VCE Biology Question Thread

[howlingwisdom]

What exactly are MHC markers and what do they do?

[Lizzy7]

What exactly are MHC markers and what do they do?

MHC markers (major histocompatibility complexes) are glycoproteins found on cell membranes that determine self from non self. So class 1 is located on all cells except red blood cells and class 2 MHC markers are located on T and B cells. So basically they are involved in "recognition"

[howlingwisdom]

MHC markers (major histocompatibility complexes) are glycoproteins found on cell membranes that determine self from non self. So class 1 is located on all cells except red blood cells and class 2 MHC markers are located on T and B cells. So basically they are involved in "recognition"

So they are basically a type of antigen?

[howlingwisdom]

I'm confused as to what are the main differences between T and B cells? :/

[vox nihili]

What exactly are MHC markers and what do they do?

MHC molecules present antigens. So when a pathogen or part of a pathogen is taken up, it is digested. Cell, however, retains a part of the pathogen and presents it on its surface. The way it presents it is by sticking it on an MHC marker. These markers then signal to other elements of the immune system (B-Cells, T_C cells, T_H cells) that a pathogen is present and that a response must be mounted.

[Jason12]

Which will cause the fastest response? A protein or steroid-based hormone?

[slothpomba]

Which will cause the fastest response? A protein or steroid-based hormone?

Like a lot of things, it depends. Keep in mind, protein hormones dock onto receptors on the membrane and elicit their effects via second messengers/signal transduction. Steroid hormones usually (especially in the sterotypical VCE examples) "slip through" the membrane and act on targets inside the cell.

It's a tricky question. Going through second messengers adds more steps and slows it down (in the case of protein hormones). It's probably the right answer here too but protein hormones sometimes can signal faster reactions too (i think..).

[RazzMeTazz]

Why do antibiotics, disinfectants and antiseptics work on bacteria but not viruses?

[vox nihili]

Why do antibiotics, disinfectants and antiseptics work on bacteria but not viruses?

Well that's not entirely true actually. Certain disinfectants will kill viruses as well... Antibiotics are targeted to specific bacterial structures.

[Rishi97]

Can someone pls help me? For part b

[alchemy]

Why do antibiotics, disinfectants and antiseptics work on bacteria but not viruses?

Antibiotics slow down (or prevent) binary fission (reproduction of bacteria) from occurring. Viruses don't undergo binary fission so antibiotics don't work on them.

[vox nihili]

Antibiotics slow down (or prevent) binary fission (reproduction of bacteria) from occurring. Viruses don't undergo binary fission so antibiotics don't work on them.

Just to be completely clear, this isn't the only mode of action for antibiotics

[alchemy]

Just to be completely clear, this isn't the only mode of action for antibiotics

Oh sorry for my wording, it definitely isn't their only mode of action. I'm not entirely sure of other modes of action though :/

[vox nihili]

Oh sorry for my wording, it definitely isn't their only mode of action. I'm not entirely sure of other modes of action though :/

That's all good! Just making sure

Well they can target a whole lot of things. Some target the ribosomes, causing them to break up or stopping from them to form (not sure exactly what they do). Points for anybody who can signal a possible issue with this method.
Another way is to target bacterial cell walls. We obviously don't have cell walls, so by degrading that we spare our own cells harm.

They're just two ways, there are plenty of others. Ask me on Thursday when I've finished my antibiotics lectures and I may have something interesting for you

[alchemy]

Can someone pls help me? For part b

First remember "there's type I and type II diabetes.
type I - is an autoimmune disease where your immune system destroy cells that produce insulin, and as a result you must take insulin shots (as you're unable to produce it)
type II - is when your cells don't respond to insulin or insulin isn't produced enough, so your cells are unable to take up glucose" (Quote: swagsxboi)

Since production of insulin is less in Group X, and there is also a greater amount of blood glucose in Group X, this would have meant cells of the body would have taken up less glucose over the period of 60 minutes in comparison to Group Y. Hence, Group X must have included the people with diabetes.