Phospholipids are complex lipids made up of fatty acids, alcohols, and phosphate. They are extremely important components of living cells, with both structural and metabolic roles. They are the chief constituents of most biological membranes. At one end of a phospholipid molecule is a phosphate group linked to an alcohol. This is a polar part of the molecule-it has an electric charge and is water-soluble (hydrophilic). At the other end of the molecule are fatty acids, which are non-polar, hydrophobic, fat soluble, and water insoluble. Because of the dual nature of the phospholipid molecules, with a water-soluble group attached to a water-insoluble group in the same molecule, they are called amphipathic or polar lipids. The amphipathic nature of phospholipids make them ideal components of biological membranes, where they form a lipid bilayer with the polar region of each layer facing out to interact with water, and the non-polar...