What is the effect of glucagon on glycogen in the liver?

Glucagon primarily functions to increase blood glucose levels, and one of its key actions in the liver is to stimulate glycogenolysis. This process involves breaking down glycogen, which is a stored form of glucose, into glucose molecules that can be released into the bloodstream. When glucagon is released, particularly in response to low blood sugar levels, it binds to specific receptors on liver cells, activating signaling pathways that result in the activation of enzymes responsible for glycogen breakdown.

This action is crucial for maintaining glucose homeostasis, especially during fasting or in between meals, ensuring that the body has a sufficient supply of glucose for energy needs. In addition to stimulating glycogenolysis, glucagon also inhibits glycolysis, preventing the use of glucose for energy and favoring its release into the bloodstream instead. This is part of the body's mechanism to increase available glucose during states of low blood sugar.

Therefore, the stimulation of glycogenolysis by glucagon is vital for regulating glucose levels and demonstrates the hormone's role in energy mobilization during metabolic stress.