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3. 3 Cleansing Action of Soap The carboxylate end of the long-chain molecule is ionic and therefore is preferentially dissolved in water The hydrocarbon tail is nonpolar and dissolves in grease and oil Soaps enable grease to be dissolved into water

4. 4 Phosphoglyceride Membranes Phosphoglycerides comprise the major lipid component of cell membranes Nonpolar tails aggregate in the center of a bilayer Ionic head is exposed to solvent

5. 5 27.4 Prostaglandins and Other Eicosanoids C 20 lipids that contain a five- membered ring with two long side chains Present in small amounts in all body tissues and fluids Hormones that have many physiological effects

6. 6 Prostaglandin Sources Biosynthesized from arachidonic acid (C 20 unsaturated fatty acid)

7. 7 27.5 Terpenoids Steam distillation of plant extracts produces “essential oils” Chemically related to compounds in turpentine (from pine sap) called terpenes and thus called terpenoids Mostly hydrocarbons (some oxygens) that do not contain esters (stable to hydrolysis)

8. 8 27.6 Steroids Steroids,are another class of nonsaponifiable lipid, defined by structure Has four fused rings A, B, C, and D, beginning at the lower left Carbon atoms are numbered beginning in the A ring The six-membered rings are in fixed chair conformations