Cell signalling (Overview #2)

Question 1

Criteria for a second messenger (6)

Answer 1

~ small molecule
~ mechanism for inducing rapid alterations in conc.
~ controlled by extracellular stimuli
~ regulate either enzyme activity or protein function
~ involved in highly specific interaction
~ amplification

Question 2

Name the two types of second messengers and give examples.

Answer 2

~ cyclic nucleotides e.g. cAMP + cGMP
~ lipid-derived messengers e.g. DAG IP3
~ ions e.g. Ca2+

Question 3

cAMP

Answer 3

~ activate protein kinase A (PKA)
~ increases lipid breakdown
~ decreases glycogen synthesis

Question 4

cGMP

Answer 4

~ activate protein kinase G (PKG)

~ opens cation channels in rod cells

Question 5

DAG

Answer 5

~ activate protein kinase C (PKC)
~ decreases glycogen synthesis
~ increases transcription

Question 6

IP3

Answer 6

opens Ca2+ channels in the endoplasmic reticulum

Question 7

Ca2+

Answer 7

activates Ca2+-dependent protein kinases

Question 8

Protein phosphorylation

Answer 8

~ kinase adds Pi
~ phosphatase removes Pi
~ reversible
~ occurs on tyrosine, serine or threonine side chains

Question 9

Tyrosine phosphorylation

Answer 9

tyrosine + Pi –> tyrosine phosphate
~ tyrosine kinase (enzyme)
~ same for serine/threonine

Question 10

Amplification

Answer 10

~ when a tiny stimulus volume creates a massive amount of product
~ occurs between perception and transduction

Question 11

Purpose of kinase cascade

Answer 11

helps to bring about large amplification