What is one of the primary functions of cholesterol in biological systems?

Cholesterol plays a critical role in the structure and function of cell membranes. It is an essential component that contributes to membrane fluidity, which is crucial for the proper functioning of cells. Cholesterol helps to stabilize the phospholipid bilayer, preventing it from becoming too rigid or too fluid, thus ensuring that cell membranes maintain their integrity and flexibility under different physiological conditions. This balance is vital for various cellular processes, including transport of substances across the membrane, cell signaling, and maintaining the overall shape of the cell.

The other options do not accurately describe the primary functions of cholesterol. Insulation for nerve cells is primarily provided by myelin sheaths, energy storage typically involves molecules like fats and carbohydrates, and glucose is derived from carbohydrates rather than from cholesterol.