What role does cholesterol play in animal cell membranes?

Cholesterol plays a crucial role in maintaining the fluidity and stability of animal cell membranes. It fits in between the phospholipid molecules in the lipid bilayer, which affects how closely the phospholipids can pack together. Cholesterol helps to prevent the membrane from becoming too rigid at lower temperatures and helps to maintain proper fluidity at higher temperatures.

Specifically, cholesterol can decrease membrane fluidity under certain conditions by stabilizing the membrane structure and making it less permeable to small water-soluble molecules. This property is particularly important for keeping the integrity and function of the cell membrane under varying physiological conditions.

In summary, cholesterol modulates the fluidity of the membrane, ensuring that it remains functional across a range of temperatures, while also regulating permeability.