Biology Unit 3 Questions Megathread

[ReganM]

How do antibodies work? I know that plasma cells produce them in response to being activated, but how do the antbodies work?

And do antibodies work on free-floating pathogens or do they also affect infected cells?

[lexitu]

They're more for things within extracellular fluid - an antibody, when colliding with its specific antigen, will form an antibody-antigen complex and this inactivates the pathogen. This 'flags' it for removal by phagocytes. Infected cells are targeted by T cells.

[amun]

Thanks alot russ , And also how much of the action potential do we need to know and the nerve impulse do we need to know in detail like refractory period and hyperpolarization ?

[scocliffe09]

Thanks alot russ , And also how much of the action potential do we need to know and the nerve impulse do we need to know in detail like refractory period and hyperpolarization ?

You don't need that much detail.
Understand that resting membrane potential is negative inside and positive outside and that as the AP moves along, K+ flow out and Na+ flow in. Understand that myelin helps insulation and conduction and that the nodes of ranvier (between myelin) allow for the AP to move along the axon. Know the structures of sensory, inter and effector neurons. Understand the concept of reflex arcs. Don't know that there's that much more to it!

[amun]

Oh okay thanks alot and do we need to know the C4 and C3 in photosynthesis or only up to the light dependent  and independent reacts that what i only know and the inputs and outs .

[WhoTookMyUsername]

I have some info that says some lipids contain nitrogen, is this correct and can anyone give me an example of this? Thanks

EDIT: Also, should i state on the exam that the polymer of amino acids is a protein or polypeptide?
I'm pretty sure polypeptide is more accurate, but i get the feeling that VCAA like protein
or should i give an answer such as

the polymer of amino acids is a polypeptide (or polypeptides, inc. func proteins?)

[Russ]

Reasonably sure there are nitrogenous lipids.

Polypeptide = many amino acids, more so than an oligopeptide. It's reasonably interchangeable with protein, I usually use polypeptide to mean an unfinished or linear chain.

RE: antibodies, they can fix complement on the surface of infected cells, which obvious allows a response. they don't necessarily have to neutralise, they can simply bind and act as markers etc.

[epinephrine]

Could someone please explain how the answer to this question is A, since I initially thought that it would be C

Question 16

The human thyroid gland is controlled by a negative feedback mechanism. The hypothalamus secretes
thyrotropin-releasing hormone (TRH). TRH stimulates the anterior pituitary to secrete thyroid stimulating
hormone (TSH). TSH induces the thyroid gland to secrete thyroxine.
The next step in the control system is
A. thyroxine will inhibit the secretion of TRH by the hypothalamus.
B. the hypothalamus will secrete a thyroid-inhibiting hormone that slows down production of thyroxine.
C. thyroxine will stimulate the increased production of TSH.
D. the rising level of thyroxine will act on the pituitary gland to slow down the production of TSH.

[Drunk]

It's not C because that would be positive feedback, seeing as it would be increasing production of TSH

[WhoTookMyUsername]

A due to negative feedback

Thanks Russ

Are transplanted organs rejected due to eosinophil action or cytotoxic T action , and how exactly does this work, as in, do phagocytes still e ngluf antigens somehow, and how does the body 'kill' the new organ

2) what should i call the membrane of mitochondria etc. plasma membrane / cell membrane / unit membrane / membrane?

Is a vector defined as a carrier of infectious disease that transmits it from one organsim to another without getting harmed itself? if it does get harmed, why is the mosquito instead of the human termed the 'vector'?

[Russ]

Transplanted organs have different HLAs so they thus stimulate an immune response via Th cells because they haven't been educated to not react to the non-self HLA. Then it's a normal CMI

Vectors are organisms that transmit disease, just because they're affected doesn't mean they're not a vector. Infectious disease is human-centric so we talk about zoonotic infections as those that will be transmitted TO humans. If you did vet science, it'd be the other way round

[WhoTookMyUsername]

Transplanted organs have different HLAs so they thus stimulate an immune response via Th cells because they haven't been educated to not react to the non-self HLA. Then it's a normal CMI

Vectors are organisms that transmit disease, just because they're affected doesn't mean they're not a vector. Infectious disease is human-centric so we talk about zoonotic infections as those that will be transmitted TO humans. If you did vet science, it'd be the other way round

thanks russ, would NK cells attack the organs as well?

[Russ]

Yes

[Drunk]

Why do lymph nodes swell up?

[Truck]

Why do lymph nodes swell up?

I'm guessing that due to an infection the node will have more macrophages and lymphocytes, so they'd need get larger to accommodate them all. Also as another guess, they could be infected themselves and inflammation could occur in the node?