That GPCRs are coupled to a GTP binding protein that is made of the parts of three animals

That GPCRs are coupled to a GTP binding protein that consists of three sub-units

That GPCRs can exert their effects in three different ways: ion channels, 2nd messengers and cyclic AMP

That the GPCR produces effects by acting on molecules such as adenylate cyclase (AC) or phospholipase C (PLC), or direct effects by regulating ion channel or kinase function.

That the ligand for the GPCR can bind to one of three sites on the GPCR