VCE Biology Exam Discussion and Solutions

[ringring]

wait will the section B answers be uploaded as well or have I missed them?

[waterangel82]

That’s what I said- I’m confused because this whole exon splicing thing producing different proteins isn’t in the study design or vcaa approved textbooks

Actually, it's in Nature of Biology 2.

[Aar0n_101]

wait will the section B answers be uploaded as well or have I missed them?

answers for section b will be up later tonight hopefully

[vox nihili]

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. 

[PhoenixxFire]

I said that the greater concentration of phenolic acid helped to activate genes which then produced a greater amount of protein products which were toxic to the caterpillars, so therefore they fed on mature leaves as they weren't so toxic.

I thought about that but the image showed one caterpillar - so if it died it could not eat the other leaf.

[vox nihili]

answers for section b will be up later tonight hopefully

They will dribble out this evening. Once they're done I'll combine all the answers into one document

[ardria]

Would anyone be able to indicate roughly what is the minimum exam score for a 50, assuming rank 1? I suppose with the difficulty of the exam in consideration!

Sine kindly estimated ~114/120 earlier in the year based on previous exams' scaling reports, but I'm wondering if this could be updated now that the exam is all done.

[Jo Kamm]

They gave us a 6 mark question that was about mass extinction of Australian MegaFauna. we had to read an excerpt of an article (something from The Conversation) and identify 3 points that provided evidence against the rapid extinction theory and why. It felt like an English exam 

After all those immunity questions people were asking yesterday, the only short answer questions were on innate immunity.

What did people pick for MC Q40? I changed my mind last minute.

They gave us a 6 mark question that was about mass extinction of Australian MegaFauna. we had to read an excerpt of an article (something from The Conversation) and identify 3 points that provided evidence against the rapid extinction theory and why. It felt like an English exam 

After all those immunity questions people were asking yesterday, the only short answer questions were on innate immunity.

What did people pick for MC Q40? I changed my mind last minute.

I chose B as  we have no evidence for A, c or D

[Jo Kamm]

I got D for that question!

[waterangel82]

I thought about that but the image showed one caterpillar - so if it died it could not eat the other leaf.

I don't really know. But if something was more toxic, wouldn't there still be a possibility for a caterpillar to survive but in a poorer condition (like if a human was exposed to a toxin, there are non-fatal symptoms like diarrhoea and anaemia).

[Spooky]

I put adaptive immunity for SA q 4 d i since wouldn't "venom inhibitors" be specific?

[Pandable]

I put adaptive immunity for SA q 4 d i since wouldn't "venom inhibitors" be specific?

Yes Venom inhibitors are specific immunity but it is also innate as the venom inhibitors do not actually trigger t helper cells so your body it self is not adapting

[PhoenixxFire]

I don't really know. But if something was more toxic, wouldn't there still be a possibility for a caterpillar to survive but in a poorer condition (like if a human was exposed to a toxin, there are non-fatal symptoms like diarrhoea and anaemia).

Yeah thats why I wasn't sure, but I figured even if it was non-fatal it wouldn't start soon enough for the caterpiller to realise the pain was due to the leaf (thanks psychology!)

[vox nihili]

 
2)   
a)   Many plants coat themselves in wax to prevent access to the plant tissue by pathogens.
b)   To serve as a negative control
c)   In runner A, 0.6 of the leaf surface area of the young ramet was eaten; whereas, in runner B <0.3 was eaten. Representing a difference of approx. 0.3.
d)   Phenolic acid leads to the production of a cytotoxic compound that is safe to the plants but makes the caterpillar ill. 

[vox nihili]

3)   
a)   Rational drug design refers to the use of structural information about a drug target to inform the synthesis of a drug capable of binding that target.
b)   It is able to bind the active site of HMG-CoA reductase.
c)   Low levels of lovastatin will see many HMG-CoA reductase enzymes disinhibited. This will allow the enzyme to catalyse the synthesis of mevalonate, prompting the production of cholesterol.

I put adaptive immunity for SA q 4 d i since wouldn't "venom inhibitors" be specific?

I haven't read the question yet, but I suspect you're right. Anything that will inhibit a venom will be specific to that venom. It's by this way that you hear stories about old kings who used to take low levels of venom and thus become immune to snake bites. This is completely bioplausible.