Glucagon or Epinephrine bind to the receptor
You can think of these as the “switch” that activates the whole cascade. They want something to happen, so they bind and turn the process on!
The G-protein subunit undergoes a conformational change that causes it to RELEASE GDP and bind GTP.
Remember, GDP is not being phosphorylated here! It is letting go of the GDP in favor of the GTP
Gas (alpha subunit and GTP) is formed by the dissociation of the beta and gamma subunits→ this just leaves the alpha subunit and GTP
I love when the names of molecules just make sense. The reaction needs “gas” to go forward.
Gas binds to adenylate cyclase
The name of this molecule gives you a helpful hint on what it does→ it catalyzes the cyclization of ATP to cAMP (cyclic AMP)
cAMP is cyclized
SECOND MESSENGER!! This is what amplifies the signal
If you are struggling to remember, you can think of camp, and the use of those loud megaphones to call all the campers; Or, if it's easier, I see the lowercase c to uppercase AMP as a sort of “amplification” which helps me to remember. (Low→ high). It's a bit of a stretch, but it works for me!
cAMP then binds protein kinase A (PKA)
This results in PKA going around and phosphorylating things. For this class, you do not have to know what exactly.
RESULT: Glycogen breakdown→ get a release of glucose!