What is the function of insulin?

• A. It controls glucose levels in the plasma by enabling glucose uptake into cells.
• B. It stimulates glucose production in the liver.
• C. It increases glucose in blood.
• D. It blocks glucose from entering cells.

Answer: (A)

Insulin’s job is to lower blood sugar by helping glucose move from the bloodstream into cells. After eating, the pancreas releases insulin, which binds to receptors on muscle and fat cells and triggers a signal that brings GLUT4 transporters to the cell surface. This lets glucose enter the cells to be used for energy or stored as glycogen, and it also signals the liver to store excess glucose. Because of this, insulin reduces the amount of glucose circulating in the plasma rather than increasing it. The other options describe effects insulin does not have: it doesn’t stimulate hepatic glucose production, it doesn’t raise blood glucose, and it doesn’t block glucose from entering cells.