AP BIOLOGY

Detailed explanation-1: -The cholesterol molecules enhance the permeability-barrier properties of the lipid bilayer. They orient themselves in the bilayer with their hydroxyl groups close to the polar head groups of the phospholipid molecules.

Detailed explanation-2: -Abstract. The role of cholesterol in bilayer and monolayer lipid membranes has been of great interest. On the biophysical front, cholesterol significantly increases the order of the lipid packing, lowers the membrane permeability, and maintains membrane fluidity by forming liquid-ordered–phase lipid rafts.

Detailed explanation-3: -The cholesterol holds the phospholipids together so that they don’t separate too far, letting unwanted substances in, or compact too tightly, restricting movement across the membrane.

Detailed explanation-4: -Cholesterol molecules insert into the bilayer with their polar hydroxyl groups close to the hydrophilic head groups of the phospholipids (Figure 2.47). The rigid hydrocarbon rings of cholesterol therefore interact with the regions of the fatty acid chains that are adjacent to the phospholipid head groups.

Detailed explanation-5: -Properties of the Phospholipid Bilayer: The bilayer is held together by weak hydrophobic interactions between the tails. Hydrophilic / hydrophobic layers restrict the passage of many substances. Individual phospholipids can move within the bilayer, allowing for membrane fluidity and flexibility.