At right is sphingomyelin , an example of a ceramide having a phosphocholine head group. Other ceramides are listed below. Sphingomelin, with a phosphocholine head group, is comparable in size and shape to the glycerophospholipid phosphatidyl choline. Sphingomyelin is a common constituent of the plasma membranes that constitute nerve myelin. Gangliosides are commonly found in the outer leaflet of the plasma membrane bilayer, with the sugar chains extending out from the cell surface.
Cholesterol is largely hydrophobic, but has one polar group, a hydroxyl , making it amphipathic .
Cholesterol is found in membranes, and is the precursor for synthesis of steroid hormones and vitamin D. Amphipathic lipids in association with water form complexes in which their polar regions are in contact with water and their hydrophobic regions are away from water. Various micelle structures. E.g., the spherical micelle is a stable configuration for amphipathic lipids with a conical shape, such as fatty acids . A bilayer . This is the most stable configuration for amphipathic lipids of more cylindrical shape, such as phospholipids .