Final answer:
Cholesterol impacts fluidity and rigidity in the cell membrane by controlling its rigidity and maintaining membrane fluidity.
Step-by-step explanation:
Cholesterol impact fluidity and rigidity in the cell membrane. Cholesterol interspersed between phospholipids in the membrane controls its rigidity. The higher the proportion of cholesterol, the more rigid the membrane becomes. Additionally, cholesterol helps maintain membrane fluidity by filling in gaps between phospholipids, preventing lower temperatures from inhibiting fluidity and preventing increased temperatures from increasing fluidity too much.