How does glucagon affect blood glucose levels?

• A. Decreases glucose by promoting glycogen synthesis.
• B. Increases glucose by promoting glycogenolysis and gluconeogenesis.
• C. No effect on glucose.
• D. Decreases appetite.

Answer: (B)

Glucagon raises blood glucose by signaling the liver to release glucose. It binds to receptors on hepatocytes, increases cAMP, and activates protein kinase A. This stimulates glycogenolysis, breaking down glycogen into glucose that is released into the bloodstream, and also promotes gluconeogenesis, producing new glucose from noncarbohydrate substrates. This dual action in the liver raises circulating glucose, especially during fasting. It does not promote glycogen synthesis, and its primary role isn’t altering appetite.