Biology Unit 3 Questions Megathread

[Russ]

HIV kills Th cells, thus reducing immune function. That means that it's much easier for infections to take hold and things that wouldn't otherwise cause disease do.

HIV is incredibly error prone. A live vaccine would inevitable spontaneously revert to a virulent form (ie we'd be giving HIV to people)

[amun]

thanx and is the chemical communication between helpter t-cells and b-cells autocrine,paracrine or endocrine ?

[Drunk]

it'd be paracrine, because the helper t-cells and b-cells would be attached to an APC or free antigen, making them right next to each other

how does a virus, like influenza, give you diarrhea?

[Inside Out]

it calls cells in the bladder to die, thus causing diarhea

[Inside Out]

is this right: B cells find an antigen which binds to its receptors (or is it antibodies that it binds to?). It waits to get activated by a T helper cell (which has binded to the same antigen) and then undergoes clonal selection?

[shinny]

it calls cells in the bladder to die, thus causing diarhea

Uh? Wrong end?

With influenza giving diarrhoea, it's not a typical presentation, but if it does occur as diarrhoea can in a wide range of illnesses, it's probably just a result of an in-built defense mechanism that causes expulsion of any foreign material in the body upon feeling sick. Basically, the body knows it sick but it doesn't know exactly where, so it just starts removing everything it can through any orifice it can.

EDIT: The above is really just a gross oversimplification and the mechanisms at hand are obviously more complex. The pathology's outlined in this article but I doubt any of that will make sense to you (barely makes sense to me). Basically though, infections which infect the entire body often lead to widespread release of cytokines which are chemicals secreted by the immune system to act on an infection. These cytokines have widespread effects throughout the body and one of these happens to be diarrhoea. But yeh, it's not well understood and there might be other mechanisms at hand.

[WhoTookMyUsername]

do T cells and B cells communicate through chemical means other than cytokines ?

[Inside Out]

how many turns of the calvin cycle is needed to produce one glucose molecule. is it 6

[liuetenant]

YEs six! 3 turns will produce 6 pgal...where 5 go back to form RuDP...and the 6th one waits....

then u have another 3 turns...5 go back and 6th one remains...

those two 6th ones join to form glucose

[liuetenant]

Oh...and is the cell membrane an organelle?

[Inside Out]

yes it is.
QUestion: Is a basophil a type of phagocyte? (it doenst engulf anything)
And is a mast cell a type of white blood cell?

[shinny]

Oh...and is the cell membrane an organelle?

Actually I don't think it is. Organelles are specialised subunits within cells, whereas the cell membrane surrounds the entire cell and basically defines the cell to begin with.

QUestion: Is a basophil a type of phagocyte? (it doenst engulf anything)
And is a mast cell a type of white blood cell?

Basophils aren't really specialised phagocytes so I wouldn't consider them a phagocyte relaly. Mast cells aren't white blood cells because they're found in the tissues rather than the blood.

[Russ]

RE: diarrhoea, the most common pathogenic reason for diarrhoea is affecting the Na/Cl export pumps and creating an osmotic gradient for water movement to the GIT

do T cells and B cells communicate through chemical means other than cytokines ?

Yes, they have several cell surface receptor/ligand pairs

Is a basophil a type of phagocyte? (it doenst engulf anything)
And is a mast cell a type of white blood cell?

Basophil = granulocyte
Mast cells are leucocytes (WBCs), yes, they're just tissue resident.

[Inside Out]

is a granucolye a macrophage?
and is a dendritic cell also a macrophage

[Russ]

Granulocyte is a class of cell that release granules. Macrophages are not. The most common granulocyte is a neutrophil.

DCs...depends. It's still up for debate. In VCE your answer will probably be "no".