What is the function of glucagon?

Glucagon serves a crucial function in maintaining blood glucose levels, particularly in response to low glucose concentrations in the bloodstream. It is a peptide hormone produced by the alpha cells of the pancreas. When blood sugar levels drop, glucagon is released to stimulate the liver to convert stored glycogen into glucose, a process known as glycogenolysis. This release of glucose into the bloodstream raises blood glucose levels, providing a vital source of energy for the body's cells, especially during fasting or between meals.

The other choices relate to functions or classes of substances that do not accurately describe glucagon's role. For example, glucagon is not responsible for lowering blood glucose levels; that function is typically associated with insulin. Additionally, glucagon is not classified as an amine that affects blood vessels or a steroid hormone; these categories characterize different biological agents with distinct mechanisms of action within the body. Understanding glucagon's specific role in glucose metabolism is essential for comprehending how the body maintains homeostasis regarding energy supply.