Increasing the amount of cholesterol in a lipid bilayer has a unique effect on its melting temperature. Cholesterol molecules fit between the fatty acid chains of the phospholipids, disrupting the regular packing of the lipids. This disruption helps maintain fluidity in the membrane over a range of temperatures.
At higher temperatures, cholesterol can stabilize the bilayer and prevent it from becoming too fluid, while at lower temperatures, it can help prevent the fatty acid chains from packing too closely together, thus avoiding a solid-like state. As a result, the overall melting temperature may remain relatively balanced; excessive cholesterol could lead to a slight increase in melting temperature, but it often serves to keep membranes fluid rather than significantly raising the melting point like saturated fats do.