Chapter 25 Lipids Jo Blackburn Richland College, Dallas, TX Dallas County Community College District 2006, Prentice Hall Organic Chemistry, 6 th Edition L. G. Wade, Jr.
Chapter 252 Introduction Classified by solubility, not structure. Can be extracted from cells by nonpolar organic solvents. Complex lipids are easily hydrolyzed. Waxes Triglycerides Simple lipids are not easily hydrolyzed. Steroids Prostaglandins Terpenes =>
Chapter 253 Examples of Lipids =>
Chapter 254 Waxes Esters of long-chain fatty acids with long-chain alcohols. Spermaceti is found in the head of the sperm whale and is probably used to control buoyancy. Most natural waxes are protective coats for plants’ leaves, insects’ exoskeletons, mammals’ fur, and birds’ feathers. =>
Chapter 255 Triglycerides Fatty acid esters of glycerol. Fats Solid at room temperature Most are derived from mammals Oils Liquid at room temperature Most are derived from plants or cold- blooded animals. =>
Chapter 256 Fatty Acids Unbranched carboxylic acids with carbons. Most contain an even number of carbons because they are built from acetic acid units. Melting points increase with increasing molecular weights. Unsaturation greatly lowers the melting point. =>
Chapter 257 Melting Points A cis double bond bends the molecule so it cannot pack efficiently. A trans double bond has less effect. =>
Chapter 258 Fats and Oils Most fats have saturated fatty acids. Most oils have unsaturated fatty acids. =>
Chapter 259 Saponification “Soap-making” Base-catalyzed hydrolysis of ester linkages in fats and oils. A soap =>
Chapter 2510 Soap Structure =>
Chapter 2511 Grease in Soap Solution =>
Chapter 2512 Detergents =>
Chapter 2513 Phospholipids Contain a phosphate ester bond. Phosphoglycerides usually have one phosphoric acid group and two fatty acids. The phosphate may have an additional alcohol attached by an ester linkage. =>
Chapter 2514 Lipid Bilayer Cell membranes are a bilayer of phosphoglycerides =>
Chapter 2515 Steroids Polycyclic, usually all trans. Common structural features: =O or -OH at C3 Side chain at C17 Double bond from C5 to either C4 or C6. =>
Chapter 2516 A-B Ring Junction May be cis, but usually is trans. =>
Chapter 2517 Cholesterol Common biological intermediate. Probably a precursor to other steroids. Side chain at C17 and double bond C5-C6. =>
Chapter 2518 Sex Hormones Female hormone has an aromatic ring and one less methyl group than the male hormone. Testosterone is converted to estradiol in the ovaries. =>
Chapter 2519 Prostaglandins Biochemical regulators more powerful than steroids. Regulate functions such as: Blood pressure Blood clotting Allergic response Digestive activity Labor onset =>
Chapter 2520 Structure of Prostaglandins Cyclopentane ring with two long side chains trans to each other. Most have 20 carbon atoms. Derived from arachidonic acid. =>
Chapter 2521 Terpenes Composed of 5-carbon isopentyl groups. Isolated from plants’ essential oils. C:H ratio of 5:8, or close to that. Pleasant taste or fragrant aroma. Examples: Anise oil Bay leaves =>
Chapter 2522 Structure of Terpenes Two or more isoprene units, 2-methyl-1,3- butadiene with some modification of the double bonds. myrcene, from bay leaves =>
Chapter 2523 Classification Terpenes are classified by the number of carbons they contain, in groups of 10. A monoterpene has 10 C’s, 2 isoprenes. A diterpene has 20 C’s, 4 isoprenes. A sesquiterpene has 15 C’s, 3 isoprenes. =>
Chapter 2524 Terpenoids =>
Chapter 2525 End of Chapter 25