VCE Biology Question Thread

[smamsmo22]

More important point: ions ALWAYS use facilitated diffusion. They need channels to get through (or in some cases carriers). They can't move directly through the plasma membrane.


You're absolutely right about autoimmune diseases potentially involving either arm of the adaptive immune system. Most autoimmune diseases involve a component of B-cells and T-cells, with one of the types of cells being more dominant. Indeed, MS for example only really involves T-helper cells (they do the majority of the damage!).

As above it's actually both T-cells and B-cells that can do it, with some involving more than others. If you take autoimmune thyroid diseases as an example (you don't need to know the details), Graves disease mainly involves B-cells producing autoantibodies, whereas Hashimoto's thyroiditis is mainly a T-cell disease.

Thanks!
When you say ions always use facilitated diffusion, does that means that they never use active transport? (Because they require channel proteins... or because they aren't usually required to be moved against a concentration gradient?) Probably a silly question but just wanted to be sure.

As for the autoimmune diseases, I guess mentioning in an answer that immune response coordinated against the self cells could occur through humoral or cell mediated mechanisms, or both?
You mentioned MS, which is also mentioned in the study design. As it involves the myelin being destroyed which is a covering of nerve cells rather than a cell itself; are Tc cells mounting an attack on nerve cells? Or on the myelin which they treat like an infected cell?
I doubt that we'd need to know all that but now I'm confused (oops). Is it sufficient enough to say that in the case of MS; an adaptive immune response is mounted against body tissue which is incorrectly identified as non self, resulting in damage to the myelin of nerve cells. The immune response may involve the production of antibodies against self antigens by B cells or the activation of Cytotoxic t cells which directly destroy self cells.

Sorry for the confusion !!!

[Nomi16]

This question keeps irritating me and i don't get a way through it. What is the mode of transport for neurotransmitters? I simply answered that they travel through synapse/synaptic gap but i knew this wasn't the answer. According to solutions, the answer was diffusion. Can anyone help me out? Anyways it was a NEAP 2017 SA question.

[PhoenixxFire]

This question keeps irritating me and i don't get a way through it. What is the mode of transport for neurotransmitters? I simply answered that they travel through synapse/synaptic gap but i knew this wasn't the answer. According to solutions, the answer was diffusion. Can anyone help me out? Anyways it was a NEAP 2017 SA question.

They diffuse across the synapse. The synapse is the location of transport but not the mode.

[vox nihili]

Thanks!
When you say ions always use facilitated diffusion, does that means that they never use active transport? (Because they require channel proteins... or because they aren't usually required to be moved against a concentration gradient?) Probably a silly question but just wanted to be sure.

As for the autoimmune diseases, I guess mentioning in an answer that immune response coordinated against the self cells could occur through humoral or cell mediated mechanisms, or both?
You mentioned MS, which is also mentioned in the study design. As it involves the myelin being destroyed which is a covering of nerve cells rather than a cell itself; are Tc cells mounting an attack on nerve cells? Or on the myelin which they treat like an infected cell?
I doubt that we'd need to know all that but now I'm confused (oops). Is it sufficient enough to say that in the case of MS; an adaptive immune response is mounted against body tissue which is incorrectly identified as non self, resulting in damage to the myelin of nerve cells. The immune response may involve the production of antibodies against self antigens by B cells or the activation of Cytotoxic t cells which directly destroy self cells.

Sorry for the confusion !!!

Mechanistically active transport and facilitated diffusion are pretty similar, to be honest, hence the reason I omitted active transport. You're right though, ions can be actively transported.


Yes you could say that both are involved. You wouldn't be expected to know the details of the variety of autoimmune disease out there.
I'm not sure what level of detail you need to know about MS (nobody really does). Our understanding of MS is actually quite poor, but if I remember correctly it's basically the T-helper cells directing an innate immune response against the myelin that causes the problem. There is also involvement from anti-myelin antibodies, which I think would be a more VCE-appropriate thing to say than the innate involvement.
MS is new to the course and it's really unclear what you actually need to know about it, so sorry about the half-arsed answer...I can only tell you what I know to be true about MS, not the VCE version of it!

This question keeps irritating me and i don't get a way through it. What is the mode of transport for neurotransmitters? I simply answered that they travel through synapse/synaptic gap but i knew this wasn't the answer. According to solutions, the answer was diffusion. Can anyone help me out? Anyways it was a NEAP 2017 SA question.

They're released by exocytosis and subsequently diffuse across the synaptic cleft to the post-synaptic neuron.

[medsci]

Am I correct in saying that MS is escalated by the death of oligodendrocytes? Thanks for any help in advance

[ringring]

Hey
Are questions like the one i've attached part of the current study design? If so, how would I go about doing it

Thanks

[medsci]

I would say so as we are expected to know the structure of DNA and hence complementary base pairing.
For this question you know thta there are 200 thyamine bases, hence 200 bases are adenine. As they have said that 200 bases = 20%, then you can infer that 100 bases=10%, hence the total number of bases is 1000.
Hence because out of the 1000 there is 400 bases of A and T (200 bases each), you will have 600 bases left of guanine and cytosine. And due to complementary base pairing this will mean that there are 300 guanine bases.
I hope that makes sense

[Seno72]

Hey guys. For VCAA Biology Exam 1 2010, question 1c.i. asks what effect would the pathways have on the fertility of the person concerned. VCAA says it leads to decereased sperm production or decreased fertility. I said it leads to infertility. Is that correct?

[vox nihili]

Hey guys. For VCAA Biology Exam 1 2010, question 1c.i. asks what effect would the pathways have on the fertility of the person concerned. VCAA says it leads to decereased sperm production or decreased fertility. I said it leads to infertility. Is that correct?

I think that would be reasonable given the other answers. I haven't looked at the question you're asking about, but it logically follows that if you've said decreased sperm/fertility then infertility could be reasonable.

[dimenc]

I was just wondering if this was acceptable for an answer regarding the introduction of a new strain of influenza?

The existing strain of influenza mutates. Genetic drift occurs gradually over time, causing a change in antigens/surface proteins. The body cannot recognize these new changes, thus creating a new response to the strain.

[Jackie Chan]

I was just wondering if this was acceptable for an answer regarding the introduction of a new strain of influenza?

The existing strain of influenza mutates. Genetic drift occurs gradually over time, causing a change in antigens/surface proteins. The body cannot recognize these new changes, thus creating a new response to the strain.

Antigenic drift not genetic drift. 
Antigenic drift is the change in surface proteins whereas genetic drift can be defined as a change in allele frequencies due to a random event.
Note that since the Influenza virus mutates, a new vaccine must be created.

[dimenc]

Thank you so much, I got the genetic drift off a practice exam answer and thought it sounded a bit strange!

[Domek]

Am I correct in saying that MS is escalated by the death of oligodendrocytes? Thanks for any help in advance

Yes! Oligodendrocytes are cells that produce myelin. The mitochondria of these cells become damaged, inducing apoptosis, and macrophages called microglia are also involved in oligodendrocyte destruction.

[areeb008]

hey guys, could someone clarify the main difference between accuracy and validity? also if an experiment is accurate is it necessarily valid as well and vice versa??

[PhoenixxFire]

hey guys, could someone clarify the main difference between accuracy and validity? also if an experiment is accurate is it necessarily valid as well and vice versa??

Accuracy is whether you are correctly measuring something. ie if you measure something that is actually 1metre and get 50cm your measurements (and therefore results) are not accurate. Validity is whether you are actually testing what you're supposed to be testing ie have you designed an experiment that tests your hypothesis?
No, a test can be accurate (measured correctly) but not valid (not testing the hypothesis) and vice versa.