Explain how the structure of cholesterol enables it to perform structural and functional roles within membranes

The plasma membrane is a continuous double layer of phospholipids which are intertwined with the help of cholesterol and proteins. Cholesterol is an amphipatic molecule, meaning it has a hydrophilic and hydrophobic portion. A part of the steroid ring is closely attracted to the fatty acid chains on the phospholipids which helps to immobilize the outer surface of the membrane. 

Cholesterol also helps to build the lipid rafts that secure the proteins while passing through membrane canals, so it participates in the process of information exchange between the cells.