AP BIOLOGY

Detailed explanation-1: -Because of its rigid ring structure, cholesterol plays a distinct role in membrane structure. Cholesterol will not form a membrane by itself, but inserts into a bilayer of phospholipids with its polar hydroxyl group close to the phospholipid head groups (see Figure 12.2).

Detailed explanation-2: -Acting as essential building blocks of the plasma membranes, cholesterol plays pivotal roles in maintaining the structural integrity and regulating the fluidity of cell membranes [17–20], therefore contributing to the homeodynamics of various membrane proteins on the cell surface.

Detailed explanation-3: -Cholesterol helps to restrict the passage of molecules by increasing the packing of phospholipids. Cholesterol can fit into spaces between phospholipids and prevent water-soluble molecules from diffusing across the membrane.

Detailed explanation-4: -Cholesterol is a major structural component of the plasma membrane (PM). The majority of PM cholesterol forms complexes with other PM lipids, making it inaccessible for intracellular transport.