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Simple Lipids Building Blocks of Lipids Draw each of the following: • Fatty acids • Glycerol Reference • Glucose • Phosphoric acid • Choline • Sphingosine • Sterol Fatty Acids: • Long chain carboxylic acids (10-20 c’s) • Usually have an even number of carbons, are unbranched and have no other functional groups attached. • In water, fatty acids will form micelles. Lipid • A biological compound that is soluble only in non-polar solvents, generally containing fatty acids or sterols. Simple Lipids (waxes, fats & oils) = Lipids formed primarily from fatty acids Found as biological food stores, protective coatings and cleansing systems. • Can be saturated (no C=C bonds) or unsaturated (has C=C bonds) • Fatty acid melting points decrease as the number of C=C bonds increases. • Most unsaturated fatty acids are liquids at room temperature. • Fatty acids with C=C bonds cannot pack closely together because of shape. This leads to decreased intermolecular attractions and lower melting points. 1 • • The unstaturated fatty acids usually contain double bonds in the cis configuration. The cis C=C causes “kinking” of the carbon chain. • These kinks prevents polyunsaturated fatty acids from packing close together, resulting in weaker attractive forces and lower melting points. Fatty Acids to Know: Saturated Unsaturated Butryic Mystric Palmitic Stearic Arachidic Oleic Linoleic Linolenic Arachidonic Waxes • Esters of fatty acids and long chain alcohols • Water insoluble and not easily hydrolyzed. Often found in protective coatings. Natures Waterproofing Essential Fatty Acids: = Those needed by the body, but not synthesized within the body in adequate amounts. • For humans, linoleic and linolenic acid are essential, but easily obtainable from plant and fish oils. Triglycerides • (triglycerols) which are triesters of long chained fatty acids and glycerol. 2 Simple Triglycerides Comprised with only one fatty acid on a glycerol backbone. Structure of a mixed triglycerol in which three different fatty acid residues are present. Mixed Triglycerides Contain different fatty acids on the same glycerol backbone. Fats and Oils • Triglycerides that are solid at room temperature are called FATS. • Usually from animal sources. • Contain a high degree of saturated fatty acids. • Triglycerides that are liquid at room temperature are called OILS. Representative triglycerols from a fat and an oil. The greater the number of unsaturated fatty acids, the more likely the triglyceride is to be an oil. • Usually from plant and fish sources. • Are liquids at room temperature. • Contain more unsaturated fatty acids. From the graphs below, we can see that different sources contain vastly different degrees of saturated and unsaturated fatty acids. Another graph showing fatty acid compositions of common fats and oils. 3 Simple lipids undergo 5 basic reactions 1. Esterification - of Glycerol and Fatty acids form triglycerides. 1. Esterification 2. Hydrolysis 3. Saponification 4. Hydrogenation 5. Oxidative Rancidity 2. Hydrolysis – important for fat and oil digestion. 4. Hydrogenation - Double bonds of unsaturated fatty acids are hydrogenated - decreases the degree of unsaturation, used to make margarines from oils. Glycerol Tristerate 3. Saponification – the commercial production of the carboxylate salts of fatty acids in triglycerides (soaps). 5.Oxidative Rancidity - the oxidation of double bonds of fatty acids in fats and oils - Results in the formation of a small carboxylic acid and an aldehyde. - Responsible for the foul odor associated with fat decomposition. Partially vs. hydrogenated 4
