How does insulin facilitate glucose uptake in cells?

• A. By inhibiting glucose metabolism
• B. By promoting excretion of glucose
• C. By binding to cell receptors
• D. By converting glucose into fat

Answer: (C)

Insulin facilitates glucose uptake in cells primarily by binding to specific receptors on the cell membrane, particularly in muscle and adipose (fat) tissues. When insulin binds to its receptor, it triggers a signaling cascade that results in the translocation of glucose transporter proteins (such as GLUT4) to the cell's surface. This process increases the permeability of the cell membrane to glucose, allowing glucose molecules to enter the cell more freely from the bloodstream. Consequently, insulin plays a crucial role in regulating blood glucose levels and assisting cells in utilizing glucose for energy or storing it for future needs.

The other options do not accurately describe the mechanism by which insulin functions. For instance, inhibiting glucose metabolism or promoting glucose excretion would contradict insulin's role in lowering blood glucose levels. Converting glucose into fat is a process called lipogenesis, which can occur after glucose has already been taken up but is not the primary mechanism for glucose uptake itself.