Draw pictures and use words to explain the three functions listed below: 1. Cholesterol decreases membrane fluidity at high temperatures. Explain how the addition of cholesterol to the lipid bilayer would decrease membrane fluidity at high temperatures. 2. Cholesterol prevents crystallization of hydrocarbons in the membrane at low temperature. Explain how the addition of cholesterol to the lipid bilayer prevents crystallization of the alkyl chains. 3. Sterols decreases the permeability of the cell membrane to small water- soluble molecules. Explain how the addition of cholesterol to the lipid bilayer would decrease the permeability of the bilayer to water and water- soluble compounds. Cholesterol in Cell Membranes The cholesterol molecule inserts itself in the membrane because it also has some amphiphilic character. . . Circle the polar end. Put a box around the non-polar end. The cholesterol molecule inserts itself in the membrane with the same orientation as the phospholipid molecules. Add a cartoon of the cholesterol to the lipid bilayer below. . OO There are several IMFs involved in the insertion of the cholesterol into the phopholipid bilayer of a cell membrane or liposome. For each of the following interactions, circle the predominant IMF. The head:head interaction is: dipole-dipole hydrogen bonding The tail:tail interaction is: a. b. C. d. HO London Dispersion ion-ion London Dispersion Cholesterol (steroid) dipole-dipole hydrogen bonding ion-ion The water:head of the cholesterol interaction is: dipole-dipole London Dispersion hydrogen bonding The water:tails of cholesterol is attractive repulsive ion-ion ion-dipole ion-dipole ion-dipole