Insulin functions in the body by:

• A. Inhibiting the uptake of glucose by cells
• B. Enabling glucose to enter the cells
• C. Stimulating glucose production in the liver
• D. Causing glucose to be excreted in urine

Answer: (B)

Insulin lowers blood glucose by enabling glucose to enter cells, especially in muscle and fat tissue. It does this by promoting the movement of GLUT4 transporters to the cell membrane, allowing glucose to cross into the cells after meals. With glucose taken up, blood glucose levels fall, and the liver stores excess glucose as glycogen while also reducing glucose production.

The other ideas don’t fit because insulin does not inhibit uptake; it promotes it. It does not stimulate glucose production in the liver; it actually suppresses hepatic glucose output. It does not cause glucose to be excreted in urine; lowering blood glucose helps prevent glucose loss in urine, which occurs only when glucose exceeds the kidney’s threshold.