Following a meal, blood glucose concentration rises, triggering the secretion of insulin from the beta (β\betaβ) cells of the islets of Langerhans. Which of the following cellular responses is directly stimulated by the binding of insulin to its specific receptors on the membrane of target muscle cells?
Vesicles containing glucose transporter proteins fuse with the cell-surface membrane, increasing the rate of facilitated diffusion of glucose into the cytoplasm.
Adenylate cyclase is activated, leading to an increase in cyclic AMP (cAMP\text{cAMP}cAMP) concentration which initiates glycogenesis.
The enzyme glycogen phosphorylase is activated, increasing the rate of glycogenolysis to release free glucose.
Sodium-potassium pumps are inactivated to allow sodium-coupled active co-transport of glucose against its concentration gradient.