Biology Practice Exam Discussion

[sunshine98]

so I just did 2004 VCAA (I know , kinda late but my school forced us to do random ones earlier and now am just trying to fill gaps. )
and there are soooo many questions I was unable to do. So I 've got questions:
- insulin is not on course, right?
-do I need to know microgilia and ependymal?
- do we need to know microscopic units and can anyone provide a run down of which ones we need to know? 
thanks 

 

[warya]

so I just did 2004 VCAA (I know , kinda late but my school forced us to do random ones earlier and now am just trying to fill gaps. )
and there are soooo many questions I was unable to do. So I 've got questions:
- insulin is not on course, right?
-do I need to know microgilia and ependymal?
- do we need to know microscopic units and can anyone provide a run down of which ones we need to know? 
thanks 

Pretty sure you don't need to know any of those things

[cosine]

I just finished the 2013 Biology exam, has anyone else done it?

I was wondering if someone was willing to cross mark with me? I will mark yours and you mark mine, because the assessors report are a bit here and there... Anyone up for it? Let me know

+ also share tips and maybe learn from each other's mistakes?

[grannysmith]

I just finished the 2013 Biology exam, has anyone else done it?

I was wondering if someone was willing to cross mark with me? I will mark yours and you mark mine, because the assessors report are a bit here and there... Anyone up for it? Let me know

+ also share tips and maybe learn from each other's mistakes?

If you post your answers here I'm sure there'll be people willing to check

[vox nihili]

Just a word of advice, the more time you spend worrying about your study score the less time you get to study to make it better. Something that I did way too much of in VCE was try to predict my study score, when I could have just worked harder on improving it

[cosine]

Question 1 cii).

Name of input: ATP
Role: The ATP molecules are derived from the light-dependent stages and are used to provide energy for the light-independent reactions

My query: Would this obtain full marks? Because the answer has provides energy for the production of glucose, but I said provides energy for the light-independent reactions. The specificity is killing me.

Question 2c:

Describe what is meant by tertiary structure and quaternary protein structures:
Tertiary structure of a protein refers tot he R-Group interactions between amino acids within the same polypeptide chains resulting in a functional three dimensional shape, and the quaternary structure describes polypeptides with more than one polypeptide chain joined together.

My query: I don't know if this will get full marks. Is what I have said about tertiary structure correct?

Question 3ii).

Suggest how epinephrine can produce different responses in smooth muscle cells and liver cells:
The signal transduction pathways in muscle cells are different to that of the signal transduction pathways of liver cells.

My query: Answer just says the receptors are different, OR the secondary messengers are different. Is my answer correct though?

Question 5b:
Explain why the autoantibody test woudl be negative even though the genetic screen was positive:
The autoimmune disease may only be a cell-mediated disease with no involvement of antibodies and hence no autoantibodies. Cytotoxic T cells recognise the antigens presented on MHC Class I markers of these 'self' cells as non-self and hence destroy them via the degranulation of perforin and granzymes.

My query: Answer says something about the response and production taking a long time.. Is my answer correct though? So in other words can antibodies be produced to agglutinate our own self cells in autoimmune diseases?

Question 9b).
What is a gene pool?
A gene pool is the collection of all the genes and their respective alleles in a given population.

My query: The report only says collection of alleles and not genes. Is my definition correct or not?

Define genetic drift and bottleneck effect:
Genetic drift occurs when the allele frequencies of a gene pool of a population changes due to chance events that are non-selective

Bottleneck effect is a form of genetic drift where non-selective events such as natural disasters change the allele frequency and the resulting frequencies may not be a representative of the original population.

My query: These are worded differently from the assessors, what do you think, are these incorrect or not?

Thank you. 

[grannysmith]

Question 1 cii).

Name of input: ATP
Role: The ATP molecules are derived from the light-dependent stages and are used to provide energy for the light-independent reactions

My query: Would this obtain full marks? Because the answer has provides energy for the production of glucose, but I said provides energy for the light-independent reactions. The specificity is killing me.

Question 2c:

Describe what is meant by tertiary structure and quaternary protein structures:
Tertiary structure of a protein refers tot he R-Group interactions between amino acids within the same polypeptide chains resulting in a functional three dimensional shape, and the quaternary structure describes polypeptides with more than one polypeptide chain joined together.

My query: I don't know if this will get full marks. Is what I have said about tertiary structure correct?

Question 3ii).

Suggest how epinephrine can produce different responses in smooth muscle cells and liver cells:
The signal transduction pathways in muscle cells are different to that of the signal transduction pathways of liver cells.

My query: Answer just says the receptors are different, OR the secondary messengers are different. Is my answer correct though?

Question 5b:
Explain why the autoantibody test woudl be negative even though the genetic screen was positive:
The autoimmune disease may only be a cell-mediated disease with no involvement of antibodies and hence no autoantibodies. Cytotoxic T cells recognise the antigens presented on MHC Class I markers of these 'self' cells as non-self and hence destroy them via the degranulation of perforin and granzymes.

My query: Answer says something about the response and production taking a long time.. Is my answer correct though? So in other words can antibodies be produced to agglutinate our own self cells in autoimmune diseases?

Question 9b).
What is a gene pool?
A gene pool is the collection of all the genes and their respective alleles in a given population.

My query: The report only says collection of alleles and not genes. Is my definition correct or not?

Define genetic drift and bottleneck effect:
Genetic drift occurs when the allele frequencies of a gene pool of a population changes due to chance events that are non-selective

Bottleneck effect is a form of genetic drift where non-selective events such as natural disasters change the allele frequency and the resulting frequencies may not be a representative of the original population.

My query: These are worded differently from the assessors, what do you think, are these incorrect or not?

Thank you.

1cii) Yeah that should be okay
2c) The main point about the tertiary structure is that it's the overall 3-d conformation of the protein due to a variety of intermolecular interactions which largely determines its function, so I think you've got it there.
3ii) That's valid.
5b) Hm.. not too sure about this one. Your reasoning is sound, but the fact that they specifically refer to the autoimmune disease as eliciting antibody production implies that this is a humoral response, not a cell-mediated one.
9b) That's alright because you mention their respective alleles

With regards to genetic drift/bottleneck effect, your definitions are okay; if they're merely worded differently then that's no problem.

[cosine]

1cii) Yeah that should be okay
2c) The main point about the tertiary structure is that it's the overall 3-d conformation of the protein due to a variety of intermolecular interactions which largely determines its function, so I think you've got it there.
3ii) That's valid.
5b) Hm.. not too sure about this one. Your reasoning is sound, but the fact that they specifically refer to the autoimmune disease as eliciting antibody production implies that this is a humoral response, not a cell-mediated one.
9b) That's alright because you mention their respective alleles

With regards to genetic drift/bottleneck effect, your definitions are okay; if they're merely worded differently then that's no problem.

Thank you man, means a lot.

As for the 5b question, my answer could be partially correct but I just realised also that autoimmune disease certainly do involve the recognition of self cells as non-self, but this does not necessarily mean that ONLY cell-mediated immunity responds. Clearly as I just discovered over some research too, that Cytotoxic T cells can destroy the targeted cells via recognition of the self antigens presented on MHC I markers as non-self, OR the production of autoantibodies that agglutinate the self cells/tissue. This is all possible because of the activated T helper cells, which in turn release cytokines to activate BOTH cytotoxic and B cells.

However, this raises another issue at hand. During transplant rejection, why is it that only the cell-mediated response occurs? Why cannot antibodies be produced to agglutinate the non-self cells? Like sure there's non-self antigens presented on the MHC I of the organ transplant, but wouldn't the T helper cells be activated either way, and thus activate B and T cells?

[grannysmith]

Thank you man, means a lot.

As for the 5b question, my answer could be partially correct but I just realised also that autoimmune disease certainly do involve the recognition of self cells as non-self, but this does not necessarily mean that ONLY cell-mediated immunity responds. Clearly as I just discovered over some research too, that Cytotoxic T cells can destroy the targeted cells via recognition of the self antigens presented on MHC I markers as non-self, OR the production of autoantibodies that agglutinate the self cells/tissue. This is all possible because of the activated T helper cells, which in turn release cytokines to activate BOTH cytotoxic and B cells.

However, this raises another issue at hand. During transplant rejection, why is it that only the cell-mediated response occurs? Why cannot antibodies be produced to agglutinate the non-self cells? Like sure there's non-self antigens presented on the MHC I of the organ transplant, but wouldn't the T helper cells be activated either way, and thus activate B and T cells?

Good question. You have to recall how the humoral response is activated - a B cell encounters a free-floating antigen to which it binds, et cetera. Is this possible in a transplant rejection? It may be, I'm not entirely sure myself, but I'd think that it's highly unlikely.

[cosine]

Good question. You have to recall how the humoral response is activated - a B cell encounters a free-floating antigen to which it binds, et cetera. Is this possible in a transplant rejection? It may be, I'm not entirely sure myself, but I'd think that it's highly unlikely.

hmm... that is a good theory, actually. It sorta makes sense, because you're right about B cells having to encounter the antigens and engulf them to present to T helper cells to be activated for proliferation.

Can someone confirm this, though? Just want to be 100%.
Thank you.

[Biology24123]

If 87% was the A+ cut-off, then receiving 87% would've given you a SS around 40. 

I really don't want such an easy exam this year

[thushan]

Good question. You have to recall how the humoral response is activated - a B cell encounters a free-floating antigen to which it binds, et cetera. Is this possible in a transplant rejection? It may be, I'm not entirely sure myself, but I'd think that it's highly unlikely.

Possible, but not entirely sure about this. In a transplant, it is not just the organ that is transplanted, but its associated interstitial fluid and some plasma, which is bound to have protein molecules swimming around. Those protein molecules can so easily initiate a humoral immune response.

However, the actual cells (eg. liver cells in a liver transplant) will initiate a cell-mediated immune response for sure.

[cosine]

Possible, but not entirely sure about this. In a transplant, it is not just the organ that is transplanted, but its associated interstitial fluid and some plasma, which is bound to have protein molecules swimming around. Those protein molecules can so easily initiate a humoral immune response.

However, the actual cells (eg. liver cells in a liver transplant) will initiate a cell-mediated immune response for sure.

Hi Thushan, thanks for replying.

So to be safe for VCE bio, should we just assume that in organ transplants, cell-mediated response should be concerned, but in autoimmune diseases, both humoral and cell-mediated responses take place?

Cheers.

[thushan]

I'd say for transplant rejection it'd be a mixture of the humoral and cell-mediated immune responses, although it would be primarily a cell-mediated immune response, unless it was a blood transfusion that was incompatible in which case it'd be primarily humoral. For autoimmune diseases, it actually depends on the disease; some diseases are primarily to do with humoral immunity (we call this type II and type III hypersensitivity, an example is rheumatoid arthritis), other diseases are mediated primarily via the cell-mediated response (we call this type IV hypersensitivity, an example is type I diabetes).

In short say:
- transplant rejection: primarily cell-mediated immune response (exception is blood transfusion)
- autoimmune diseases: a mixture of humoral and cell mediated immune responses depending on the actual disease

[Sine]

Is everyone going to do the sample supplied by VCAA in 2013? it seems to comprise of mostly past questions with a few new ones I think?