What physiological effect does glucagon have on liver cells?

Glucagon is a hormone produced by the alpha cells of the pancreas, and its primary role in the body is to increase blood glucose levels, particularly during fasting or low glucose levels. One of the key physiological actions of glucagon in liver cells is to stimulate gluconeogenesis, which is the metabolic process of generating glucose from non-carbohydrate substrates such as amino acids and glycerol. This process occurs primarily in the liver and helps maintain adequate glucose levels in the blood, especially when carbohydrate intake is low.

When glucagon binds to its receptors on liver cells, it activates a signaling pathway that enhances the expression of enzymes involved in gluconeogenesis. As a result, liver cells increase the conversion of substrates into glucose, facilitating the release of glucose into the bloodstream. This action directly opposes insulin's effects, which promotes glucose uptake and storage.

In contrast to stimulating gluconeogenesis, glucagon does not stimulate glycogenesis (the formation of glycogen from glucose), nor does it inhibit gluconeogenesis. It also does not inhibit lipolysis; instead, it tends to promote the breakdown of fats to provide additional substrates for gluconeogenesis. Therefore, the correct understanding of glucagon's action clearly supports its role in stimulating gluconeogenesis within liver