VCE Biology Question Thread

[sandrag]

Thanks for your answers guys Could someone please explain how antibody-antigen reactions provide evidence for evolutionary relationships?

[RazzMeTazz]

Could someone please explain to me why the answer to this question is C? 

Any help would be appreciated!

[jessica666]

Hey guys, can somebody please help me out with MHC markers, I'm still quite confused about them! From what I understand:
MHC Class 1: Found on all nucleated cells
MHC Class 2: Found on B and T cells and macrophages
Could someone please help me with the function of each class and anything else we should know about them? thanks

[RazzMeTazz]

Would this be a sufficient explanation of what rational drug design is:

The formation of drugs in terms of shape to specifically target molecules associated with disease.

Or do we have to talk about the active site of enzymes and how these drugs are tailored to act as inhibitors?

[RazzMeTazz]

I'm pretty sure this is no longer on the study design but just out of curiosity when plants show geotropism in their shoots, in a horizontally placed plant does the auxin accumulate horizontally on the lower side of the shoot or on the top horizontal side of the shoot?

I thought it was on the top, hence resulting in cell elongation at the horizontal top part of the shoots and causing the roots to bend towards gravity but a practice exam I just did said it was in the lower horizontal part of the shoots.

Just a bit confused, any help would be great.

Also do we need to know in detail about the structure of cholesterol? Such as the fact that it is a 'steroid 4 ring structure' (came across this in a TSFX exam)

And final question  I don't quite understand how enzymes can work as receptor proteins for signalling molecules. I just did a practice TSFX exam which said the enzyme tyrosine kinase is an enzyme but then went on to explain how it is found on the membrane of cells and activates a G protein to trigger signal transduction etc.

[dankfrank420]

Hey guys, can somebody please help me out with MHC markers, I'm still quite confused about them! From what I understand:
MHC Class 1: Found on all nucleated cells
MHC Class 2: Found on B and T cells and macrophages
Could someone please help me with the function of each class and anything else we should know about them? thanks

MHC 1 - helps immune system distinguish self from non-self
MHC 2 - Found on APC that present antigens to Helper T cells, which relay messages to either B or T cells with cytokines to begin proliferation

[vox nihili]

Would this be a sufficient explanation of what rational drug design is:

The formation of drugs in terms of shape to specifically target molecules associated with disease.

Or do we have to talk about the active site of enzymes and how these drugs are tailored to act as inhibitors?

I probably wouldn't use the word formation and would reference enzymes.

Rational drug design is the development of a molecule that can specifically target and inhibit a particular enzyme, facilitated by the complimentarily of the structure of the molecule and binding sites on the enzyme.

MHC 1 - helps immune system distinguish self from non-self
MHC 2 - Found on APC that present antigens to Helper T cells, which relay messages to either B or T cells with cytokines to begin proliferation

That's not precisely what MHC class I is for. MHC class I presents things that are inside the cell, whereas class II presents things that have been found in the environment. So if there's a virus in a cell, that'll pop up on class I and will "encourage" the immune system to kill it.

[jessica666]

That's not precisely what MHC class I is for. MHC class I presents things that are inside the cell, whereas class II presents things that have been found in the environment. So if there's a virus in a cell, that'll pop up on class I and will "encourage" the immune system to kill it.

So when a macrophage has engulfed something foreign, are antigens presented on class 2?

[slothpomba]

And final question  I don't quite understand how enzymes can work as receptor proteins for signalling molecules. I just did a practice TSFX exam which said the enzyme tyrosine kinase is an enzyme but then went on to explain how it is found on the membrane of cells and activates a G protein to trigger signal transduction etc.

The way tyrosine kinase works regarding signalling is rather complicated, here is a simplified version just to illustrate that:



This kind of thing is taught in 3rd year pharmacology. It's been awhile since i've done bio so i could be dead wrong (so check for yourself) but i honestly don't think VCAA would ask you a question about tyrosine kinase signalling in a VCE biology exam. Tyrosine Kinase is an enzyme but it is linked to other things, which is probably what they were describing when they were talking about the cell membrane etc.

TSFX is notorious for including things that you don't need or are not in the course design. If you want to be charitable, you could say they want their students to have a deeper understanding. If you wanted to be critical, you could say they include things you dont need to know so they can test you on them and feel like you've actually learned something (unnecessarily though) to justify their prices.

[RazzMeTazz]

Thanks so much for your answers slothpomba and Mr. T-Rav!

[RazzMeTazz]

I didn't quite understand this question.

The correct answer is B but if the donor was blood type A- wouldn't they have anti-B antibodies in their blood which would then bind to the B antigens on the surface of the blood cells of the recipient organ and cause agglutination?


Thanks!

[vox nihili]

So when a macrophage has engulfed something foreign, are antigens presented on class 2?

Perfect!

[vox nihili]

I didn't quite understand this question.

The correct answer is B but if the donor was blood type A- wouldn't they have anti-B antibodies in their blood which would then bind to the B antigens on the surface of the blood cells of the recipient organ and cause agglutination?


Thanks!

You ignore the antibodies in the donor blood. They're in nowhere near high enough concentration to cause any issue.

AB is the universal recipient because it can take blood from anywhere, O is the universal donor because it can give to anything (despite having both A and B antibodies)

[althepal]

I'm pretty sure this is no longer on the study design but just out of curiosity when plants show geotropism in their shoots, in a horizontally placed plant does the auxin accumulate horizontally on the lower side of the shoot or on the top horizontal side of the shoot?

It's because auxin has a different effect in the shoots - it inhibits cell elongation on the lower side causing the top side to continue growing and curl downwards whereas in the stem it promotes cell elongation on the dark side of the plant.

[millie96]

In the allergic response, what actually causes the production of IgE antibodies? these are the steps i have, can somebody please check them??

• organism is exposed to the allergen for the first time
• results in the production of IgE antibodies which travel in the blood stream and bind to mast cell
• mast cells are primed
• second encounter with the allergen produces IgE antibodies which bind to mast cells
• results in the release of histamine, resulting in an allergic response