cAMP as second messager in G protien (epinephrine example)

Step 1

First messanger (ligand) binds to GPCR activating it

Step 2

Activated GPCR binds to G protein, which is then bound by GTP, activating the G protein.

Step 3

Activated G protein/GTP binds to adenylyl cyclase. GTP is hydrolyzed, activating adenylyl cyclase.

Step 4

Activated adenylyl cyclase converts ATP to CAMP

Step 5

CAMP, a second messenger, activates another protein, leading to cellular responses.