Final answer:
Cholesterol in plasma membranes of animals affects rigidity, temperature effects, and organization of proteins.
Step-by-step explanation:
The presence of cholesterol in the plasma membranes of some animals has several effects. First, it controls the rigidity of the membrane, making it more rigid with a higher proportion of cholesterol. Second, cholesterol dampens the effects of temperature on the membrane, acting as a buffer to prevent lower temperatures from inhibiting fluidity and higher temperatures from increasing fluidity too much. Lastly, cholesterol also functions in organizing clusters of transmembrane proteins into lipid rafts.