VCE Biology Questions Thread

sandali_5

chimichurri I think it is probably because that the substrates can't actually 'outnumber' the non-competitive inhibitors as they aren't competing and bind to different sites.
So if the concentration of enzymes is constant while the substrate's is unlimited, we know that the rate of reaction will plateau after a certain point, so when non-competitive inhibitors added, even though those may be in a limited quantity, the rate is likely to go down instead of increasing.
I'm not too familiar with what happens after non competitive inhibition has occurred, but I found some information on sciencedirect.com that could be of use >> https://www.sciencedirect.com/topics/neuroscience/non-competitive-inhibition

chimichurri

thank you sandali_5 !

sandali_5

Hi!
I was wondering if anyone knew how should one's responses differ when a question asks you to analyse the results of an experiment, as opposed to explaining them?

Smartiestarz

Hi guys- could someone please help explain Q13 (Multiple Choice) of the VCAA 2003 Exam 1 (sorry I don't really know how to add pictures on this like it dosent seem to be working for me)
The examiners report dosent have a marked answer.. Why wouldn't N be correct if the cell was undergoing anaerobic respiration? Wouldn't the alcohol levels increase with c02 as both are products of the reaction?
The examiners report says its not N
I think its P because even though the rate of co2 production is decrease, the amount is probs still increasing as the graph is in the positive axis right- so at point P when oxygen is introduced it undergoes aerobic cellular respiration and with this as the rate of production of co2 increases the alcohol levels would decrease.. thats why its not Q
Does my logic make sense? Basically im confused between point N and point P
so if someone could explain the concept behind how to think about this question thatd be great!
thanks so much!! 😃

Moskva

Hello Smartiestarz!

Hi guys- could someone please help explain Q13 (Multiple Choice) of the VCAA 2003 Exam 1 (sorry I don't really know how to add pictures on this like it dosent seem to be working for me)
The examiners report dosent have a marked answer.. Why wouldn't N be correct if the cell was undergoing anaerobic respiration? Wouldn't the alcohol levels increase with c02 as both are products of the reaction?
The examiners report says its not N
I think its P because even though the rate of co2 production is decrease, the amount is probs still increasing as the graph is in the positive axis right- so at point P when oxygen is introduced it undergoes aerobic cellular respiration and with this as the rate of production of co2 increases the alcohol levels would decrease.. thats why its not Q
Does my logic make sense? Basically im confused between point N and point P
so if someone could explain the concept behind how to think about this question thatd be great!
thanks so much!! 😃

You are right, the answer is P because the question asks for concentration (amount) of alcohol, which is cumulative. If it asked for rate of alcohol production then the answer would be N instead, but that would be a different question altogether.

chemistry1111

With competitive inhibition, the inhibitor is similar/complementary in shape to substrate? Is it complementary or similar?
Thanks

_sophiestudies_

chemistry1111 yep. More specifically, the competitive inhibitor will have a very similar, if not the same, shape as the binding site on the substrate (the rest of it could be a very different shape). This is why it is able to bind to the enzyme's active site and prevent the substrate binding.

chemistry1111

also what is difference between antigenic drift and antigenic shift?

_sophiestudies_

chemistry1111
Antigenic drift = Small and gradual mutations in the genes encoding for viral surface antigens.

At first, the memory cells that were formed when the viral pathogen was previously encountered can recognise the mutated surface antigens.
Over time -> The viral antigens gradually become very different, meaning the memory cells can no longer recognise them. This is when a new subtype of a virus is formed.

Antigenic shift = Sudden and significant mutations in the genes encoding for viral surface antigens.

Commonly occurs when two or more different strains of a virus combine when coinfecting the same host to form a completely new subtype (this is quite a sudden change compared to small antigen changes on the surface of the virus). This process known as viral recombination.
Natural immunity to this new subtype is very uncommon, meaning it is very infectious and able to potentially develop into an epidemic or pandemic.

bioho4

hi there, does anyone have answers for the 2022 vcaa sample exam? if your teachers gave them to you or if you've seen them online cos i cant find any answers for section B. thanks in advance!!!

_sophiestudies_

bioho4 VCAA doesn't seem to provide answers for any of their sample exams (well, nothing that involves short answer responses that is). You might need to ask your teacher if they have an answer document for it (as in, one they have put together themselves). It's quite annoying, especially since it's the only VCAA exam material given for this new study design.

bioho4

_sophiestudies_ it is very very annoying - not sure why they don't provide sample answers. my teachers haven't provided any. if you're teachers have it'd be great if you could send it through!

God

Neap or insight or someone wouldn't have made their own sample answer's would they?

I vaguely remember checkpoints containing last (last) years's exam with sample answers. Although I could be wrong. (Perhaps it was just copied from the exam report)

bioho4

God i don't think so...so annoying

_sophiestudies_

bioho4 Sadly, I haven't had any answers provided for me by my teacher either, which is frustrating. Sorry!

Smartiestarz

What is the significance that methionine isn’t present in any of the insulin polypeptides? (Insulin A/B) - like why do we specifically use methionine? Is it that if we used a different codon ex- the codon for Lys that’s lets say, present in the insulin A chain it would form part of the polypeptide and so we won’t be able to seperate the insulin A from beta galactosidase in the fission protein ?
Ahah just a lil bit confused on this- would be great if someone could give me an idea of what the reason is 🙂
Also to what depth do you guys reckon we should know the process of insulin production in humans? Like in terms of explaining the whole process for ex- for a 4/5 mark question? 🙂

Thanks so much!

chimichurri

hey! I've just been told that a lot of the resources - including textbooks and company summary notes - have incorrect information about the amount of ATP produced by aerobic cellular respiration because vcaa is now only accepting the amount that has been indicated to be true as per recent findings (changed from the 36-38). but they don't make it clear what these findings are.
do any of you know what the ATP yield we are now supposed to state for aerobic cellular respiration is?
thanks!

_sophiestudies_

chimichurri You can find the new ATP yield information in the VCAA biology frequently asked questions document. This can be found with the biology study design web page under "Support - Planning".

The info specified on the document is as follows:
Glycolysis = 2 ATP
Krebs Cycle = 2 ATP
Electron Transport Chain = 26 or 28 ATP
Total = 30 or 32 ATP
(must say "or", not "-" for the new study design).

This information cannot be found in most textbooks due to VCAA having released the new info after they were written, I think, which is why there has been a lot of confusion.

chimichurri

thank you so so much _sophiestudies_ ! this is so helpful

_sophiestudies_

chimichurri no problem!

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