In the liver, glucagon promotes which process to increase blood glucose?

• A. It inhibits glycogen breakdown
• B. It promotes glycogen synthesis in the liver
• C. It promotes glycogen breakdown in the liver
• D. It has no effect on liver metabolism

Answer: (C)

Glucagon raises blood glucose by triggering liver pathways that release glucose into the bloodstream, primarily through glycogen breakdown (glycogenolysis) in the liver. It binds to receptors on hepatocytes, activating a signaling cascade that increases cAMP and protein kinase A, which then activates glycogen phosphorylase and inhibits glycogen synthase. This shifts the balance toward breaking down glycogen stored in the liver into glucose-1-phosphate, then glucose-6-phosphate, and finally glucose that can exit the liver into the blood. While glucagon also promotes gluconeogenesis, the immediate way it increases blood glucose is by breaking down glycogen.