So this is the protein complex. The green is our beta adrenergic receptor. It contains the receptor that basically binds our epinephrine. So when the epinephrine binds to this section, it basically causes the alpha subunit to decrease its affinity for the beta subunit and the alpha subunit. And what happens is our GDP, which is the guanosine diphosphate, is converted into the guanosine triphosphate or GTP and that decreases the affinity of the alpha subunit, our G protein. And this goes on and bind onto this adenylate cyclase.