VCE Biology Question Thread

[whys]

Why does the high specific heat capacity of water make it efficient for cooling organisms down

Adding onto SmartWorker's very good answer, I found this online:
- The change of water from liquid to vapour (evaporation) requires an input of energy
- This energy comes from the surface of the skin when it is hot, therefore when the sweat evaporates the skin is cooled
- Because water has a high specific heat capacity, it absorbs a lot of thermal energy before it evaporates
- Thus water functions as a highly effective coolant, making it the principal component of sweat

[Chocolatepistachio]

Hello
i was having trouble with this question if someone could explain 

[Owlbird83]

Hello
i was having trouble with this question if someone could explain

Anyone please correct me if I'm wrong, but I'm pretty sure the reason why the number of viruses isn't a constant up, is because they replicate by hijacking a cell and using the cell's machinery to create more viruses, and then then lysis occurs where the cell bursts and all the new viruses are released to infect more cells. So the upwards sudden rise would correspond to when the cell bursts and releases all the new viruses, and the plateau would correspond to the time when viruses are hijacking the cells and creating new viruses, but they are all still accumulating inside the cells.
(Bacteria increases exponentially because they double in number each time they undergo binary fission, in a set time it takes each cell to divide.)

[Coolgalbornin03Lo]

What is the purpose of DNA having 5 prime and 3 prime ends

In the neap twenty 18 exam this was the answer but I do not understand why

Any two of:
• The two strands are antiparallel.
• Enzymes manufacture new strands along template strands by placing new
nucleotides onto the 3¢ end of the growing polynucleotide strand.
• This means that DNA can only be read in one direction, making the code specific.

How does this sufficiently explain why there is a those ends

[Sine]

What is the purpose of DNA having 5 prime and 3 prime ends

In the neap twenty 18 exam this was the answer but I do not understand why

Any two of:
• The two strands are antiparallel.
• Enzymes manufacture new strands along template strands by placing new
nucleotides onto the 3¢ end of the growing polynucleotide strand.
• This means that DNA can only be read in one direction, making the code specific.

How does this sufficiently explain why there is a those ends

It's not answering the question but 5' and 3' are defined by the number of the carbon atom on the pentose sugar of the DNA at each end.

I think the use of the word "why" is poor for that question.
A better question would be to describe DNA with 3' and 5' ends and note the implications of this.

[whys]

What is the purpose of DNA having 5 prime and 3 prime ends

In the neap twenty 18 exam this was the answer but I do not understand why

Any two of:
• The two strands are antiparallel.
• Enzymes manufacture new strands along template strands by placing new
nucleotides onto the 3¢ end of the growing polynucleotide strand.
• This means that DNA can only be read in one direction, making the code specific.

How does this sufficiently explain why there is a those ends

DNA has a 3' and 5' end because the antiparallel, asymmetric structure gives DNA a direction, and like the answers have said, makes it specific since it can only be read in a 3' to 5' direction by polymerase, and new nucleotides are attached from 5' to 3'. If DNA didn't have a specified direction then polymerase would have trouble figuring out which way it's supposed to go and there could be more chance of error during transcription or DNA replication, so having 3' and 5' ends makes the code specific. I think this is the type of answer that question wanted you to give, but I've provided more explanation so it makes sense.

[PhoenixxFire]

thanks
For this question why is the answer 5- 7 micrometers

You just have to use the scale given of 20 micrometers and compare that to the size of the cells to work out that they're approximately 5-7 micrometers

[Coolgalbornin03Lo]

DNA has a 3' and 5' end because the antiparallel, asymmetric structure gives DNA a direction, and like the answers have said, makes it specific since it can only be read in a 3' to 5' direction by polymerase, and new nucleotides are attached from 5' to 3'. If DNA didn't have a specified direction then polymerase would have trouble figuring out which way it's supposed to go and there could be more chance of error during transcription or DNA replication, so having 3' and 5' ends makes the code specific. I think this is the type of answer that question wanted you to give, but I've provided more explanation so it makes sense.

Raw fifty whys!! Thankyou very much Whys, phoenixxFire and Sine!

Also I need some bio related advice. In practise exams I extensivley review them but my mistakes are not from huge gaps in knowledge its more things like this.....so do I just do another exam? Because for example in chem if I forgot a whole topic I would go back to textbook, and checkpoints and make posters on that concept before doing another exam (which I still have not done lol] what do you do if you are at a level where you feel confident?

[whys]

Also I need some bio related advice. In practise exams I extensivley review them but my mistakes are not from huge gaps in knowledge its more things like this.....so do I just do another exam? Because for example in chem if I forgot a whole topic I would go back to textbook, and checkpoints and make posters on that concept before doing another exam (which I still have not done lol] what do you do if you are at a level where you feel confident?

Can't answer in terms of biology specifically since I haven't started practice exams and am still learning the content, but this is exactly what happened to me in psychology last year. I know it can be frustrating to make mistakes that aren't due to a lack of knowledge, namely silly mistakes, misreading the question, etc etc but you just have to keep powering on. Imo, it's totally okay to make mistakes like these as long as you're learning from them. The more you practise, the more these mistakes will begin to fade away. I know it can be easy to remain demotivated (which happened to me), but if you've practised enough then come exam day you'll usually do much better than in your practice exams if everything goes well. No matter how well you know the content there will always be tricksy questions that want to trip you up, but if you can begin to see past that to the core of the question then you'll do much better than the state. And that only comes with practice.

[Chocolatepistachio]

You just have to use the scale given of 20 micrometers and compare that to the size of the cells to work out that they're approximately 5-7 micrometers

So is it 20/3 and 20/4 because the average yeast cell is between 3 and 4 micrometers

[PhoenixxFire]

So is it 20/3 and 20/4 because the average yeast cell is between 3 and 4 micrometers

no maths involved, you just treat the scale provided as a ruler and measure one of the cells next to it

[Chocolatepistachio]

For this question
All of the following plant transport processes are directly driven by osmosis, except one .which one does not directly involve osmosis?
A guard cells losing turgor pressure
B oxygen diffusion into leaves
C transpiration
D translocation

The answer is b but how could translocation directly involve osmosis as it is the movement of sugars not water

[SmartWorker]

For this question
All of the following plant transport processes are directly driven by osmosis, except one .which one does not directly involve osmosis?
A guard cells losing turgor pressure
B oxygen diffusion into leaves
C transpiration
D translocation

The answer is b but how could translocation directly involve osmosis as it is the movement of sugars not water

Yeah but the sugars are dissolved in the solvent (water) so the pressure of water directly affects the rate of translocation.

[SmartWorker]

I had a few questions:

1. To what level of detail do we need to know about how neurotransmitters work? Because the study design mentions the "sources and mode of transmission of various signalling molecules, including... neurotransmitters". Do we need to know about how the action potential is fired and moves through the neuron? (Sodium-Potassium pump)

2. In some of past study design exams: MC says that the greater the stimulus, the size of the nerve impulse does not change. Can you please explain this and how the action potential/nerve impulse works.

3. Is the mechanism of Antigen Presenting Cells (APCs) that activates specific T helper cells considered the 2nd line of defence (innate) or is it part of the 3rd line of defence (adaptive immunity)? The APCs would engulf the pathogen via phagocytosis (2nd line phagocytes do this?) and then present its pathogenic antigens on its surface.

4. Also, in the question below for, why is rough endoplasmic reticulum considered as the producer of these proteins, what is its role if it is not involved in transport and packaging the protein as purported by the examiner's report?

5. What is the difference between structural homology and comparative anatomy? Is it the same thing?

6. Does the out of Africa theory suggest that there was a first exodus of Homo. erectus from Africa that evolved into Homo sapiens in Europe or outside of Africa. And simultaneously at the same time remaining Homo. erectus in Africa evolved into Homo sapiens and there was a second exodus. Or is does the theory say that the Homo. Erectus evolved into Homo. Sapiens and then moved out of Africa and there was remaining Homo sapiens in Africa? Hope it made sense

EDIT: Is this considered double posting (sorry if it is idk the rules)?

[Coolgalbornin03Lo]

I had a few questions:

1. To what level of detail do we need to know about how neurotransmitters work? Because the study design mentions the "sources and mode of transmission of various signalling molecules, including... neurotransmitters". Do we need to know about how the action potential is fired and moves through the neuron? (Sodium-Potassium pump)


EDIT: Is this considered double posting (sorry if it is idk the rules)?

My school taught us the whole thing with calcium gated protein channels etc and sodium gated ligands etc I’m not sure if this is necessary I think not but maybe just in case? I think just knowing the action potential changing the voltage and allowing for opening of the voltage gated calcium ion channels onwards is enough.

I had a few questions:


2. In some of past study design exams: MC says that the greater the stimulus, the size of the nerve impulse does not change. Can you please explain this and how the action potential/nerve impulse works.

EDIT: Is this considered double posting (sorry if it is idk the rules)?

I had a few questions:


3. Is the mechanism of Antigen Presenting Cells (APCs) that activates specific T helper cells considered the 2nd line of defence (innate) or is it part of the 3rd line of defence (adaptive immunity)? The APCs would engulf the pathogen via phagocytosis (2nd line phagocytes do this?) and then present its pathogenic antigens on its surface.

EDIT: Is this considered double posting (sorry if it is idk the rules)?

It’s considered a part of adaptive immunity (3rd line) this is why APCs are said to be the link between innate and adaptive immunity. The engulfing part is 2nd but the MHCII to present to T -helper is third line.

I’m sorry I can’t quote anymore!!

4. The endoplasmic reticulum is probably considered as the production area of protein as it has ribosomes on it which is where translation takes place. But I also understand the rough endo....to be intracrllular transport as well (after being protein production due to having ribosomes). It I wouldn’t state it’s the place but I would say it has ribosomes so therefore....... P.S these are proteins for export only.

5. Homologous and analogous structures are like under the umbrella of comparative anatomy

6. Maybe Teacher said for this there’s thousands of theories BUT in VCE: Out if Africa suggested Homo sapiens first migrated out of Africa? Or was it homo erectus? She said it was homo erectus at first then they died but the homo erectus  still in Africa evolved into sapien and migrated. Really not sure about this one so maybe we should see what others say

2. For question 2 I think I came across this in the VCAA 2010 exam it seemed irrelevant to current SD but I’d also like to know the answer )