VCE Biology Question Thread

[EllingtonFeint]

Is it worth doing the sample exams? They don’t have answers for short answer

Your teacher should have suggested answers

[vox nihili]

What properties allow proteins to be embedded in the plasma membrane? Wouldn't they get expelled by the hydrophobic tails?

What if the part of the protein embedded in the membrane were hydrophobic?

I’ve got a few questions.

1. Where is chlorophyll located? Is it embedded in the thylakoids membrane of grana
2. In regards to photosynthesis is this correct?
the oxygen element in water is converted to oxygen gas, while the oxygen from the reactant, CO2 ends up in glucose and water.
3. Also how is cell mediated immunity activated. Does this process involve T helper cells. Secreting Cytokines to naive cytotoxic T cells
4. Why is Taq polymerase used in PCR? I know it can withstand heat but how does this help?
5. Also in terms of hominin evolution does the Homo genus have a broader bowl shaped pelvis or narrower pelvis than Australopithecus?
Thanks

1. Yep
2. Yes, but it's a little irrelevant on an exam—good thinking though!
3. You know what, I've never fully known the answer to this question. I suspect that you're right in part, although I'm still not sure how populations of cytotoxic T-cells become preferentially activated. Definitely not a VCE-level question though
4. I think this one is definitely one you can work out—why do you think it would be useful for taq pol to withstand heat?
5. Look at the pelvises on google and tell me

[PhoenixxFire]

“Nerve pumps are facilitated by Na+/K+ pumps on the membrane of the neuron” is this kinda like a transport protein for swapping potassium and sodium ions across the membrane??

You don't need to know that much detail with the sodium potassium pump, but sodium goes in and potassium comes out, allowing for action potential to move across neuron.

1.^somebody check tho cause I don't think im 100% right

So capillaries becoming permeable and leaked causes swelling, true?
- that indirectly causes swelling
2.- the swelling is due to the increased blood flow as a result of these capillaries becoming more permeable

Is synthesis of DNA relevant for the 2018 exam??

3.Nup. Just know that it involves DNA polymerase.

1. For bio you don't need to know anything about how they work (I think they used to be on the study design though), just need to recognise whether something is active or passive transport by whether it uses ATP.

2. The increased blood flow is due to vasodilation, the increase in permeability is what makes them 'leaky', it doesn't really increase blood flow though.

3. Don't even need to know that much.

Hi,
So I have been just done the 2016 VCAA exam and came across this question (2) (attached). For part c, it asks for us to design an experiment. With these questions, is it best to write out a method, or just identify components like the IV and DV and basic experimental set-up as the answers seem to identify (also attached).
Thanks!

Nah, it's testing experimental design not method. Experimental design is the way an experiment is setup, not the way it's run (if that distinction makes any sense). So it just wants to know how you would set up the experiment as well as the DV and IV. The second and third dot points on the answers are the 'setup' part of it.

1. I understand that lysozymes break down the bacterial cell wall, but how does this affect the bacterial cell?

Could this be an appropriate answer?
- results in cell integrity being affected, as there is no cell wall to limit expansion of bacterial cell
- thus, disrupts cell ability to function properly
- resulting in death of bacteria

1. I'd just say that it stops the bacteria from controlling what can enter/exit the cell, which is necessary for survival. Without this ability, it dies.

Is it worth doing the sample exams? They don’t have answers for short answer

Vox wrote solutions to the 2017 one here

[vox nihili]

Vox wrote solutions to the 2017 one here

Not gonna lie, when I saw someone mention the sample exam I was like "I should really write some solutions for that". Well I'll be damned.

[Robot10]

1.With the pelvis in terms of hominin evolution is this correct?

The pelvis has become more bowl shaped and narrower from Australopithecus to Homo.

2.Also in regards to PCR, Taq polymerase has an optimum temperature of 72 degC but why is it useful to use Taq polymerase, because during denaturation, DNA is heated to 95degC so wouldn’t Taq polymerase be denatured?

3.With this question(see attached), the answer is B but why can’t Option D also be correct since can’t large non polar  molecules cross the plasma membrane also by simple diffusion.

[PopcornTime]

1.With the pelvis in terms of hominin evolution is this correct?

The pelvis has become more bowl shaped and narrower from Australopithecus to Homo.

2.Also in regards to PCR, Taq polymerase has an optimum temperature of 72 degC but why is it useful to use Taq polymerase, because during denaturation, DNA is heated to 95degC so wouldn’t Taq polymerase be denatured?

Yeh so it is heated to 95ºC to denature Taq Polymerase during 1st step, to prevent the action of Taq polymerase during this step (because we want the enzyme to work during extension phase)

3.With this question(see attached), the answer is B but why can’t Option D also be correct since can’t large non polar  molecules cross the plasma membrane also by simple diffusion.

According to khan academy, large non polar molecules can pass through. I think its looking for most correct answer, so in that case B. Was this a VCAA question?

https://www.khanacademy.org/test-prep/mcat/cells/cell-membrane-overview/a/fluid-mosaic-model-cell-membranes-article

I thought that the cell wall was porous, so anything could get through it (just not the cell membrane??)?
Mod edit (PF): Merged double post

[PhoenixxFire]

Yeh so it is heated to 95ºC to denature Taq Polymerase during 1st step, to prevent the action of Taq polymerase during this step (because we want the enzyme to work during extension phase)

According to khan academy, large non polar molecules can pass through. I think its looking for most correct answer, so in that case B. Was this a VCAA question?

https://www.khanacademy.org/test-prep/mcat/cells/cell-membrane-overview/a/fluid-mosaic-model-cell-membranes-article

Taq Polymerase is from a species called thermus aquaticus which lives in hot springs. The reason it’s used for PCR is because it doesn’t denature at high temperatures (well it does, they just have to be really high). Previously polymerase would have to be added after every step of the process because it would be denatured every time it was heated up. Taq Polymerase can withstand the heat, which means it can be added at the start and then left which is why it’s used. The pcr solution is heated to seperate the double stranded DNA into single strands, not to denature the Taq Polymerase.

[C14M8S]

What sort of tissues make 38 ATP instead of 36 in aerobic respiration? Correct me if I'm wrong, but it relates to the substrates not having to be actively transported into the mitochondria, correct?

[Bell9565]

What sort of tissues make 38 ATP instead of 36 in aerobic respiration? Correct me if I'm wrong, but it relates to the substrates not having to be actively transported into the mitochondria, correct?

It's heart tissue if I remember correctly, and our teacher just described it as 'there is something different that happens during the electron transport chain which makes more ATP'.... very vague I know..
Anyway, considering VCAA don't actually mind if you say 34 or 36 ATP as a product, I don't think (emphasise the think) there will be a question about why certain tissues have an average higher yield of ATP. Because in reality, much less ATP is produced than 36 in a normal cell anyway.
I could be very wrong so I'm more than happy to be corrected if so

[EllingtonFeint]

2015 BIO exam Q7
The production of adenosine triphosphate (ATP) is represented by the following equation:
ADP + Pi —> ATP

The production of ATP requires an overall input of energy.

So to make ATP, energy is required?
Should I know more about this?


-Q35.
 Potassium 40 has a half life of 1.25 billion years. In igneous rocks closely associated w a fossil layer, the ratio of potassium 40 to its radioactively breakdown product is approx 1:1

The age of fossils in the fossil layer will be close to 1.25 billion years

Is it really as simple as that? I guess all that jargon just threw me off. What if the ration was 1:2, or 2:1 or something?


-Q38
Fossil remains of a no of individuals from the genus Australopithecus were found at various sites in the eastern half of Africa an have been dated to bw 3-4 million years old.
These fossil remains
A. Are descendants of homo erectus
B. represent the oldest evidence found of primates
C. Show early evidence that humans are bi pedal
D. Represent the earliest example of the hominoid super family.

The answer is C. But how do the fossils show this?? Is it cos “various sites” so they moved around heaps...?
Australopithecus are NOT descendants of homo erectus, true of false?
I don’t even understand what d is saying... what is a hominoid super family?

[vox nihili]

What sort of tissues make 38 ATP instead of 36 in aerobic respiration? Correct me if I'm wrong, but it relates to the substrates not having to be actively transported into the mitochondria, correct?

Don't worry about this point. Irrelevant to the course

[EllingtonFeint]

2015 Q 5c
A possible answer given is B cell produces antibodies
And rough er produces proteins that make up these antibodies.

So are there rough er INSIDE of a B cell?

[juntyhee]

2015 BIO exam Q7
The production of adenosine triphosphate (ATP) is represented by the following equation:
ADP + Pi —> ATP

The production of ATP requires an overall input of energy.

So to make ATP, energy is required?
Should I know more about this?


-Q35.
 Potassium 40 has a half life of 1.25 billion years. In igneous rocks closely associated w a fossil layer, the ratio of potassium 40 to its radioactively breakdown product is approx 1:1

The age of fossils in the fossil layer will be close to 1.25 billion years

Is it really as simple as that? I guess all that jargon just threw me off. What if the ration was 1:2, or 2:1 or something?


-Q38
Fossil remains of a no of individuals from the genus Australopithecus were found at various sites in the eastern half of Africa an have been dated to bw 3-4 million years old.
These fossil remains
A. Are descendants of homo erectus
B. represent the oldest evidence found of primates
C. Show early evidence that humans are bi pedal
D. Represent the earliest example of the hominoid super family.

The answer is C. But how do the fossils show this?? Is it cos “various sites” so they moved around heaps...?
Australopithecus are NOT descendants of homo erectus, true of false?
I don’t even understand what d is saying... what is a hominoid super family?

1\  Yep, energy is used to join ADP and Pi to ATP, and that energy is mostly stored in the second and third phosphate groups of ATP. Only when ATP is broken down back into ADP and Pi, is energy released.

2\ If it's 1:1, that means HALF of potassium has broken down into argon. Think about it like this, if we have 1:0 (potassium and no argon), and half of it breaks down then we have 0.5 potassium and 0.5 argon. 0.5:0.5 = 1:1.

3\ Australopithecus are one of the first few species in the hominin family. Remember that all hominin species are bidepal, hence, they show earliest evidence of bipedalism. You should use process of elimination for these sorts of questions: can't be A because Erectus evolves AFTER australopithecus, can't be B because there's gorillas, chimps, etc. and can't be D because Australopithecus is a hominin.

[peachxmh]

For q4(d) in Section B of the 2011 VCAA Exam 1, can someone explain why it is necessary to include that the baby is receiving antibodies from the mother? My answer was simply that probiotics would be passed from the mother to baby via the umbilical cord, and the baby is receiving probiotics, so its TLRs are being exposed to a wide variety of antigens and thus being stimulated, resulting in the babies in Group 1 being less likely to develop asthma or eczema. What are the antibodies being produced against, and how does this protect against autoimmunity? The probiotics are beneficial bacteria, so I'm unsure how the maternal antibodies would protect the baby..

[vox nihili]

2015 Q 5c
A possible answer given is B cell produces antibodies
And rough er produces proteins that make up these antibodies.

So are there rough er INSIDE of a B cell?

There's rough ER in every cell basically. Plasma B-cells have a particularly large one.

For q4(d) in Section B of the 2011 VCAA Exam 1, can someone explain why it is necessary to include that the baby is receiving antibodies from the mother? My answer was simply that probiotics would be passed from the mother to baby via the umbilical cord, and the baby is receiving probiotics, so its TLRs are being exposed to a wide variety of antigens and thus being stimulated, resulting in the babies in Group 1 being less likely to develop asthma or eczema. What are the antibodies being produced against, and how does this protect against autoimmunity? The probiotics are beneficial bacteria, so I'm unsure how the maternal antibodies would protect the baby..

I initially typed out a response to this that focused on the fact that probiotics is a bad word that shouldn't be used because it's more of a marketing term than a scientific one. I then went on to say that bacteria aren't present in fetal or indeed maternal circulation and therefore it was a silly idea that probiotics are passed down the umbilical cord. But VCAA told you both of these things. Ignore this question. The information VCAA have given you is absurd.