Glucagon acts primarily on the liver during fasting.

Its two principal metabolic effects are:

• Stimulation of glycogenolysis
• Stimulation of gluconeogenesis

Together, these processes increase hepatic glucose output and maintain blood glucose concentration.

Exam rule: Glucagon raises blood glucose by stimulating glycogenolysis and gluconeogenesis.

Why not the other options?

Gluconeogenesis and glycogenesis: Glucagon stimulates gluconeogenesis but inhibits glycogen synthesis.

Glycolysis and glycogenesis: Both processes are inhibited by glucagon.

Glycogenesis and glycolysis: Both are suppressed during fasting.

Lipogenesis and glycogenesis: Both are promoted by insulin in the fed state.