cAMP-dependent pathway. Molecular model of dopamine (red, top left) binding to a G-protein-coupled receptor (GPCR, blue, left) and triggering a signalling cascade. The binding of dopamine causes the alpha subunit of the G-protein to exchange its bound molecule of GDP (guanosine triphosphate, yellow, centre left) for a molecule of GTP (guanosine triphosphate, yellow, centre) and to be released from the GPCR. The G-alpha subunit binds to the enzyme adenylyl cyclase (blue, right), activating it. Adenylyl cyclase catalyses the conversion of ATP (adenosine triphosphate, leftmost red molecule at right) to cyclic adenosine monophosphate (cAMP, red, lower right of ATP) and pyrophosphate (red, above cAMP). cAMP regulates numerous cell functions. For a version of this image with labels see F032/8002.