L02

Question 1

How does heterotrimeric G protein reasociate

Answer 1

After effects, alpha subunit hydrolyses GTP back to GDP which then associated with alpha subunit and all subunits join together and reassociate so cycle can continue

Question 2

What does g alpha s do

Answer 2

Activates AC which phosphorylates ATP into cyclic AMP which acts as a sendonary messager in the cell

Question 3

What does G alpha i/o do

Answer 3

Inhibits AC - deactivates it

Question 4

What does G alpha q do

Answer 4

That and Beta subunit Stimulates phopholipase C

Question 5

What does G a 12/13 do

Answer 5

Regulates small G proteins for cytoskeleton contraction

Question 6

Domains of G protein

Answer 6

7 domains (7TM)
Weave in and out of the membrane
Alpha helices

Question 7

AC functions and cAMP phosphodiesterase

Answer 7

Converts ATP into cAMP which then binds to several mediators such as protein kinases or ion channels causing responses

cAMP phosphodiesterase keeps rxn under control by degrading cAMP - prevents reaction reacuring

Question 8

Phospholipase C actions

Answer 8

Phospholipase C is a membrane bound enzyme that is Activated by G alpha q
It uses phospholipids as substrates eg. pip2
Breaks down substrate into 2 messengers - DAG and IP3
DAG activates protein kinase C resulting in enzyme cascade - leads to a response
IP3 (lipid) interacts with smooth ER releasing Ca ions - activate proteins- response
Results in biological responses