VCE Biology Question Thread

[RazzMeTazz]

Shivaji's answer was quite complex. Depending on the number of marks, the following should suffice:
•a B cell with specific antibodies binds to the antigens on the bacteria
•T-helper cells detect the antigens expressed on MHC II
•T helper cells release cytokines which stimulate the B cell to proliferate and differentiate into B memory cells and B plasma cells, which produce specific antibodies
•antibodies attach to antigens on bacteria, causing them to agglutinate/neutralising them/activating complement proteins
•phagocytes engulf and destroy bacteria

Oh so is it correct to say the antigen-antibody complexes activate complement proteins?

[RazzMeTazz]

Are booster shots essentially just doses of the initial vaccine administered to the individual again?

Also, what is meant by cross-links form between antigens and the IgE antibodies on the surface of mast cells, in the allergic response?

Thankyou

[RazzMeTazz]

In the questions I've seen you get a table with the number of offspring of each genotype or something... More offspring will have the parental combination.

So if the parents are SsWw x ssww and the ratio is not 1:1:1:1, the genes are linked. And the two most common genotypes will be the parental combination

Thanks

[Tyleralp1]

Are booster shots essentially just doses of the initial vaccine administered to the individual again?

Also, what is meant by cross-links form between antigens and the IgE antibodies on the surface of mast cells, in the allergic response?

Thankyou

Booster shots are essentially new vaccines administered to the person in order to increase the amount of specific memory B cells a person has for a specific antigen. This is because Memory B cells don't last forever and gradually decline with time. By doing so, re-encountering the same antigen at a later date will cause an increased amount of specific antibodies to be produced at an even faster rate. Also, booster shots also help to cover any new strains or mutations.

Cross linking between allergens (antigen) and IgE antibodies occurs during the re-exposure to an allergen the person is sensitive to. The allergn binds to the specific IgE antibodies found on the mast cell, forming cross-links, which then trigger the release of histamine from the mast cell. This leads to allergic symptoms of a severe nature such as constriction of the airways, itching, etc.

[shivaji]

If a question asks about why is it difficult to develop vaccines against a pathogen which constantly changes its antigens, how would you go about it?

Is this ok: Vaccines are antigen specific. They stimulate the body's immune system to make antibodies specific against a specific antigen. If the pathogen is constantly changing its antigens, the memory cells produced against the former antigens of the pathogen from the previous vaccine will no longer be effective.  Therefore, it is hard to create a vaccine which will cater for all possible antigens of the pathogen.


Can someone please provide a more concise and better answer please?


PS. also, can a vaccine stimulate the production of Tc cells as well or is it just antibodies?

thanks

[Jason12]

where in the body does clonal expansion occur?

In translation, does  the ribosome actually make the amino acids in the polypeptide chain or does it just join ones brought by the tRNA?

[mahler004]

In translation, does  the ribosome actually make the amino acids in the polypeptide chain or does it just join ones brought by the tRNA?

It just joins the amino acids together (i.e. forms the peptide bond.)

Amino acids are made elsewhere in the cell or supplied in the diet.

[doomdestroyer]

If a question asks about why is it difficult to develop vaccines against a pathogen which constantly changes its antigens, how would you go about it?

I'm just going to give this one a crack as practice.

Vaccines include a non-active form of a pathogen which only contains one type of antigens. Therefore the immune response triggered by a vaccine will only produce antibodies specific to the antigens used in the vaccine. If the pathogen constantly changes its antigens, a vaccine against it will only be effective for so long until it changes its antigens, therefore the vaccine will have to keep up and change along with the pathogen which is quite a long, difficult and expensive process.

[Tyleralp1]

It just joins the amino acids together (i.e. forms the peptide bond.)

Amino acids are made elsewhere in the cell or supplied in the diet.

Pretty sure it's the lymph nodes, as the process of mitosis usually leads to swelling in those areas.

[nerdmmb]

In regards to integral and peripheral proteins,

Are integral proteins membrane proteins that extend througout the membrane and act as channels for substances to pass through?

And are peripheral proteins surface proteins to which carbohydrate attaches to?

[shivaji]

In regards to integral and peripheral proteins,

Are integral proteins membrane proteins that extend througout the membrane and act as channels for substances to pass through?

And are peripheral proteins surface proteins to which carbohydrate attaches to?

wait what's integral and peripheral proteins? someone plz explain?!

[doomdestroyer]

wait what's integral and peripheral proteins? someone plz explain?!

I'm in the same boat as you, man.

[nerdmmb]

wait what's integral and peripheral proteins? someone plz explain?!

I don't know if we need to know about them but they're basically just different types of membrane proteins found in a cell membrane.

[dankfrank420]

wait what's integral and peripheral proteins? someone plz explain?!

Relax guys, not in the study design.

[mahler004]

In regards to integral and peripheral proteins,

Are integral proteins membrane proteins that extend througout the membrane and act as channels for substances to pass through?

And are peripheral proteins surface proteins to which carbohydrate attaches to?

Integral proteins extend through the membrane, but don't necessarily have to form a pore (although all the transporters I can think of are integral proteins.)

Peripheral proteins are (basically) everything that's not an integral protein. They can be associated with another protein, or bind the membrane though for example a lipid anchor or a carbohydrate anchor.

Relax guys, not in the study design.

In that case, ignore the above answer because I'd already typed it out. Sounded a bit advanced for VCE tbh, but wasn't sure (I did my high school in the ACT, I just like answering questions.)

Pretty sure it's the lymph nodes, as the process of mitosis usually leads to swelling in those areas.

What do you mean?