Which of the following best describes the mode of action of glucagon in maintaining glucose levels?

Glucagon plays a crucial role in maintaining glucose homeostasis, especially during fasting or low blood sugar levels. Its primary function is to increase glucose availability in the bloodstream, and it achieves this mainly through two key processes: glygenolysis and gluconeogenesis.

When glucagon is released by the alpha cells of the pancreas, it acts on the liver, where it stimulates gluconeogenesis—the process of synthesizing glucose from non-carbohydrate precursors such as lactate, amino acids, and glycerol. This process is vital for raising blood glucose levels when they are low. By promoting gluconeogenesis, glucagon ensures that there is a continuous supply of glucose available for tissues, especially for the brain, which relies heavily on glucose as its primary energy source.

Glucagon also promotes glycogenolysis, the breakdown of stored glycogen into glucose, but that option does not highlight the direct creation of new glucose that gluconeogenesis represents. Thus, it's essential to recognize that while glucagon does stimulate glycogenolysis, its action in stimulating gluconeogenesis is a more prominent and direct mechanism for increasing glucose levels, particularly in periods of fasting.

Overall, the stimulation of gluconeogenesis is the defining action of glucagon in maintaining