VCE Biology Question Thread

[Biology24123]

I don't think it's specifically listed in the study design but it doesn't hurt to know.

What about characteristics of secondary structures (e.g. flexible)

[vox nihili]

Do we need to know fibrous and globular proteins

I'm not sure if they struck it in 2013, but it was certainly on the 2008-12 study design.

[BakedDwarf]

What about characteristics of secondary structures (e.g. flexible)

I remember explicitly asking my teacher that question and she said no. Just knowing what the secondary structures are (alpha helices, beta-pleated sheets and random coils) is sufficient.

[heids]

Classifications of, and differences between, different types of proteins such as globular and fibrous proteins are not required.

FYI.

[vox nihili]

FYI.

Champ. Glad it's gone. It was never really well covered by most schools.

[Biology24123]

The answer to this question say C. I thought high cholesterol increases fluidity?

[Biology24123]

A question in a exam was "How are foreign cells recognised as 'non self' by the persons body"

And the answer was "Different MHC markers on the surface of the cells compared to the host cells"

Is the answer correct? Don't MHC simply present antigens, they are not the only proteins on the plasma membrane that can act as antigens and be recognised as non self

[cosine]

The answer to this question say C. I thought high cholesterol increases fluidity?

Really weird question, because Cholesterol actually maintains membrane fluidity, so when it's too cold, it prevents solidification of membranes, and prevents the membranes from becoming excessively fluidy at hot temperatures.

A. Low temps will decrease flexibility.
B. This one is a bit of logic - the more rigid structures are sticking into the membrane, the more stiff it will get
C. Ambiguous101 again, because honestly, depends on the temperature the cell experiences. If high temperatures, and if there is little cholesterol present, then nothing is preventing it from becoming excessively fluidly so this is only correct at high temperatures.
D. Saturated phospholipids actually means that the membrane has a greater chance of solidifying because of the lipids being able to tightly pack together due to the abundance of single bonds in the fatty acid chains.

Bit ambiguous, but the other answers are definitely incorrect.

[cosine]

A question in a exam was "How are foreign cells recognised as 'non self' by the persons body"

And the answer was "Different MHC markers on the surface of the cells compared to the host cells"

Is the answer correct? Don't MHC simply present antigens, they are not the only proteins on the plasma membrane that can act as antigens and be recognised as non self

This is incorrect to a degree actually, but in a sense also correct. As you know (because you're the one who taught me, also shout out to T-Rav) that only Cytotoxic T cells interact with MHC markers to recognise self and non-self cells. So the host cells are not recognised as foreign by the Tc cells of your own body, however if i plucked a cell of mine into you, your Tc cells will recognise the MHC markers of mine as non-self, because that is what Tc cells do, they recognise the MHC I markers of cells, and initiate an immune response.

But other cells of the immune system, such as phagocytes, these do not use MHC markers to detect the foreign cells, they use some other mechanism which is not required for VCE biol (Think it is PPR receptors) that actually detect non-self cells. Also, B cells actually use their transmembrane antibodies to detect and bind to foreign pathogens.

So to a degree, their answer is correct but it does not apply to ALL cells of the immune system, only Cytotoxic T cells use this MHC I mechanism to detect foreign cells.

[BakedDwarf]

Can't the answer be 'foramen magnum located towards the lack of the skull'?

The solutions say 'longer upper limbs or prehensile toe'

[tashhhaaa]

not sure if I'm posting in the right thread but did any of you guys get a copy of the Unit 4 lecture notes?

wasn't able to make the lecture due to personal reasons and the notes sold out online really quick :SSSSS

[jyodesh.com]

Can't the answer be 'foramen magnum located towards the lack of the skull'?

The solutions say 'longer upper limbs or prehensile toe'

Positioning of the foramen magnum has more to do with posture (quadripedal/bipedal) than tree climbing suitability so I'd say no because it doesnt tell you anything about how well it can climb a tree e.g. goats also have a foramen magnum positioned towards the posterior of the skull but only the ones with the right hooves can climb trees.

[Sine]

Can't the answer be 'foramen magnum located towards the lack of the skull'?

The solutions say 'longer upper limbs or prehensile toe'

I get why your saying the position of the foramen magnum (as it indicates the hominin is more so quadrepedal thus climbing trees, I'm pretty sure the answer apply to the ability of climbing trees directly. The position of the foramen magnum is more directly related to bipedalism.

If this is from a VCAA exam(I think it is) just mark yourself directly from the examiners report otherwise don't worry too much about external company marking schemes, as they sometimes just give you one possible answer. However if it's not on the solutions guide for the examiner and it makes sense they may give you a mark.

EDIT: Beaten by jyodesh.com

[Biology24123]

This is incorrect to a degree actually, but in a sense also correct. As you know (because you're the one who taught me, also shout out to T-Rav) that only Cytotoxic T cells interact with MHC markers to recognise self and non-self cells. So the host cells are not recognised as foreign by the Tc cells of your own body, however if i plucked a cell of mine into you, your Tc cells will recognise the MHC markers of mine as non-self, because that is what Tc cells do, they recognise the MHC I markers of cells, and initiate an immune response.

But other cells of the immune system, such as phagocytes, these do not use MHC markers to detect the foreign cells, they use some other mechanism which is not required for VCE biol (Think it is PPR receptors) that actually detect non-self cells. Also, B cells actually use their transmembrane antibodies to detect and bind to foreign pathogens.

So to a degree, their answer is correct but it does not apply to ALL cells of the immune system, only Cytotoxic T cells use this MHC I mechanism to detect foreign cells.

Thanks. So another bad question there.

[warya]

Sorry to keep bringing this up but hopefully it can be settled once and for all, is my understanding correct?

• phagocytes and other leukocytes recognise non self using some type of receptor
• immature T cells recognise non self as per antigens displayed on the mhc2 of antigen presenting cells using complementary T cell receptors- these T cells then proliferate into t helper(?) and t killer cells
• killer T cells recognise non self using mhc1 which are themselves 'self antigens' unique to individuals. Any cells displaying the specific (?) non self mhc1 complementary to cytotoxic T cell receptors are attacked
• b cells recognise non self using their antibodies