Final answer:
Cholesterol helps maintain the fluidity and rigidity of the cell membrane when interacting with phospholipids.
Step-by-step explanation:
Cholesterol, when interacting with phospholipids, helps maintain the fluidity and rigidity of the cell membrane. It acts as a buffer, preventing excessive changes in fluidity due to temperature changes. Cholesterol also organizes clusters of transmembrane proteins into lipid rafts. The more cholesterol present in the membrane, the more rigid it becomes.