Final answer:
The statement that the cell membrane normally contains substantial amounts of cholesterol is true. Cholesterol functions to regulate membrane fluidity, provides rigidity, and comprises about 30% of the membrane's structure.
Step-by-step explanation:
True, the cell (plasma) membrane normally contains substantial amounts of cholesterol. Cholesterol plays a critical role in the cell membrane by regulating its fluidity and providing rigidity. In animal cells, cholesterol is important for maintaining the structure of the membrane, especially in varying temperatures, functioning somewhat like antifreeze. It is more abundant in the cells of animals living in colder climates because it helps to prevent the membrane from becoming too rigid in the cold. Additionally, cholesterol is an integral component of the cell membrane and can often comprise around 30% of the membrane's structure, participating in signaling pathways and involved in the synthesis of vitamin D and steroid hormones.