G-protein Coupled Receptors

Question 1

General mechanism

Answer 1

Ligand binding.
Conformation change in receptors which leads to actiavation of the G protein via ADP exchange for ATP.
Alpha subunit of the G protein goes onto to elicit effects.
- formed from a polypeptide chain with 7 transmembrane domains

Question 2

G protein: Alpha s

Answer 2

Alpha subunit activates adenylate cyclase. This leads to the production of cAMP and the activation of PKA.

Question 3

G protein: Alpha I

Answer 3

Inhibits the activity of adenylate cyclase and therefore prevents synthesis of cAMP.

Question 4

G protein: Alpha q

Answer 4

Alpha q activates PLC (phospholipase C). PLC cleaves PIP2 to produce DAG (diacylglycerol) and IP3 (inositol-3, 4, 5- phosphate). IP3 stimulates Calcium release from the ER whilst DAG activates PKC (protein kinase C)

Question 5

Example G protein coupled receptor

Answer 5

Nicotinic adrenoreceptor, serotonin receptors, muscarinic receptors