cell signalling

Question 1

what are first and second messengers?

Answer 1

second messengers are intracellular signalling molecules released in response to extracellular signalling molecules (first messengers)

Question 2

what are the three types of signal receptors?

Answer 2

G-protein coupled receptors (GPCR)
enzyme coupled receptors or protein kinase receptors
steroid hormones

Question 3

how do GPCRs act?

Answer 3

via hydrolysis of GTP

Question 4

what are the steps of GPCRs binding?

Answer 4

bind to ligands then transmit signal across to heterotrimeric G-proteins:
GPCR binds ligand to activate
activated G protein triggers signal cascade

Question 5

what is cAMP?

Answer 5

cyclic AMP
a second messenger of some G proteins
activated PKA

Question 6

what does PKA do?

Answer 6

binds regulatory subunits and phosphorylates many target protein

Question 7

what is IP3?

Answer 7

a second messenger of GPCRs
G protein activates PLC which cleabes PIP2 into DAG and IP3 (ligand-gated ion channel) that activates Ca2+ channel at ER

Question 8

what happens to enzyme coupled receptors or protein kinase receptors?

Answer 8

activation induces conformation change to expose the kinase

Question 9

what type of messenger is an insulin receptors?

Answer 9

enzyme coupled receptors or protein kinase receptors

Question 10

what is an example of steroid hormones?

Answer 10

moulting hormones (ecdysone for insects)