VCE Biology Question Thread

[Sine]

Um so apparently the answer is C and apparently MHC I markers present antigens to B cells too?

Haha VCAA got it wrong, however A,B & D are blatantly incorrect so it was a matter of just going against your knowledge base.

The attached question asks for two advantages of having these memory B cells when the student receives their immunisation in Year 10, the answer said that there will be a more rapid production of antibodies when the students get immunised again, but how is that an advantage? Would this be more correct: "Because there already exists specific memory B cells for the bacterial antigen, reinvasion means a higher rate of proliferation leading to a rapid increase of memory B cells that will provide the student long-term immunity"

I don't see why having antibody production during an immunisation would be an advantage, because don't antibodies only stay in blood plasma for a couple of days? Thanks

Rapid production mean less time nothing is being done, think of it like this. People say your immune to something once you've already got it before, but it's just your immune system acting so fast you don't notice it.

If that was your answer for 2 advantages I don't think you will get the marks possibly 1/2 for your understanding of higher rate of proliferation but I would give 0/2.

Remember for memory response its :Faster, Longer, Stronger

1. Does stomach acid affect viruses?

2. For the attached question, where does it say that the polypeptides are subjected to being broken down by enzymes? Am I missing something or?

Not sure for the 1st one but I'd say no because their non-living so you can't kill it. I would say foreign bacterium.

2nd one was quite controversial, I remember it on my mid-year exam, due to the ambiguity there was a possibility of two different answers.

[vox nihili]

Um so apparently the answer is C and apparently MHC I markers present antigens to B cells too?

The most correct answer is C. It isn't right though, MHC molecules don't present antigens to B-cells. (Have checked in with an immunology major).

The attached question asks for two advantages of having these memory B cells when the student receives their immunisation in Year 10, the answer said that there will be a more rapid production of antibodies when the students get immunised again, but how is that an advantage? Would this be more correct: "Because there already exists specific memory B cells for the bacterial antigen, reinvasion means a higher rate of proliferation leading to a rapid increase of memory B cells that will provide the student long-term immunity"

I don't see why having antibody production during an immunisation would be an advantage, because don't antibodies only stay in blood plasma for a couple of days? Thanks

If there are more B-cells to proliferate, after the vaccine has been cleared, there'll be even more B-cells left at the end. Let's say—and this is completely wrong—that for each B-cell in existence you get 10 more after immunisation; therefore, the more B-cells you start off with, the more you end up with after the immunisation. Essentially, it just strengthens the response by adding even more memory B-cells.

EDIT: sine got in first, just didn't post properly when I wrote it ages ago....ego demands I still post because otherwise wasted work

[vox nihili]

1. Does stomach acid affect viruses?

2. For the attached question, where does it say that the polypeptides are subjected to being broken down by enzymes? Am I missing something or?

1. Yep. Most viruses will get destroyed by stomach acid. Remember, viruses are just chunks of protein, nucleic acids and sometimes membrane. They respond to such conditions in much the same way as cells. Of course, some viruses have adapted to survive in that environment.

2. HAHAHA yeah, what sine said. This question caused headaches.

[cosine]

The most correct answer is C. It isn't right though, MHC molecules don't present antigens to B-cells. (Have checked in with an immunology major).

If there are more B-cells to proliferate, after the vaccine has been cleared, there'll be even more B-cells left at the end. Let's say—and this is completely wrong—that for each B-cell in existence you get 10 more after immunisation; therefore, the more B-cells you start off with, the more you end up with after the immunisation. Essentially, it just strengthens the response by adding even more memory B-cells.

EDIT: sine got in first, just didn't post properly when I wrote it ages ago....ego demands I still post because otherwise wasted work

That is essentially what I was thinking of man, but just could not put it into scientific words, would this suffice, if not could you fix up for me or anyone else?

The Year 10 had been previously immunised meaning that memory B cells also exist in abundance in his lymph nodes, once reinvasion occurs, the detection of the antigen is much quicker and the production of more memory and plasma B will increase rapidly because the existing memory cells proliferate. There will also be a faster antibody production as the number of plasma B cells will increase rapidly.

[vox nihili]

That is essentially what I was thinking of man, but just could not put it into scientific words, would this suffice, if not could you fix up for me or anyone else?

The Year 10 had been previously immunised meaning that memory B cells also exist in abundance in his lymph nodes, once reinvasion occurs, the detection of the antigen is much quicker and the production of more memory and plasma B will increase rapidly because the existing memory cells proliferate. There will also be a faster antibody production as the number of plasma B cells will increase rapidly.

I think you would get full marks, but you need to be more succinct. For instance, the point about lymph nodes is extraneous and unnecessary. One of the things I struggled with a lot was not adding on extra details. There are no extra points for knowing extra information, just answer the question

[cosine]

I think you would get full marks, but you need to be more succinct. For instance, the point about lymph nodes is extraneous and unnecessary. One of the things I struggled with a lot was not adding on extra details. There are no extra points for knowing extra information, just answer the question

Yah I have realised that one of my biggest weakness, unfortunately, is writing too much info, this kills time during the exam but I always worry if I have put in enough information or not.. Something i need to work on but unsure of how to refine this man, any ideas?

Thank you

[vox nihili]

Yah I have realised that one of my biggest weakness, unfortunately, is writing too much info, this kills time during the exam but I always worry if I have put in enough information or not.. Something i need to work on but unsure of how to refine this man, any ideas?

Thank you

Marking schemes are a good reference. Anything you say that isn't on the marking scheme should be cut off. Do some internal feedback as well. Reread your answer and ask yourself whether it responds to the question they've asked

[chemzy]

can someone pls explain the different types of amino acid differences..ambiguous, universal, degenerate etc. ??
 pls

[Sine]

can someone pls explain the different types of amino acid differences..ambiguous, universal, degenerate etc. ??
 pls

So the genetic code is:

• Universal: The same code is found in all living organisms. e.g AUG codes for methionine in all organisms
• Unambigious: A specific codon(a triplet of bases) will code for only one amino acid
• Degenerate/Redundant: More than 1 codon will code for the same amino acid
• Non-overlapping: A nucleotide may be part of only a single codon. e.g DNA sequence AGACAT---->AGACAT the third base(A) cant be used to form another codon like in this example ACA from bases 3-->5

[/list]

[cosine]

So the genetic code is:

• Universal: The same code is found in all living organisms. e.g AUG codes for methionine in all organisms
• Unambigious: A specific codon(a triplet of bases) will code for only one amino acid
• Degenerate/Redundant: More than 1 codon will code for the same amino acid
• Non-overlapping: A nucleotide may be part of only a single codon. e.g DNA sequence AGACAT---->AGACAT the third base(A) cant be used to form another codon like in this example ACA from bases 3-->5

We meant to know this?

[Sine]

We meant to know this?

Not too sure about the current SD but questions have come up on this before on exams before 2013.

[chemzy]

Thank you so much! 

1. do we need stabilising, directional and disruptive selection?
2. do we need monoclonal and polyclonal antibodies in depth?
3. do we need to know fungi and parasite lifecycles etc?

thanks

[Biology24123]

Thank you so much! 

1. do we need stabilising, directional and disruptive selection?
2. do we need monoclonal and polyclonal antibodies in depth?
3. do we need to know fungi and parasite lifecycles etc?

thanks

1. Not sure
2. No
3. Need to know primary and secondary hosts

[Jay.C]

Alright I'm a tad confused. I heard that once an mhc class 2 marker attaches to a helper T cell it releases interlukin 2 which stimulates specific B cells. However I also heard that the helper T cell brings the antigen to B cells and they attach to antibodies on the B cells surface and that's what stimulates them. Can any one explain this to me!?

[Biology24123]

Alright I'm a tad confused. I heard that once an mhc class 2 marker attaches to a helper T cell it releases interlukin 2 which stimulates specific B cells. However I also heard that the helper T cell brings the antigen to B cells and they attach to antibodies on the B cells surface and that's what stimulates them. Can any one explain this to me!?

The 2nd explanation is correct