VCE Biology Question Thread

[Reus]

what is the correct name for when a body overreacts to a harmless antigen? Allergic response, allergy, hypersensitivity?

Is it not Autoimmunity?

[Reus]

Do helper T cells also stimulate cytotoxic T cells to proliferate into memory cytotoxic T cells and effector cytotoxic T cells?

Yes, once again T helper cells mainly serve to help/activate cells in the immune system.

[Jason12]

Is it not Autoimmune?

i thought autoimmune was when they react to their own self cells

[Jason12]

whats the difference between receiving a vaccine or injection with antibodies? which one is natural/artificial and active/passive

[Reus]

i thought autoimmune was when they react to their own self cells

Yes you're right, I thought that is what you meant by "harmless antigens".
What do you mean by that?

[Jason12]

Yes you're right, I thought that is what you meant by "harmless antigens".
What do you mean by that?

sorry i got it wrong i was meant to say harmless allergens

so if its allergens then what is the correct name?

[Reus]

whats the difference between receiving a vaccine or injection with antibodies? which one is natural/artificial and active/passive

A vaccination is the process in which the injection contains an attenuated (weakened), dead or synthetic form of the antigen/pathogen that cause an immune response. Whereas the injection of antibodies is introduced to the body in order to act on pathogens that already exist in you. (eg. against a snake bite).

Vaccination is Natural Induced/Artificial.
Injection of antibodies is Passive Induced/Artificial.

[nhmn0301]

For one gene you can normally encode one polypeptide but for the genes encoding antibodies or TCRs you can encode many different varieties of polypeptides from the same basic 'gene'. In the germline (eg stem cells) you have many different DNA 'segments' that might be chosen to contribute to an antibody - only one of a large group of these varieties will be chosen by the developing B cell or T cell and this gives them a unique and specific receptor from the same original germline DNA.  But in each individual cell, the DNA has been changed from what was in the zygote that gave rise to all cells - special immunity enzymes actually modify the genome of the T and B cells so that they can express only one TCR or antibody each.  Thus, stem cells have the capacity to produce many different antibodies somewhere down the line but once they actually start differentiating to a lymphocyte they become restricted to producing only one antibody through the modification of their DNA coding sequences (basically cutting and pasting of DNA).
So overall, the antibody gene locus can give rise to every possible antibody.
But in an individual cell, the 1 gene = 1 polypeptide/protein (interchangeable terms for these in this context) rule still applies because it's the gene that got changed, the change doesn't occur at the protein level.

Does that answer your question?  I'm not sure, I think I understood what you were trying to ask but I could be wrong.

It's definitely outside the scope of this course.

Thanks simpak, that definitely helps a lot!
I might be wrong here but the fact that we can use the word "polypeptide" and "protein" in "1 gene= 1 polypeptide/protein" is a bit...unclear? Since I thought a protein is a polypeptide, but a polypeptide doesn't necessarily called a protein. To be a protein, that polypeptide must have a specific function? Correct me if I'm wrong . Thanks for you help again.

[vox nihili]

Thanks simpak, that definitely helps a lot!
I might be wrong here but the fact that we can use the word "polypeptide" and "protein" in "1 gene= 1 polypeptide/protein" is a bit...unclear? Since I thought a protein is a polypeptide, but a polypeptide doesn't necessarily called a protein. To be a protein, that polypeptide must have a specific function? Correct me if I'm wrong . Thanks for you help again.

So a polypeptide is just a continuous chain of amino acids. It's called polypeptide because the bonds between amino acids are called peptide bonds. A protein on the other hand can be just one polypeptide, or it can have quaternary structure and be made of a number of different polypeptides.

Major difference. Polypeptide is just a chain of amino acids. A protein has a specific function and is made of amino acids all the same.

One polypeptide could also be one protein, but a number of polypeptides together could be one protein as well.

[Jason12]

if blood group A contains anti-b antibodies what does this mean?

[alondouek]

if blood group A contains anti-b antibodies what does this mean?

It means that erythrocytes (RBCs) from the A group will recognise as foreign and reject cells from the B group that are introduced to an organism of type A.

The B erythrocytes are 'B' because they possess B-type antigens, which are what the A erythrocytes' anti-B antibodies recognise and initiate an immune response against.

Let me know if you need any further explanation!

[Jason12]

where does the differentiation of cells take place?

what are the role of platelets in inflammatory response?

[RazzMeTazz]

How would you describe/define naturally acquired immunity?

[RazzMeTazz]

Is the only example of naturally acquired passive immunity, the passing of antibodies from a mother to her foetus or through breast milk to the baby?

[Reus]

Page 58, question 132

Well I finally got to it haha. I got the answer right based on the data/table they have given. (no prior knowledge on blood types and antibodies)
It was really straight forward, just need to interpret the table correctly.

But for your sake!
I asked my teacher if knowing 'blood types' was a part of our course, and she said that it isn't, however it's touched on briefly in unit 4.
She mentioned that questions like that frequently appear on exams, where information is foreign however you apply the knowledge you know.

"Analyse the question! They like to trick you." Direct quote