G-protein cycle

G-protein coupled receptors are named after the guanosine nucleotides GTP and GDP (guanosine triphosphate and -diphosphate) with which they interact. The G-protein exists of 3 subunits: α, β, and γ. The first is associated with the receptor; the latter has a lipophilic tail in the cell membrane.

Also check here for an animation of the G-protein cycle.