VCE Biology Question Thread

[BitcoinEagle]

Awesome thanks so much phoeonixxFire and ssillyssnakes!
You've both been a great help.
Just so I can get a perfect definition of the ATP ADP  as well as other coenzymes, how much detail should I go into PhoenixxFire? Did you have an example answer on hand?

[PhoenixxFire]

Awesome thanks so much phoeonixxFire and ssillyssnakes!
You've both been a great help.
Just so I can get a perfect definition of the ATP ADP  as well as other coenzymes, how much detail should I go into PhoenixxFire? Did you have an example answer on hand?

I've never seen a vcaa question that's asked to define the role of any of them, so I can't tell you what they'd expect. Just had a flick through the past exams and all they've asked in the short answer questions is either just saying that they're outputs/inputs of various processes, and there's one question that asks for the role in photosynthesis and the suggested answer is "provides energy to form glucose" and in the same question NADPH's role is "carries hydrogen ions."

Don't worry about getting perfect definitions, you'll have to change them to be applicable to the scenario you're given for most questions anyway.

[DBA-144]

Does anyone know if the previous discussion about the functions of Poly-A tails and Methyl caps is actually on the study design? If anyone can confirm, that would be great, but I'm pretty sure you'd just need to know that they are added rather than what they are there for, right?

[PhoenixxFire]

Does anyone know if the previous discussion about the functions of Poly-A tails and Methyl caps is actually on the study design? If anyone can confirm, that would be great, but I'm pretty sure you'd just need to know that they are added rather than what they are there for, right?

As far as I know it's never been tested, however it's included within:

• the genetic code as a degenerate triplet code and the steps in gene expression including transcription, RNA processing in eukaryotic cells and translation.

and they have tested intron/exon splicing in more detail than just knowing it's happened (eg. past suggested answers have included talking about alternative splicing which isn't mentioned elsewhere in the study design) so it's not entirely impossible it could come up - I'd say it's very unlikely though.

[alexthenerd]

could someone please explain to me the difference between cofactors and coenzymes?
are cofactors and coenzymes likely to be examined in a general sense or more specifically?

thanks

[Erutepa]

could someone please explain to me the difference between cofactors and coenzymes?
are cofactors and coenzymes likely to be examined in a general sense or more specifically?

thanks

A cofactor is a broad term for compounds/Metalic ions that are needed to enable an enzyme to function. cofactors can be divided into inorganic ions and coenzymes (organic cofactors).

You do not need to know this however, all you really need to know is that ATP, NADH, NADPH are coenzymes and they are needed to help an enzyme carry out its function. You also need to understand that they are 'cycled' between loaded and unloaded forms and the functions of those specific coenzymes.

For reference, this is the relevant point in the study design:

the cycling of coenzymes (ATP, NADH, and NADPH) as loaded and unloaded forms to move energy, protons
and electrons between reactions in the cell.

[Geoo]

Does the electron transport happen in the cristae, or the inner membrane. I was taught the inner membrane of the mitochondria, but practice exams are telling me different.

So which one do I use?

[caqiu]

From an insight exam 2006 U3 -
"No mark awarded for 'mitochondria' - only one is indicated on the diagram, therefore singular form is correct.''

diagram was of a neuron. it was pointing to only one mitochondrion but there were more depicted in the diagram.
 
does this apply to all exams?

[Erutepa]

Does the electron transport happen in the cristae, or the inner membrane. I was taught the inner membrane of the mitochondria, but practice exams are telling me different.

So which one do I use?

The cristae are actually the folds of the inner membrane, so you could say either.

From an insight exam 2006 U3 -
"No mark awarded for 'mitochondria' - only one is indicated on the diagram, therefore singular form is correct.''

diagram was of a neuron. it was pointing to only one mitochondrion but there were more depicted in the diagram.
 
does this apply to all exams?

I'm not sure, but I'd think most exams would award the mark for mitochondria, however it can't hurt to be safe and write mitochondrion when a diagram points at a single mitochondrion.

[Evolio]

You need to say "environmental condition" and have a comparison. Higher chance of survival than what?

The spear is just a tool. The selection pressure would be hunting, and the selective agent humans. I'd just refer to both (ie say "humans hunting") because VCAA doesn't distinguish between them.

Ok. So, in VCAA exams, do we basically treat selective agent and selection pressure as the same thing?
Thank you for your help!

[PhoenixxFire]

Ok. So, in VCAA exams, do we basically treat selective agent and selection pressure as the same thing?
Thank you for your help!

Yeah, VCAA doesn't talk about selective agents at all, they just use selection pressures to describe all of it.

[DBA-144]

Do cytotoxic T cells lyse cells and induce apoptosis or do they just initiate apoptosis? I believe that perforin lysing the cell leads to apoptosis, through granzymes (enabling them to enter the cell) right?

[Sine]

Do cytotoxic T cells lyse cells and induce apoptosis or do they just initiate apoptosis? I believe that perforin lysing the cell leads to apoptosis, through granzymes (enabling them to enter the cell) right?

Yeah, my understanding is perforin is the pore-forming complex  and Granzyme is the molecule that goes through perforin into the cell and mess with the apoptic signalling pathways resulting in apoptosis.

I think perforin definitely creates pores like complement and can start lysis but not sure if lysis actually occurs since repair mechanisms do occur for the membrane so the main effector component imo is Granzymes inducing apoptosis.

Honestly I am a bit unsure about the details so hopefully, someone can give a clear answer.

[caffinatedloz]

Hello AN,
I was just wondering what the best way to answer this question would be:
"A human cell has approximately 25,000 genes and E. coli has approximately 4000 genes. Explain why the number of genes is not an indicator of the size of the genome."

I'm not quite sure if I'm right but I was thinking that the genes in humans are more complex...? So there would be more bases coding for each one?
Or that there may be more alternate forms of genes?

But I'm not sure...

[sweta_thar]

Hello AN,
I was just wondering what the best way to answer this question would be:
"A human cell has approximately 25,000 genes and E. coli has approximately 4000 genes. Explain why the number of genes is not an indicator of the size of the genome."

I'm not quite sure if I'm right but I was thinking that the genes in humans are more complex...? So there would be more bases coding for each one?
Or that there may be more alternate forms of genes?

But I'm not sure...

I'm pretty sure that the question isn't asking you to compare the number of genes in a human cell and E.coli, it's asking you why the size of the genome for a species can differ from the number of genes from a cell of that same species.

Based on my understanding I would answer it something like this:

o   The genome is the complete set of genes or DNA in an organism.
o   While the genome varies between species, all organisms of a single species will share the same genome.
o   However, even if the genome is shared between organisms of a single species, not all the genes of that particular genome are inherited by 
        an organism as there are multiple forms of a single gene (alleles).
o   (For example, if a person has blue eyes they will only have the allele for the eye
        colour gene that codes for blue eyes as it is recessive. This means that the alleles coding for brown, green or other eye colour will not be present in
        a cell of that particular human. However, there are still other humans that will have alleles coding for brown eyes or green eyes. The genome
        includes ALL the alleles present in ALL humans and not just one.)
o   The genes present in a single human cell or a single E.coli will NOT have a copy of all the multiple forms of a single gene.
o   Therefore, the genes of a single cell cannot indicate the size of the genome.

Hope this helps!