VCE Biology Question Thread

[vox nihili]

Given they’ve called it the mitochondrial pathway on the study design, rather than just calling it the intrinsic pathway, I think it’s important to understand the basics of the mitochondria’s involvement.

This is a very good point, and a reminder that even though some of you here think that I know everything about the course, I am wrong at least a lot of the time. Also a helpful opportunity to saythat if you think anyone, even the old hands like PF and I, have said something bullshit, just raise it. Neither of us is perfect!!

[PhoenixxFire]

Also in the intrinisic pathway does the signalling molecule bind to an intracellular receptors or is it just called this because its initiated by internal signals? And is it correct to say that caspases cleave specific proteins in the nucleus, cytoplasm and cytoskeleton to cause the cell to lose its shape?

Intracellular receptors.

This might help you visualise it

You don’t need to know all the steps though.

Yep. They also activate DNAses which cut up nuclear DNA, don’t think you have to know that though. Also I would add ‘and form blebs’ onto the end of that sentence.

[Azim.m]

The solutions say the answer is B, but wouldn't it also be D?

[darkz]

The solutions say the answer is B, but wouldn't it also be D?

By saying that the rate of apopsosis is out of control, it suggests that the rate of apoptosis is occuring at a rapid rate signifying that the rate of apoptosis is greater than the rate of cell replacement

[vox nihili]

The solutions say the answer is B, but wouldn't it also be D?

I'd argue that none of these answers is true, to be honest. There are plenty of other cases in which the rate of replacement is greater than the rate of apoptosis, whilst this seems to imply that cell reproduction>apoptosis is always cancer, which is bullshit.

[Erutepa]

The solutions say the answer is B, but wouldn't it also be D?

I agree with Vox, however...
with multiple choice questions you are to choose the most correct answer
My interpretation is that while D can be seen as correct in that Alzheimers and cancer may very well occur when the rate of apoptosis is out of control,
B is more accurate as it states specifically a lower rate of apoptosis compared to cell replication.
This is just my take anyway.

[vox nihili]

I agree with Vox, however...
with multiple choice questions you are to choose the most correct answer
My interpretation is that while D can be seen as correct in that Alzheimers and cancer may very well occur when the rate of apoptosis is out of control,
A is more accurate as it states specifically a lower rate of apoptosis compared to cell replication.
This is just my take anyway.

EDIT: redundant reply due to typographical error on Erutepa's part now corrected

A is certainly not right. Alzheimer's sees the rate of apoptosis climb higher than the rate of replacement; therefore, nerve cells die. As an aside, the rate of replacement of neurones is 0. You're effectively born with all of them.

Sage advice about the most correct answer though! VCAA try to avoid writing questions like that above, but when two seem similar, you need to choose the "more" correct one.

[Erutepa]

A is certainly not right. Alzheimer's sees the rate of apoptosis climb higher than the rate of replacement; therefore, nerve cells die. As an aside, the rate of replacement of neurones is 0. You're effectively born with all of them.

Sage advice about the most correct answer though! VCAA try to avoid writing questions like that above, but when two seem similar, you need to choose the "more" correct one.

Sorry, meant to wright 'B' instead of 'A'. I corrected it in the post

[Hiea]

If there are two populations of animals, and one of them has a lower genetic diversity than the other, would it be more likely that they've experienced the founder effect or bottleneck effect?

On that note, do many animals other than humans experience the founder effect without human intervention (e.g. transporting populations of domesticated animals from one place to another)?

I don't think I've seen the founder effect listed as a solution for a question like this before, but I'm not sure if it's best to always say it's an example of the bottleneck effect rather than the founder effect, either.

[Erutepa]

If there are two populations of animals, and one of them has a lower genetic diversity than the other, would it be more likely that they've experienced the founder effect or bottleneck effect?

On that note, do many animals other than humans experience the founder effect without human intervention (e.g. transporting populations of domesticated animals from one place to another)?

I don't think I've seen the founder effect listed as a solution for a question like this before, but I'm not sure if it's best to always say it's an example of the bottleneck effect rather than the founder effect, either.

I don't think you will just be given a question asking why a second population (of the same species) has a lower genetic diversity. I would think that this question would follow a scenario with enough content that you could probably infer what happened in terms of the bottleneck effect or the founder effect.
If this is not the case, then you could always simply answer by stating genetic drift could have occurred involving either a bottleneck existing population or the founder effect in producing another population of lowered genetic diversity.

I do think that other animals can experience the founder effect. Many animals like turtles and some spiders float across waters to colonize new lands, as such often the new populations would have decreased genetic variation.

[EllingtonFeint]

Are anabolic reactions always energy requiring (endergonic), and catabolic pathways always energy releasing (exergonic)?

In the Krebs Cycle is FAD an input and FADH2 an output?

[persistent_insomniac]

Hey thanks so much for the help I have a few more qs:
1) What is the difference between NK cells and cytotoxic t-cells besides the fact that NK belong to innate and cytotoxic to adaptive?
2) If there are 369 base pairs what would be the maximum no. of amino acids? Would it be 122 as the last one has to be a STOP codon which is not considered an amino acid?
3) What is the difference between self and non-self antigens? Do they both trigger an immune response (identified as foreign?).
Thanks!

[darkz]

If there are two populations of animals, and one of them has a lower genetic diversity than the other, would it be more likely that they've experienced the founder effect or bottleneck effect?

On that note, do many animals other than humans experience the founder effect without human intervention (e.g. transporting populations of domesticated animals from one place to another)?

I don't think I've seen the founder effect listed as a solution for a question like this before, but I'm not sure if it's best to always say it's an example of the bottleneck effect rather than the founder effect, either.

I don't believe you can really determine whether it was a case of the bottleneck effect or the founder effect, as both can drastically reduce genetic diversity as they involve non-representative samples of the original population

Animals can experience the founder effect via changes in the environment due to climate change. e.g. there may be two populations of frogs living in a large river, however overtime the river dries up, so then the frogs on either side of the river are separated. Or maybe climate change causes a large iceberg to break off from the larger iceberg and travels away

Are anabolic reactions always energy requiring (endergonic), and catabolic pathways always energy releasing (exergonic)?

Yes

[EllingtonFeint]

In the Krebs cycle, is FAD an input and FADH2 an output?

[PhoenixxFire]

Hey thanks so much for the help I have a few more qs:
1) What is the difference between NK cells and cytotoxic t-cells besides the fact that NK belong to innate and cytotoxic to adaptive?
2) If there are 369 base pairs what would be the maximum no. of amino acids? Would it be 122 as the last one has to be a STOP codon which is not considered an amino acid?
3) What is the difference between self and non-self antigens? Do they both trigger an immune response (identified as foreign?).
Thanks!

1. Don't need to know more than that for VCE.
2. This depends who's asking the question. I'd say you're correct but I've seen company exams that seem to ignore STOP codons
3. self antigens are only antigens in an autoimmune response. They're not supposed to trigger an immune response, but they do when they're mistakenly identified as foreign. Non-self antigens are always supposed to trigger an immune response.