VCE Biology Exam Discussion and Solutions

[PhoenixxFire]

Anyone else feel pretty disappointed in how they (presumably) did? I feel like the concepts I spent extra time solidifying and all the techniques I really tried to develop from doing past exams and 2017 practice papers weren't reflected in my exam at all Not having a go at the exam or anything, I just generally feel quite disconcerted with that (and my own efforts) and wanted to know how other people found it (or any advice etc).
Thanks

I think the reason I really hated this exam was because I walked in expecting it to be like it has been previously. I understand them changing it but I'm annoyed that the sample exam did not refelect how the actual exam would be. The sample exam was typical of the last study design + an experimental design question, so that is what I expected. Not a 3+6 mark interpret the paragraph and 4 pages of experimental design...

[Sine]

sadly VCAA does a very bad job in creating a sample exam often the majority of it just being actual past questions and the new ones are for the newly input content to the study design.

[IsabellaBrown]

The general consensus seems that everyone found it super hard and I was hyped to see the exam. In my opnion I would say it's a little trickier than usual, but not overly tricky. The megafauna questions requires careful reading though..definitely an interesting question.

However, the one gene multiple proteins question was tough! I did that in the 2015 question and was one of the few that got it right. I don't think it's fair to expect students to know that alternative exon shuffling leads to different proteins...

I found the alternative splicing question slightly easier to understand than the experimental design questions and the article analysis. I just wish they made the exam cover everything equally rather than just predominantly on experimental design.

[PhoenixxFire]

I found the alternative splicing question slightly easier to understand than the experimental design questions and the article analysis. I just wish they made the exam cover everything equally rather than just predominantly on experimental design.

I found the alternate splicing fairly easy too. My teacher has talked about it and so has edrolo. I suspect next year the exam will be a bit more even - I had been told they over assess new content.

[IsabellaBrown]

I found the alternate splicing fairly easy too. My teacher has talked about it and so has edrolo. I suspect next year the exam will be a bit more even - I had been told they over assess new content.

I watched it on Edrolo too! Edrolo helped a lot. I must admit, when I read it I wasn't sure if alternative splicing would be correct but it was the only thing I could think of. Yes, that is what I think will happen too.

[neenah]

Question 1 SAQ below...others will come out slowly (I have exams coming up too! )



Author comments in [brackets].


1)
a)   
i)   The arrow should point downwards from the extracellular environment to the intracellular environment and should cross the phospholipid component of the membrane.
ii)   The concentration of the molecular is higher in the extracellular environment than in the intracellular; therefore, it will diffuse from the latter to the former down its concentration gradient. Owing to its hydrophobicity, it is able to cross the phospholipid bilayer directly.
b)   
i)   Molecule T
ii)   Rough endoplasmic reticulum [ribosome may be accepted as an alternative, but is less correct].
iii)   tRNAs, via their own anticodons, bind to complementary codons of the mRNA situated in the ribosome. The tRNAs bring amino acids to the ribosome, which joins the amino acids together in a condensation reaction. The process is repeated until a stop codon is reached, ejecting the nascent polypeptide from the ribosome. [this question is challenging and I am unclear on whether they expect students to discuss translation or the specifics of the chemistry that leads to polypeptide formation. I have chosen the former, because I believe there is not enough VCE-relevant information to justify 3 marks for the latter].
c)   Expression of a gene generates pre-mRNA. This molecule is then subjected to post-transcriptional modification, which includes splicing of introns from the RNA. In some cases, it is possible to splice different sections of the pre-mRNA, in a process called alternate splicing. As the name implies, this leads to the generation of alternate forms of mRNA from the pre-mRNA, each with different nucleotide sequences, which upon translation, will result in the generation of polypeptides with different amino acid sequences. 

Hey for the question about joining amino acids it said "chemical reaction" and I assumed it referred to a condensation reaction rather than the process of translation. Is my answer completely wrong?

[vox nihili]

Hey for the question about joining amino acids it said "chemical reaction" and I assumed it referred to a condensation reaction rather than the process of translation. Is my answer completely wrong?

I’m not sure to be honest. In my answers I think I mentioned that I wasn’t sure if they were after that or translation. The question was a little vague and I couldn’t understand how you could get 3 marks out of condensation polymerisation.

[vox nihili]

Hey for the question about joining amino acids it said "chemical reaction" and I assumed it referred to a condensation reaction rather than the process of translation. Is my answer completely wrong?

I’m not sure to be honest. In my answers I think I mentioned that I wasn’t sure if they were after that or translation. The question was a little vague and I couldn’t understand how you could get 3 marks out of condensation polymerisation.

[neenah]

I’m not sure to be honest. In my answers I think I mentioned that I wasn’t sure if they were after that or translation. The question was a little vague and I couldn’t understand how you could get 3 marks out of condensation polymerisation.

maybe a mark for stating how it occurs, a mark for the name of the reaction, product and the bond, and a mark for saying water is a by product? Idk I was thinking about writing translation but the whole "chemical reaction" thing put me off.

[PhoenixxFire]

I’m not sure to be honest. In my answers I think I mentioned that I wasn’t sure if they were after that or translation. The question was a little vague and I couldn’t understand how you could get 3 marks out of condensation polymerisation.

It was mentioned in detail in the SD this year. I wrote that a OH was lost from the carboxyl group, a H from the amino group, that these formed a water molecule and a peptide bind was formed.

[IsabellaBrown]

It was mentioned in detail in the SD this year. I wrote that a OH was lost from the carboxyl group, a H from the amino group, that these formed a water molecule and a peptide bind was formed.

Yeah I wrote that too, but I linked in that this occurs during translation at the end.

[IsabellaBrown]

I wrote ribosome though instead of the rough endoplasmic reticulum because technically protein synthesis can occur on a ribosome in the cytosol or on a ribosome in the rER, depending on where it is needed. Would ribosome still be accepted??

[vox nihili]

It was mentioned in detail in the SD this year. I wrote that a OH was lost from the carboxyl group, a H from the amino group, that these formed a water molecule and a peptide bind was formed.

Yeah I wrote that too, but I linked in that this occurs during translation at the end.

It sounds like that would be reasonable. As I said, I was unsure was to whether they expected to hear the detail of the reaction. You've convinced me that this is probably the case. I'll amend the answers to reflect this, with a statement about the possibility that they could be after translation.

I wrote ribosome though instead of the rough endoplasmic reticulum because technically protein synthesis can occur on a ribosome in the cytosol or on a ribosome in the rER, depending on where it is needed. Would ribosome still be accepted??

It depends on how harsh they want to be. It's a membrane protein, so we actually know that it was made in the rER rather than a free ribosome. I think the answer they take will come down to whether or not their exam is coming up too easy or too hard.

[IsabellaBrown]

Cool, thank you for the help! 

Wait I'm confused, sorry! Why would it be on the rER? I thought that proteins that are needed within the cell are made at a ribosome in the cytosol and those that are exported are synthesised in the rER..? I'm probably wrong. I just remember reading it somewhere.

[HubHub]

Hi guys,
For question 7a) about structural features differentiating Australipithecus and Homo, do you think accessors may accept traditional trends in hominin development? I'd never looked at whole genus' in isolation so was very taken aback by this one. I wrote that features may include 1) a less pronounced brow bone than the latest Australopithecus species, and a more parabolic jaw shape than the jaw of the (latest) Australopithecus species. I don't know if these would scrape by.....