- Sphingolipids are a second type of lipid found in cell membranes, particularly nerve cells and brain tissues. They do not contain glycerol, but retain the two alcohols with the middle position occupied by an amine.
- A wax is a simple lipid which is an ester of a long-chain alcohol and a fatty acid. The alcohol may contain from 12-32 carbon atoms. Waxes are found in nature as coatings on leaves and stems. The wax prevents the plant from losing excessive amounts of water.
Thumbnail: Sphingolipids consist of a long-chain base (green) amide linked to a fatty acid (black). Various modifications can be made to the basic structure (red) including desaturations (4, 8 and n-9), hydroxylations (2 & 4) and headgroups (R). (CC SA BY 4.0; Jonathan E. Markham at the Department of Biochemistry, University of Nebraska-Lincoln).