What role does cholesterol play in cellular membranes?

Cholesterol plays a critical role in cellular membranes by stabilizing them and decreasing their permeability. It is an integral component of the lipid bilayer, interspersed among phospholipids, and contributes to membrane fluidity. Cholesterol helps maintain a balance in membrane fluidity by preventing phospholipids from packing too closely together when the membrane is cold, which would make the membrane too rigid. Conversely, at higher temperatures, cholesterol can help prevent excessive fluidity by restraining the movement of the fatty acid chains of phospholipids.

This stabilizing effect is crucial for maintaining the overall integrity and function of the membrane, allowing it to properly house membrane proteins and maintain selective permeability. Thus, cholesterol is essential for ensuring that the cellular environment is optimal for the processes that occur within the cell.