The function of insulin is to _______.

• A. inhibit glucose uptake by cells
• B. stimulate the breakdown of glycogen to increase blood glucose
• C. increase gluconeogenesis in the liver
• D. promote the uptake of glucose into cells, lowering blood glucose levels

Answer: (D)

Verified step by step guidance

1. Understand the role of insulin in the body: Insulin is a peptide hormone produced by the beta cells of the pancreas. Its primary function is to regulate blood glucose levels by promoting glucose uptake into cells.
2. Clarify the mechanism of glucose uptake: Insulin binds to insulin receptors on the surface of cells, triggering a signaling cascade that leads to the translocation of glucose transporter proteins (such as GLUT4) to the cell membrane. These transporters facilitate the entry of glucose into the cell.
3. Differentiate insulin's function from other processes: Insulin does not stimulate glycogen breakdown (glycogenolysis) or increase gluconeogenesis (glucose production in the liver). Instead, it promotes glycogen synthesis and inhibits gluconeogenesis to lower blood glucose levels.
4. Relate insulin's function to blood glucose regulation: By promoting glucose uptake into cells, insulin reduces the concentration of glucose in the bloodstream, maintaining homeostasis and preventing hyperglycemia.
5. Summarize the correct answer: Insulin's primary function is to promote the uptake of glucose into cells, thereby lowering blood glucose levels. This is distinct from the other options provided in the question.