three groups of lipids are?
The important class of lipids called steroids are actually metabolic derivatives of terpenes, but they are customarily treated as a separate group. Steroids may be recognized by their tetracyclic skeleton, consisting of three fused six-membered and one five-membered ring, as shown in the diagram to the right.
The triesters of fatty acids with glycerol (1,2,3-trihydroxypropane) compose the class of lipids known as fats and oils. These triglycerides (or triacylglycerols) are found in both plants and animals, and compose one of the major food groups of our diet.
While fat and oil lipids have three fatty acid chains joined to a glycerol molecule, phospholipids have two chains joined to the glycerol with a phosphate group, which you might have guessed from the first part of this lipid type's name. Phospholipids are the main constituent of cell membranes.