it and only getting a short amount memorised in a long time. Tips please?

Doing lots of questions, trying to answer questions on forums like this, reading of your textbook and other literature are the best ways to remember definitions. Personally, I never had a definitive structure and I managed. Also trying to remember key points and key elements of definitions. So for example

Diffusion is a passive transport process whereby molecules move from an area of high concentration to an area of low concentration until reaching equilibrium.

So the bolded points are the two really key points there.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 20, 2014, 04:14:55 pm
Okay thanks. So far I have this been re-writing on a whiteboard to Memorise definition not sure best method but yeah. Oh also about the definition of diffusion- could I substitute the from an area if low concentration to area if high concentration with down the concentration gradient, or would that not own me a mark
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 20, 2014, 04:45:22 pm
Okay thanks. So far I have this been re-writing on a whiteboard to Memorise definition not sure best method but yeah. Oh also about the definition of diffusion- could I substitute the from an area if low concentration to area if high concentration with down the concentration gradient, or would that not own me a mark

It is best if you include both the aspects. Maybe something like "Diffusion is the transport of molecules from an area of high concentration to an area of low concentration. Thus, the molecules move down a concentration gradient and expend no energy"
How does that sound? Pls give your opinions
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 20, 2014, 04:57:08 pm
It is best if you include both the aspects. Maybe something like "Diffusion is the transport of molecules from an area of high concentration to an area of low concentration. Thus, the molecules move down a concentration gradient and expend no energy"
How does that sound? Pls give your opinions

I agree.
And your definition is good :) However, I would probably try to condense it into one sentence; perhaps: 'Diffusion is the passive net movement of particles from an area of high concentration to an area of low concentration, along a concentration gradient.'

Btw passive indicates that no energy was expended.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 20, 2014, 07:55:07 pm
Perfect. I agree with MM1.
Short and sweet
Title: Re: VCE Biology Question Thread
Post by: Blurple on February 20, 2014, 08:20:27 pm
Ive got my SAC coming up, apparently the first one for this year for Unit 3.One is on enzymes, dialysis tubing and photosynthesis. Can anyone tell me how things works? How did it go dor you and what do you write about exactly? I know its a prac but the teacher hasnt been through how anything works and we just got a weeks notice. Im in Year 11 and things are already so confusing when you dont get told things properly. Im sorry if this sounda like a silly question but I just want to be prepared.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 20, 2014, 08:28:23 pm
Ive got my SAC coming up, apparently the first one for this year for Unit 3.One is on enzymes, dialysis tubing and photosynthesis. Can anyone tell me how things works? How did it go dor you and what do you write about exactly? I know its a prac but the teacher hasnt been through how anything works and we just got a weeks notice. Im in Year 11 and things are already so confusing when you dont get told things properly. Im sorry if this sounda like a silly question but I just want to be prepared.

Hey, not a silly question at all! :)

I think for everyone the first SAC is on movement through membranes in which you investigate osmosis. You would perform an experiment and then have to write some sections of a scientific report; so the aim, hypothesis, results, discussion and conclusion. I'd suggest doing some reading on different pracs about dialysis tubing (if that's the one your school is doing) and then familiarising yourself on how to write a good scientific report. And of course, thoroughly study everything about movement through membranes and how they could apply in your experiment.

Good-luck :)
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 20, 2014, 09:21:40 pm
Hey
I have a sac coming up on osmosis and here are the key concepts we need to know:

•   Draw and label fluid mosaic model of the plasma membrane
•   What are the functions of all its components in the plasma membrane?
•   Define and give an example of Diffusion
•   Define and give an example of Osmosis
•   Define and give an example of Facilitated diffusion
•   Define and give an example of Active transport
•   Identify the differences between all modes of transport
•   Define and understand hypertonic, hypotonic and isotonic.
•   What can/cannot readily pass through the cell membrane
•   Define and understand the terms hydrophobic and hydrophilic.

It would be awesome if someone could answer a couple and I could compare it with my answers. I want my answers to be perfect and include all the important stuff
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 20, 2014, 09:48:34 pm
Hey
I have a sac coming up on osmosis and here are the key concepts we need to know:

•   Draw and label fluid mosaic model of the plasma membrane
•   What are the functions of all its components in the plasma membrane?
•   Define and give an example of Diffusion
•   Define and give an example of Osmosis
•   Define and give an example of Facilitated diffusion
•   Define and give an example of Active transport
•   Identify the differences between all modes of transport
•   Define and understand hypertonic, hypotonic and isotonic.
•   What can/cannot readily pass through the cell membrane
•   Define and understand the terms hydrophobic and hydrophilic.

It would be awesome if someone could answer a couple and I could compare it with my answers. I want my answers to be perfect and include all the important stuff

The role of the phospholipid membrane in general is to control the inputs and outputs in a cell. The carbohydrate chains (glycoproteins and glycolipids) are involved in intercellular communication and also recognises self and non-self (foreign substances). Cholesterol increases fluidity and prevents solidification of the membrane at low temperatures. The protein channels enable ions (charged particles) and large hydrophilic substances to diffuse through the membrane and is also involved in active transport (the energy-requiring passage of molecules against the concentration gradient). The pores between the phospholipids allow small uncharged and lipophilic substances such as alcohol and urea to diffuse through.

Diffusion is the net movement of solutes from a region of high solute concentration to a region of low solute concentration along a concentration gradient until equilibrium is reached. For example, when you add food colouring to water, the water will eventually be coloured as the colouring will diffuse to the clear regions (where the concentration of the food colouring is low) hence making the whole water solution coloured.

Osmosis is the net movement of water molecules from a region of high water potential (low solute concentration) to a region of low water potential (high solute concentration) along the osmotic gradient. For example, imagine a frog in a pond; if the pond has a lot of salt dissolved in it- it is hypertonic to the frog and water will therefore diffuse out of the frog possibly making it burst. This is because the cells in our body are semi-permeable- solutes cannot exist easily therefore water diffuses to make the two mediums reach equilibrium. Note that osmosis is a form of passive transport or in other words does not require energy.

Facilitated diffusion is the net movement of solutes along a concentration from an area of high solute concentration to an area of low solute concentration with the aid of protein channels. For example, sodium ions require protein channels as they cannot "simply" diffuse through the membrane.

Active transport is the net movement of solutes from an area of low solute concentration to an area of high solute concentration AGAINST the concentration gradient. This requires an expenditure of energy and is highly important for cells. For example, the roots of plants require active transport to absorb ions in the soil- this is because there is already a higher concentration of ions in the roots so energy is required. Energy that is used in active transport must be in the form of ATP (chemical energy) which is produced by the mitochondria in the cells.

Passive transport includes facilitated diffusion, simple diffusion and carrier mediated transport. It requires no energy as solutes are being diffused along the concentration gradient. In contrast, active transport requires energy as the solutes must be taken up against the concentration gradient.

Small uncharged particles, volatile substances and lipophilic molecules such as alcohol, urea, water, ethanol can readily pass through the membrane whereas hydrophilic polar substances such as sodium cannot- they require protein channels. Larger molecules are taken into the cell via endocytosis whereby the cell membrane simply engulfs the substances such as food and forms a vesicle in the cell.

Hydrophilic literally means water loving --> hydro - water and philic - loving
Hydrophobic means water fearing --> hydro - water and phobic - fearing

Forgot to mention, when a solution is isotonic to another solution, this means that they have the same solute concentration therefore diffusion is occurring at a constant rate between the two mediums.
Also endocytosis and exocytosis are other forms of transport as well. Exocytosis is the opposite of endocytosis whereby large particles exits the cell - the vesicles fuses with the membrane and releases its contents. This is common with lysosomes.

Hope this helped and please correct me if I'm wrong :)
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 20, 2014, 10:04:49 pm
OMG!!! Thank you sooo much. This is so helpful :)
It's actually really hard to believe that u r in yr 11. Do u do yr 12 biology?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 20, 2014, 10:08:08 pm
OMG!!! Thank you sooo much. This is so helpful :)
It's actually really hard to believe that u r in yr 11. Do u do yr 12 biology?

No worries. Thank-you too- it helped me revise :P

Haha yeah I do :) nothing big though. Glad it helped! :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 20, 2014, 10:12:38 pm
Hey
I have a sac coming up on osmosis and here are the key concepts we need to know:

•   Draw and label fluid mosaic model of the plasma membrane

This is a really great representation of the bilayer.
Spoiler

The pores between the phospholipids allow small uncharged and lipophilic substances such as alcohol and water to diffuse through.

For example, imagine a frog in a pond; if the pond has a lot of salt dissolved in it- it is hypertonic to the frog and water will therefore diffuse into the frog possibly making it burst.

Water is polar(not lipophilic) and therefore hydrophilic. However it is able to diffuse through the bilayer.

Water will diffuse out of the organism because the pond is more concentrated; it's hypertonic to the frog so water moves from an area of low solute con. to high solute con.  :)
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 20, 2014, 10:29:12 pm
Is there a difference when mentioning just high concentration and high solute concentration for diffusion.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 20, 2014, 10:31:01 pm
Is there a difference when mentioning just high concentration and high solute concentration for diffusion.

Yes, you need to mention what concentration you are referring to. Concentration of water, solute, etc. otherwise the examiner can misinterpret it and it may cost you marks.

Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 20, 2014, 10:44:25 pm
But then if its saying diffusing Is the passive net movement of solute it ignores water molecules, and despite it being a special case of diffusion being osmosis, isn't it still diffusion to. And water molecules aren't solute. Just wondering, I maybe wrong??  It seems like just having to write as much info for definitions as possible, as we don't know which points the examiners want for definition. This seems really time consumer- there is no other way is there????
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 20, 2014, 10:52:11 pm
But then if its saying diffusing Is the passive net movement of solute it ignores water molecules, and despite it being a special case of diffusion being osmosis, isn't it still diffusion to. And water molecules aren't solute. Just wondering, I maybe wrong??

Osmosis is the term used to refer to movement of water molecules. When speaking about 'diffusion', it's a tendency to mention solute. Actually, referring to either solute or water concentration in your definition is fine but, don't just leave your response "vague" by saying "high concentration". You need to mention high concentration of (what?).
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 20, 2014, 10:52:30 pm
But then if its saying diffusing Is the passive net movement of solute it ignores water molecules, and despite it being a special case of diffusion being osmosis, isn't it still diffusion to. And water molecules aren't solute. Just wondering, I maybe wrong??  It seems like just having to write as much info for definitions as possible, as we don't know which points the examiners want for definition. This seems really time consumer- there is no other way is there????

Unfortunately there isn't. Osmosis refers to the net movement of water molecules not solutes. Osmosis is an example of diffusion.
Another reason why you need to mention what you are referring to is because you need to state what is being diffused at a higher rate between the two mediums.
Simply stating that diffusion is a net movement from a higher solution is too vague :)
Having said that, it's good to be concise but also specific. :)
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 20, 2014, 10:55:18 pm
Water is polar(not lipophilic) and therefore hydrophilic. However it is able to diffuse through the bilayer.
Water will diffuse out of the organism because the pond is more concentrated; it's hypertonic to the frog so water moves from an area of low solute con. to high solute con.  :)

Good pick up MM1.

Great answers by nerdmmb as well. I tried making my own answers for those questions and they ended up being much worse :(
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 20, 2014, 10:58:37 pm
Good pick up MM1.

Great answers by nerdmmb as well. I tried making my own answers for those questions and they ended up being much worse :(

Thanks! Haha I actually didn't notice that! Biological terms confuse the crap out of me!

I'm pretty sure yours are better! I guess practice just makes perfect :)
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 20, 2014, 10:58:59 pm
Okay then thanks. Helps. Also another question when referring to hypotonic or hypertonic is it always with relation to the cell. As in if I was to say hypertonic is the net movement of water molecules from outside the cell to inside the cell, along the concentration gradient, across a semi-permeable membrane until equilibrium is reached. Is it implied that the water is going inside cell. Or do we have to say its the movement of water molecules ... to the concentration in question. Also hypertonic, hypertonic is always across a semi-permeable membrane right??
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 20, 2014, 11:01:37 pm
Okay then thanks. Helps. Also another question when referring to hypotonic or hypertonic is it always with relation to the cell. As in if I was to say hypertonic is the net movement of water molecules from outside the cell to inside the cell, along the concentration gradient, across a semi-permeable membrane until equilibrium is reached. Is it implied that the water is going inside cell. Or do we have to say its the movement of water molecules ... to the concentration in question. Also hypertonic, hypertonic is always across a semi-permeable membrane right??

Yupp! You only mention hypertonic or hypotonic when you're making a comparison between two solutions :)

Hypertonic and hypotonic is not necessarily always in relation to a semi permeable membrane :)
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 20, 2014, 11:06:52 pm
Okay then thanks. Helps. Also another question when referring to hypotonic or hypertonic is it always with relation to the cell. As in if I was to say hypertonic is the net movement of water molecules from outside the cell to inside the cell, along the concentration gradient, across a semi-permeable membrane until equilibrium is reached. Is it implied that the water is going inside cell. Or do we have to say its the movement of water molecules ... to the concentration in question. Also hypertonic, hypertonic is always across a semi-permeable membrane right??

The terms hypertonic and hypotonic are in relation to solute concentration. You might want to recheck over what you wrote. There seems to be a few errors in your expression such as, "hypertonic is the net movement of water molecules..."
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 20, 2014, 11:10:01 pm
In the secondary structure, the polypeptide chain undergoes coiling (alpha helices) and folding (beta sheets) due to hydrogen bonding between the different amino acids.

Is this hydrogen bonding between the R groups of the amino acids?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 20, 2014, 11:10:32 pm
Good pick up MM1.

Great answers by nerdmmb as well. I tried making my own answers for those questions and they ended up being much worse :(

You should've posted your answers as well regardless; it's a way to improve by practice :) I'd recommend perhaps memorising some good definitions for the types of movements and picking up on key words. It's pretty hard to formulate a good response at first but with practice, it'll surely improve.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 20, 2014, 11:20:40 pm
In the secondary structure, the polypeptide chain undergoes coiling (alpha helices) and folding (beta sheets) due to hydrogen bonding between the different amino acids.

Is this hydrogen bonding between the R groups of the amino acids?

Thanks!

No, the R group interactions are only for the tertiary structure, I believe.
In the secondary structure, the hydrogen bonds form between the  C=O and H-N (carbonyl and amide), or just say segments on the chain.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 20, 2014, 11:23:35 pm
No, the R group interactions are only for the tertiary structure, I believe.
In the secondary structure, the hydrogen bonds form between the  C=O and H-N (carbonyl and amide), or just say segments on the chain.

Carboxyl*
Amine*
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 20, 2014, 11:28:45 pm
Carboxyl*
Amine*

It is actually Carbonyl and Amide in this case. Although I do see what you mean. Do you want an explanation?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 20, 2014, 11:38:13 pm
It is actually Carbonyl and Amide in this case. Although I do see what you mean. Do you want an explanation?

That's fine. I never knew they existed though; was in the context of amino acids.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 20, 2014, 11:40:47 pm
That's fine. I never knew they existed though; was in the context of amino acids.

Still is about amino acids but in their peptide form. None of this is needed for VCE Biol though.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 21, 2014, 07:26:03 am
I've read the Biology FAQS and I was surprised to see that you do not need to know the different types of bonding.

From VCAA:
"The names for the specific types of bonds (for example, glycosidic, peptide) or bonding (for example hydrogen, covalent, disulfide) in carbohydrates, lipids, proteins and nucleic acids are not required."

So essentially (and correct me if I'm wrong), you only need to know that 'bonding' occurs to help form the conformational shape of a protein and each level of structure (primary, secondary, tertiary, quaternary). You could perhaps refer to these as 'intermolecular' bonds or attractions.

Of course, it's still good to know the different types of bonds :)
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 21, 2014, 05:02:01 pm
Can someone please explain to me what the terms  'control' and 'variable' mean, when referring to a scientific experiment?

Thanks!  :)
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on February 21, 2014, 05:12:18 pm
Can someone please explain to me what the terms  'control' and 'variable' mean, when referring to a scientific experiment?

Thanks!  :)
Variable - a factor that can impact on the outcome of the experiment
There are 2 types of variables:  Independent variable (one that is deliberately changed)
Dependent variable (one that is changed due to the change in Independent variable)
Controlled: usually "controlled experiment" which refers to an experiment in which everything is keep at constant and does not change EXCEPT only the independent and dependent variable. This helps to validate the changes those above variables really have an effect but not the other.
Hope this helps.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 21, 2014, 05:44:43 pm
Would active transport be considered as the net movement of particles or not?
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on February 21, 2014, 05:52:24 pm
Would active transport be considered as the net movement of particles or not?
Yes, but remember that it occurs against the concentration gradient thus requiring the expenditure of energy in the form of ATP for it to occur.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 21, 2014, 07:26:34 pm
Would active transport be considered as the net movement of particles or not?

Absolutely. You're always talking about net movement. There is no naturally occurring (or for that matter unnaturally occurring) instance when particles aren't moving at all.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 21, 2014, 09:16:27 pm
If I were to define endosmosis and exosmosis, could I just say that endosmosis is the net movement of water, across a differentially permeable membrane into a cell and that exosmosis is the net movement of water across a differentially permeable membrane, out of a cell?

I am not sure if that is right or wrong :/

Thanks!
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 21, 2014, 09:25:02 pm
If I were to define endosmosis and exosmosis, could I just say that endosmosis is the net movement of water, across a differentially permeable membrane into a cell and that exosmosis is the net movement of water across a differentially permeable membrane, out of a cell?

I am not sure if that is right or wrong :/

Thanks!

That's right, but nobody really uses these terms anyway.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 21, 2014, 10:06:11 pm
That's right, but nobody really uses these terms anyway.

oh thanks!
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 21, 2014, 10:07:29 pm
What is the definition of osmosis? Do I need to include info about the semi permeable membrane?
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 21, 2014, 10:09:00 pm
Is it generally easier for small non-polar substances to pass through the cell membrane by simple diffusion or is it easier for small polar substances to?

I always thought polar substances had a bit more trouble, as the interior of the phospholipid bilayer is non-polar?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 21, 2014, 10:14:23 pm
What is the definition of osmosis? Do I need to include info about the semi permeable membrane?

Yes, you should.
Osmosis is the passive, net movement of water molecules across a semi permeable membrane, from a region of high water concentration (low solute concentration) to a region of low water concentration (high solute concentration).
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 21, 2014, 10:15:17 pm
What is the definition of osmosis? Do I need to include info about the semi permeable membrane?

Osmosis the net movement of water molecules from a region of high water potential to a region of low water potential along the osmotic gradient.

You don't have to mention the semi-permeable membrane but you can :)
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 21, 2014, 10:16:27 pm
Yes, you should.
Osmosis is the passive, net movement of water molecules across a semi permeable membrane, from a region of high water concentration (low solute concentration) to a region of low water concentration (high solute concentration).

Thanks heaps...  :)
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 21, 2014, 10:16:51 pm
Is it generally easier for small non-polar substances to pass through the cell membrane by simple diffusion or is it easier for small polar substances to?

I always thought polar substances had a bit more trouble, as the interior of the phospholipid bilayer is non-polar?

Well, small non polar substances would diffuser across easier, although some small polar substances are tiny enough to slip through the tiny pores of the plasma membrane (e.g. water).
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 21, 2014, 10:18:14 pm
Is it generally easier for small non-polar substances to pass through the cell membrane by simple diffusion or is it easier for small polar substances to?

I always thought polar substances had a bit more trouble, as the interior of the phospholipid bilayer is non-polar?

Non-polar substances can easily diffuse through the membrane and small polar molecules can as well but larger polar (hydrophilic) and charged molecules require protein channels.

The interior of the phospholipid is non-polar however the phosphate heads are not but since the membrane is porous, water molecules and certain other substances can diffuse through.

Note that the factors which affect diffusion are size, charge and polarity.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 21, 2014, 10:18:52 pm
Osmosis the net movement of water molecules from a region of high water potential to a region of low water potential along the osmotic gradient.

You don't have to mention the semi-permeable membrane but you can :)
Thanks nerdmmb. You have really helped me heaps for this upcoming bio sac :) :) :)
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 21, 2014, 10:18:58 pm
Well, small non polar substances would diffuser across easier, although some small polar substances are tiny enough to slip through the tiny pores of the plasma membrane (e.g. water).

Sorry oddly,
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 21, 2014, 10:20:15 pm
Is it generally easier for small non-polar substances to pass through the cell membrane by simple diffusion or is it easier for small polar substances to?

I always thought polar substances had a bit more trouble, as the interior of the phospholipid bilayer is non-polar?

Yes, non-polar substances are able to readily diffuse through the cell membrane because it has a greater affinity for the hydrophobic region. Whilst, polar molecules such as water are able to diffuse through small spaces between the phospholipids (because of their small size), it is relatively  harder for them to break that initial barrier/repulsion to enter. But they are able to, nonetheless.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 21, 2014, 10:21:36 pm
What is the definition of osmosis? Do I need to include info about the semi permeable membrane?

Yes, you always need to, whatever the scenario may be.

'Osmosis is the passive net movement of free water molecules across a semi-permeable membrane from a region of low solute concentration (high water potential) to a region of high solute concentration (low water potential), along an osmotic gradient. [To attain equilibrium].

Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 21, 2014, 10:22:22 pm
I was just wondering, do water molecules enter through the pores or do they push against the phosphate heads to do so?

Just a little confused because I was told that they break off a small portion of the phosphate heads to enter which doesn't really make sense.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 21, 2014, 10:25:25 pm
Sorry oddly,

Thanks for the help, guys! :)
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 21, 2014, 10:44:21 pm
I was just wondering, do water molecules enter through the pores or do they push against the phosphate heads to do so?

Just a little confused because I was told that they break off a small portion of the phosphate heads to enter which doesn't really make sense.

They pass through the gaps (pores).
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 21, 2014, 10:49:15 pm
I was just wondering, do water molecules enter through the pores or do they push against the phosphate heads to do so?

Just a little confused because I was told that they break off a small portion of the phosphate heads to enter which doesn't really make sense.

They pass through gaps in the membrane, but as alondouek has mentioned here before (don't worry that's not being snippy, it's just giving credit where it's due!), most water actually passes through channel proteins called aquaporins.
Title: Re: VCE Biology Question Thread
Post by: Reus on February 21, 2014, 10:53:23 pm
Got the enzyme prac sac, in about 2 weeks time! Anything I should know prior to it, or will it be straight forward?
Thanks!
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 21, 2014, 11:21:52 pm
Got the enzyme prac sac, in about 2 weeks time! Anything I should know prior to it, or will it be straight forward?
Thanks!

Should be pretty straight forward if you know your enzymes
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 21, 2014, 11:34:32 pm
If large molecules have trouble diffusing across the plasma membrane, does that mean even if they are large hydrophobic molecules, they will need to partake in facilitated diffusion in order to cross the plasma membrane?

Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 21, 2014, 11:36:10 pm
If large molecules have trouble diffusing across the plasma membrane, does that mean even if they are large hydrophobic molecules, they will need to partake in facilitated diffusion in order to cross the plasma membrane?

Presumably there'd be a point where they got too big, but they often don't. Hydrophobic molecules can move through the membrane as though it were a sheet of water.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 22, 2014, 11:12:07 am
Are the terms, isotonic, hypertonic and hypotonic strictly limited to talking about Osmosis?

Or can you use it when talking about diffusion as well:

Eg. - There is a net movement of particles from a hypertonic solution ( relatively high solute concentration) to a hypotonic solution (relatively low solute concentration)

Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 22, 2014, 11:39:36 am
Are the terms, isotonic, hypertonic and hypotonic strictly limited to talking about Osmosis?

Or can you use it when talking about diffusion as well:

Eg. - There is a net movement of particles from a hypertonic solution ( relatively high solute concentration) to a hypotonic solution (relatively low solute concentration)

No, the terms isotonic, hypertonic and hypotonic can be used when describing all types of passive and active transport including osmosis.

In your example, I think try to mention that it is along the concentration gradient :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 22, 2014, 12:38:19 pm
Are the terms, isotonic, hypertonic and hypotonic strictly limited to talking about Osmosis?

Or can you use it when talking about diffusion as well:

Eg. - There is a net movement of particles from a hypertonic solution ( relatively high solute concentration) to a hypotonic solution (relatively low solute concentration)

They're exclusive to osmosis. Tonicity refers to osmotic pressure so it only relates to solvents. I would only use it for osmosis, not diffusion.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 22, 2014, 12:43:21 pm
What can/cannot readily pass through the cell membrane?
Preferably 2-3 sentences.
Thanks ;)
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 22, 2014, 12:48:39 pm
I will have a try at this. Non-polar/ uncharged/ small molecules can pass through membrane. Whilst large, charged, polar molecules can not pass through the plasma membrane unless aided by a membrane protein. Don't trust me In just guessing, someone please correct me
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 22, 2014, 12:51:53 pm
Also about enzymes they can change shapes. From listening to podcast, some hormones can bind to enzymes changing their active shape and hence able other molecules to bind to active site or something. I'm not to sure
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 22, 2014, 12:54:17 pm
If anyone can clarify the following that would be greatly appreciated :)

Would you say that facilitated diffusion is the passive, net movement of particles from a region of high concentration to a region of low concentration, via transmembrane proteins?
Or do you have to specify carrier/channel proteins?

Also, cholesterol helps stabilise the phospholipid bilayer by maintaining its rigidity at high temperatures, whilst it maintains the cell membrane's fluidity at low temperatures. If it asks for an explanation, I would say that at high temperatures, it decreases the membrane's permeability to polar substances, while it increases the membrane's permeability to polar substances at low temperatures.

Thanks
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 22, 2014, 01:29:35 pm
They're exclusive to osmosis. Tonicity refers to osmotic pressure so it only relates to solvents. I would only use it for osmosis, not diffusion.

Do you mean hypertonic, hypotonic and isotonic are restricted to osmosis?
I'm very sure they can be used when describing any form of diffusion. After all, osmosis is a form of diffusion.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 22, 2014, 01:41:30 pm
Do you mean hypertonic, hypotonic and isotonic are restricted to osmosis?
I'm very sure they can be used when describing any form of diffusion. After all, osmosis is a form of diffusion.

Usually we refer to solutions as being hypertonic, isotonic or hypotonic to another solution. Because of this, I'd say it's mainly referring to osmosis.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 22, 2014, 01:45:02 pm
Do you mean hypertonic, hypotonic and isotonic are restricted to osmosis?
I'm very sure they can be used when describing any form of diffusion. After all, osmosis is a form of diffusion.

Like I mentioned, tonicity refers to osmotic pressure so it only relates to solvents such as water. Osmosis is a form of diffusion. Diffusion isn't always about water (tonicity), it can relate to particles and other substances. It would be incorrect to mention hyper/iso/hypo-tonic when referring to regular diffusion.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 22, 2014, 01:54:15 pm
If anyone can clarify the following that would be greatly appreciated :)

Would you say that facilitated diffusion is the passive, net movement of particles from a region of high concentration to a region of low concentration, via transmembrane proteins?
Or do you have to specify carrier/channel proteins?

Also, cholesterol helps stabilise the phospholipid bilayer by maintaining its rigidity at high temperatures, whilst it maintains the cell membrane's fluidity at low temperatures. If it asks for an explanation, I would say that at high temperatures, it decreases the membrane's permeability to polar substances, while it increases the membrane's permeability to polar substances at low temperatures.

Thanks

I think it would be better to say ' through specific channel/carrier transmembrane proteins'. Also, I think you should specify what type of particles pass through the proteins; so large, polar and charged molecules perhaps.

On that note, any idea on what's the function of peripheral proteins?
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 22, 2014, 03:35:27 pm
Why do scientists study the proteome of an organism, instead of single proteins?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 22, 2014, 03:42:53 pm
Does anyone know what is the order of the organelles, in terms of heaviest to lightest?  :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 22, 2014, 03:45:49 pm
Why do scientists study the proteome of an organism, instead of single proteins?

Thanks!

Most proteins do not act in isolation, most of them interact with other proteins. So by studying the proteome, scientists are able to discover more information about them, compared to a single protein.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 22, 2014, 04:00:20 pm
Thankyou!!  :)
Title: Re: VCE Biology Question Thread
Post by: kx4y on February 22, 2014, 05:33:35 pm
What substances are found in the cell membrane?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 22, 2014, 05:43:59 pm
What substances are found in the cell membrane?

Protein carriers, protein channels and cholesterol.
The membrane itself is primarily composed of phospholipids and carbohydrate chains (glycolipids and glycoproteins) are attached to some protein channels and phospholipids on the surface of the membrane.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 22, 2014, 06:04:15 pm
Are the terms, isotonic, hypertonic and hypotonic strictly limited to talking about Osmosis?

Or can you use it when talking about diffusion as well:

Eg. - There is a net movement of particles from a hypertonic solution ( relatively high solute concentration) to a hypotonic solution (relatively low solute concentration)

You can't just say a net movement of particles, because we don't know whether these particles are water or whether they are a solute. Hypertonic and hypotonic merely describe the nature of the solution. The nature of the movement also needs to be described.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 22, 2014, 06:12:48 pm

You can't just say a net movement of particles, because we don't know whether these particles are water or whether they are a solute. Hypertonic and hypotonic merely describe the nature of the solution. The nature of the movement also needs to be described.

Oh okay thanks!

I think I'll just leave those terms for osmosis then  :P
So that things dont get too confusing

Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 22, 2014, 06:29:28 pm
Oh okay thanks!

I think I'll just leave those terms for osmosis then  :P
So that things dont get too confusing

Probably the best way to go about it I'd say. You need to really specify what particles are doing the moving though, particularly if you're talking about osmosis. In diffusion, you can get away with a bit more, it's obvious that you're not talking about water particles. But anyway, I'm confused, so you're right hahaha just stick with what you know
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 22, 2014, 08:22:21 pm
In the upcoming biology SAC, where we have to do a practical-report write up it says we have to include the controls and variables of the experiment,

Where would I include this part?

Should it go in the limitations, about how the errors were minimised due to the use of a control and a variable, so that the results were able to be clearly analysed?

Sorry I have never talked about controls and variables in a practical report before!

Thanks :)
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 22, 2014, 08:23:46 pm
Probably the best way to go about it I'd say. You need to really specify what particles are doing the moving though, particularly if you're talking about osmosis. In diffusion, you can get away with a bit more, it's obvious that you're not talking about water particles. But anyway, I'm confused, so you're right hahaha just stick with what you know

Yeah! goodpoint! I was kind of careless about that!
LOLL
thanks :)
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 22, 2014, 08:33:46 pm
In the upcoming biology SAC, where we have to do a practical-report write up it says we have to include the controls and variables of the experiment,

Where would I include this part?

Should it go in the limitations, about how the errors were minimised due to the use of a control and a variable, so that the results were able to be clearly analysed?

Sorry I have never talked about controls and variables in a practical report before!

Thanks :)

Discussion
Title: Re: VCE Biology Question Thread
Post by: millie96 on February 22, 2014, 08:53:13 pm
what is the use of turgor pressure in plant cells?
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 22, 2014, 08:56:22 pm
To give the plant rigidity. Just wondering I know how on the study design It says we only need to know inputs and outputs if cellular respiration and photosynthesis (does that simply meaning only knowing the molecules going into photosynthesis/ cellular respiration and coming out?) cause there seems to be question about briefly describe process of light dependent stage/ light- independent stage??? But we only need to know inputs/ outputs. Confused?? Help please
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 22, 2014, 09:01:58 pm
To give the plant rigidity. Just wondering I know how on the study design It says we only need to know inputs and outputs if cellular respiration and photosynthesis (does that simply meaning only knowing the molecules going into photosynthesis/ cellular respiration and coming out?) cause there seems to be question about briefly describe process of light dependent stage/ light- independent stage??? But we only need to know inputs/ outputs. Confused?? Help please

I do remember this question. IT was a mean one.

You ought to know the inputs and outputs of each stage and where those stages occur. That will be sufficient to answer those questions. Without a really good knowledge of chem (well beyond VCE), you're not really going to get anything more useful out of photosynthesis.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 22, 2014, 09:08:18 pm
I do remember this question. IT was a mean one.

You ought to know the inputs and outputs of each stage and where those stages occur. That will be sufficient to answer those questions. Without a really good knowledge of chem (well beyond VCE), you're not really going to get anything more useful out of photosynthesis.

Would Acetyl-CoA be an input in respiration or intermediate? Is this required knowledge? Thanks!
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 22, 2014, 09:33:34 pm
The 2012 VCAA assessment report for Biology says that ". Students should not repeat the stem of the

What exactly does this mean?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 22, 2014, 09:41:04 pm
The 2012 VCAA assessment report for Biology says that ". Students should not repeat the stem of the

What exactly does this mean?

Oh, I think it means that you shouldn't need to repeat part of the question to begin your answer. For example, if the question was "List the main function of the cell membrane", you shouldn't have to write "The main functions of the cell membrane are.."; you should just list and describe them instead.
It's common sense, I guess, but perfectionists might try incorporate every little bit into their answer (incl. the stem of the question).
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 22, 2014, 09:44:02 pm
Would Acetyl-CoA be an input in respiration or intermediate? Is this required knowledge? Thanks!

It's an intermediate in cellular respiration.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 22, 2014, 09:45:51 pm
Would Acetyl-CoA be an input in respiration or intermediate? Is this required knowledge? Thanks!

A bit of both. Given that CoA is recycled and that the acetyl- group comes from the actual process, I'd probably go with alchemy and say it's an intermediate. Although, when I do inputs and outputs for resp I include it as an input. Both are right as far as I'm concerned.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 22, 2014, 09:46:37 pm
Oh, I think it means that you shouldn't need to repeat part of the question to begin your answer. For example, if the question was "List the main function of the cell membrane", you shouldn't have to write "The main functions of the cell membrane are.."; you should just list and describe them instead.
It's common sense, I guess, but perfectionists might try incorporate every little bit into their answer (incl. the stem of the question).

Thanks so much! :)

Oh okay yeah I get what you mean!
Hahaha I actually have a bad habit of including the stem of the question, so it's good I figured that out!
Thanks again! :)
Title: Re: VCE Biology Question Thread
Post by: katie101 on February 23, 2014, 09:43:56 am
Fats are generally transported in the blood in the form of small particles, called chylomicrons. Examine the three examples given in figure 2.34. Note the 63 compounds that make up these particles. Explain why the components of the particles aggregate in the way they do, ending up as spherical.
Title: Re: VCE Biology Question Thread
Post by: kx4y on February 23, 2014, 09:48:21 am
In the Dialysis tubing prac, we tested for starch using Iodine solution and tested for glucose using Benedict's solution. What is the Independent Variable, Dependant variable and controlled variables?
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 23, 2014, 09:59:35 am
Fats are generally transported in the blood in the form of small particles, called chylomicrons. Examine the three examples given in figure 2.34. Note the 63 compounds that make up these particles. Explain why the components of the particles aggregate in the way they do, ending up as spherical.

The components of the particles aggregate in the way they do because of the way they interact with water molecules. The phospholipid bi-layer is organised to keep water out of the cell due to the hydrophobic tails. The tails point inwards into the cell, thus it ends up in a spherical shape.
Title: Re: VCE Biology Question Thread
Post by: katie101 on February 23, 2014, 10:36:31 am
Is X a ribosome or mitochondria?

What is Y, maybe ER?
Title: Re: VCE Biology Question Thread
Post by: aqple on February 23, 2014, 10:47:18 am
Is X a ribosome or mitochondria?

What is Y, maybe ER?

X is mitochondria
Y is rough ER
Title: Re: VCE Biology Question Thread
Post by: MagicGecko on February 23, 2014, 10:48:59 am
X is definitely a mitochondria, its too big to be a ribsome, not so sure about Y, but it looks like the Endoplasmic Reticulum, possibly rough.
Title: Re: VCE Biology Question Thread
Post by: katie101 on February 23, 2014, 10:55:51 am
Thanks i think thats right!
Title: Re: VCE Biology Question Thread
Post by: katie101 on February 23, 2014, 10:58:20 am
How might an examination of cells help diagnose disease?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 12:17:40 pm
How might an examination of cells help diagnose disease?

Well the form of the cells can often tell you whether or not they're diseased. They will, in many cases, actually appear diseased. Especially cancer cells, which often have multiple nuclei and really jagged edges, for example. Or in sickle cell anaemia, the cells appear to be shrunken and sickle-shaped. Just a couple of examples, but by looking at the cells, often you can see the characteristic signs of certain diseases.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 23, 2014, 02:52:07 pm
Not sure if my answer to this question is correct. Can someone verify?

Carbon monoxide, a molecule in cigarette smoke and car exhaust fumes, binds irreversibly with iron groups. What effect would this have on your red blood cells?

Carbon monoxide can bind to the iron groups present in hemoglobin. This can cause the irreversible disruption of ionic bonds in hemoglobin, causing it to denature and lose its function in red blood cells.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 03:00:42 pm
Not sure if my answer to this question is correct. Can someone verify?

Carbon monoxide, a molecule in cigarette smoke and car exhaust fumes, binds irreversibly with iron groups. What effect would this have on your red blood cells?

Carbon monoxide can bind to the iron groups present in hemoglobin. This can cause the irreversible disruption of ionic bonds in hemoglobin, causing it to denature and lose its function in red blood cells.

Don't repeat the stem of the question. It's not really binding to iron groups either, that's somewhat of an incorrect way to put it so bad question.

It's competitive inhibition, not denaturation. The way to pick that would've been to take note that it says "irreversibly", it will not leave that place once it has bound.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 23, 2014, 03:02:20 pm
Not sure if my answer to this question is correct. Can someone verify?

Carbon monoxide, a molecule in cigarette smoke and car exhaust fumes, binds irreversibly with iron groups. What effect would this have on your red blood cells?

Carbon monoxide can bind to the iron groups present in hemoglobin. This can cause the irreversible disruption of ionic bonds in hemoglobin, causing it to denature and lose its function in red blood cells.

I'm going to attempt this; Carbon monoxide inhibits oxygen to bind to haemoglobin which is needed to be delivered to cells for cellular respiration. RBC would not be able to deliver oxygen so cells would eventually die.

My wording is not the best, but would I be correct, anyone?

Title: Re: VCE Biology Question Thread
Post by: alchemy on February 23, 2014, 03:23:41 pm
It's competitive inhibition, not denaturation. The way to pick that would've been to take note that it says "irreversibly", it will not leave that place once it has bound.

If it binds "irreversibly" shouldn't it be an example of non-competitive (permanent) inhibition, as carbon monoxide binding to haemoglobin would have caused its active site to change shape, preventing oxygen from binding onto its active site?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 03:27:12 pm
I'm going to attempt this; Carbon monoxide inhibits oxygen to bind to haemoglobin which is needed to be delivered to cells for cellular respiration. RBC would not be able to deliver oxygen so cells would eventually die.

My wording is not the best, but would I be correct, anyone?

You're right about the cell thing as well too of course. Carbon monoxide is bloody dangerous. You hear stories every so often particularly about it killing kids. Faulty heaters and stuff like that produce it. It's also what gets people when they use car fumes to commit suicide, an all too common occurrence sadly.

The binding is technically not reversible, but haemoglobin's affinity for carbon monoxide is about 10,000 times that for oxygen, so you're pretty well toast if you're exposed.

If it binds "irreversibly" shouldn't it be an example of non-competitive (permanent) inhibition, as carbon monoxide binding to haemoglobin would have caused its active site to change shape, preventing oxygen from binding onto its active site?

You're probably right actually. It's been a few years since I've done inhibition and I always found the terminology to be a little odd, so if that's the case then sure it's probably right. Would love someone else to confirm.
I'd thought that competitive inhibition was when another molecule binds to the active site. Hence, competitive because it competes for the active site. And non-competitive when it's bound to another area and changed the config of the active site.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 23, 2014, 03:27:33 pm
According to A+ biol notes, Inhibition is reversible..

Edit: Denaturing and the binding of poisons is irreversible. So since CO is a poison, it would be irreversible.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 23, 2014, 03:45:48 pm
But it's still competitive inhibition, no? I'm guessing because the bonding is so strong, it might as well be irreversible.
But don't they like treat severe cases of carbon monoxide poisoning with 100% oxygen?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 03:48:34 pm
According to A+ biol notes, Inhibition is reversible..

Edit: Denaturing and the binding of poisons is irreversible. So since CO is a poison, it would be irreversible.

Assume that your edit is true. Technically it's not, every process is reversible, but yes this process is practically irreversible.

But it's still competitive inhibition, no? I'm guessing because the bonding is so strong, it might as well be irreversible.
But don't they like treat severe cases of carbon monoxide poisoning with 100% oxygen?

Yeah, just to get some oxygen into the blood presumably. Haemoglobin doesn't stick around too long, and it would be somewhat unlikely for CO to saturate all the sites, although the majority yes.

Important: what I said about inhibition earlier was correct. It is competitive inhibition.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 23, 2014, 04:38:16 pm
If the lock and key model were true, only one enzyme would be able to catalyze a reaction. However, some enzymes can catalyze multiple reactions. What are some examples of enzymes that can catalyze multiple reactions?

Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 04:48:32 pm
Another point to make about haemoglobin as well: it's not an enzyme. The process of ligation, though, is fairly similar in this case, hence the reason they've asked this question.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 23, 2014, 04:55:01 pm
If the lock and key model were true, only one enzyme would be able to catalyze a reaction. However, some enzymes can catalyze multiple reactions. What are some examples of enzymes that can catalyze multiple reactions?

Lysozyme perhaps?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 04:58:42 pm
If the lock and key model were true, only one enzyme would be able to catalyze a reaction. However, some enzymes can catalyze multiple reactions. What are some examples of enzymes that can catalyze multiple reactions?

You'll be hard pressed to find an example to be honest. The reality is that enzymes really don't catalyse different reactions at the same active site, though some will have multiple active sites. I'm sure there are probably a very specific few exceptions to that rule, but none would do it "normally".
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 23, 2014, 05:44:07 pm
Can someone describe the structure of the membrane of organelles?

Do they also have protein channels, etc.?

Also, is ribosome referred to a  non-membrane bound organelle because it does not have a phospholipid bilayer? If so, what is the membrane of ribosome like?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 05:57:03 pm
Can someone describe the structure of the membrane of organelles?

Do they also have protein channels, etc.?

Also, is ribosome referred to a  non-membrane bound organelle because it does not have a phospholipid bilayer? If so, what is the membrane of ribosome like?

Thanks!

The structure of organelle membranes is pretty different to that of the cell itself, but in a very broad stroke, they are essentially the same kind of thing. Phospholipid and whatnot, most will have protein channels though it does depend on the organelle. FOr example, you should already have some insights into the membrane of most of the organelles you've already encountered. A little bit of a recap:

Nucleus: bilayer that folds in on itself to make pores.
Mitochondria: internal and external membranes, lots of membrane proteins particularly in the internal membrane (think ETC). Naturally, there are channels/carriers on the external membrane to let proteins in and out
Chloroplast: similar story to mitochondria, two membranes (gram -), thylakoids on the inside
ER: pretty similar to cell, though studied with ribosomal complexes
Golgi: practically identical to the cellular membrane. Pretty much all golgi membrane eventually becomes cell membrane anyway, so they have to be very similar. Although, the membrane in the Golgi actually undergoes changes, becoming more and more structurally similar to the cell as it gets closer to budding off.

Ribosomes don't have a membrane at all. They're just a big hunk of protein and rRNA
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 23, 2014, 05:57:44 pm
Also, is ribosome referred to a  non-membrane bound organelle because it does not have a phospholipid bilayer? If so, what is the membrane of ribosome like?

A ribosome is a small non-membrane bound organelle. 'Non-membrane bound' means it doesn't have a membrane surrounding itself.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 06:22:46 pm
This is what one looks like (only a very recent discovery, and actually earned them a nobel prize!)

(http://www.rcsb.org/pdb/education_discussion/molecule_of_the_month/images/ribosome.gif)
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 23, 2014, 06:35:56 pm
Just wondering which topic everyones school is up to?
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 23, 2014, 06:37:05 pm
Just wondering which topic everyones school is up to?

Our school is doing ezymes atm but we have a sac on osmosis on tuesday.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 23, 2014, 06:44:49 pm
Has anyone done the osmosis prac on potatoes?
If yes, what were some of the questions asked? I have my sac on tuesday and I want to cover EVERYTHING!!!
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 23, 2014, 07:07:48 pm
Has anyone done the osmosis prac on potatoes?
If yes, what were some of the questions asked? I have my sac on tuesday and I want to cover EVERYTHING!!!

Yes :)
It was actually quite fun, although we've only done part 1 which is the experiment.

I think just try and link how everything is related to eachother - a mind map might be helpful!
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 23, 2014, 07:08:32 pm
This is what one looks like (only a very recent discovery, and actually earned them a nobel prize!)

(http://www.rcsb.org/pdb/education_discussion/molecule_of_the_month/images/ribosome.gif)

Would it be correct to say that ribosomes were synthesised by other ribosomes?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 07:11:41 pm
Would it be correct to say that ribosomes were synthesised by other ribosomes?

No, not entirely. The protein component yes, the rRNA component no. The rRNA comes straight from RNA pol.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 23, 2014, 07:27:51 pm
Has anyone done the osmosis prac on potatoes?
If yes, what were some of the questions asked? I have my sac on tuesday and I want to cover EVERYTHING!!!

You need to cover the main things but perhaps not everything; there are still things on membranes that scientists don't yet know (as with almost anything else)...
I had my SAC 2 weeks ago and I would advise you to read the questions carefully and respond using important key words that you've been taught to use. This doesn't mean pick fancy wording you found on the internet, as teachers hate that. Also, don't paraphrase many of the answers here on AN as we try to explain what we can in the most detail so you comprehend the entirety of the biological concepts, whereas in SAC's there's probably not enough time for that.
There's really not much content on the 'Movement across Membranes' topic in VCE, so just make sure your wording is precise and succinct. Working on timing will surely help as well C: Good Luck!
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 23, 2014, 07:29:26 pm
Just wondering which topic everyones school is up to?

Biomacromolecules
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 23, 2014, 07:34:37 pm
Biomacromolecules

LOL, that's a joke right. haha
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 23, 2014, 07:48:03 pm
You need to cover the main things but perhaps not everything; there are still things on membranes that scientists don't yet know (as with almost anything else)...
I had my SAC 2 weeks ago and I would advise you to read the questions carefully and respond using important key words that you've been taught to use. This doesn't mean pick fancy wording you found on the internet, as teachers hate that. Also, don't paraphrase many of the answers here on AN as we try to explain what we can in the most detail so you comprehend the entirety of the biological concepts, whereas in SAC's there's probably not enough time for that.
There's really not much content on the 'Movement across Membranes' topic in VCE, so just make sure your wording is precise and succinct. Working on timing will surely help as well C: Good Luck!

Thanks heaps Alchemy... Yeah, there's not much to remember so I'm trying to make my answers make sense atm. Lol, I have a little problem of rambling on sometimes. haha ;D
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 07:53:07 pm
Has anyone done the osmosis prac on potatoes?
If yes, what were some of the questions asked? I have my sac on tuesday and I want to cover EVERYTHING!!!

You'll need to be able to relate changes in the potato cells with the nature of the cellular and external fluid, and explain that in terms of osmosis. That's pretty much what that prac is going to be about. Being able to describe under what circumstances osmosis will occur and also explain why it will occur. The same will go with diffusion, you must be able to relate that to the concentrations externally and internally, as well as to osmosis—why will diffusion occur in some circumstances, and osmosis in others?

Lastly, I expect that you'll need to make some sort of comment on turgour pressure. You may be asked to comment on why lysis doesn't occur.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 23, 2014, 07:55:01 pm
LOL, that's a joke right. haha

Unfortunately, it isn't. I would've expected most schools to be up to here by now but, our school started early during orientation and it's such that our pace is considerably slower than expected.

EDIT: 500'th post D: I really need to get a life...
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 23, 2014, 07:57:37 pm
You'll need to be able to relate changes in the potato cells with the nature of the cellular and external fluid, and explain that in terms of osmosis. That's pretty much what that prac is going to be about. Being able to describe under what circumstances osmosis will occur and also explain why it will occur. The same will go with diffusion, you must be able to relate that to the concentrations externally and internally, as well as to osmosis—why will diffusion occur in some circumstances, and osmosis in others?

Lastly, I expect that you'll need to make some sort of comment on turgour pressure. You may be asked to comment on why lysis doesn't occur.

I'm going to attempt this question, could someone please correct me if I'm wrong?

Lysis doesn't occur as the plant cells are encapsulated in a cell wall which makes them turgor and prevents the cell from rupturing.

If we were asked as to why lysis doesn't occur in a salt solution that is hypertonic to the potato slices, would it also be correct to say that there was a net movement of water molecules from the potato tuber cells via osmosis therefore the cells shrunk-this was evidenced by the significant decrease in mass.
And can we say that lysis doesn't occur since it's a plant cell? Instead, plasmolysis occurs?
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 23, 2014, 08:01:57 pm
Unfortunately, it isn't. I would've expected most schools to be up to here by now but, our school started early during orientation and it's such that our pace is considerably slower than expected.

EDIT: 500'th post D: I really need to get a life...

Idk if trolling but okay good luck :P
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 08:04:18 pm
I'm going to attempt this question, could someone please correct me if I'm wrong?

Lysis doesn't occur as the plant cells are encapsulated in a cell wall which makes them turgor and prevents the cell from rupturing.

If we were asked as to why lysis doesn't occur in a salt solution that is hypertonic to the potato slices, would it also be correct to say that there was a net movement of water molecules from the potato tuber cells via osmosis therefore the cells shrunk-this was evidenced by the significant decrease in mass.

Yeah that's essentially right, except turgour can't be made, it is a quality of the cell. Plant cells don't undergo plasmolysis in hypotonic solutions because of the effect of the cell wall, which prevents the membrane from breaking and limits the amount of water that can move into the cell. The plant cell is said to be turgid when osmosis ceases despite there being a clear concentration gradient between the cellular fluid and the external fluid.

Well lysis doesn't occur in salt because, as you pointed out, it's hypertonic so the water moves out.

Unfortunately, it isn't. I would've expected most schools to be up to here by now but, our school started early during orientation and it's such that our pace is considerably slower than expected.

EDIT: 500'th post D: I really need to get a life...

We finished our course a day before the exam, don't worry mate :)
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 23, 2014, 08:17:16 pm
Do we need to know the meaning of phagocytosis in unit3/4 biology?
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 23, 2014, 08:34:30 pm
Do we need to know the meaning of phagocytosis in unit3/4 biology?

Yes.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 08:37:24 pm
Do we need to know the meaning of phagocytosis in unit3/4 biology?

It'll be something you remember pretty easily by the end of this unit because you get introduced to cells called phagocytes. What they do, eat things essentially, will give you that cue to remember. But as MM1 said, you definitely need to know it.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 23, 2014, 08:38:26 pm
Phagocytosis is basically when bulk material is taken up by a cell as a solid yeah?
Any more detail required?
Also, what is the function of the nucleus? Its pretty simple but I am having trouble wording it :(

thanks
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 08:42:56 pm
Phagocytosis is basically when bulk material is taken up by a cell as a solid yeah?
Any more detail required?
Also, what is the function of the nucleus? Its pretty simple but I am having trouble wording it :(

thanks

Yeah, that's pretty much it. Phagocytosis mainly involves cells and pieces of cells really. And nope, no more detail required other than perhaps how it works (which is the same as endocytosis because it is endocytosis).

That is a hard one to word, so I'll leave that to someone else for practice.
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on February 23, 2014, 08:58:35 pm
Also, what is the function of the nucleus? Its pretty simple but I am having trouble wording it :(

thanks

Controls all cellular activity within the cell [by controlling what proteins are synthesized?]

(Please quote me if I'm wrong/should use better wording haha)
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 09:01:25 pm
Controls all cellular activity within the cell [by controlling what proteins are synthesized?]

(Please quote me if I'm wrong/should use better wording haha)

Right track, but yeah, needs better wording.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 23, 2014, 09:05:05 pm
Do we need to know what the cell skeleton is? Such as tubules, microtubules etc.
Also, how is everyone making their summary notes? Summarising the textbook chapter by chapter or summarising stuff they learn at school?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 09:06:31 pm
Do we need to know what the cell skeleton is? Such as tubules, microtubules etc.
Also, how is everyone making their summary notes? Summarising the textbook chapter by chapter or summarising stuff they learn at school?

I think it has been said here before that this is no longer in the course. TO be honest, I didn't know it in year 12
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 23, 2014, 09:07:27 pm
I think it has been said here before that this is no longer in the course. TO be honest, I didn't know it in year 12

oh really? That makes life so much easier :)
Is this correct? " Osmosis is the passive, net movement of water molecules across a semi-permeable membrane, from a hypotonic solution to a hypertonic solution."
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 23, 2014, 09:10:32 pm
Also, what is the function of the nucleus? Its pretty simple but I am having trouble wording it

The nucleus contains chromosomes that control the hereditary characteristics of an organism. DNA is mainly located in the nucleus and is responsible for protein synthesis and maintenance of the genetic features of an individual.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 23, 2014, 09:11:47 pm
Is this correct? " Osmosis is the passive, net movement of water molecules across a semi-permeable membrane, from a hypotonic solution to a hypertonic solution."

Maybe mention "free water molecules" instead, but otherwise it sounds like a good definition.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 23, 2014, 09:15:14 pm
Maybe mention "free water molecules" instead, but otherwise it sounds like a good definition.

Good point. Ill add that in. Will this definition get me full marks?
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on February 23, 2014, 09:31:46 pm
Right track, but yeah, needs better wording.
How would you define it properly?

Also, what do we exactly have to know about the 'ATP-ADP cycle; factors affecting rate of energy transformations' which is in the current study design? I'm confused with what we are actually required to know.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 09:40:47 pm
How would you define it properly?

Also, what do we exactly have to know about the 'ATP-ADP cycle; factors affecting rate of energy transformations' which is in the current study design? I'm confused with what we are actually required to know.

Hmmm it's difficult. To be honest, I'm finding it a bit difficult myself to word it properly.

I'd say it's function is to store and synthesise hereditary information, but even that sounds a little shit.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 23, 2014, 10:12:26 pm
How would you define it properly?

Also, what do we exactly have to know about the 'ATP-ADP cycle; factors affecting rate of energy transformations' which is in the current study design? I'm confused with what we are actually required to know.

Hm.. the nucleus encodes the hereditary information of the cell in the form of DNA, necessary for the synthesis of proteins, and in turn the activities of the cell.

ATP-ADP cycle; that ATP is formed through an endergonic process involving ADP + Pi, and that ADP + Pi is formed through an exergonic process, involving the breakdown of ATP by ATPase.

Edit: grammar
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 23, 2014, 10:15:40 pm
I'm going to cheat on the nucleus question (because I've already passed Biology, making it ok!):

Penguin Dictionary of Biology says: the organelle in eukaryotic cells making about 10% of the cell's volume and containing the cell's chromosomes
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 24, 2014, 07:27:48 am
wow that is a reallly brief explanation of nucleus. Can I use it in the exam?
Title: Re: VCE Biology Question Thread
Post by: hobbitle on February 24, 2014, 07:34:44 am
If you can't explain it (anything) in one sentence, you need to understand it better!! :-P
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on February 24, 2014, 09:29:52 am
Just a few questions:
1)Which cell organelles are the heaviest and which are the lightest? Could someone please make a list for me!
2)How do you determine the size (in micrometers) of cells when given the magnification?
3)What's the average size of prokaryotic and eukaryotic cells (in micrometers)?
4)Why is protein and RNA more prevalent than DNA, lipids, and glycogen in prokaryotic cells?
5)Are the sequence of bases which code for amino acids universal over all organisms?

Thanks! :)
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 24, 2014, 04:34:03 pm
Can water ever be actively transported? Example of such a scenario if it's a possibility?
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 24, 2014, 04:38:03 pm
Just a few questions:
1)Which cell organelles are the heaviest and which are the lightest? Could someone please make a list for me!
2)How do you determine the size (in micrometers) of cells when given the magnification?
3)What's the average size of prokaryotic and eukaryotic cells (in micrometers)?
4)Why is protein and RNA more prevalent than DNA, lipids, and glycogen in prokaryotic cells?
5)Are the sequence of bases which code for amino acids universal over all organisms?

Thanks! :)

Care to share some thoughts or attempt these first :) ?

Can water ever be actively transported? Example of such a scenario if it's a possibility?

I don't think thats in the VCE course, i wouldn't worry too much about it.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 24, 2014, 05:25:59 pm
Are the roles of glycoproteins on the cell membrane surface just cellular communication and cellular recognition?

Or can some protein channels be composed of glycoproteins? :)
Thanks!
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 24, 2014, 05:32:38 pm
Are the roles of glycoproteins on the cell membrane surface just cellular communication and cellular recognition?

Or can some protein channels be composed of glycoproteins? :)
Thanks!

Carbohydrate chains that are attached to protein channels are referred to as glycoproteins whereas carbohydrate chains that are attached to the phospholipids are referred to as glycolipids.
Generally speaking, these carbohydrates are involved in cellular communication and recognition of foreign substances.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 24, 2014, 05:48:08 pm
Can water ever be actively transported? Example of such a scenario if it's a possibility?

Yes, it is transported to some desert plants (I can't remember the name) to help maintain their tumour pressure, even though the concentration of water is probably greater inside the plant than the hot and dry desert.

I don't think thats in the VCE course, i wouldn't worry too much about it.

Actually, my Osmosis SAC had a question regarding this that was worth a fair few marks. However, they gave enough information for a logical conclusion to be drawn even if you weren't familiar about water being actively transported.
Title: Re: VCE Biology Question Thread
Post by: MagicGecko on February 24, 2014, 05:50:27 pm
Are the roles of glycoproteins on the cell membrane surface just cellular communication and cellular recognition?
Glycoproteins are also involved in immunity, as you will learn in AOS 2.
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 24, 2014, 06:01:18 pm
Yes, it is transported to some desert plants (I can't remember the name) to help maintain their tumour pressure, even though the concentration of water is probably greater inside the plant than the hot and dry desert.

I think you mean tugor/turgidity or osmotic pressure over tumour pressure  :P. Just a hunch.

Actually, my Osmosis SAC had a question regarding this that was worth a fair few marks. However, they gave enough information for a logical conclusion to be drawn even if you weren't familiar about water being actively transported.

I was talking more in the context of mammalian or even animal cells where its likely to be far beyond the context of the VCE study design. No idea about plants though.
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 24, 2014, 06:02:57 pm
Yes, it is transported to some desert plants (I can't remember the name) to help maintain their tumour pressure, even though the concentration of water is probably greater inside the plant than the hot and dry desert.

Actually, my Osmosis SAC had a question regarding this that was worth a fair few marks. However, they gave enough information for a logical conclusion to be drawn even if you weren't familiar about water being actively transported.

Thanks! Btw did you mean turgor pressure?
Title: Re: VCE Biology Question Thread
Post by: popoy111 on February 24, 2014, 06:10:37 pm
in the potato osmosis sac i have been asked to explain 3 possible sources of error? What are these?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 24, 2014, 06:28:32 pm
Can water ever be actively transported? Example of such a scenario if it's a possibility?

As slothpumba pointed out, not part of the course.

But, because it's relatively basic, the answer is no. Water itself isn't actively transported. Although, active transport can be used to maintain water balance and that's by actively transport salts either in or out of the cell, thereby setting up a concentration gradient and receiving water via osmosis.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 24, 2014, 06:33:06 pm
in the potato osmosis sac i have been asked to explain 3 possible sources of error? What are these?

Don't know why my last post didn't show but anyways, my guess is:
-You may have read the mass of the potato or amount of solution (whilst measuring) inaccurately
-You may have dried the potato slices with paper towel excessively
-There may have been more or less salt in one or more of the solutions
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 24, 2014, 06:36:09 pm
As slothpumba pointed out, not part of the course.

But, because it's relatively basic, the answer is no. Water itself isn't actively transported. Although, active transport can be used to maintain water balance and that's by actively transport salts either in or out of the cell, thereby setting up a concentration gradient and receiving water via osmosis.

Thanks! Also, can it be said that a small-scale concentration gradient between two solutions means that osmosis would occur at a slower rate?
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 24, 2014, 06:37:37 pm
How does water get through the semi-permeable membrane when the main role of this phospholipid bi-layer is to keep water out?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 24, 2014, 06:42:44 pm
How does water get through the semi-permeable membrane when the main role of this phospholipid bi-layer is to keep water out?

The main role of the membrane isn't to keep water out; it's to manage the inputs and outputs of the cell. The membrane has tiny pores between the phospholipids which allow water molecules to diffuse through. Conversely, it is impermeable to charged and polar molecules which therefore require protein channels or specific protein carrier molecules.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 24, 2014, 06:46:35 pm
ok.  :-\
So if the water travels through the tiny pores, the hydrophobic tails wont stop it from entering the cell?
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 24, 2014, 06:47:03 pm
sorry for posting it twice. My computer stuffed up

Mod: don't worry, fixed it
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 24, 2014, 06:49:58 pm
Thanks! Also, can it be said that a small-scale concentration gradient between two solutions means that osmosis would occur at a slower rate?

Absolutely! This is a really important factor in diffusion and osmosis. The larger the conc. gradient, the faster the rate of diffusion/osmosis.
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 24, 2014, 06:53:17 pm
ok.  :-\
So if the water travels through the tiny pores, the hydrophobic tails wont stop it from entering the cell?

It's not VCE level but the membrane has specific channels to allow water in called Aquaporins. It's been awhile since i've done biochem so i could be mistaken but i thought water was in the category of molecules that are so small that they can simply just slip through the membrane by diffusion without any specific need for channels, carriers, etc.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 24, 2014, 06:59:23 pm
It's not VCE level but the membrane has specific channels to allow water in called Aquaporins. It's been awhile since i've done biochem so i could be mistaken but i thought water was in the category of molecules that are so small that they can simply just slip through the membrane by diffusion without any specific need for channels, carriers, etc.

All of that's right (as far as I know).

Water slips through the gaps, it's just a bit of a slower process than aquaporins obviously.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 24, 2014, 07:01:14 pm
All of that's right (as far as I know).

Water slips through the gaps, it's just a bit of a slower process than aquaporins obviously.

So, if we be a bit specific and mention aquaporins instead of pores, will that be okay?
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 24, 2014, 07:01:58 pm
How do peripheral proteins work? What do they do?
Title: Re: VCE Biology Question Thread
Post by: slothpomba on February 24, 2014, 07:13:08 pm
So, if we be a bit specific and mention aquaporins instead of pores, will that be okay?

Consult your teacher, it definitely wasn't taught in VCE when i did it and it's a relatively (for biology anyway) new discovery.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 24, 2014, 07:39:33 pm
So, if we be a bit specific and mention aquaporins instead of pores, will that be okay?

No, don't talk about them at all, they're not in the course as slothpomba and I have both indicated. As far as you're concerned, water can filter through the tiny holes of the membrane itself and that's how it gets through. You will not receive any credit for talking about aquaporins no matter how correct it is.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 24, 2014, 07:52:27 pm
In the potato sac for osmosis, Why do we have to calculate the percent change in mass instead of just using the change in
mass itself?
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 24, 2014, 07:53:53 pm
In the potato sac for osmosis, Why do we have to calculate the percent change in mass instead of just using the change in
mass itself?

So you can graph it and refer to it when explaining your results.
Title: Re: VCE Biology Question Thread
Post by: millie96 on February 24, 2014, 07:53:58 pm
What travels through carrier proteins and what type of transport is it?
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 24, 2014, 07:56:57 pm
What travels through carrier proteins and what type of transport is it?

Generally, large, charged, lipid insoluble substances must travel through carrier proteins in a process called 'Facilitated Diffusion'.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 24, 2014, 07:58:39 pm
Thanks! Btw did you mean turgor pressure?

Yes, I did. Sorry for the spelling error!
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 24, 2014, 07:59:12 pm
So you can graph it and refer to it when explaining your results.

But u can also graph the actual weight so why percent change in mass?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 24, 2014, 08:03:52 pm
But u can also graph the actual weight so why percent change in mass?

Because some of the potatoes may have decreased in mass so by graphing the percentage, it makes it much more easier to understand.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 24, 2014, 08:05:15 pm
But u can also graph the actual weight so why percent change in mass?

You can, if you want, and if your teacher allows it. However, you will find that it's slightly more readable to sketch the graph against percent change in mass. Explaining, your results using percentage change in mass probably sounds better? Idk, there's not all that much of a big difference really.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 24, 2014, 08:07:47 pm
When you are defining terms such as 'active transport' or 'carrier proteins' and you talk about the movement of substances across membranes, would it be correct to say 'plasma membrane' or 'membrane' in general?

eg. - Active transport is the movement of dissolved substances across the plasma membrane, which requires energy in order to move against a concentration gradient (from a region of relatively low solute concentration to a region of relatively high solute concentration) or:

Active transport is the movement of dissolved substances across a membrane, which requires energy in order to move against a concentration gradient (from a region of relatively low solute concentration to a region of relatively high solute concentration)?

Thanks! :)
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 24, 2014, 08:08:40 pm
You can, if you want, and if your teacher allows it. However, you will find that it's slightly more readable to sketch the graph against percent change in mass. Explaining, your results using percentage change in mass probably sounds better? Idk, there's not all that much of a big difference really.

Thanks. Our teacher said that % change in mass will remove any errors in weighing the potato. Removes variation in initial mass. But that doesn't make sense to me. Ah well, I'll just memorise it
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 24, 2014, 08:10:06 pm
Does anyone have any good sample questions, involving the movement of substances across membranes, in preparation for the upcoming SAC? :)

Title: Re: VCE Biology Question Thread
Post by: rhinwarr on February 24, 2014, 08:11:35 pm
What are the functional roles of alpha helices and beta sheets in proteins?
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 24, 2014, 08:17:08 pm
Does anyone have any good sample questions, involving the movement of substances across membranes, in preparation for the upcoming SAC? :)

Check out pg 48 :P
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 24, 2014, 08:20:41 pm
What are the functional roles of alpha helices and beta sheets in proteins?

They give a protein it's physical characteristics. For example, silk is composed mostly of beta pleated sheets, and as a result is not very stretchy. However, most proteins have actually a combination of both alpha Helices and beta pleated sheets. Some have separate versions of both secondary structures, such as alpha keratin and beta keratin.

It's more of its tertiary or quaternary structure that gives it a 'functional role' as in the case of enzymes.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 24, 2014, 08:35:16 pm
Check out pg 48 :P

Thanks! :)
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 24, 2014, 08:36:32 pm
Does anyone have any good analogies they use when remembering things for biology?

I remember that "All good things are pure"
So, Adenine and Guanine are purines :)

- I read it off some website!
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on February 25, 2014, 12:09:26 am
Care to share some thoughts or attempt these first :) ?

1)Which cell organelles are the heaviest and which are the lightest? Could someone please make a list for me!
I know that the nucleus is the heaviest, but I'm not entirely sure what order the other organelles follow.
2)How do you determine the size (in micrometers) of cells when given the magnification?
No idea.  :-[
3)What's the average size of prokaryotic and eukaryotic cells (in micrometers)?
Once again, I have no idea. I only know that prokaryotic cells are generally smaller than eukaryotic cells.
4)Why is protein and RNA more prevalent than DNA, lipids, and glycogen in prokaryotic cells?
Prokaryotic cells are simpler, therefore their structures mainly consist of proteins........not too sure about the rest!
5)Are the sequence of bases which code for amino acids universal over all organisms?
I have a feeling that they are because, after all, all DNA and RNA are made up from the same basic nucleotide structures. The question from the practice exam that I was doing specifically referred to TAG which I know is stop codon. It asked if it was present in cat's as a stop codon too.
Title: Re: VCE Biology Question Thread
Post by: Rod on February 25, 2014, 12:12:40 am
Does anyone have any good analogies they use when remembering things for biology?

I remember that "All good things are pure"
So, Adenine and Guanine are purines :)

- I read it off some website!
Pyramids are sharp. They CUT - Cytosine, guanine, thymine (pyrimidines)

A greedy cat ate eggs = auxin, gibberilin, cytokinis, absisic acid, ethelene (sorry for spelling errors)

Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 25, 2014, 12:15:10 am
Care to share some thoughts or attempt these first :) ?

1)Which cell organelles are the heaviest and which are the lightest? Could someone please make a list for me!
I know that the nucleus is the heaviest, but I'm not entirely sure what order the other organelles follow.
2)How do you determine the size (in micrometers) of cells when given the magnification?
No idea.  :-[
3)What's the average size of prokaryotic and eukaryotic cells (in micrometers)?
Once again, I have no idea. I only know that prokaryotic cells are generally smaller than eukaryotic cells.
4)Why is protein and RNA more prevalent than DNA, lipids, and glycogen in prokaryotic cells?
Prokaryotic cells are simpler, therefore their structures mainly consist of proteins........not too sure about the rest!
5)Are the sequence of bases which code for amino acids universal over all organisms?
I have a feeling that they are because, after all, all DNA and RNA are made up from the same basic nucleotide structures. The question from the practice exam that I was doing specifically referred to TAG which I know is stop codon. It asked if it was present in cat's as a stop codon too.
Better to make your own thread if you're going to bomb with heaps of questions
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on February 25, 2014, 04:21:45 pm
Hi, just have some questions regarding movement of substances through membrane.
In my experiment, I have to place beet root slices in different alcohol concentration and observe the movement. My teacher said that I can not refer the concentrated alcohol solution as a hypertonic environment since this is not about the amount of solute in the extra cellular fluid. What should I refer this type of alcohol solution to? Secondly, what I have observed through the experiment is that the more concentrated the alcohol solution, the more pink pigment from beet root diffuse out of the cell, is it because when alcohol moves into the cell through diffusion, the membrane is under stressed and hence release its pigment to balance the concentration gradient.

Finally, in the experiment, I also need to place beet root slices in different type of pH range solution as well. In a pH of 2, I realize that the pink pigment is released much significantly compared to the pH of 6 and 8, is it because the acidity of pH has denatured the protein channels, leaving a huge gaps in the membrane, hence the cell releases its cell content more readily?

Thanks heaps guys :d!
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 25, 2014, 04:45:45 pm
Pyramids are sharp. They CUT - Cytosine, guanine, thymine (pyrimidines)

A greedy cat ate eggs = auxin, gibberilin, cytokinis, absisic acid, ethelene (sorry for spelling errors)

Do we need to know the second part? What is that for anyways?
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on February 25, 2014, 04:53:40 pm
Do we need to know the second part? What is that for anyways?
Auxins, cytokinis,...etc are different type of hormones in plants, they all play different role in the growth and development if the plant body. You will study those in AOS 2 as long as I can remember.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 25, 2014, 05:47:55 pm
How is the amylase in fungi similar/different from amylase in humans?
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 25, 2014, 05:49:59 pm
Can someone please concisely explain the factors affecting enzyme activity/rate of reaction? Cheers :)
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 25, 2014, 06:50:34 pm
Can someone please concisely explain the factors affecting enzyme activity/rate of reaction? Cheers :)

pH- Can change enzyme shape by changing the charge on amino acids.
Temperature- Kinetic energy causes molecules to move around faster. At a low temp, the molecules (enzyme/substrate) move more slowly and thus, lower rate of reaction. At a higher temp, the molecules move around faster so there are more collisions. However, if the temp increases above the optimum, enzymes will dentaure permanently.
Substrate concentration- Reaction rate increases with increasing substrate concentration. There is a limit to this increase however - once all active sites are occupied (saturated), adding more substrate will not increase the reaction rate
Enzyme Concentration-  As the enzyme concentration increases the rate of the reaction increases linearly, because there are more enzyme molecules available to catalyse the reaction. At high enzyme concentration, the substrate becomes limiting so the reaction becomes constant.
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on February 25, 2014, 07:07:18 pm
Why does glucose contain polar groups and not triglycerides?
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 25, 2014, 07:14:04 pm
Does endocytosis and exocytosis require energy?
Title: Re: VCE Biology Question Thread
Post by: alondouek on February 25, 2014, 07:16:40 pm
Does endocytosis and exocytosis require energy?

Yes - they are both active processes.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 25, 2014, 07:35:14 pm
Is the word 'osmose' a proper term?
For example " The higher the osmotic pressure of a solution, the more likely it is that water will osmose into the solution."

Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 25, 2014, 07:37:35 pm
Is the word 'osmose' a proper term?
For example " The higher the osmotic pressure of a solution, the more likely it is that water will osmose into the solution."

I found it in the dictionary so it is a proper term
Osmose= "undergo diffusion by osmosis: to cause something to diffuse by osmosis, or undergo osmosis"
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 25, 2014, 07:58:37 pm
I found it in the dictionary so it is a proper term
Osmose= "undergo diffusion by osmosis: to cause something to diffuse by osmosis, or undergo osmosis"

Thankyou so much! :)
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on February 25, 2014, 08:06:02 pm
Thankyou so much! :)

Do you happen to have any practise osmosis questions? I have my sac on friday on osmosis
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on February 25, 2014, 08:11:55 pm
Why is nitrogen an essential inorganic element for all organisms? :(
Title: Re: VCE Biology Question Thread
Post by: alondouek on February 25, 2014, 08:21:45 pm
Why is nitrogen an essential inorganic element for all organisms? :(

Think back to the composition of biomacromolecules. Which classes of biomacromolecules require nitrogen as part of their structure?

Proteins (CHON(S)) and Nucleic Acids (CHONP(S))

Without nitrogen, these biomacromolecules couldn't exist.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 25, 2014, 08:22:21 pm
Do you happen to have any practise osmosis questions? I have my sac on friday on osmosis

Yeah! But they are pretty typical, but still good for revision!

- What will happen to an animal/plant cell when placed in a strong salt solution? A pure water solution?

- Describe the conditions under which plant cells lose turgor

- Why are red blood cells suspended in saline (salt) solution and not pure water.

- The amoeba a single celled organism, lives in fresh water. Identify a problem foe this organism and investigate how this organism overcomes this problem.

Goodluck! My SAC is tomorrow! :)
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 25, 2014, 08:24:55 pm
When you say that an animal cell loses water, via osmosis and becomes shriveled up, is it right to say that the animal cell is 'crenated'?

Or can that term only be used with red blood cells?

:)
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on February 25, 2014, 08:27:14 pm
When you say that an animal cell loses water, via osmosis and becomes shriveled up, is it right to say that the animal cell is 'crenated'?

Or can that term only be used with red blood cells?

:)

From my understanding, that term can be used with any type of animal cell when there is a considerable net water loss from the cell :)
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on February 25, 2014, 08:28:44 pm
Hi, just have some questions regarding movement of substances through membrane.
In my experiment, I have to place beet root slices in different alcohol concentration and observe the movement. My teacher said that I can not refer the concentrated alcohol solution as a hypertonic environment since this is not about the amount of solute in the extra cellular fluid. What should I refer this type of alcohol solution to? Secondly, what I have observed through the experiment is that the more concentrated the alcohol solution, the more pink pigment from beet root diffuse out of the cell, is it because when alcohol moves into the cell through diffusion, the membrane is under stressed and hence release its pigment to balance the concentration gradient.

Finally, in the experiment, I also need to place beet root slices in different type of pH range solution as well. In a pH of 2, I realize that the pink pigment is released much significantly compared to the pH of 6 and 8, is it because the acidity of pH has denatured the protein channels, leaving a huge gaps in the membrane, hence the cell releases its cell content more readily?

Thanks heaps guys :d!
Just repost it since I still don't know how to deal with these questions :( !
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on February 25, 2014, 08:37:29 pm
Would adding a cofactor or coenzyme help maximise the rate of a enzyme-controlled reaction?
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 25, 2014, 08:42:16 pm
Would adding a cofactor or coenzyme help maximise the rate of a enzyme-controlled reaction?

Enzymes require either a cofactor or coenzyme in order to function. You shouldn't describe them as "maximising" the rate of the reaction. They are essential for an enzyme to function as a biological catalyst.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 25, 2014, 09:04:46 pm
Do the factors that affect enzymes apply to all proteins?
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 25, 2014, 09:22:29 pm
Do the factors that affect enzymes apply to all proteins?

Not all. Factors such as increasing substrate concentration don't really have an effect on structural or fibrous proteins. Factors such as pH and temperature do. However, not all proteins have an optimum temperature or pH like enzymes do, and so will not be affected in this regard.

EDIT: I didn't read the your question properly the first time, so I fixed up my answer now C:
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 25, 2014, 10:19:40 pm
Do the factors that affect enzymes apply to all proteins?

Proteins that aren't enzymes seldom do anything. They normally are something rather than do something. So no. Anything relating to functionality is irrelevant when talking about other proteins.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 25, 2014, 10:27:47 pm
How is the amylase in fungi similar/different from amylase in humans?

Bump...This was in my SAC and I have no clue :/
+1 to anybody who gives an answer!
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 25, 2014, 10:33:03 pm
Bump...This was in my SAC and I have no clue :/
+1 to anybody who gives an answer!

That should not be in your SAC at all....

I'm fairly certain that that has absolutely nothing to do with the course at all, very weird!
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 25, 2014, 10:44:24 pm
That should not be in your SAC at all....

I'm fairly certain that that has absolutely nothing to do with the course at all, very weird!

That's what I thought...then I remembered that it was meant to relate to our starch/amylase experiment somehow (which I payed no attention to), but it's still a slightly vague question IMO
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 25, 2014, 10:47:19 pm
That's what I thought...then I remembered that it was meant to relate to our starch/amylase experiment somehow (which I payed no attention to), but it's still a slightly vague question IMO

So would it be correct in the slightest to say that fungal amylase and human amylase break down the same substances (starch to glucose)?
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on February 25, 2014, 10:48:45 pm
That's what I thought...then I remembered that it was meant to relate to our starch/amylase experiment somehow (which I payed no attention to), but it's still a slightly vague question IMO

yeah it is quite strange but just going to take a guess -- There should be no difference because amino-acids are universal so amylase in both fungi and humans should be the same - their structure, function, etc.

But I may be wrong --> http://www.wisegeek.com/what-is-an-amylase-protein.htm

Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 25, 2014, 10:49:59 pm
If there is more information given, such as in a SAC/experiment, then that's a perfectly reasonable question. It's just not something you should know off the top of your head.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on February 26, 2014, 05:17:00 pm
If you get one average sac mark, does that affect your whole study score? :/
Title: Re: VCE Biology Question Thread
Post by: MM1 on February 26, 2014, 05:22:22 pm
If you get one average sac mark, does that affect your whole study score? :/

Not really. Don't be deterred by your SAC marks. Just try to do well on the exam.
Title: Re: VCE Biology Question Thread
Post by: millie96 on February 26, 2014, 05:23:14 pm
In a hypertonic solution- as there is a higher concentration of solutes outside the cell relative to inside, does this mean that there is a higher concentration of h20 within the cell compared to outside? Is this why osmosis occurs and the cells lose mass in a hypertonic solution?
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 26, 2014, 05:25:18 pm
In a hypertonic solution- as there is a higher concentration of solutes outside the cell relative to inside, does this mean that there is a higher concentration of h20 within the cell compared to outside? Is this why osmosis occurs and the cells lose mass in a hypertonic solution?

Yes.
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on February 26, 2014, 05:56:49 pm
If I place plant cell in a very high alcohol concentration solution, then alcohol will diffuse into the cell. Hence, will cause the cell to burst ? Even though I know that plant have cell wall, but is there any chances where the pressure inside is too high and the cell burst out, releasing its content?
Thanks guys!
Title: Re: VCE Biology Question Thread
Post by: Sup on February 26, 2014, 06:09:21 pm
If I place plant cell in a very high alcohol concentration solution, then alcohol will diffuse into the cell. Hence, will cause the cell to burst ? Even though I know that plant have cell wall, but is there any chances where the pressure inside is too high and the cell burst out, releasing its content?
Thanks guys!

Wouldn't water move out of the plant cell via osmosis (because the plant cell is hypotonic to the alcohol solution) causing the plant cell to shrink?
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 26, 2014, 06:23:05 pm
If I place plant cell in a very high alcohol concentration solution, then alcohol will diffuse into the cell. Hence, will cause the cell to burst ? Even though I know that plant have cell wall, but is there any chances where the pressure inside is too high and the cell burst out, releasing its content?
Thanks guys!

Net movement of water will be to outside the cell to begin with. Remember, the plant cell wants to maintain an Isotonic environment, hence the reason for water to move out. Some solute particles will move in but, there will never be too much moving in as once the concentration gradient is equal there will be no net movement of water or solute into or out of the cell.
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on February 26, 2014, 06:37:16 pm
Net movement of water will be to outside the cell to begin with. Remember, the plant cell wants to maintain an Isotonic environment, hence the reason for water to move out. Some solute particles will move in but, there will never be too much moving in as once the concentration gradient is equal there will be no net movement of water or solute into or out of the cell.
Wouldn't water move out of the plant cell via osmosis (because the plant cell is hypotonic to the alcohol solution) causing the plant cell to shrink?
Thanks guys. I'm a bit confused when placing plant cell inside the alcohol solution. For instance, my experiment is to place a beetroot cell inside different alcohol concentration solutions. I observe that the more concentrated the alcohol, the more pink pigment from beetroot moves out of the cell. So just repeating what you guys have mentioned, "there will be a net movement of alcohol into the cell through simple diffusion due to the lipid nature of alcohol, however, there will also be a net movement of pink pigment (anthocyanin) from the beetroot cell out side of the cell to balance the concentration gradient. Consequently, the more concentrated the alcohol solution, the more anthocyanin moves out of the cell, generating an equilibrium state." Is this explanation right?

Also, when I write down the word "hypertonic solution" to refer to the alcohol environment, by teacher said it wasn't right since this is not talking about the amount of solute, she just wants me to refer to it as "a high concentration of alcohol solution", but somehow, this still doesn't make sense to me. Is she right? Can anyone give me a  more detailed explanation?
Thanks so much :D!
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 26, 2014, 07:27:33 pm
Also, when I write down the word "hypertonic solution" to refer to the alcohol environment, by teacher said it wasn't right since this is not talking about the amount of solute, she just wants me to refer to it as "a high concentration of alcohol solution", but somehow, this still doesn't make sense to me. Is she right? Can anyone give me a  more detailed explanation?
Thanks so much :D!

If the solution is not pure alcohol, alcohol is the solute and your teacher is wrong. However, it's also important to remember that alcohol can go straight through the membrane and will diffuse pretty quickly.
Title: Re: VCE Biology Question Thread
Post by: rhinwarr on February 26, 2014, 07:44:16 pm
Situation:
Protein solution is placed in a cellulose membrane and submerged in a beaker full of alkaline solution.

What would be expected to happen? I think water and salt from the alkaline solution would enter the membrane, but what would go out? Would it be right in saying nothing goes out or should I say that water and salt goes out of the membrane (since particles move in both directions but the net movement is into the membrane?)
Title: Re: VCE Biology Question Thread
Post by: Frozone on February 26, 2014, 09:29:12 pm
Hey guys I am stumped on this question.
In eukaryotic cells the conversion of adp and phosphate into ATP occurs:.....

I put my answer as "in both the mitochondria and the cytoplasm, and releases energy" since cellular respiration involves a catabolic reaction.
But the answer is "in both the mitochondria and the cytoplasm, and requires energy".
Why is this so? I have a hunch  that it's because energy is needed to convert adp and phosphate into ATP but I'm not sure.  :-\
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 26, 2014, 09:44:36 pm
yeah it is quite strange but just going to take a guess -- There should be no difference because amino-acids are universal so amylase in both fungi and humans should be the same - their structure, function, etc.

But I may be wrong --> http://www.wisegeek.com/what-is-an-amylase-protein.htm

There are normally small differences between the primary structures of human and fungal proteins. There was an exam question a few years ago that compared cow, horse, human and pig insulin and the differences can actually be quite large, meaning that the protein tends to operate a little differently under different temperatures.
Title: Re: VCE Biology Question Thread
Post by: Jason12 on February 26, 2014, 09:57:12 pm
for hypotonic solutions my revision sheet says "remember to say compared to the cytosol the solution is hypotonic. How is cytosol involved in hypertonic/hypotonic solutions.?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 26, 2014, 10:03:13 pm
for hypotonic solutions my revision sheet says "remember to say compared to the cytosol the solution is hypotonic. How is cytosol involved in hypertonic/hypotonic solutions.?

Hypotonic means "the solutes are less concentrated than ____". The cytosol is the fluid you often compare it to.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 26, 2014, 10:12:23 pm
Hey guys I am stumped on this question.
In eukaryotic cells the conversion of adp and phosphate into ATP occurs:.....

I put my answer as "in both the mitochondria and the cytoplasm, and releases energy" since cellular respiration involves a catabolic reaction.
But the answer is "in both the mitochondria and the cytoplasm, and requires energy".
Why is this so? I have a hunch  that it's because energy is needed to convert adp and phosphate into ATP but I'm not sure.  :-\
Yeah, the formation of ATP from ADP + Pi is an anabolic process, hence an endergonic (energy-requiring) process.
Title: Re: VCE Biology Question Thread
Post by: Jason12 on February 27, 2014, 04:27:19 pm
I know there are hydrogen bonds between nucleotides in DNA but what about rna since it is single stranded so where do the h bonds go
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 27, 2014, 04:29:45 pm
For hypertonic and hypertonic. Is it true that it always compares the cell to the external solution. So the cell is hypertonic to the sucrose solution, so the cell is hypertonic and hence has more sugar. Or not???
Title: Re: VCE Biology Question Thread
Post by: grannysmith on February 27, 2014, 04:51:31 pm
For hypertonic and hypertonic. Is it true that it always compares the cell to the external solution. So the cell is hypertonic to the sucrose solution, so the cell is hypertonic and hence has more sugar. Or not???
Yeah, pretty much, although it refers to solutions and their relative concentration of solutes in general.
So if the cell is hypertonic to its extracellular fluid, then the extracellular fluid is hypotonic to the cell. But it doesn't necessarily refer to a specific solute (sucrose), rather it refers any type of solute (substances which dissolve in the solvent, water).
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on February 27, 2014, 05:41:18 pm
If I place a beetroot cell inside a solution with a pH of 10 and observes that there is not net movement of pink pigment from the beetroot cell (anthocyanin substance) outside of the cell. Is it possible for me to assume that the alkalinity of pH 10 has no effect on the cell's membrane and hence create no net movement of solute?
Thanks guys.
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on February 27, 2014, 06:15:06 pm
In the Calvin cycle, does the anabolism of RuBP and CO2 produce water? I'm trying to figure out where the water product in the photosynthesis equation comes from! Also, when CO2 combines with RuBP, is O2 released?

Does the amount of PGAL/G3P released for glucose synthesis vary in photosynthesising organisms?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: Jason12 on February 27, 2014, 09:35:01 pm
in diffusion and osmosis what is meant by NET movement of a substance/water molecules?

Also what is a good definition/explanation of a protein channel?
Title: Re: VCE Biology Question Thread
Post by: rhinwarr on February 27, 2014, 09:50:26 pm
In reality, the particles move in both directions but due to the concentration gradient, the overall movement is down the concentration gradient. Even in equilibrium when the concentrations are the same, the particles are still moving between the solutes but there is no overall movement (change in concentration).

A protein channel is a protein embedded in the plasma membrane which facilitates the movement of particles across the membrane by facilitated diffusion or active transport.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on February 27, 2014, 11:22:15 pm
Every atom, even those that are metallic, are always on the move. It's impossible for them not to be (practically).
Title: Re: VCE Biology Question Thread
Post by: eagles on February 28, 2014, 06:27:37 pm
How is the amylase in fungi similar/different from amylase in humans?

They're different because they function at different optimum temperatures.

While the optimum temperate for amylase in humans may be around 35 degrees Celsius, it is much higher in fungi because of the warm environments they live in, thus contributing in an increased optimum temperature.
Title: Re: VCE Biology Question Thread
Post by: alchemy on February 28, 2014, 08:41:49 pm
They're different because they function at different optimum temperatures.

While the optimum temperate for amylase in humans may be around 35 degrees Celsius, it is much higher in fungi because of the warm environments they live in, thus contributing in an increased optimum temperature.

Yeah, I guess. Now I really know I got that one wrong..uhhh
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on February 28, 2014, 11:55:31 pm
Hey. For plant hormones gibberellins are we required to know the process of seed germination?? Thanks.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on March 01, 2014, 10:17:45 am
List three possible death signals a cell might receive to initiate apoptosis

Thanks  :D
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on March 01, 2014, 02:20:46 pm
If the cells are no longer needed, if they are malfunctioning/ not working properly anymore. If there are too many of the cells in the body. Think I'm missing one
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on March 01, 2014, 08:14:48 pm
To what extent do we need to know about photosynthesis?
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 01, 2014, 08:25:54 pm
To what extent do we need to know about photosynthesis?

I asked my teacher this yesterday and she said that we do need to know the inputs and outputs mainly, the conditions affecting it and a brief overview of what happens in each of the stages. They've toned photosynthesis down a lot in the study design so you don't need to know about C3 and C4 plants, and definitely don't need to know all those intermediates in the Calvin Cycle and even in the Kreb's cycle. Good question though, and I hope my answer will save you from wasting your time (:
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on March 01, 2014, 08:36:28 pm
I asked my teacher this yesterday and she said that we do need to know the inputs and outputs mainly, the conditions affecting it and a brief overview of what happens in each of the stages. They've toned photosynthesis down a lot in the study design so you don't need to know about C3 and C4 plants, and definitely don't need to know all those intermediates in the Calvin Cycle and even in the Kreb's cycle. Good question though, and I hope my answer will save you from wasting your time (:

Thanks alchemy! It sure will :)
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on March 01, 2014, 08:51:12 pm
Can someone please explain how cis and trans fats work?
Do we need to know about them in the course?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 01, 2014, 09:11:26 pm
Can someone please explain how cis and trans fats work?
Do we need to know about them in the course?

Something you definitely don't need to know. In fact, it's not even covered in the chemistry course, not until first year of Uni. It's about the arrangement of the bond though. Cis-fats have a larger kink than trans-fats. Trans-fats are therefore normally more solid than cis-fats.

Title: Re: VCE Biology Question Thread
Post by: Chang Feng on March 01, 2014, 10:19:46 pm
I understand how for steroid hormones they eventually attach to receptors to hormone- receptor complexes, and then this attached to gene to create mRNA for protein. But for peptide hormones how does it eventually cause changes in cytoplasmic function/ gene transcription, I understand that the hormone attaches to receptor on membrane which amplifies it but then I'm sorta confused after here
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 01, 2014, 10:24:49 pm
I understand how for steroid hormones they eventually attach to receptors to hormone- receptor complexes, and then this attached to gene to create mRNA for protein. But for peptide hormones how does it eventually cause changes in cytoplasmic function/ gene transcription, I understand that the hormone attaches to receptor on membrane which amplifies it but then I'm sorta confused after here

Signal molecules inside the cell are activated when the peptide hormone finds its receptor and in turn, activate proteins causing the result.
Title: Re: VCE Biology Question Thread
Post by: MM1 on March 01, 2014, 10:28:08 pm
Why does Acetyl-CoA gain and then loose the CoA before entering into the Krebs Cycle?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 01, 2014, 11:03:15 pm
Why does Acetyl-CoA gain and then loose the CoA before entering into the Krebs Cycle?

CoA helps to facilitate forthcoming reactions in the Krebs cycle.
Title: Re: VCE Biology Question Thread
Post by: MM1 on March 02, 2014, 12:38:36 am
CoA helps to facilitate forthcoming reactions in the Krebs cycle.

Thanks! Also, it is required to learn about the intricacies of the cycle? Or literally just the inputs/outputs?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 02, 2014, 12:42:17 am
Thanks! Also, it is required to learn about the intricacies of the cycle? Or literally just the inputs/outputs?

Inputs and outputs
Where things happen
Things that may affect the overall process

The intricacies aren't covered until second year biochem at uni :)
Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 02, 2014, 08:13:03 am
Inputs and outputs
Where things happen
Things that may affect the overall process

The intricacies aren't covered until second year biochem at uni :)
Which inputs and outputs specifically?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 02, 2014, 11:16:58 am
Which inputs and outputs specifically?

Everything apart from the various intermediates in glycolysis and the krebs cycle.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on March 02, 2014, 06:40:02 pm
Just wondering how would you define the words hypertonic, hypertonic and isotonic?? I know what they mean just not sure how to define them. Thanks
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 02, 2014, 07:58:01 pm
Just wondering how would you define the words hypertonic, hypertonic and isotonic?? I know what they mean just not sure how to define them. Thanks

Hypertonic describes a solution in which the solutes are more highly concentrated than the solution with which you compare it.
Isotonic describes two solutions with equal concentration of solutes.
Hypotonic describes a solution in which the solutes are less concentrated than the solution with which you compare it.
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on March 02, 2014, 08:22:54 pm
Okay thanks, seems like what i had to. thought i needed to include movement of water by osmosis along the osmotic gradient and stuff too. Am I required to know osmotic pressure too? And if so what is high and low osmotic pressure in terms of hypertonic and hypotonic
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 02, 2014, 08:40:10 pm
Okay thanks, seems like what i had to. thought i needed to include movement of water by osmosis along the osmotic gradient and stuff too. Am I required to know osmotic pressure too? And if so what is high and low osmotic pressure in terms of hypertonic and hypotonic

Nope, those descriptors only apply to solutions and shouldn't be used to describe the movement. OBviously movement will happen if possible, but they don't necessarily indicate it well.

Osmotic pressure is the amount of pressure you have to apply to a membrane to stop osmosis from occurring. So it's from low to high (I think). I'm pretty sure they don't use it anymore.
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on March 02, 2014, 09:20:35 pm
How would one describe the role of ADP in energy transformations? I keep wanting to call ADP a carrier, even though I know that it's not one. However, could it be defined as an energy carrier? It still harnesses energy, but of a lower level...I just don't really know what to define ADP as! Thanks :)
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 03, 2014, 07:30:55 am
How would one describe the role of ADP in energy transformations? I keep wanting to call ADP a carrier, even though I know that it's not one. However, could it be defined as an energy carrier? It still harnesses energy, but of a lower level...I just don't really know what to define ADP as! Thanks :)

I don't think you need to specifically define ADP. For he role of ADP in energy transformations, you just need to know that ADP combines with an inorganic phosphate to form ATP. And ATP, upon hydrolysis of its high energy bonds between phosphates, releases energy.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 03, 2014, 03:16:53 pm
I don't think you need to specifically define ADP. For he role of ADP in energy transformations, you just need to know that ADP combines with an inorganic phosphate to form ATP. And ATP, upon hydrolysis of its high energy bonds between phosphates, releases energy.

Completely right.
Title: Re: VCE Biology Question Thread
Post by: popoy111 on March 04, 2014, 04:56:22 pm
So im doing sac 2 about enzymes and catalase. In one of my discussion question it asks 8. When hydrogen peroxide is added to a sample, bubble rate is high initially but then slows down.  Explain why this happens.
Title: Re: VCE Biology Question Thread
Post by: Scooby on March 04, 2014, 05:15:51 pm
So im doing sac 2 about enzymes and catalase. In one of my discussion question it asks 8. When hydrogen peroxide is added to a sample, bubble rate is high initially but then slows down.  Explain why this happens.

Catalase catalyses the conversion of hydrogen peroxide to oxygen gas and water. As hydrogen peroxide is converted to water and oxygen its concentration decreases; therefore, the rate at which this reaction takes place also decreases (and so does the rate which the oxygen gas bubbles are evolved)
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on March 04, 2014, 07:48:10 pm
Would someone be able to help explain the answer to this question to me? :(

'An inhibitor of a key enzyme that catalyses a part of the light independent stage is added to a plant cell. Would oxygen be produced at the same, lower or higher rate in this plate cell? Explain.

The answer is lower rate but I'm not sure why? :/
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 04, 2014, 08:00:51 pm
Would someone be able to help explain the answer to this question to me? :(

'An inhibitor of a key enzyme that catalyses a part of the light independent stage is added to a plant cell. Would oxygen be produced at the same, lower or higher rate in this plate cell? Explain.

The answer is lower rate but I'm not sure why? :/

Well if you inhibit an enzyme you slow down the process. Given that O2 is the product of the reaction, slowing down the process will slow down the rate of production of oxygen.
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on March 04, 2014, 08:15:44 pm
Well if you inhibit an enzyme you slow down the process. Given that O2 is the product of the reaction, slowing down the process will slow down the rate of production of oxygen.
Thank you! :)

Though the suggested answer is 'products of light independent reaction are reactants for light dependent reaction' - but to me it doesn't really make sense/is way too general?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 04, 2014, 08:25:38 pm
Thank you! :)

Though the suggested answer is 'products of light independent reaction are reactants for light dependent reaction' - but to me it doesn't really make sense/is way too general?

It's an important point to make, but it's not the answer entirely
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on March 04, 2014, 09:49:19 pm
When just the word 'control' is mentioned in a question, is it referring to the control group or controlled variables?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 04, 2014, 10:26:49 pm
When just the word 'control' is mentioned in a question, is it referring to the control group or controlled variables?

Variable
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on March 04, 2014, 10:47:30 pm
In glycolysis, why is ATP needed? The breakdown of glucose is catabolic, therefore energy releasing (exergonic), so where in glycolysis do anabolic (endergonic) reactions occur?

Also, why is H2O produced?
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 04, 2014, 10:56:08 pm
In glycolysis, why is ATP needed? The breakdown of glucose is catabolic, therefore energy releasing (exergonic), so where in glycolysis do anabolic (endergonic) reactions occur?

Also, why is H2O produced?

If you think about it, to start a fire you need a spark. That spark produces a tiny fire, that let's the fire go. Undeniably, the overall process of burning all the wood though produces a lot more heat than the spark. Likewise, every reaction needs a spark like that, it's called its activation energy. ATP supplies that spark. It supplies a tiny bit of energy to get the reaction going, then that reaction is able to release a lot of energy itself.

Just the groups that react. There are a couple of protons and an oxygen spare, so they make H2O
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on March 04, 2014, 11:11:30 pm
URGENT!!
In an enzyme sac where the effect of hydrogen peroxide is observed on sand, liver and liver & sand, is the dependent variable the temperature change and rate of reaction?
Is the controlled variable the amount of hydrogen peroxide which is constant in all of the test tubes?

If so, then is the independent variable the substances (1. sand, 2. Liver, 3. Sand and Liver) that the hydrogen peroxide acts on?

What is the function of catalase? And would it be correct to say that catalase acts on hydrogen peroxide therefore bubbles are formed and there is an increase in temperature?

Also wondering, for the question 'what two factors affect the active site of an enzyme', can I say any of the following factors?
-Temperature
-pH
-Chemical inhibitors?

Thank-you so much.
Title: Re: VCE Biology Question Thread
Post by: FarAwaySS2 on March 04, 2014, 11:16:23 pm

URGENT!!
In an enzyme sac where the effect of hydrogen peroxide is observed on sand, liver and liver & sand, is the dependent variable the temperature change and rate of reaction?
Is the controlled variable the amount of hydrogen peroxide which is constant in all of the test tubes?

If so, then is the independent variable the substances (1. sand, 2. Liver, 3. Sand and Liver) that the hydrogen peroxide acts on?

What is the function of catalase? And would it be correct to say that catalase acts on hydrogen peroxide therefore bubbles are formed and there is an increase in temperature?

Also wondering, for the question 'what two factors affect the active site of an enzyme', can I say any of the following factors?
-Temperature
-pH
-Chemical inhibitors?

Thank-you so much.

You seem right about the variables. The function of catalase in the human body is simple to perform the decomposition of the highly corrosive/dangerous hydrogen peroxide into gaseous oxygen and water molecules that can actually be usable for cells. I'm not sure about that question though.
Yup those three are fine. :)
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on March 04, 2014, 11:22:15 pm
Thanks FarAwaySS2

Also, what are the types of errors in an experiment?

Is it just technical and human errors?
Title: Re: VCE Biology Question Thread
Post by: FarAwaySS2 on March 04, 2014, 11:25:24 pm
Yeah, simple human errors e.g. Reading errors, timing error, etc.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 04, 2014, 11:51:59 pm
Thanks FarAwaySS2

Also, what are the types of errors in an experiment?

Is it just technical and human errors?

Contamination, natural variation in biological material etc etc
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on March 04, 2014, 11:58:38 pm
Why does liver have more catalase?

How does pH affect enzyme activity?

In the liver/hydrogen peroxide experiment, can there be two dependent variables --> Temperature change and rate of reaction?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 05, 2014, 01:59:28 pm
Why does liver have more catalase?

How does pH affect enzyme activity?

In the liver/hydrogen peroxide experiment, can there be two dependent variables --> Temperature change and rate of reaction?

Thanks!

The liver detoxifies the blood, hydrogen peroxide is a toxin.
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on March 05, 2014, 02:16:02 pm
How can glycolysis be said to occur in the cytoplasm if the cytoplasm includes all organelles inside the cellular membrane (excluding the nucleus)? Doesn't it occur in the cytosol?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 05, 2014, 03:19:56 pm
How can glycolysis be said to occur in the cytoplasm if the cytoplasm includes all organelles inside the cellular membrane (excluding the nucleus)? Doesn't it occur in the cytosol?
It's still essentially in the cytoplasm even though it really occurs in the cytosol; does not occur within organelles but amidst them in the cytosol if that makes sense
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 05, 2014, 03:56:10 pm
How can glycolysis be said to occur in the cytoplasm if the cytoplasm includes all organelles inside the cellular membrane (excluding the nucleus)? Doesn't it occur in the cytosol?

You do make a true point, though if it occurred in any one of those organelles you'd assume that that would be explicitly said.

It definitely can't occur in the cytosol. Nothing is really in the cyotosol at all, it's just a liquid, it describes all of the liquid contents. So any process that occurs "in" the cytosol is actually part of the cytosol.
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on March 05, 2014, 07:35:37 pm
Thanks everyone!

Also, is my understanding of light dependent photosynthesis correct:

When photons hit photosystem II and I, their electrons become excited. This excitement 'reaches' the chlorophyll inside the photosystems which excites a chlorophyll electron. The excited chlorophyll electron is lost to an electron acceptor in the ETC, leaving the photosystems with a positive charge. The electrons lost from photosystem I combine with H+ from the stroma to form NADPH. Acting as a means of replenishment, the electrons lost from photosystem II move along the ETC to photosystem I. As they do this, H+ ions move against their concentration gradients into the lumen of the thylakoid. The electrons provide the energy for this to occur, as it is an active form of transport. H2O is split to form H+, O2 and e- (electrons). The electrons (e-) from the catabolism of water are used to replenish those that were lost from photosystem II. Oxygen is released from the exergonic reaction as a by-product. The H+ ions (or protons) released add to the H+ concentration forming in the lumen. These H+ then travel through ATP synthase, creating a concentration gradient which releases energy. I'm pretty sure that free electrons are also used in this process. ATP is formed as a result of this process.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 05, 2014, 08:13:23 pm
Thanks everyone!

Also, is my understanding of light dependent photosynthesis correct:

When photons hit photosystem II and I, their electrons become excited. This excitement 'reaches' the chlorophyll inside the photosystems which excites a chlorophyll electron. The excited chlorophyll electron is lost to an electron acceptor in the ETC, leaving the photosystems with a positive charge. The electrons lost from photosystem I combine with H+ from the stroma to form NADPH. Acting as a means of replenishment, the electrons lost from photosystem II move along the ETC to photosystem I. As they do this, H+ ions move against their concentration gradients into the lumen of the thylakoid. The electrons provide the energy for this to occur, as it is an active form of transport. H2O is split to form H+, O2 and e- (electrons). The electrons (e-) from the catabolism of water are used to replenish those that were lost from photosystem II. Oxygen is released from the exergonic reaction as a by-product. The H+ ions (or protons) released add to the H+ concentration forming in the lumen. These H+ then travel through ATP synthase, creating a concentration gradient which releases energy. I'm pretty sure that free electrons are also used in this process. ATP is formed as a result of this process.

Haha, that's very detailed and I think a little extraneous for the purpose of VCE Biology. That being said, Khan Academy IS awesome ;)
Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 05, 2014, 08:15:17 pm
You do make a true point, though if it occurred in any one of those organelles you'd assume that that would be explicitly said.

It definitely can't occur in the cytosol. Nothing is really in the cyotosol at all, it's just a liquid, it describes all of the liquid contents. So any process that occurs "in" the cytosol is actually part of the cytosol.
I had always thought it occurred in the cytosol :/
Title: Re: VCE Biology Question Thread
Post by: rhinwarr on March 05, 2014, 08:20:12 pm
What happens to enzymes at very cold temperatures? I know their ability to catalyse reactions is reduced but is it because they do not have enough energy to faciliate the reactions or because their shape is changed temporarily (or neither)?
Title: Re: VCE Biology Question Thread
Post by: Seige on March 05, 2014, 08:25:21 pm
What happens to enzymes at very cold temperatures? I know their ability to catalyse reactions is reduced but is it because they do not have enough energy to faciliate the reactions or because their shape is changed temporarily (or neither)?
Its because at low temperatures the kinetic energy is greatly decreased so therefore reactions will occur really slowly.
Title: Re: VCE Biology Question Thread
Post by: Tyleralp1 on March 05, 2014, 08:29:23 pm
Yeah, when temperatures become too low, the movement of substrates + enzymes is incredibly slow. From my reading, the enzyme simply becomes inactive, or catalyzes at low rates. It is a reversible thing, and the structure doesn't change.
Title: Re: VCE Biology Question Thread
Post by: Seige on March 05, 2014, 08:34:58 pm
I've heard that at extremely low temperatures, the enzyme actually denatures. Is this true??
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 05, 2014, 08:36:16 pm
I've heard that at extremely low temperatures, the enzyme actually denatures. Is this true??

At extremely low temperatures, the enzymes can become inactivated but not denatured.
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on March 05, 2014, 09:34:38 pm
When an enzyme is inactive, molecular movement is so slow that the substrate barely makes contact with the active site (hence on temperature  enzyme activity graphs, it starts at 0)

EDIT: spelling, wrote this too fast :P
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 05, 2014, 10:33:05 pm
When an enzyme is inactive, molecular movement is so slow that the substrate barely makes contact with the active site (hence on temperature  enzyme activity graphs, it starts at 0)

EDIT: spelling, wrote this too fast :P

This is part of it, but not all of it. It means that the proportion of molecules that have activation energy sufficient enough to cause the reaction is lower, because that's what temperature is a record of, the kinetic energy of a system. So it's not that they're not making contact, they are, that contact just isn't forceful enough to supply the energy needed to start the reaction.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 06, 2014, 10:57:45 am
In the light dependent reactions of photosynthesis, when the energy provided by the excited electrons is used to pump hydrogen ions into the lumen, where are these hydrogen ions coming from? Is it from the water molecules that are split up?

And when they say that NADP+ becomes reduced into NADPH, when it combines with a hydrogen ion, how is this so?
I thought when something is reduced it gains electrons, not protons?

So confused :/
Title: Re: VCE Biology Question Thread
Post by: MagicGecko on March 06, 2014, 11:25:42 am
In the light dependent reactions of photosynthesis, when the energy provided by the excited electrons is used to pump hydrogen ions into the lumen, where are these hydrogen ions coming from? Is it from the water molecules that are split up?

The H+ ions came from the break down of water.
2H20 ---> 2H+ + O2 + 2e-
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 06, 2014, 06:49:26 pm
And when they say that NADP+ becomes reduced into NADPH, when it combines with a hydrogen ion, how is this so?
I thought when something is reduced it gains electrons, not protons?

Yes, when something is reduced it gains electrons but, Hydrogen has one electron, remember? Therefore, in this context, it can reduce NADP+ to NADPH. However, the idea of hydrogen having electrons, or otherwise, is interchangeable. For bio, you just need to know that it reduces NADP+.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 08, 2014, 01:27:04 am
Oh so it combines with hydrogens, not hydrogen ions?

Because hydrogen ions are just protons right?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: PB on March 08, 2014, 10:45:19 am
This post serves no purpose other than to claim the 1000th reply spot. Now give me that cookie.
Title: Re: VCE Biology Question Thread
Post by: popoy111 on March 08, 2014, 11:37:34 am
SAC 2: an investigation of enzyme action

TITLE: Estimating relative levels of catalase from a variety of sources.

AIM: To test for the relative amounts of Catalase enzyme in a variety of organic sources

Does anyone know what the dependent variable will be in this experiment?
Title: Re: VCE Biology Question Thread
Post by: aqple on March 08, 2014, 12:10:39 pm
SAC 2: an investigation of enzyme action

TITLE: Estimating relative levels of catalase from a variety of sources.

AIM: To test for the relative amounts of Catalase enzyme in a variety of organic sources

Does anyone know what the dependent variable will be in this experiment?

Rate of reaction of the enzyme catalase
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 08, 2014, 06:17:54 pm
Hi I just wanted to explain what happens in the light dependent aof photosynthesis, so that someone could correct me if I'm wrong and tell me if my explanation needs to be changed :)

Light dependent reactions:
Photons from the sun are absorbed by chlorophyll molecules in Photosystem 2 and this excites the electrons of the chlorophyll molecules, thus they move to excited states. These electrons then travel through the electron transport chain, releasing their energy in a series of stops, through a range of molecules. The chlorophyll molecules of photosystem 2 however, now have a lack of electrons and so they split water into oxygen, electrons and protons (H+). This oxygen gas is released as a by product and Photosystem 2 takes these electrons, so that it has electrons once again. The energy released by the electrons travelling in the electron transport chain is then used to pump the protons (H+) produced through the photolysis of water, into the thylakoid lumen. This creates a concentration gradient of charge, and the positive charge is greater in the interior of the thylakoid lumen. Therefore the hydrogen ions move through ATP synthase in order to return to regions of low concentration, and the movement of the hydrogen ions through ATP synthase, provides energy for the phosphorylation of ADP to form ATP.

The spent electrons at the end of the electron transport chain get accepted by the carrier molecule NADP+ and so do the hydrogen ions that moved through ATP synthase. Thus NADP+ forms into NADPH.

The energy contained within the NADPH and ATP molecules produced in the light dependent reactions are then used in the Calvin cycle.

Is this correct? Thanks  :)
Title: Re: VCE Biology Question Thread
Post by: Jason12 on March 09, 2014, 12:45:11 am
is osmosis the net movement of water molecules from a region of high to low water concentration or low to high?
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on March 09, 2014, 12:46:53 am
After my first 3/4 bio sac- I seem to still always make simple mistakes/ errors which cost me a couple of marks which I shouldn't have lost. Do you people have any tips in how I could reduce it, and hopefully until I make no mistakes in my sacs, so I can start getting 100%
Title: Re: VCE Biology Question Thread
Post by: MagicGecko on March 09, 2014, 01:42:46 am
After my first 3/4 bio sac- I seem to still always make simple mistakes/ errors which cost me a couple of marks which I shouldn't have lost. Do you people have any tips in how I could reduce it, and hopefully until I make no mistakes in my sacs, so I can start getting 100%

3. Read every question at least twice
4. Refer to #1 because this will hopefully enable you to finish your SAC early and hence have time to find those 'simple mistakes/errors'
5. Pick out (and highlight if you want) key words

Nothing else I can say really, just pay attention to every little detail and choose your words carefully, good luck :)
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on March 09, 2014, 01:53:41 am
After my first 3/4 bio sac- I seem to still always make simple mistakes/ errors which cost me a couple of marks which I shouldn't have lost. Do you people have any tips in how I could reduce it, and hopefully until I make no mistakes in my sacs, so I can start getting 100%

Succinct answers that answer the question, using biological terminology. The way to do this is to read the questions at least twice, and answer the question in your head before delivering it to the paper. Also be confident that you have answered the question in a punchy manner, to avoid ranting on about irrelevant things that may possibly cause you to score 0 marks for that question because of contradiction.
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 09, 2014, 09:48:04 am
is osmosis the net movement of water molecules from a region of high to low water concentration or low to high?

..high to low water concentration.
..low to high solute concentration.
Title: Re: VCE Biology Question Thread
Post by: shadows on March 09, 2014, 09:59:06 am
..high to low water concentration.
..low to high solute concentration.

I'd stick with high to low solute concentration.

For some reason I defined osmosis as high to low water concentration and lost a mark. Supposedly examiners do prefer the latter response.

Or was I just marked too harshly?
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on March 09, 2014, 10:02:22 am
I'd stick with high to low solute concentration.

For some reason I defined osmosis as high to low water concentration and lost a mark. Supposedly examiners do prefer the latter response.

Or was I just marked too harshly?
I write both actually,"...... a net movement of free water molecules from a region if low solute (high water) concentration to a region of high solute (low water) concentration through a semi-permeable membrane"
Title: Re: VCE Biology Question Thread
Post by: Yacoubb on March 09, 2014, 10:11:34 am
I write both actually,"...... a net movement of free water molecules from a region if low solute (high water) concentration to a region of high solute (low water) concentration through a semi-permeable membrane"

VCAA prefers you write short succinct answers. It'll be too long of a definition if you include both. My definition of osmosis is the passive, net movement of free water molecules across the semi-permeable plasma membrane, from an area of low solute concentration to an area of high solute concentration. You should discuss that its a passive means of transport, include 'net movement' and the rest of what I wrote (an assessor gave me this definition).

Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on March 09, 2014, 11:27:21 am
VCAA prefers you write short succinct answers. It'll be too long of a definition if you include both. My definition of osmosis is the passive, net movement of free water molecules across the semi-permeable plasma membrane, from an area of low solute concentration to an area of high solute concentration. You should discuss that its a passive means of transport, include 'net movement' and the rest of what I wrote (an assessor gave me this definition).
Thanks Yacoubb! I totally forgot the most important "passive" word.
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 09, 2014, 12:13:32 pm
I'd stick with high to low solute concentration.

For some reason I defined osmosis as high to low water concentration and lost a mark. Supposedly examiners do prefer the latter response.

Or was I just marked too harshly?

Yeah that may be true, but it's "low to high solute concentration" not "high to low solute concentration" like you mentioned.
Title: Re: VCE Biology Question Thread
Post by: MM1 on March 09, 2014, 12:49:08 pm
Can a protein have more than one function; i.e - can it be ,say, both enzymatic and an immunoglobulin?
The proteins in a cell membrane are used for transport, but since some have an active site, can they also said to be enzymatic? Or does that only apply to enzymes. Cytochromes as well; they're said to be enzymes?

Also what is the function of peripheral proteins?

Thanks! :)
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 09, 2014, 01:40:24 pm
Can a protein have more than one function; i.e - can it be ,say, both enzymatic and an immunoglobulin?
The proteins in a cell membrane are used for transport, but since some have an active site, can they also said to be enzymatic? Or does that only apply to enzymes. Cytochromes as well; they're said to be enzymes?

Also what is the function of peripheral proteins?

Thanks! :)

I guess so, thinking of proteins like ATPsynthase and Haemoglobin.
Title: Re: VCE Biology Question Thread
Post by: shadows on March 09, 2014, 01:59:03 pm
Yeah that may be true, but it's "low to high solute concentration" not "high to low solute concentration" like you mentioned.
LOL opps

I meant low to high solute conc
Title: Re: VCE Biology Question Thread
Post by: slothpomba on March 09, 2014, 02:09:05 pm
Can a protein have more than one function; i.e - can it be ,say, both enzymatic and an immunoglobulin?
The proteins in a cell membrane are used for transport, but since some have an active site, can they also said to be enzymatic? Or does that only apply to enzymes. Cytochromes as well; they're said to be enzymes?

Also what is the function of peripheral proteins?

Thanks! :)

Where did you obtain these questions from? Unless things have changed they're not need for VCE (*to the best of my memory). It really depends where you draw the line of it being a different function or having a different domain. Serotonin is involved in mood but it also causes blood to clot. They are different functions but on a broad level, it's not like it's becoming and enzyme or a structural protein, it's still a molecule to communicate something to another cell. If you draw very big lines like enzyme or immunoglobulin, i'd imagine you wouldn't find many, if any, proteins that could cross huge boundaries like that. I can't think of many things that are enzymes that have important actions in things not related to them being an enzyme.

It's a very poorly put question if it was on an exam, so, i doubt something like this will be.
Title: Re: VCE Biology Question Thread
Post by: MM1 on March 09, 2014, 02:16:33 pm
Where did you obtain these questions from? Unless things have changed they're not need for VCE (*to the best of my memory).

Just a thought(s). I guess it really isn't needed for VCE, but it'll be good to know? ..

Edit: Thanks slothpomba!
Title: Re: VCE Biology Question Thread
Post by: slothpomba on March 09, 2014, 02:21:25 pm
I edited some answers into my post probably while you were typing yours. The active site isn't the only important bit, especially if we're talking about things that aren't enzymes, it's also the overall shape and structure of the protein. That said most proteins (on my limited knowledge) tend to be useful for only a handful of somewhat related tasks. I can't think of many enzymes that are heavily important for non-enzymatic things so you can cross that one out.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 09, 2014, 02:47:18 pm
The general rule for passive transport is that the molecules move to a space where there is less of them; they want to be spread out equally.
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on March 09, 2014, 03:30:09 pm

When you are increasing the substrate or enzyme concentration, does this mean you are generating more product or just decreasing the time it takes to get to a certain amount of product?
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 09, 2014, 03:54:59 pm

When you are increasing the substrate or enzyme concentration, does this mean you are generating more product or just decreasing the time it takes to get to a certain amount of product?

Very important question. Enzymes do not affect the equilibrium of a reaction. That means more product isn't prouduced in an enzyme catalysed reaction. All enzymes do, by increasing the rate of the reaction, reduce the time required to yield a certain amount of product.
Title: Re: VCE Biology Question Thread
Post by: katie101 on March 09, 2014, 05:08:37 pm
The ‘white’ of a hen's egg is the protein albumin, which changes from a clear jelly-like substance to solid white matter when it is cooked. The protein has been irreversibly denatured. Sometimes denaturation of a protein is reversible.

Examine the illustration below. Protein X was denatured as its sulfide bonds broke when the molecule was exposed to a particular chemical. However, when the chemical was removed, protein X reformed its original tertiary structure. Explain whether you think that, after such treatment, protein X would still be able to perform its original function.

Image Attached

Thanks, as I'm a little confused
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 09, 2014, 05:17:19 pm
The ‘white’ of a hen's egg is the protein albumin, which changes from a clear jelly-like substance to solid white matter when it is cooked. The protein has been irreversibly denatured. Sometimes denaturation of a protein is reversible.

Examine the illustration below. Protein X was denatured as its sulfide bonds broke when the molecule was exposed to a particular chemical. However, when the chemical was removed, protein X reformed its original tertiary structure. Explain whether you think that, after such treatment, protein X would still be able to perform its original function.

Image Attached

Thanks, as I'm a little confused

It has the same conformation as the original protein, so of course. That's all that matters. Is the protein in the same shape again? Yep. Any inhibitors? Nope. Does it work? Yep! Shape determines function of an eznyme
Title: Re: VCE Biology Question Thread
Post by: kx4y on March 09, 2014, 05:40:00 pm
Can someone please explain to me what happens to the reaction rate when there is:
- unlimited enzymes
- limited enzymes
- unlimited substrates
- limited substrates?

:-\
Title: Re: VCE Biology Question Thread
Post by: katie101 on March 09, 2014, 05:52:08 pm
Can the Calvin cycle can occur only in the dark?
Title: Re: VCE Biology Question Thread
Post by: slothpomba on March 09, 2014, 05:54:25 pm
Can someone please explain to me what happens to the reaction rate when there is:
- unlimited enzymes
- limited enzymes
- unlimited substrates
- limited substrates?

:-\

Care to try these first? As for the plant one, sorry, got no idea about plants.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on March 09, 2014, 06:08:04 pm
Are endothermic reactions and endergonic reactions the same as an anabolic reaction? :-\
Title: Re: VCE Biology Question Thread
Post by: slothpomba on March 09, 2014, 06:10:34 pm
Are endothermic reactions and endergonic reactions the same as an anabolic reaction? :-\

First two are chemistry terms, last one is a biology term. That's why there is a duplication. "Anabolism (from Greek: ανά "upward" and βάλλειν "to throw") is the set of metabolic pathways that construct molecules from smaller units.[1] These reactions require energy. " Which one of those two chemistry terms refer to reactions which require an input of energy? Figure that ou9t and you'll have your answer.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on March 09, 2014, 06:15:28 pm
First two are chemistry terms, last one is a biology term. That's why there is a duplication. "Anabolism (from Greek: ανά "upward" and βάλλειν "to throw") is the set of metabolic pathways that construct molecules from smaller units.[1] These reactions require energy. " Which one of those two chemistry terms refer to reactions which require an input of energy? Figure that ou9t and you'll have your answer.

Is it endergonic?
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 09, 2014, 06:34:37 pm
In my Biology book it says that coenzymes are small cofactor molecules and my biology teacher said that you can classify coenzymes as cofactors, but then my biology book says cofactors are "small inorganic substances" and coenzymes are "small organic non-protein molecules"

How can coenzymes be organic, if they are considered to be a type of cofactor, when cofactors are inorganic?

o.O
Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 09, 2014, 06:39:25 pm
Is it endergonic?
Yes
Title: Re: VCE Biology Question Thread
Post by: nhmn0301 on March 09, 2014, 06:41:58 pm
In my Biology book it says that coenzymes are small cofactor molecules and my biology teacher said that you can classify coenzymes as cofactors, but then my biology book says cofactors are "small inorganic substances" and coenzymes are "small organic non-protein molecules"

How can coenzymes be organic, if they are considered to be a type of cofactor, when cofactors are inorganic?

o.O
Cofactors include BOTH inorganic and organic particles. The difference between these 2 is that the inorganic particles are not changed during the reaction whilst organic particles (which include coenzymes) are altered.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 09, 2014, 06:42:10 pm
In my Biology book it says that coenzymes are small cofactor molecules and my biology teacher said that you can classify coenzymes as cofactors, but then my biology book says cofactors are "small inorganic substances" and coenzymes are "small organic non-protein molecules"

How can coenzymes be organic, if they are considered to be a type of cofactor, when cofactors are inorganic?

o.O
The term cofactor is a collective term encompassing both organic and inorganic non-protein substances which are necessary for particular enzymes to function. However, coenzymes specifically refer to organic molecules (e.g. vitamins)
Edit: beaten
Title: Re: VCE Biology Question Thread
Post by: MagicGecko on March 09, 2014, 07:00:03 pm
Can the Calvin cycle can occur only in the dark?
Nope that would mean that plants only have 'dinner' :P
But yeah, the Calvin cycle can also occur in broad daylight, the only reason why it is called the 'dark-reaction' is because unlike the 'light-reaction', the Calvin cycle does not need an input of sunlight.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 10, 2014, 12:02:00 am
What would be the exact inputs and outputs for the light dependent reactions, Calvin Cycle, glycolysis, Kreb's cycle and the Electron transport system - for a vce level?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: howlingwisdom on March 10, 2014, 12:21:55 pm
If more substrate is added (assuming that enzyme, temperature etc is constant) will this increase the amount of product produced or just increase the rate of the reaction up until the enzyme becomes saturated with substrate?
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on March 10, 2014, 06:17:14 pm
Bio sac Wednesday. My sac was about putting liver (catalase) in test tube and then seeing the height of bubbles produced (due to detergent to see rate of reaction) in 2min. This was under different temp, different size if liver?? So I have 3 independent variables being size of liver, temp, and time?? I have to plot a graph, but it doesn't say how many different functions (as in height bubbles produced VS enzyme size, etc) I have to do. Could anyone help me?
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 10, 2014, 06:53:31 pm
If more substrate is added (assuming that enzyme, temperature etc is constant) will this increase the amount of product produced or just increase the rate of the reaction up until the enzyme becomes saturated with substrate?

It will increase the rate of the reaction up until the enzyme becomes saturated with substrate. Like I mentioned earlier, enzymes do not affect how much product is formed by a reaction...
Title: Re: VCE Biology Question Thread
Post by: eagles on March 10, 2014, 09:16:37 pm
Urgent!!

Why do we avoid punching veins of leaf discs and must ensure that leaf discs are punched from leaf blade? This is for a prac involving punched leaf discs immersed in bicarbonate solution and measuring rate of photosynthesis with different coloured lights.

Thanks :)
Title: Re: VCE Biology Question Thread
Post by: DJA on March 10, 2014, 09:25:33 pm
Urgent!!

Why do we avoid punching veins of leaf discs and must ensure that leaf discs are punched from leaf blade? This is for a prac involving punched leaf discs immersed in bicarbonate solution and measuring rate of photosynthesis with different coloured lights.

Thanks :)

I haven't personally done this prac but thinking about it logically I'd think that the reason why you wouldn't want leaf veins in your discs of leaves is because plant veins don't contain chlorophyll. Hence in order to maintain a relatively constant amount of chlorophyll in every leaf disk (for accurate comparison for rate of photosynthesis)  the prac requires you to cut only disks from the green leaf blade and not the veins.

If you have veins in some leaf disks, you WILL have some inaccuracies due to different amounts comparatively of areas on the disk with chorophyll.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on March 10, 2014, 09:33:44 pm
Quick question,
6) How do enzymes affect activation energy
I know that the answer is basically "Enzymes lower the activation energy" but this doesn't sound like a yr 12 answer. It sounds too simple and unscientific. Could someone tell me how they would explain it.
Thanks :D
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on March 10, 2014, 09:53:42 pm
Quick question,
6) How do enzymes affect activation energy
I know that the answer is basically "Enzymes lower the activation energy" but this doesn't sound like a yr 12 answer. It sounds too simple and unscientific. Could someone tell me how they would explain it.
Thanks :D

Enzymes weaken and break the bonds present in the substrate which in turn speeds up the rate of the reaction by lowering the activation.

Someone please correct me if I'm wrong.
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 10, 2014, 10:14:59 pm
Enzymes weaken and break the bonds present in the substrate which in turn speeds up the rate of the reaction by lowering the activation.

Someone please correct me if I'm wrong.

Not only that; they can bind more than one substrate molecules together to build a more complex one. Such reactions are termed 'anabolic' or 'synthesis' reactions, requiring energy. What you've described are 'catabolic' reactions.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on March 10, 2014, 11:19:38 pm
Not only that; they can bind more than one substrate molecules together to build a more complex one. Such reactions are termed 'anabolic' or 'synthesis' reactions, requiring energy. What you've described are 'catabolic' reactions.

How do they reduce activation energy in anabolic reactions then?
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on March 11, 2014, 05:25:13 pm
Urgent questions for enzyme sac. How does increase product concentration slow down rate of reaction. Do they bind to enzyme like an inhibitor- but aren't they not complementary to substrate so how do they bind
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on March 11, 2014, 05:26:30 pm
Also how is activation energy reduced by enzyme...ie something with enzyme putting stress one substrate so the bonds break easier and moving the substrate closer together so bind easily in anabolic reactions?? Help clarify please
Title: Re: VCE Biology Question Thread
Post by: Chang Feng on March 11, 2014, 05:27:17 pm
Do cofactors and coenzymes simply just fill in active site of enzyme and what else do they do (required in VCE biology)
Title: Re: VCE Biology Question Thread
Post by: Vicbelgaus on March 11, 2014, 06:08:41 pm
hey there i'm not certain of how much we know about coe-enzymes and co-factors

But i do know that they don't simply fill the active site of an enzyme.
Co-enzymes: usually act as carrier molecules and help bring the substrate to the enzyme.
Co-factors: actively participating with the catalysis of the substrate, by attaching to the enzyme itself and helping the substrate or substrates undergo their reaction easier.

hope that helps  :)
Title: Re: VCE Biology Question Thread
Post by: Tyleralp1 on March 11, 2014, 06:16:06 pm

From my understanding, I don't believe the concentration of product effects the rate of reaction of an enzyme. Maybe in a confined area, the number of products may increase overtime, thus limiting the space through which enzymes+substrates can travel. Therefore, there are less enzyme-substrate collisions in a given time frame, hence slowing down the rate of reaction. Or maybe even, as the product fills up the area of enzymes, the space is limited for which substrates can come in. Hence, less and less enzymes can catalyse reactions as time goes on. Though I've personally never come across this given situation.

As for enzymes reducing the activation enegy: An enzyme’s selective three dimensional shape, the active site, is complimentary to the substrate it binds to. When in the active site, the chemical bonds are closer, therefore allowing the chemical bonds to weaken and change with less energy. An enzyme therefore lowers the entropy of substrate, freeing them from translational and rotational movements.

Coenzymes are organic molecules that are required by certain enzymes to carry out catalysis. They bind to the active site of the enzyme and participate in catalysis but are not considered substrates of the reaction. Coenzymes often function as intermediate carriers of electrons, specific atoms or functional groups that are transfered in the overall reaction. An example of this would be the role of NAD in the transfer of electrons in certain coupled oxidation reduction reactions.
Cofactors are often classified as inorganic substances that are required for, or increase the rate of, catalysis. This binds to the active side, and still allows for the complimentary pairing of the specific substrate, but provides the necessary inputs for the reaction to take place.

Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 11, 2014, 07:22:22 pm
Can someone please define 'optimum range', in terms of enzymes?

Because I thought this was a bit different between the definition of the optimum range, we learnt for abiotic factors in Biology Units 1/2.

Is this true?

Thanks! :)
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on March 11, 2014, 07:26:37 pm
Can someone please define 'optimum range', in terms of enzymes?

Because I thought this was a bit different between the definition of the optimum range, we learnt for abiotic factors in Biology Units 1/2.

Is this true?

Thanks! :)

I'll attempt this:
Optimum range is the specific environment range in which an enzyme works best. This so called "environment" may be temperature, pH etc. So there is a specfic range in which an enzyme best functions at
Pls correct me if I'm wrong
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 11, 2014, 07:30:13 pm
My textbook says that proteins influence the pH of a solution by donating hydrogen ions or hydroxyl ions. I thought that hydroxide ions made a solution more alkaline, not hydroxyl?

Or are they the same thing?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: Tyleralp1 on March 11, 2014, 07:48:47 pm
An acid is a substance that donates hydrogen ions. Because of this, when an acid is dissolved in water, the balance between hydrogen ions and hydroxyl ions is shifted. Now there are more hydrogen ions than hydroxyl ions in the solution. This kind of solution is acidic.

A base is a substance that accepts hydrogen ions. When a base is dissolved in water, the balance between hydrogen ions and hydroxyl ions shifts the opposite way. Because the base "soaks up" hydrogen ions, the result is a solution with more hydroxyl ions than hydrogen ions. This kind of solution is alkaline.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 11, 2014, 07:53:25 pm
An acid is a substance that donates hydrogen ions. Because of this, when an acid is dissolved in water, the balance between hydrogen ions and hydroxyl ions is shifted. Now there are more hydrogen ions than hydroxyl ions in the solution. This kind of solution is acidic.

A base is a substance that accepts hydrogen ions. When a base is dissolved in water, the balance between hydrogen ions and hydroxyl ions shifts the opposite way. Because the base "soaks up" hydrogen ions, the result is a solution with more hydroxyl ions than hydrogen ions. This kind of solution is alkaline.

ohhh thanks! :) Makes more sense now!
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 11, 2014, 07:54:02 pm
I'll attempt this:
Optimum range is the specific environment range in which an enzyme works best. This so called "environment" may be temperature, pH etc. So there is a specfic range in which an enzyme best functions at
Pls correct me if I'm wrong

Thankyou! :)
Title: Re: VCE Biology Question Thread
Post by: DJA on March 11, 2014, 08:49:18 pm
Do cofactors and coenzymes simply just fill in active site of enzyme and what else do they do (required in VCE biology)

Coenzymes and cofactors  (VCE level)
Having been confused about these two terms in the past, I thought I had better post.
VCE level biology is actually quite contradictory at times and even though Tyleralp1's definitions are perfectly correct, they actually may not get you the marks in VCE level bio because VCE bio has weird definitions at times.

Definition of a cofactor and its function: A cofactor is a molecule (either a coenzyme or inorganic ion) which assists an enzyme with its biological activity. A cofactor increases the affinity of the enzyme to the substrate in a metabolic reaction and is required to be present for that enzyme to function correctly.

Definition of coenzyme: Essentially a cofactor which is biological in nature - for example Vitamin C.
Definition of inorganic ion: Essentially a cofactor which is non-biological in nature - for example Fe2+

That's as much detail as you will likely need. Hope that helped clarify things.
Title: Re: VCE Biology Question Thread
Post by: Blurple on March 11, 2014, 09:10:57 pm
I'm in year 11 doing biology 3/4. Well today I had my first SAC and it went really bad. Yes I reckon I passed and got 50%. It was on Affects of temperature and pH on amylase. The thing is the sheet had told us it was a write up. So I had literally memorized the Aim, Hypothesis,Materials + Methods etc. None of that happened. There was no write up. We got sheets full of questions about what we did at GTAC. I'm just so disappointed as to how other classes got told they were going to be tested on how temperature affected amylase not both temp and pH. And they also got told they would have to draw 2 graphs as well. I'm just devastated that I had to memorize a whole bunch of things without me being properly told whats happening. I know how things work now and would like to ace all my other SACS + the exam itself. Is it still possible? I'm just so. In biology do you ever do a write up, by write up I mean a lab report. I didnt know things were going to turn out this way. Is it still possible for me to get a study score of 35 if I do well in all my other SACS/Exam this year. By the way my next SAC is on Dialysis Tubing. What type of questions are do they ask on the SAC? And its not a lab report we have to write? Is it? I'm just really pissed off as to how our teacher didnt tell us some things and other students in other classes got told these thing.
Title: Re: VCE Biology Question Thread
Post by: Jason12 on March 11, 2014, 09:44:48 pm
Is it still possible for me to get a study score of 35 if I do well in all my other SACS/Exam this year.

yes definitely bio sacs for unit 3 and 4 are only worth 40% of the total study score so if you divide by the amount of sacs for both units you will find it is a very small percentage. As long as you do well on the exam you will be fine
Title: Re: VCE Biology Question Thread
Post by: Jason12 on March 11, 2014, 09:46:25 pm
what is a simple way to explain the induced fit model and what exactly is the active site? Is it just the shape of a molecule that fits with the substrate?
Title: Re: VCE Biology Question Thread
Post by: shadows on March 12, 2014, 08:34:15 am
I'm in year 11 doing biology 3/4. Well today I had my first SAC and it went really bad. Yes I reckon I passed and got 50%. It was on Affects of temperature and pH on amylase. The thing is the sheet had told us it was a write up. So I had literally memorized the Aim, Hypothesis,Materials + Methods etc. None of that happened. There was no write up. We got sheets full of questions about what we did at GTAC. I'm just so disappointed as to how other classes got told they were going to be tested on how temperature affected amylase not both temp and pH. And they also got told they would have to draw 2 graphs as well. I'm just devastated that I had to memorize a whole bunch of things without me being properly told whats happening. I know how things work now and would like to ace all my other SACS + the exam itself. Is it still possible? I'm just so. In biology do you ever do a write up, by write up I mean a lab report. I didnt know things were going to turn out this way. Is it still possible for me to get a study score of 35 if I do well in all my other SACS/Exam this year. By the way my next SAC is on Dialysis Tubing. What type of questions are do they ask on the SAC? And its not a lab report we have to write? Is it? I'm just really pissed off as to how our teacher didnt tell us some things and other students in other classes got told these thing.

Don't fret. If you are willing to work hard for the rest of the year and ace the exams then getting a 35+ is very achievable :).
Every school has different SACS so it would be best to ask your teacher about the layout and structure of the SAC.
Eg: ask if you will have to write a full discussion or is it structured like a test etc.....
Title: Re: VCE Biology Question Thread
Post by: JadedBlack on March 12, 2014, 05:28:47 pm
If a question involving the products of glycolysis is asked; is it better to say 4 ATP molecules are produced, or just 2? My teacher said that we should answer with 2, but I'm unsure whether that would be considered the correct answer seeing as it's a net of 2
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 12, 2014, 06:39:35 pm
How is the active site of enzymes formed?

Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 12, 2014, 06:50:45 pm
If a question involving the products of glycolysis is asked; is it better to say 4 ATP molecules are produced, or just 2? My teacher said that we should answer with 2, but I'm unsure whether that would be considered the correct answer seeing as it's a net of 2
I'd say 2, but it depends what it's asking; a net gain of 2 ATP or a total of 4 ATP produced.

How is the active site of enzymes formed?
It is formed by the various intermolecular bonds within the tertiary structure of the protein, as the tertiary structure largely determines the function of the enzyme
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 12, 2014, 07:24:37 pm
Hi, I just did the enzyme liver prac today that involved placing fresh liver pieces in hydrogen peroxide and measuring the height of the bubbles present.

I was wondering, what are the bubbles that are produced?
Is it the water that is formed as a result of hydrogen peroxide being broken down into oxygen and water?

Thanks
Title: Re: VCE Biology Question Thread
Post by: Scooby on March 12, 2014, 07:32:21 pm
Hi, I just did the enzyme liver prac today that involved placing fresh liver pieces in hydrogen peroxide and measuring the height of the bubbles present.

I was wondering, what are the bubbles that are produced?
Is it the water that is formed as a result of hydrogen peroxide being broken down into oxygen and water?

Thanks

Catalase converts hydrogen peroxide to water and oxygen. The bubbles are of oxygen gas
Title: Re: VCE Biology Question Thread
Post by: millie96 on March 12, 2014, 08:16:38 pm
how does the induced fit model work to break down substrates?
Title: Re: VCE Biology Question Thread
Post by: sammiegan on March 12, 2014, 08:19:24 pm
Would it be correct to say that inhibitor molecules, stop enzyme activity altogether?

Or do they only decrease it?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: sarahsmiggle on March 12, 2014, 08:20:46 pm
hi, um i did an enzyme prac the other day, and was wondering if anyone knew how to answer this question:

Humans produce two types of amylase, salivary amylase which acts in the mouth and pancreatic amylase which acts in the small intestine. Suggest one reason why it is necessary to produce the enzyme in both places.

thank you
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on March 12, 2014, 08:21:49 pm
how does the induced fit model work to break down substrates?

In the induced fit model, the active site of an enzyme changes temporarily to fit the binding site of the substrate molecule/s with the aid of co-enzymes/co-factors. The induced fit model isn't only for the decomposition of substrates but also for the synthesis of other biomolecules. Once the substrate has been altered, the enzyme's active site returns to it's initial shape.
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 12, 2014, 08:28:03 pm
Would it be correct to say that inhibitor molecules, stop enzyme activity altogether?

Or do they only decrease it?

Permanent inhibitors stop enzyme activity altogether. Temporary inhibitors slow down the reaction from occurring.

Humans produce two types of amylase, salivary amylase which acts in the mouth and pancreatic amylase which acts in the small intestine. Suggest one reason why it is necessary to produce the enzyme in both places.

All metabolic reactions in the body require enzymes to occur. Enzymes are substrate specific. Thus, an enzyme must be present at the place where there are complementary substrates for it, in order to catalyse the required reaction at that place.
Title: Re: VCE Biology Question Thread
Post by: sarahsmiggle on March 12, 2014, 08:30:20 pm
Permanent inhibitors stop enzyme activity altogether. Temporary inhibitors slow down the reaction from occurring.

All metabolic reactions in the body require enzymes to occur. Enzymes are substrate specific. Thus, an enzyme must be present at the place where there are complementary substrates for it, in order to catalyse the required reaction at that place.

thank you so much!
Title: Re: VCE Biology Question Thread
Post by: bio12345 on March 12, 2014, 08:48:59 pm

Hi we did a prac today which I've pasted above ^ . But I'm stuck on Q9, I'm hoping somebody could help me. :(
Q9 is:  A customer returned to the hardware store complaining that the DIF wallpaper stripper did not work and demanded a refund. During the discussion with the shop owner it was realised that the customer had originally used a new style of synthetic vinyl wall paper glue on his wall paper. Suggest one reason why DIF wall paper stripper did not work for the customer.
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 12, 2014, 08:54:34 pm

Hi we did a prac today which I've pasted above ^ . But I'm stuck on Q9, I'm hoping somebody could help me. :(
Q9 is:  A customer returned to the hardware store complaining that the DIF wallpaper stripper did not work and demanded a refund. During the discussion with the shop owner it was realised that the customer had originally used a new style of synthetic vinyl wall paper glue on his wall paper. Suggest one reason why DIF wall paper stripper did not work for the customer.

Sorry I haven't read all the details in that link, but the answer should be because the enzyme was unable to act on the new style of synthetic vinyl. Like I mentioned before, enzymes are substrate specific. So, the enzyme might not have been able to act on the substrate molecules on the synthetic vinyl wallpaper.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on March 12, 2014, 09:11:30 pm
Sorry I haven't read all the details in that link, but the answer should be because the enzyme was unable to act on the new style of synthetic vinyl. Like I mentioned before, enzymes are substrate specific. So, the enzyme might not have been able to act on the substrate molecules on the synthetic vinyl wallpaper.

Ill try this too. The DIF wallpaper did not work because the amylase only breaks down starch and the new style of synthetic vinyl may not have contained starch. Thus, the amylase in the paint stripper had nothing to break down.
Title: Re: VCE Biology Question Thread
Post by: sarahsmiggle on March 12, 2014, 09:32:36 pm

hi, i also need help with this question too, i'm finding amylase really difficult to understand for some reason, or probably its just biology in general :(

Amylase is produced in germinating plant seeds so that starch can be used as an energy source. Use evidence from your experiment to suggest how seeds are able to germinate in both cold and warm climates.  (we tested amylase in both hot and cold temperatures, but i cannot understand how it relates to plant seeds)

many thanks hehe
Title: Re: VCE Biology Question Thread
Post by: Tyleralp1 on March 12, 2014, 09:36:11 pm
Amylase is an enzyme which breaks down starch into glucose. Therefore, the amylase works on the energy stores of starch, breaking it down into glucose. This can then be used by the cell for cellular respiration to grow and develop. The growth may be different in different weather climates, due to the temperatures effecting the enzyme. Too hot =  no growth (enzyme denatures, hence can't bind to active site), warm = optimum conditions (best growth as enzymes work best), too cold = slow growth (enzyme becomes inactive due to less kinetic energy).

Hope that's it :)
Title: Re: VCE Biology Question Thread
Post by: sarahsmiggle on March 12, 2014, 09:58:49 pm
Amylase is an enzyme which breaks down starch into glucose. Therefore, the amylase works on the energy stores of starch, breaking it down into glucose. This can then be used by the cell for cellular respiration to grow and develop. The growth may be different in different weather climates, due to the temperatures effecting the enzyme. Too hot =  no growth (enzyme denatures, hence can't bind to active site), warm = optimum conditions (best growth as enzymes work best), too cold = slow growth (enzyme becomes inactive due to less kinetic energy).

Hope that's it :)

thank you!
Title: Re: VCE Biology Question Thread
Post by: JadedBlack on March 13, 2014, 08:41:59 am
Wow, that wallpaper glue prac was part of our enzyme SAC. l didn't do too badly, ended up losing 1 mark for not stating the pH of the environments of salivary amylase and pancreatic amylase were different  and so affected the optimum pH at which each enzyme would work.
Title: Re: VCE Biology Question Thread
Post by: millie96 on March 13, 2014, 07:31:51 pm
can somebody elaborate on how enzymes speed up chemical reactions? Like what happens with the chemical bonding etc
Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 13, 2014, 07:41:27 pm
can somebody elaborate on how enzymes speed up chemical reactions? Like what happens with the chemical bonding etc
Enzyme catalyse or speed up chemical reactions by lowering the activation energy of the reaction. They achieve this by influencing the stability of the bonds within the reactants; in anabolic reactions, they facilitate the formation of the product by essentially binding the reactants together, while in catabolic reactions, they facilitate the breakdown of bonds within the reactant.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 13, 2014, 07:44:53 pm
Is it correct to say that all catabolic reactions are exergonic and all anabolic reactions are endergonic?

Thanks!
Title: Re: VCE Biology Question Thread
Post by: millie96 on March 13, 2014, 07:48:47 pm
thank you oddly!

also, do we need to know much detail as to why factors such as pH and temperature increase enzyme activity (until a point of denaturing)? E.g. why does an increasing temperature cause an increase in enzyme activity? Does the heat energy increase collisions?
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 13, 2014, 08:02:59 pm
Is a metabolic pathway the same thing as a biochemical pathway?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 13, 2014, 08:12:38 pm
Is it correct to say that all catabolic reactions are exergonic and all anabolic reactions are endergonic?
Yes
thank you oddly!

also, do we need to know much detail as to why factors such as pH and temperature increase enzyme activity (until a point of denaturing)? E.g. why does an increasing temperature cause an increase in enzyme activity? Does the heat energy increase collisions?
Definitely; often you'll be required to interpret graphs, which an understanding of the factors influencing enzyme activity is necessary.
Is a metabolic pathway the same thing as a biochemical pathway?
Yes
Title: Re: VCE Biology Question Thread
Post by: millie96 on March 13, 2014, 08:30:57 pm
yes but how much detail do we need to go into?

can someone please explain why  increasing temperature (before passing optimal point) actually increases enzyme activity? does it have to do with heat energy and collisions?
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 13, 2014, 08:33:20 pm
Is the enzyme catalase an intracellular or extracellular enzyme?

Title: Re: VCE Biology Question Thread
Post by: alchemy on March 13, 2014, 08:34:15 pm
can someone please explain why  increasing temperature (before passing optimal point) actually increases enzyme activity? does it have to do with heat energy and collisions?

Denatures the enzymes. Therefore, the substrate molecules no longer have an active site to bind to.
Title: Re: VCE Biology Question Thread
Post by: millie96 on March 13, 2014, 08:36:41 pm
Is the enzyme catalase an intracellular or extracellular enzyme?
intracellular
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 13, 2014, 08:39:59 pm
Is the enzyme catalase an intracellular or extracellular enzyme?

Good question. Amylase is an extracellular enzyme. It's secreted from salivary glands in the mouth and the pancreas. Therefore, evidently it is secreted into the body from the cells where it was made.
Title: Re: VCE Biology Question Thread
Post by: millie96 on March 13, 2014, 08:40:29 pm
Denatures the enzymes. Therefore, the substrate molecules no longer have an active site to bind to.

sorry if I'm unclear with my question - but I'm asking about why increasing temperature increases enzyme activity, before it reaches the optimal temp and denatures.

For example, why would enzyme activity increase as a result of a change from 5degrees to 20deg?
Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 13, 2014, 08:43:31 pm
sorry if I'm unclear with my question - but I'm asking about why increasing temperature increases enzyme activity, before it reaches the optimal temp and denatures.

For example, why would enzyme activity increase as a result of a change from 5degrees to 20deg?
Increase in temperature increases the kinetic energy of the enzymes and substrates, which in turn increases the number of collisions between the molecules, thereby the formation of enzyme-substrate complexes increases. In turn, the rate of the reaction increases.
Yes, increases.

Edited
Title: Re: VCE Biology Question Thread
Post by: millie96 on March 13, 2014, 08:46:57 pm
perfect thank you!
Title: Re: VCE Biology Question Thread
Post by: auds on March 13, 2014, 08:48:23 pm
Haha, seems like so many of us have enzyme-related questions x]

Does anyone know if exergonic reactions still need addition of energy at the beginning, given that they actually release energy ?? ;x
Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 13, 2014, 08:55:45 pm
Haha, seems like so many of us have enzyme-related questions x]

Does anyone know if exergonic reactions still need addition of energy at the beginning, given that they actually release energy ?? ;x
To an extent, yes. Consider cellular respiration; although it is deemed an exergonic reaction, 2 ATP molecules are required to drive the Krebs cycle, which produces a net total of 2 ATP.
I guess you could generalise exergonic reactions as producing a net amount of energy.

Edit: Refer below
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 13, 2014, 09:16:10 pm
Haha, seems like so many of us have enzyme-related questions x]

Does anyone know if exergonic reactions still need addition of energy at the beginning, given that they actually release energy ?? ;x

Absolutely they do. You need energy to start a reaction. If this didn't occur, then everything would just disintegrate and bonds would never exist. Think about what would happen if you didn't need an activation energy for an exergonic reaction, it'd just be a straight down slope to the lowest form: individual atoms.

If that confused you, look at it this way: you need a spark to start a fire. That's an energy input, to get a much bigger output. You must, however, input extra energy to start a reaction though.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 13, 2014, 09:40:51 pm
Does the salinity affect enzyme catalysed reactions?

I thought I read this somewhere...
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 13, 2014, 09:51:04 pm
Does the salinity affect enzyme catalysed reactions?

I thought I read this somewhere...

Yes, salts can disturb protein binding. Completely irrelevant for VCE though
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 13, 2014, 10:41:31 pm
Ohh okay thankyou! :)
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 14, 2014, 12:17:06 am
How would an increased surface area to volume ratio, increase the rate of enzyme action?

:)
Title: Re: VCE Biology Question Thread
Post by: Scooby on March 14, 2014, 12:53:27 am
To an extent, yes. Consider cellular respiration; although it is deemed an exergonic reaction, 2 ATP molecules are required to drive the Krebs cycle, which produces a net total of 2 ATP.

2 ATP molecules are invested in the preparatory phase of glycolysis (not the Krebs cycle) and 4 are produced in the pay-off phase :)
Title: Re: VCE Biology Question Thread
Post by: DJA on March 14, 2014, 09:50:38 pm
What are the effect of limiting Cofactors and Coenzymes from enzymes which require them to function normally?

What would a graph look like say for limiting the % conc of cofactors and coenzymes to 0% to increasing it?
Will the enzyme activity rise and plateau or what? How does this work?

And thus are cofactors and coenzymes limiting factors in enzyme-mediated reactions? (Is this correct terminology? - How would you refer to reactions which require enzymes to occur - I know all reactions in living organisms need enzymes to occur but how would I word this?)

(SORRY for the stream of consciousness questions - I'm thinking as I type...)
Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 14, 2014, 09:58:21 pm
What are the effect of limiting Cofactors and Coenzymes from enzymes which require them to function normally?

What would a graph look like say for limiting the % conc of cofactors and coenzymes to 0% to increasing it?
Will the enzyme activity rise and plateau or what? How does this work?

And thus are cofactors and coenzymes limiting factors in enzyme-mediated reactions? (Is this correct terminology? - How would you refer to reactions which require enzymes to occur - I know all reactions in living organisms need enzymes to occur but how would I word this?)

(SORRY for the stream of consciousness questions - I'm thinking as I type...)
Well, considering they are necessary for some enzymes to function, limiting them would decrease enzyme activity. In a way, they could be limiting factors, although I'm uncertain as to whether this would be asked in an exam.

Enzyme-mediated reaction sounds legitimate.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 15, 2014, 01:06:50 pm
What is an apoenzyme?
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 15, 2014, 01:14:04 pm
What is an apoenzyme?

The protein component of the enzyme, by itself. A coenzyme attaches onto the apoenzyme to form the holoenzyme (active enzyme).
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 15, 2014, 01:23:11 pm
The protein component of the enzyme, by itself. A coenzyme attaches onto the apoenzyme to form the holoenzyme (active enzyme).

Oh okay thanks!
What about when cofactors bind with an enzyme to activate it?
Is the enzyme referred to as an apoenzyme in this case as well?

Title: Re: VCE Biology Question Thread
Post by: alchemy on March 15, 2014, 01:25:33 pm
Oh okay thanks!
What about when cofactors bind with an enzyme to activate it?
Is the enzyme referred to as an apoenzyme in this case as well?

Yes.
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 15, 2014, 01:38:25 pm
Why do chemical reactions occur in a biochemical pathway?

Is it so that the amount of energy released can be controlled, so that not too much energy is released all at once?

Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 15, 2014, 01:40:21 pm
Why do chemical reactions occur in a biochemical pathway?

Is it so that the amount of energy released can be controlled, so that not too much energy is released all at once?
One reason is that enzymes are substrate-specific, and there is no uber-enzyme which can catalyse every single reaction
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 15, 2014, 02:22:06 pm
Why do chemical reactions occur in a biochemical pathway?

Is it so that the amount of energy released can be controlled, so that not too much energy is released all at once?

Yeah complex biochemical pathways allow you to be very precise with various physiological levels etc. So the more complex it is, the more control the system has in some ways. It also makes everything even out as well, so you're getting endothermic reactions that are fuelled by exothermic reactions etc. (as you suggested).

In respiration, the reason that you get those steps is also what you suggested, the energy release would be too high. If you just catalysed the production of CO2 and water from glucose, you'd boil the cell. It's massively exothermic, so it needs to be taken in steps.

Title: Re: VCE Biology Question Thread
Post by: lzxnl on March 15, 2014, 02:27:39 pm
Why do chemical reactions occur in a biochemical pathway?

Is it so that the amount of energy released can be controlled, so that not too much energy is released all at once?

There are several reasons.
From a chemistry perspective, chemical reactions, like the complete oxidation of glucose, take several steps. Glucose, as we all know, won't spontaneously combust upon contact with air because although the reaction with oxygen to form CO2 and H2O is thermodynamically favourable, there is an activation energy barrier required, which prevents the reaction from being fast at all. For the combustion of glucose (respiration) to occur at a useful rate, it needs to be catalysed by enzymes, and it so happens that the enzymes we have in our body don't catalyse the complete conversion of glucose to CO2; rather, we have enzymes that catalyse specific steps in the biochemical pathway.
Also, as you've said, if we combusted too much glucose in one step, we'd heat up way too fast. Combusting it step-wise allows our body to take in the energy gradually.

From a biological perspective, the energy released from each step can then individually drive further chemical reactions that may be useful, such as the motion of dynein motors across microtubules. This is in contrast to getting a HUGE spike in the amount of ATP produced.
Title: Re: VCE Biology Question Thread
Post by: DJA on March 15, 2014, 10:04:25 pm
Please have a look at the question regarding experimental design and see if my answer which is CONTRARY to the VCAA answer is valid
Source: VCAA 2010, Biology Exam 1, Section B, Q2b

It has been suggested that less energy is retained when hard food is the major part of an animal's diet compared with the energy retained when soft food is eaten. The difference in energy retained would be indicated by the weight of an animal.

A pet food company has made two different types of food pellets, one hard and the other soft. Each kind of pellet has the same energy content. The company intends to test the pellets on a group of adult mice. Each mouse is genetically identical and of the same weight.

You are provided with many adult mice. Each mouse is genetically identical and of the same weight
two types of pellets, one hard and one soft. Each kind of pellet has the same energy content.
Outline an experiment that would allow you to determine if the hardness of the food pellets affects the balance between energy intake and energy expenditure.

-state the hypothesis that you are testing
-outline the experimental procedure
-describe the results that would support or negate your hypothesis.

Mice fed hard pellets will weigh less by the end of the experiment when compared to mice fed soft pellets.

We could set up two groups of many mice and weigh each of them at the beginning of the experiment. Then for a period of time (for say 3 weeks) we could feed one group only soft food pellets and the other group only hard food pellets and control the other variables by supplying both groups with the same amount of water and oxygen as well as environment to live in. After three weeks we could reweigh the mice and record the change in weight. We could repeat this process many times - for example, 20 times.

If the mass gain was consistently smaller for the group of mice taking hard pellets for food, then we could verify the hypothesis and conclude that less energy is retained when hard food is a major part of a mice's diet.

Hypothesis: Mice fed hard pellets will weigh more than mice that are fed soft pellets
Experimental procedure: Two groups of mice: one group fed hard pellets and the other soft, and all other variables
controlled
Results: Mice fed hard pellets weighed more than mice fed soft pellets

**In blue above are the phrases I strongly disagree with.
What do you guys think. Could you fault my logic?
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 15, 2014, 10:37:04 pm
Mice fed hard pellets will weigh less by the end of the experiment when compared to mice fed soft pellets.

We could set up two groups of many mice and weigh each of them at the beginning of the experiment. Then for a period of time (for say 3 weeks) we could feed one group only soft food pellets and the other group only hard food pellets and control the other variables by supplying both groups with the same amount of water and oxygen as well as environment to live in. After three weeks we could reweigh the mice and record the change in weight. We could repeat this process many times - for example, 20 times.

If the mass gain was consistently smaller for the group of mice taking hard pellets for food, then we could verify the hypothesis and conclude that less energy is retained when hard food is a major part of a mice's diet.

Hypothesis: Mice fed hard pellets will weigh more than mice that are fed soft pellets
Experimental procedure: Two groups of mice: one group fed hard pellets and the other soft, and all other variables
controlled
Results: Mice fed hard pellets weighed more than mice fed soft pellets

**In blue above are the phrases I strongly disagree with.
What do you guys think. Could you fault my logic?

To be honest, it's perfectly fine to agree or disagree with the hypothesis VCAA (or whoever) specifies. The Hypothesis is what YOU think will happen, after all. Since you haven't actually carried out the experiment, the 'results' will be much the same case. However, remember that the aim is something to be careful with. There are usually a few (but only a few) responses that would be given marks for.
Title: Re: VCE Biology Question Thread
Post by: DJA on March 15, 2014, 10:46:23 pm
To be honest, it's perfectly fine to agree or disagree with the hypothesis VCAA (or whoever) specifies. The Hypothesis is what YOU think will happen, after all. Since you haven't actually carried out the experiment, the 'results' will be much the same case. However, remember that the aim is something to be careful with. There are usually a few (but only a few) responses that would be given marks for.

I'm confused. My answer directly contradicts the VCAA provided answer in that according to their given stem of the question "less energy is retained when hard food is the major part of an animal's diet" my interpretation of this is obviously that hence less weight would be retained as more energy would be used up OR lost when hard food is taken.

So VCAA is right with their faulty logic? - that makes no sense -- at least until someone can prove me otherwise - if you can please do.
Title: Re: VCE Biology Question Thread
Post by: vox nihili on March 15, 2014, 11:06:20 pm
Please have a look at the question regarding experimental design and see if my answer which is CONTRARY to the VCAA answer is valid
Source: VCAA 2010, Biology Exam 1, Section B, Q2b

It has been suggested that less energy is retained when hard food is the major part of an animal's diet compared with the energy retained when soft food is eaten. The difference in energy retained would be indicated by the weight of an animal.

A pet food company has made two different types of food pellets, one hard and the other soft. Each kind of pellet has the same energy content. The company intends to test the pellets on a group of adult mice. Each mouse is genetically identical and of the same weight.

You are provided with many adult mice. Each mouse is genetically identical and of the same weight
two types of pellets, one hard and one soft. Each kind of pellet has the same energy content.
Outline an experiment that would allow you to determine if the hardness of the food pellets affects the balance between energy intake and energy expenditure.

-state the hypothesis that you are testing
-outline the experimental procedure
-describe the results that would support or negate your hypothesis.

Mice fed hard pellets will weigh less by the end of the experiment when compared to mice fed soft pellets.

We could set up two groups of many mice and weigh each of them at the beginning of the experiment. Then for a period of time (for say 3 weeks) we could feed one group only soft food pellets and the other group only hard food pellets and control the other variables by supplying both groups with the same amount of water and oxygen as well as environment to live in. After three weeks we could reweigh the mice and record the change in weight. We could repeat this process many times - for example, 20 times.

If the mass gain was consistently smaller for the group of mice taking hard pellets for food, then we could verify the hypothesis and conclude that less energy is retained when hard food is a major part of a mice's diet.

Hypothesis: Mice fed hard pellets will weigh more than mice that are fed soft pellets
Experimental procedure: Two groups of mice: one group fed hard pellets and the other soft, and all other variables
controlled
Results: Mice fed hard pellets weighed more than mice fed soft pellets

**In blue above are the phrases I strongly disagree with.
What do you guys think. Could you fault my logic?

Yeah, they've buggered it up
Title: Re: VCE Biology Question Thread
Post by: RazzMeTazz on March 16, 2014, 08:55:39 am
For a graph representing the rate of enzyme reaction when there is an increasing concentration of enzyme would the graph be shaped like a bell curve (As the substrate would eventually all be used, so enzyme reaction would cease?)

Title: Re: VCE Biology Question Thread
Post by: alchemy on March 16, 2014, 09:55:42 am
For a graph representing the rate of enzyme reaction when there is an increasing concentration of enzyme would the graph be shaped like a bell curve (As the substrate would eventually all be used, so enzyme reaction would cease?)

Depends if there is a limited or unlimited concentration of substrate. If substrate was limited, it would plateau no matter how much the increase in enzyme concentration. If substrate was unlimited, however, the graph would increase linearly (not quite the 'bell curve').
Title: Re: VCE Biology Question Thread
Post by: anon9884 on March 16, 2014, 10:59:27 am
Since a non competitive inhibitor does not occupy the active site, but attaches to another area of the enzyme and thus changes the shape of the enzyme so that it no longer has affinity for the substrate, how is this process reversible? The bonds in the enzyme have changed, so how can it go back to catalysing the initial reaction?
Title: Re: VCE Biology Question Thread
Post by: DJA on March 16, 2014, 11:09:43 am
Since a non competitive inhibitor does not occupy the active site, but attaches to another area of the enzyme and thus changes the shape of the enzyme so that it no longer has affinity for the substrate, how is this process reversible? The bonds in the enzyme have changed, so how can it go back to catalysing the initial reaction?

I always thought that non competitive inhibition is irreversible so yeah...
Correct me if I'm wrong but that's what we got taught at school for VCE level.
Title: Re: VCE Biology Question Thread
Post by: DJA on March 16, 2014, 11:12:48 am
A couple of questions regarding enzymes--

1) With enzymes, do extremes of pH cause the denaturing of the enzyme?
2) What bonds in the polypeptide (enzyme) are affected by changing the pH from the optimum? (I thought ionic and H-bonds - am I right or did I miss any? Are disulfide bonds affected?)
Is this break down of the tertiary structure reversible?

Title: Re: VCE Biology Question Thread
Post by: Tyleralp1 on March 16, 2014, 11:35:42 am
1. Yes, extremes in pH do cause enzymes do denature. The majority of eznymes will denature with pH 2 or less (except Pepsin), and denature with pH 12 or more. High temperatures may also denature enzymes.
2. The non-neighbouring bonds between the amino acids are broken. Bonds which are broken are part of the 3D tertiary structure. So anything from disulfide bridges, hydrogen bonds, ionic, etc. Just not the peptide bonds! Finally, the denaturation of a protein is irreversible. You are unable to regain functioning of a denatured enzyme. That can only occur to enzymes which are inactive due to low temperatures.
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on March 16, 2014, 12:34:31 pm
I always thought that non competitive inhibition is irreversible so yeah...
Correct me if I'm wrong but that's what we got taught at school for VCE level.

Reversible non-competitive inhibitors have weaker bonds, therefore allowing the enzyme to eventually revert back to its original shape. In non-competitive inhibition, it's all dependent on the characteristics of the inhibitor. Heavy metals, for example, usually act permanently on the enzyme due to the strong bonds created and their consequence on the enzyme's conformation. Irreversible non-competitive inhibitors form strong covalent bonds with enzymes, affecting the enzyme's conformational structure. Comparatively, reversible inhibitors would not form bonds as great.
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on March 16, 2014, 12:44:46 pm
A couple of questions regarding enzymes--

1) With enzymes, do extremes of pH cause the denaturing of the enzyme?
2) What bonds in the polypeptide (enzyme) are affected by changing the pH from the optimum? (I thought ionic and H-bonds - am I right or did I miss any? Are disulfide bonds affected?)
Is this break down of the tertiary structure reversible?

According to Checkpoints 2014, denaturation by high temperatures break hydrogen bonds and val der Waals forces and denaturation by extremes of pH break ionic bonds.

Denaturation is the breakdown of the quaternary and tertiary structures.
Title: Re: VCE Biology Question Thread
Post by: grannysmith on March 16, 2014, 12:55:41 pm
Can the products of an enzyme-mediated reaction act as non-competitive inhibitors of the enzyme?
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on March 16, 2014, 12:57:14 pm
Three questions:
1) If the quaternary structure of an enzyme is destroyed, does an enzyme denature or does denaturation specifically concern the destruction of the tertiary structure?
2) Concerning photosynthesis and cellular respiration, do we ACTUALLY only need to know the outputs and inputs? Teachers always tell us this, but that seems too simple. Do we at least need to know the exact reaction that results in, for example, the oxidation of ATP into ADP? So for glycolysis, the expenditure of ATP occurs during step 1 and step 3. Is that complex enough, or do I need to know the specific names of the enzymes?
3) ATP synthase harnesses the energy from the proton gradient to catalyse the anabolism of ATP from ADP and Pi. HOWEVER, I read somewhere that free e- are also used to help 'fuel' ATP synthase, so to speak. Is this true?

Thank you!!
Title: Re: VCE Biology Question Thread
Post by: katiesaliba on March 16, 2014, 01:01:04 pm
Can the products of an enzyme-mediated reaction act as non-competitive inhibitors of the enzyme?

Feedback inhibition is normally non-competitive.
Title: Re: VCE Biology Question Thread
Post by: Vicbelgaus on March 16, 2014, 03:38:08 pm
In regards to the first question, denaturation involves un-folding the protein's secondary, tertiary or quaternary structure.
So if the quaternary structure of an enzyme is destroyed, it is indeed denatured.
Title: Re: VCE Biology Question Thread
Post by: Rishi97 on March 16, 2014, 03:52:23 pm
I have a biology sac tomorrow on the prac that we did. Basically, to measure effects on enzymes, we had different concentrations of protease in each test tube. We then put a bit of photographic film in there and had to time how long it took for each film in each test tube to go clear.
Does anyone have a good aim and hypothesis for this prac?
Thanks ;)
Title: Re: VCE Biology Question Thread
Post by: Jason12 on March 16, 2014, 06:03:49 pm
what is the purpose of a control in an experiment?

for the experiment boiled liver was placed in a test tube and H202 added to breakdown the enzyme catalase inside the liver.

- one group of students recorded a breakdown of hydrogen peroxide in the sample using boiled liver. suggest a possible explanation for this result?

also how exactly do enzymes lower the activation energy required to start a reaction?
Title: Re: VCE Biology Question Thread
Post by: Tyleralp1 on March 16, 2014, 06:23:36 pm
Three questions:
1) If the quaternary structure of an enzyme is destroyed, does an enzyme denature or does denaturation specifically concern the destruction of the tertiary structure?
2) Concerning photosynthesis and cellular respiration, do we ACTUALLY only need to know the outputs and inputs? Teachers always tell us this, but that seems too simple. Do we at least need to know the exact reaction that results in, for example, the oxidation of ATP into ADP? So for glycolysis, the expenditure of ATP occurs during step 1 and step 3. Is that complex enough, or do I need to know the specific names of the enzymes?
3) ATP synthase harnesses the energy from the proton gradient to catalyse the anabolism of ATP from ADP and Pi. HOWEVER, I read somewhere that free e- are also used to help 'fuel' ATP synthase, so to speak. Is this true?

Thank you!!

1. As mentioned earlier on, the quaternary does indeed effect enzyme functioning. If the enzyme is disrupted on this level, the enzyme is denatured as it's specific 3D shape will have changed. Therefore, it won't be able to bind to its specific substrate to catalyse reactions.

2. It is true in the sense that we only need to know the inputs and outputs for each section. However, VCAA can test on the knowledge of whether a specific reaction is endergonic or exergonic, catabolic or anabolic. Also, it won't hurt to have a general understanding of what is happening, and where. You must definitely don't know to know the specific names of enzymes , or proteins involved.

3. Doesn't hydrogen ions move from the matrix into the inner membrane space, and then comes back in via ATP Synthase along the cristae and combines with ADP + Pi to form ATP?

Title: Re: VCE Biology Question Thread
Post by: Tyleralp1 on March 16, 2014, 06:27:33 pm
what is the purpose of a control in an experiment?

for the experiment boiled liver was placed in a test tube and H202 added to breakdown the enzyme catalase inside the liver.

- one group of students recorded a breakdown of hydrogen peroxide in the sample using boiled liver. suggest a possible explanation for this result?

also how exactly do enzymes lower the activation energy required to start a reaction?

1. The purpose of a control group is provide a basis of comparison of which to compare the effects of your experimental (independent) variable.

2. The liver sample contained the enzyme catalase. When in contact with the hydrogen peroxide, a catabolic reaction occurred to break it down as H2O2 is a complimentary fit to the active site of catalase. The increased temperature due to the boiling, caused an increased rate of reaction due to more kinetic energy thus resulting in more enzyme-substrate collisions in a given time.

3. I believe...The complimentary fitting of substrates aids with this. With combined with an enzyme, two individual substrates are within close proximity for a bond to be formed. If it is a larger molecule to be broken down, the bond is being weakened by the enzyme.
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 16, 2014, 06:35:29 pm
what is the purpose of a control in an experiment?

for the experiment boiled liver was placed in a test tube and H202 added to breakdown the enzyme catalase inside the liver.

- one group of students recorded a breakdown of hydrogen peroxide in the sample using boiled liver. suggest a possible explanation for this result?

also how exactly do enzymes lower the activation energy required to start a reaction?

1) To ensure that the dependent variable isn't affected by any other factors other than the independent variable.
2) I haven't done this prac, so I'd have to take a guess. The liver may not have been boiled adequately by the group, meaning the enzyme catalase had not been denatured. Thus, catalse would have still been able to catalyse the breakdown of hydrogen peroxide into water and oxygen.
3) Substrates bind to an enzyme's active site, in the presence of a coenzyme or cofactor, allowing the enzyme to catalyze a reaction.
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 16, 2014, 06:39:19 pm
2. The liver sample contained the enzyme catalase. When in contact with the hydrogen peroxide, a catabolic reaction occurred to break it down as H2O2 is a complimentary fit to the active site of catalase. The increased temperature due to the boiling, caused an increased rate of reaction due to more kinetic energy thus resulting in more enzyme-substrate collisions in a given time.

Sorry, but I don't think this is really correct. Although I haven't done the experiment, I'm sure it'd be safe to assume that they added a piece of pre-boiled liver into the test tube hydrogen peroxide (as opposed to boiling the liver in Hydrogen peroxide like I think you mean).
Title: Re: VCE Biology Question Thread
Post by: Tyleralp1 on March 16, 2014, 07:11:10 pm
Aha sorry for the confusion..

I interpreted that as a boiled liver piece, hence being a higher temperature than a room temperature liver piece.
Title: Re: VCE Biology Question Thread
Post by: nerdmmb on March 16, 2014, 08:57:21 pm

I know that they're both acceptor molecules but can one difference be that FAD accepts two hydrogen molecules?

Also, in regards to cellular respiration, do we need to know about the chemical composition of pyruvate molecules,etc?

And when glucose is converted into two pyruvate molecules, what happens to the water molecules (6H20) and oxygen (602) ?

Thanks heaps!
Title: Re: VCE Biology Question Thread
Post by: alchemy on March 16, 2014, 09:10:36 pm