Membrane Receptors

Question 1

4 main receptor types

Answer 1

• Ligand-gated ion channel
• G-protein-coupled receptor
• Kinase-linked receptor
• Nuclear receptor

Question 2

Timescales of different receptor types

Answer 2

• Ligand-gated = milliseconds
• GPCR = seconds
• Kinase-linked = hours
• Nuclear = hours

Question 3

Mechanism of action of GPCRs

Answer 3

1. Ligand binds to receptor, causing it to bind to a heterotrimeric G-protein
2. Binding promotes release of GDP for GTP
3. G-protein dissociates into alpha and beta-gamma subunits
4. Subunits regulate different effectors in membrane

Question 4

What is the function of adenylyl cyclase?

Answer 4

Converts ATP to cyclic AMP (cAMP) - the second messenger

Question 5

What enzyme deactivates cAMP and what is formed?

Answer 5

• cAMP phosphodiesterase
• Forms AMP