Pharmacology: G protein coupled receptors

Question 1

give an example of a G protein coupled receptor(GPCR)

Answer 1

adrenergic receptors

Question 2

describe a GPCR when there is no signal present (3)

Answer 2

receptor unoccupied
G protein binds GDP
effector not modulated

Question 3

what happens to turn on the signal for the GPCR

Answer 3

agonist activates receptor

Question 4

describe activity of GDP and GTP when GPCR is activated

Answer 4

GDP dissociates from and GTP binds to alpha sub unit, then G protein dissociates from receptor

Question 5

what happens after receptor is activated

Answer 5

G protein couples with receptor

Question 6

what happens after GTP binds alpha subunit

Answer 6

alpha subunit combines with and modifies activity of effector

Question 7

describe activity of agonist after is activates receptor

Answer 7

it may dissociate from receptor, but signalling continues

Question 8

how is the signal turned off in the GPCR

Answer 8

alpha sub unit acts as enzyme to hydrolyse GTP to GDP(GTPase)

Question 9

what happens after GTP is hydrolysed to GDP

Answer 9

G protein alpha subunit recombines with the beta subunit, completing the G protein cycle