Final answer:
Cholesterol molecules enhance membrane fluidity by filling in the gaps between phospholipids and buffering the effects of temperature on the membrane. This helps maintain the appropriate fluidity needed for membrane function.
Step-by-step explanation:
Cholesterol molecules enhance membrane fluidity by filling in the gaps between phospholipids in the hydrophobic interior of the membrane, reducing the lateral mobility of phospholipid and protein components. This reduces fluidity and membrane permeability to some ions. Additionally, cholesterol acts as a buffer, preventing lower temperatures from inhibiting fluidity and higher temperatures from increasing fluidity too much. It extends the temperature range in which the membrane is appropriately fluid and functional. Cholesterol also plays a role in organizing clusters of transmembrane proteins into lipid rafts.