AP BIOLOGY

Detailed explanation-1: -Cholesterol molecules also keep the phospholipid tails from coming into contact and solidifying. This ensures that the cell membrane stays fluid and flexible. Some plasma membrane proteins are located in the lipid bilayer and are called integral proteins.

Detailed explanation-2: -What: The plasma membrane is strong and flexible because of its phospholipid structure that keeps them together while allowing the membrane to be fluid.

Detailed explanation-3: -The fatty acids of most natural phospholipids have one or more double bonds, which introduce kinks into the hydrocarbon chains and make them difficult to pack together. The long hydrocarbon chains of the fatty acids therefore move freely in the interior of the membrane, so the membrane itself is soft and flexible.

Detailed explanation-4: -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-5: -Cholesterol is also a key determinant of membrane fluidity: at high temperatures, cholesterol acts to stabilize the cell membrane and increase its melting point; while at low temperatures, it inserts into phospholipids and prevents them from interfering with each other to avoid aggregation [39].