What is the function of insulin on the cellular level?

• A. Causes glucose to be released from the cells into the bloodstream
• B. Inhibits glucose uptake by cells
• C. Allows glucose to enter the cells
• D. Converts glucose into fatty acids

Answer: (C)

Insulin’s action at the cellular level is to promote glucose entry into cells. In muscle and adipose tissue, insulin triggers the movement of GLUT4 glucose transporters to the cell surface, allowing glucose to move from the blood into the cell by facilitated diffusion. This uptake lowers blood glucose and provides cells with a source of energy or building blocks for storage. It does not cause glucose to be released from cells, nor does it inhibit glucose uptake. While insulin also promotes processes like glycogen synthesis and lipogenesis, the immediate cellular function described here is enabling glucose to enter cells, which makes this option the best choice.