Learning Objectives When you have completed Chapter 13, you should be able to fulfill all of the detailed objectives listed under each individual section. distinguish among fats and oils, phospholipids, prostaglandins, terpenes and steroids, and be familiar with the sources and biological roles of these substances. define, and use in context, the key terms introduced in this chapter. 13.1: Introduction to Lipids 13.2: Waxes, Fats, and Oils Fats play an important role in human nutrition, and most people are aware of the desirability of limiting their dietary intake of saturated fats, as these compounds have been associated with heart disease. Unsaturated fats are generally considered to be much more desirable from the point of view of good health. Notice that all the fatty acids derived from naturally occurring fats have a Z (i.e., cis) configuration. 13.3: Soap 13.4: Phospholipids 13.5: Prostaglandins and Other Eicosanoids Prostaglandins were first discovered and isolated from human semen in the 1930s by Ulf von Euler of Sweden. Thinking they had come from the prostate gland, he named them prostaglandins. It has since been determined that they exist and are synthesized in virtually every cell of the body. Prostaglandins, are like hormones in that they act as chemical messengers, but do not move to other sites, but work right within the cells where they are synthesized. 13.6: Terpenoids 13.7: Steroids 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. 13.8: Biosynthesis of Steroids 13.9: Additional Problems 13.S: Biomolecules - Lipids (Summary)