Final answer:
Cholesterol functions as a buffer in the plasma membrane, maintaining fluidity across temperature changes by lying alongside phospholipids within the membrane.
Step-by-step explanation:
The truth about cholesterol is that it acts as a buffer to preserve the fluidity of the lipid bilayer in cell membranes under environmental extremes. Unlike a flexible planar structure, the cholesterol molecule is stiff due to restricted movements around its C-C bonds locked in the cyclic structure. Cholesterol helps in preventing lower temperatures from inhibiting fluidity and prevents increased temperatures from making the membrane too fluid. In animal cells, cholesterol is found within the plasma membrane, lying alongside the phospholipids, and works to extend the range of temperatures in which the membrane is appropriately fluid.