receptors

Question 1

what are paracrine and autocrine signalling?

Answer 1

paracrine = one signalling cell with a few surrounding target cells

autocrine = cell has receptors for its own signal perhaps to let it know when there’s enough like negative feedback

Question 2

what is quorum sensing?

Answer 2

communication between bacterial cells in colonies, allowing them to coordinate things like toxin production, or when there’s no more room to grow

Question 3

what is notch-delta signalling?

Answer 3

notch = a receptor that causes a signalling cascade that inhibits delta in neighbouring cells
delta = signal when a cell is differentiating into a neurone, to tell surrounding cells they don’t need to

this is contact dependent signalling

Question 4

how do dimers work to cause a cascade, and what often are they?

Answer 4

often protein kinases, like tyrosine kinase responding to growth factors (like in the Ras signalling pathway)
there are two dimers pulled together upon binding of a ligand

Question 5

how does adrenaline work?

Answer 5

G coupled protein receptor - ligand causes GDP to be switvhed for GTP, Galpha S released - adenylate cyclase - cAMP - protein kinase A - phosphorylation of calcium channel results in a Ca2+ influx - increases contraction

Question 6

after ligand binds, what is the pathway involving phospholipase C?

Answer 6

again - G coupled protein receptor, once GTP is bound, the alpha subunit activates phospholipase C , this enzyme breaks down PIP2, leaving DAG in the membrane which activates protein kinase C, the other part its broken down into is IP3, a ligand for an ion channel that allows Ca2+ out of the ER and into the cytosol

Question 7

in general, how do GPCRs work?

Answer 7

have 7 transmembrane alpha helices, ligand binding - conformational change - G protein causes GDP to switch with GTP like a GEF, the now activated G protein moves away and activates effector enzyme