VCE Biology Exam Discussion and Solutions

[vox nihili]

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.

That’s partially true. Any protein that is exported or needed within an organelle is made in the rER.
Any protein that is needed within the cytoplasm or the nucleus is made by free ribosomes. There are a couple of sneaky exceptions to this but they wouldn’t expect you to know them.

The means by which the rER gets proteins out of the cell or into organelles is by vesicular transport, in a process that is basically exocytosis. If you think about how that works, the vesicle fuses with the membrane (be it of the organelle or the PM) and actually ends up becoming a part of that membrane.

So with membrane proteins, if you had a protein on the membrane of that vesicle, it would then become part of the plasma membrane.

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.....

I’m not really sure what answers they’ll accept and how broad they’ll go. It sounded like they were looking for something specific, but I’ve never heard the details of what separates those two genera in VCE before. Indeed, when I did some research on this to try to find some clarity on this question I actually couldn’t really find anything. As I mentioned in my answers, there’s not a commonly agreed upon set of rules governing this so it’s hard to say what actually does separate those genera.

[HubHub]

Thanks vox nihili.
For question 11d) about the improvements do you think they would accept 1) make concentration of oxygen constant in the chamber before the cockroach was admitted? On the graph in the front page it shows a graph where there are small fluctuations in O2 concentration, so I said that if this wasn't controlled it may slightly skew the results because the results about O2 conc may be convoluted by the small variations in oxygen gas of the chamber but not necessarily due to the cockroaches cellular respiration.2) make temperature in the chamber constant prior to admitting the cockroach. I had the same line of reasoning, stating that if temperature was not controlled it could dwindle the accuracy and reliability of results because the temperature could flucuate within the experiment because the original temperature starting the results may not have been 30 degrees as recorded. Do these seem acceptable, everyones getting such diferent answers and this is a 4 mark..... I really cant afford to lose this whole section. What do you think?

[vox nihili]

So do you reckon it would possible to get any marks if you just discussed translation and not condensation polymerisation - explained in reference with tRNA and mRNA and mentioned the formation of peptide bonds but no other biochemical details??

I’m not really sure. As you can see, we’ve had a bit of debate about it. I’m leaning towards no at this point, but we’ll have to wait and see.

Thanks vox nihili.
For question 11d) about the improvements do you think they would accept 1) make concentration of oxygen constant in the chamber before the cockroach was admitted? On the graph in the front page it shows a graph where there are small fluctuations in O2 concentration, so I said that if this wasn't controlled it may slightly skew the results because the results about O2 conc may be convoluted by the small variations in oxygen gas of the chamber but not necessarily due to the cockroaches cellular respiration.2) make temperature in the chamber constant prior to admitting the cockroach. I had the same line of reasoning, stating that if temperature was not controlled it could dwindle the accuracy and reliability of results because the temperature could flucuate within the experiment because the original temperature starting the results may not have been 30 degrees as recorded. Do these seem acceptable, everyones getting such diferent answers and this is a 4 mark..... I really cant afford to lose this whole section. What do you think?

The first sounds reasonable and as long as you provided a good justification should be fine.
You might have a bit of trouble with the second, as the experimental design implies that the temperate is already controlled in the chamber before the cockroach goes in. 

[vox nihili]

Was there an error in question 18- the two patients were administered the hormone insulin. The Glucose levels of both were measured after that- in that case both should have responded in the same way? I think the question should have said " glucose levels were measured after administering glucose to both patients". This would have shown that Shani's levels stayed the same (due to the mutated insulin gene) and Eleni's levels dropped to active insulin.

The question states that the mutation is in the receptor for insulin, not the insulin gene itself.

[Cloudy99]

For the question about the physical development of plants i wrote the development of galls, would this be wrong ?, and for the phenolic acid one i said it the young plants produced a chemial that detered the capterpillar from eating it leaving it to eat the mature one, (
I feel like i bombed the whole exam right now  (

[Arif422]

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'm glad someone else feels the same way. Honestly, as you said I'm not here to beat on the exam, I'm just disheartened.. as most of us probably are. We've all worked through the "new study design" with the initial 69 dot points, which was only later to be cut down to about 10. I mean, surely there could've been like three less long stimulus questions.. as we only had a certain amount of time to complete it all. And who would've known that we had to know where each restriction enzyme would cut. Ye, a year's worth of study only left me to dread my end performance 

[ardria]

For the question about the physical development of plants i wrote the development of galls, would this be wrong ?, and for the phenolic acid one i said it the young plants produced a chemial that detered the capterpillar from eating it leaving it to eat the mature one, (
I feel like i bombed the whole exam right now  (

I also wrote formation of galls but I explained in probably excessive detail what that actually means and how galls do their job. It's definitely a physical defense!

[IsabellaBrown]

That’s partially true. Any protein that is exported or needed within an organelle is made in the rER.
Any protein that is needed within the cytoplasm or the nucleus is made by free ribosomes. There are a couple of sneaky exceptions to this but they wouldn’t expect you to know them.

The means by which the rER gets proteins out of the cell or into organelles is by vesicular transport, in a process that is basically exocytosis. If you think about how that works, the vesicle fuses with the membrane (be it of the organelle or the PM) and actually ends up becoming a part of that membrane.

So with membrane proteins, if you had a protein on the membrane of that vesicle, it would then become part of the plasma membrane.

Ohhhhhhh. Well. That makes a lot of sense. Thanks!!

[IsabellaBrown]

I'm glad someone else feels the same way. Honestly, as you said I'm not here to beat on the exam, I'm just disheartened.. as most of us probably are. We've all worked through the "new study design" with the initial 69 dot points, which was only later to be cut down to about 10. I mean, surely there could've been like three less long stimulus questions.. as we only had a certain amount of time to complete it all. And who would've known that we had to know where each restriction enzyme would cut. Ye, a year's worth of study only left me to dread my end performance 

Same here. I can't believe I spent a whole year revising so much content that wasn't even on the exam.

[IsabellaBrown]

Hey guys,
For the plasmids and antibiotics questions, would you get any marks if you didn't mention ampicillin or tetracycline?

[PhoenixxFire]

Hey guys,
For the plasmids and antibiotics questions, would you get any marks if you didn't mention ampicillin or tetracycline?

I doubt it, but it was worth 3 marks so I suppose it's possible.
For some strange reason I interpreted it as all the bacteria had taken up a plasmid and we had to figure out which had taken up a correct plasmid...so I said culture them individually, split them in half, dose half with tetra and whichever died, use the other half of that culture. All those that hadn't taken up any plasmid would die too though 🤦‍♀️🤦‍♀️🤦‍♀️🤦‍♀️ No marks for me 😰 I completely bombed the exam, now I gotta hope someone in my cohort did better (I'm rank one) or I'm well and truly screwed.

[Ahmad_A_1999]

I doubt it, but it was worth 3 marks so I suppose it's possible.
For some strange reason I interpreted it as all the bacteria had taken up a plasmid and we had to figure out which had taken up a correct plasmid...so I said culture them individually, split them in half, dose half with tetra and whichever died, use the other half of that culture. All those that hadn't taken up any plasmid would die too though 🤦‍♀️🤦‍♀️🤦‍♀️🤦‍♀️ No marks for me 😰 I completely bombed the exam, now I gotta hope someone in my cohort did better (I'm rank one) or I'm well and truly screwed.

WHAT thats how I interpreted it to, omg why is it wrong

[PhoenixxFire]

WHAT thats how I interpreted it to, omg why is it wrong

Not all the bacteria took up any plasmid. So you have to give them amp to kill bacteria without a plasmid then do the rest. Good to know I'm not the only one. For next year I need to improve my reading 😂 But if I'd read them all really well, I would have run out of time. (I used my extra few minutes to badly reread the last MC and change my answer...to another wrong answer.)

[Ahmad_A_1999]

Not all the bacteria took up any plasmid. So you have to give them amp to kill bacteria without a plasmid then do the rest. Good to know I'm not the only one. For next year I need to improve my reading 😂 But if I'd read them all really well, I would have run out of time. (I used my extra few minutes to badly reread the last MC and change my answer...to another wrong answer.)

I failed bio and I failed methods today hahaha fml

[vox nihili]

Just going to jump in and say this thread isn’t for study score prediction; it’s for exam discussion. Please don’t request predicted study scores and please don’t answer those requests.

Also, regarding the plasmid question; don’t beat yourselves up for it. It was a stunningly hard question for VCE. Easy for anyone who’s used that technique, but otherwise extremely challenging. It won’t have been well answered.