What does insulin do to glucose regulation?

• A. Increases glucose production by liver.
• B. Inhibits glucose transport into cells.
• C. Causes glucose to be released in urine.
• D. Increases glucose uptake into cells.

Answer: (D)

Insulin lowers blood sugar by signaling cells to take in glucose from the bloodstream. When insulin binds its receptor on muscle and fat cells, it triggers a cascade that moves GLUT4 glucose transporters to the cell surface, allowing glucose to enter the cells. This increases glucose uptake and storage, especially as glycogen in the liver and muscles, helping to bring blood glucose down after meals. The other ideas don’t fit because: increasing liver glucose production would raise blood sugar, not lower it; blocking glucose transport would prevent uptake; and glucose in urine occurs only when blood sugar is very high and the kidneys can’t reabsorb it, not as a normal insulin action.