What is expected to happen when epinephrine binds to its receptor in a myocyte?
A) Intracellular cAMP levels will rise.
B) Glycogen synthase will become active.
C) Glycogen phosphorylase will be phosphorylated.
D) Intracellular cAMP levels will rise, and glycogen phosphorylase will be phosphorylated.
E) Glycogen synthase will become active, and glycogen phosphorylase will be phosphorylated.

Question

Quizplus · Accepted Answer

When epinephrine binds to its receptor in a myocyte, it activates the G-protein coupled receptor signaling pathway, which leads to the activation of adenylate cyclase and subsequent production of cAMP. Elevated levels of cAMP activate protein kinase A, which in turn phosphorylates glycogen phosphorylase, activating it and increasing glycogen breakdown. Therefore, intracellular cAMP levels will rise, and glycogen phosphorylase will be phosphorylated. Glycogen synthase is actually inhibited by protein kinase A, so choice E is incorrect. Choice B, where glycogen synthase becomes activated, is also incorrect as it is not a direct effect of epinephrine binding to its receptor.

What Is Expected to Happen When Epinephrine Binds to Its