Final answer:
The pathway activated by NO binding to guanylyl cyclase is the cGMP pathway, leading to vasodilation and other physiological effects, differing from the cAMP pathway where adenylyl cyclase converts ATP to cAMP following G-protein activation.
Step-by-step explanation:
The pathway activated by the binding of nitric oxide (NO) to guanylyl cyclase (GC) is the cGMP pathway. Nitric oxide acts as a signaling molecule and when it binds to guanylyl cyclase, it leads to the synthesis of cyclic guanosine monophosphate (cGMP) from guanosine triphosphate (GTP). This second messenger, cGMP, then activates protein kinases and other target molecules which can lead to various physiological effects such as vasodilation. Unlike the cAMP pathway, which is activated by adenylyl cyclase catalyzing the conversion of ATP to cAMP following activation by a G-protein, the cGMP pathway is directly activated by NO binding. Nitric oxide, because of its gaseous nature and ability to readily diffuse across membranes, binds to an intracellular receptor such as guanylyl cyclase, rather than to a cell surface receptor.