Practice question

Both β-adrenergic receptors and glucagon receptors couple to the stimulatory G protein Gs. Activated Gs stimulates adenylyl cyclase, elevating cAMP and activating protein kinase A. PKA phosphorylates enzymes of glycogen metabolism, ultimately raising blood glucose. Insulin opposes these effects by promoting dephosphorylation of the same target proteins, illustrating reciprocal control of carbohydrate homeostasis.