Humber Admissions Practice Test

Which feature of cell membranes is attributed to cholesterol?

1. Fluidity and rigidity

2. Energy production

3. Passive transport facilitation

4. Cellular attachment

The correct answer is: Fluidity and rigidity

Cholesterol plays a significant role in maintaining the structure and functionality of cell membranes. It is primarily located within the phospholipid bilayer and interacts with the lipids and proteins that make up the membrane. One of the critical features that cholesterol contributes to is the balance between fluidity and rigidity of the membrane. It helps to stabilize the membrane's structure, preventing it from becoming too fluid at higher temperatures and too rigid at lower temperatures. This dual function allows for membrane flexibility while preserving essential cellular processes. The presence of cholesterol ensures that the cell membrane remains functionally versatile, allowing for proper signaling, transport, and interaction with the environment. By modulating the viscosity of the membrane, cholesterol enables cells to maintain homeostasis and optimize the function of membrane proteins. Other options do not accurately reflect the role of cholesterol. While energy production is a function associated with cellular mitochondria, passive transport is more directly related to the phospholipid bilayer and specific channel proteins. Cellular attachment typically involves proteins and carbohydrates, not cholesterol. Thus, the contribution of cholesterol to fluidity and rigidity is a fundamental characteristic essential for the overall integrity and function of cell membranes.