VCE Biology Question Thread

[Rachelle]

How can q36 be worked out?
Thanks

[sparkyblossom]

How/why does signal transduction start at the synapse between neurones?

[grannysmith]

How can q36 be worked out?
Thanks

So you have to work out how many half lives have past, and a half life is the amount of time it takes for half of a radioactive sample to decay.
0.1 -> 0.05 -> 0.025 -> 0.0125
That's 3 half lives.
3 x 5730 = 17 190 years old. (C)

[Reus]

So you have to work out how many half lives have past, and a half life is the amount of time it takes for half of a radioactive sample to decay.
0.1 -> 0.05 -> 0.025 -> 0.0125
That's 3 half lives.
3 x 5730 = 17 190 years old. (C)

We wouldn't be asked a question like this right? Seems to be more physics really haha

[Rachelle]

Is it required that we know how to numerically calculate allele frequencies?
Also, is experimental design still in the study design?

[katiesaliba]

We wouldn't be asked a question like this right? Seems to be more physics really haha

You may be asked to calculate half lives.

[Reus]

The cap there is, like Reus said, as a guide for translation. It just tells the ribosome which end is which (very basically). The more complicated answer is that the ribosome binds to the cap and then assemblies itself. Only then does it start translating.

The Poly A tail, however, does prevent degradation and helps to stabilise the mRNA molecule.

You don't need to know any of this

Would it hurt if you added this information (not the roles) if a question asked for the steps of protein synthesis? Or is it just a waste of time? Thanks.

Is it required that we know how to numerically calculate allele frequencies?
Also, is experimental design still in the study design?

Yes and yes!

[Reus]

You may be asked to calculate half lives.

How do you know this? There's no mention of half lives in the study design. :/

[katiesaliba]

Are antigens displayed on MHC Markers?

So when asked how does an immune cell differentiate self from non-self molecules, is this a suitable response:

Immune cells have receptors which are able to identify the antigen presented on MHC markers of nucleated cells, and recognise whether these antigens are self or non'self.

First off, for the purpose of VCE the entire MHC molecule is used to differentiate between 'self' and 'non-self'. Past assessment reports just mention MHC, as does the NOB text book.

With that being said, from my understanding (which by no means will be correct) is that all cells in an organism have a select variety of MHC I markers which express different peptide fragments (like you have suggested). Glycoproteins can also be self molecules because they have a protein portion. The self-receptors present on immune cells identify both MHC and the peptide fragments. BUT YOU DON'T NEED TO KNOW THIS!

Here's a video that may help you conceptualise this if you're interested: https://www.youtube.com/watch?v=DS8myTf4RUk

ALSO, I wouldn't have included 'nucleated' because MHC markers are only ever present on nucleated cells.

[katiesaliba]

How do you know this? There's no mention of half lives in the study design. :/

I've been to some lectures and I have a tutor...they both clarified that we need to know it.

[grannysmith]

How do you know this? There's no mention of half lives in the study design. :/

Haven't you done 1/2 physics Reus? :p
It's not explicitly mentioned, but it may fall under radiometric dating and  whatnot.

[katiesaliba]

Do all protein hormones have a quaternary structure?

[Damo23]

Does anyone happen to  know where to find the solutions for the sample exam? It only has multiple choice:/

Found a link if you need it 
http://melba12biology.weebly.com/uploads/1/0/9/9/10997732/2_vcaa_yr.12_sample_exam_answers.pdf

[grannysmith]

First off, for the purpose of VCE the entire MHC molecule is used to differentiate between 'self' and 'non-self'. Past assessment reports just mention MHC, as does the NOB text book.

With that being said, from my understanding (which by no means will be correct) is that all cells in an organism have a select variety of MHC I markers which express different peptide fragments (like you have suggested). Glycoproteins can also be self molecules because they have a protein portion. The self-receptors present on immune cells identify both MHC and the peptide fragments. BUT YOU DON'T NEED TO KNOW THIS!

Here's a video that may help you conceptualise this if you're interested: https://www.youtube.com/watch?v=DS8myTf4RUk

ALSO, I wouldn't have included 'nucleated' because MHC markers are only ever present on nucleated cells.

In fact, one past paper merely mentioned that immune cells "have receptors which can distinguish between differs types of protein markers of cells, and thus distinguish  between self and non self" or something along those lines.
It didn't require you to mention "MHC" (I think it was bracketed).

Probably the most simplified way of looking at non/self identification is that:
•immune cells have self receptors for self antigens/protein markers/MHC
•they also have non self receptors for foreign antigens
•if a cell marker/protein molecule is complementary to a self receptor, it is recognised as self
•if it is complementary to a non self receptor, it is treated as foreign and non self

Remember that RBCs and self protein molecules wouldn't have MHCs, so the immune system must have a way of identifying these.

Just a question - to what extent do leukocytes of the innate response (NK cells, macrophages, neutrophils etc.) identify non-self?
Do they merely have receptors for self and anything that doesn't have self antigens are treated as foreign?

[chekside]

Is it sufficient to define the secondary structure of proteins as: Local 3-dimensional folding resulting in alpha helices and beta pleated sheets and the tertiary structure as: Overall 3-dimensional folding composed of secondary structures?