VCE Biology Question Thread

[cosine]

Would it be reasonable to say, that because the antibodies come from B cells, that memory B cells are also produced during the first response, and these memory B cells over-produce IgE anitbodies upon the second detection at a much greater rate?

please

[StupidProdigy]

Why not A for question 3? And for question 4 why can I cancel out cellulose and say that C is correct? Ta

[vox nihili]

The answer is B, but if a group B person receives blood from a group O person, then the blood from group O has antibodies for A and B proteins, and the group B person has B proteins on its surface? So wouldnt that mean the antibodies from the plasma of the group O blood will neutralise the proteins on the group B blood ?

The antibodies from the donor get diluted out and don't have an effect.

Would it be reasonable to say, that because the antibodies come from B cells, that memory B cells are also produced during the first response, and these memory B cells over-produce IgE anitbodies upon the second detection at a much greater rate?

This does explain why subsequent responses to allergens get worse and worse, though probably isn't the answer they're looking for.

The first response to an allergen produces IgE antibodies, which sensitise mast cells. The first response usually involves very mild to no symptoms at all, because the allergen doesn't have an opportunity to bind with sensitised mast cells (because the first response is doing the sensitising). The second exposure, however, sees the allergen bind to IgE antibodies on the mast cells, prompting the release of histamine (and other stuff) from mast cells, which is what produces symptoms.

In the allergic reaction, it is the degranulation of mast cells and not the production of IgE that produces symptoms. The production of IgE merely gives mast cells the opportunity to respond to the allergen.

[cosine]

Why not A for question 3? And for question 4 why can I cancel out cellulose and say that C is correct? Ta

Because cellulose is only made up of repeating monomers of glucose, and we know that glucose only contains carbon, hydrogen and oxygen. I would choose chitin, but no idea why that would have nitrogen if it's also a polysaccharide?

[Marmalade]

Why not A for question 3? And for question 4 why can I cancel out cellulose and say that C is correct? Ta

For the first one animal cells have cholesterol in their plasma membranes but plant cells do not.
~~~

Also I have questions as well.
How would you answer this? The answer is B, but isn't changing the shape of the active site like what non competitive inhibitors do considered denaturing?
And how would you explain desensitizing to lessen allergic responses? I learnt it was exposing yourself to small doses of allergens, which block the IgE antibodies in your body preventing them from future reactions, but on the internet they say IgG antibodies are involved somewhere?

[Biology24123]

For the first one animal cells have cholesterol in their plasma membranes but plant cells do not.
~~~

Also I have questions as well.
How would you answer this? The answer is B, but isn't changing the shape of the active site like what non competitive inhibitors do considered denaturing?
And how would you explain desensitizing to lessen allergic responses? I learnt it was exposing yourself to small doses of allergens, which block the IgE antibodies in your body preventing them from future reactions, but on the internet they say IgG antibodies are involved somewhere?

How do igG actually desensitize to allergies. I'm guessing we don't need to know this

[vox nihili]

Why not A for question 3? And for question 4 why can I cancel out cellulose and say that C is correct? Ta

I highly doubt you'd get asked question 3. Personally I didn't know that A was wrong. That said though, there are three years olds that no more about advanced calculus than I know about plants...

As for question 4, this is a tricky question. You should know, however, that chitin contains glucose monomers to which an amide group has been attached (the monomers are called glucosamine). Chitin is a structural polysaccharide found in the cell walls of fungi.

How do igG actually desensitize to allergies. I'm guessing we don't need to know this

I'm not really sure what you're asking here, context?

As far as I'm aware, IgG isn't involved in allergies.

[mahler004]

Also I have questions as well.
How would you answer this? The answer is B, but isn't changing the shape of the active site like what non competitive inhibitors do considered denaturing?

Here, we hit one of the limitations of the VCE course - proteins can change shape without being denatured. Crudely, the drug acts on the protein, causing a change in shape (conformational change) that blocks substrate binding.

Denaturation occurs when the protein loses all structure - a protein bound to a competitive inhibitor still has structure, it's just the wrong shape for substrate binding.

[Marmalade]

How do igG actually desensitize to allergies. I'm guessing we don't need to know this

Yeah I think so too. It's just that in one of the practice exams, they talked about getting desensitized to allergies because the allergen ends up binding to IgG instead of IgE, therefore histamine is not released etc. etc. so I got confused about the process of allergy desensitization.

[BakedDwarf]

Are memory cells stored in lymph nodes?

[jyodesh.com]

Are memory cells stored in lymph nodes?

They are found in the highest abundance in the lymph nodes and spleen yeah

[cosine]

For VCE Bio do we need to know much about memory T Cells?

[BakedDwarf]

So i know that one way of causing B-cells to proliferate/differentiate is by:
1. Macrophages engulfing the pathogen and expressing its antigens on its MHC class II markers to a
 specific helper T cell 

2. The helper T-cell proliferates; the produced helper T-cells bind to the specific B cell via the B
 cell’s MHC class II marker 

3. The B cells proliferate and differentiate into plasma and memory cells

However, is there another way that an antigen is presented to a specific helper T cell other than involving a macrophage?
I know that B-cells can present antigen fragments to th-hell, but how? Does the antigen bind to its immunoglobulins and the b-cell then presents this to a th-cell?

[Biology24123]

So i know that one way of causing B-cells to proliferate/differentiate is by:
1. Macrophages engulfing the pathogen and expressing its antigens on its MHC class II markers to a
 specific helper T cell 

2. The helper T-cell proliferates; the produced helper T-cells bind to the specific B cell via the B
 cell’s MHC class II marker 

3. The B cells proliferate and differentiate into plasma and memory cells

However, is there another way that an antigen is presented to a specific helper T cell other than involving a macrophage?
I know that B-cells can present antigen fragments to th-hell, but how? Does the antigen bind to its immunoglobulins and the b-cell then presents this to a th-cell?

B cells also have MHC II. Works the same as a macrophage as far as I know

[cosine]

So i know that one way of causing B-cells to proliferate/differentiate is by:
1. Macrophages engulfing the pathogen and expressing its antigens on its MHC class II markers to a
 specific helper T cell 

2. The helper T-cell proliferates; the produced helper T-cells bind to the specific B cell via the B
 cell’s MHC class II marker 

3. The B cells proliferate and differentiate into plasma and memory cells

However, is there another way that an antigen is presented to a specific helper T cell other than involving a macrophage?
I know that B-cells can present antigen fragments to th-hell, but how? Does the antigen bind to its immunoglobulins and the b-cell then presents this to a th-cell?

Yes, macrophages are not the only Antigen Presenting Cells. You also have dendritic cells that present antigens on their MHC II markers. There are three APCs: B cells, Dendritic cells and macrophages. Only these three cells actually engulf foreign material and present antigenic fragments on their MHC II markers. xD