Optometry Admission Test (OAT) Practice

What is the primary effect of glucagon on liver cells?

1. Stimulates protein synthesis

2. Inhibits glucose production

3. Converts stored glycogen to glucose

4. Increases fat storage

The correct answer is: Converts stored glycogen to glucose

The primary effect of glucagon on liver cells is to convert stored glycogen into glucose. Glucagon is a hormone produced by the alpha cells of the pancreas, and it plays a crucial role in maintaining blood glucose levels, especially during fasting or between meals. When blood glucose levels drop, glucagon signals the liver to break down glycogen, a polysaccharide stored in the liver, into glucose molecules through a process called glycogenolysis. This glucose can then be released into the bloodstream to provide energy for various body functions and to keep blood sugar levels stable. This physiological response is essential for preventing hypoglycemia and ensuring that the body's tissues have access to glucose when they need it. Therefore, the action of glucagon is vital for glucose homeostasis, especially in situations where the body requires quick energy, such as during exercise or fasting periods. Other options, like stimulating protein synthesis or increasing fat storage, are not functions associated with glucagon; rather, those actions are typically influenced by insulin. Additionally, inhibiting glucose production would contradict glucagon's role as a hyperglycemic agent, further affirming that its main action is indeed the conversion of glycogen to glucose.