25: Lipids
- Page ID
- 183187
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- 25.1: Introduction
- Although many lipids have complex structures, they are all insoluble in water. The major lipid classifications are: fatty acids, steroids, waxes, triglycerides (fats and oils), phospholipids, sphingolipids, glycolipids, terpenes, and prostaglandins (eicosanoids).
- 25.2: 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.
- 25.3: Saponification of Fats and Oils; Soaps and Detergents
- Soaps are the carboxylate salts of fatty acids, while detergents are sulfonate salts with long hydrocarbon tails.
- 25.4: Phospholipids
- Phospholipids are the main constituents of cell membranes.
- 25.5: Prostaglandins and other Eicosanoids
- 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.
- 25.6: Terpenes and Terpenoids
- The terpenoids are an estimated 60% of known natural products and a diverse group of lipids derived from five-carbon isoprene units assembled in thousands of combinations. Technically a terpenoid contains oxygen, while a terpene is a hydrocarbon, however, the two terms are commonly used to refer collectively to both groups.
- 25.7: Steroids
- Steroids may be recognized by their tetracyclic skeleton consisting of three fused six-membered and one five-membered ring.
- 25.8: Biosynthesis of Steroids
- A series of cation-like cyclizations and rearrangements, known as the Stork-Eschenmoser hypothesis, were identified in the biosynthesis of the triterpene lanosterol. Lanosterol is a precursor in the biosynthesis of steroids.