ch23 - Chapter 23 Lipids Introduction Lipids are compounds...

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Chapter 23 Lipids
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Chapter 23 2 Introduction Lipids are compounds of biological origin that dissolve in nonpolar solvents such as chloroform and diethyl ether Lipids are defined by the physical operation used to isolate them Lipids include a variety of structural types, represented by the following examples:
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Chapter 23 3 Fatty Acids and Triglycerides Most long-chain carboxylic acids of biological origin are found as esters (b) of glycerol(a) Oils from plants and fats of animal origin are triacylglycerols Oils are generally liquids at room temperature, fats are solid Hydrolysis of tracylglyerols yields fatty acids Most natural fatty acids have unbranched chains with an even number of carbon atoms In natural unsaturated fatty acids the double bonds are all cis and are usually not conjugated
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Chapter 23 4 » Insert table 23.1 page 1132
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Chapter 23 5
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Chapter 23 6 Saturated fatty acids have higher melting points than unsaturated fatty acids Saturated fatty acids adopt a fully extended conformation, pack well, and have strong van der Waals attractions between molecules Cis double bonds in unsaturated fatty acids put bends in the chain Unsaturated fatty acid chains pack poorly and have weaker van der Waals attractions between molecules than saturated fatty acids Unsaturated fatty acids have lower melting points than saturated fatty acids with the same number of carbons Triacylglycerols with a higher content of saturated fatty acids have higher melting points Triacylglycerols in animal fats contain mostly saturated fatty acids and are solids are room temperature Triacylglycerols in oils have a large proportion of unsaturated and polyunsaturated fatty acids and are therefore liquids are room temperature
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Chapter 23 7
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Chapter 23 8 Hydrogenation of Triacylglycerols Liquid vegetable oils can be partially hydrogenated to yield solid cooking fats Partial hydrogenation isomerizes some of the cis double bonds to trans double bonds “Trans” fats have been associated with increased risk of cardiovascular disease
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Chapter 23 9 Biological Functions of Triacylglycerols Triacylglycerols are primarily used as an energy reserve in animals When they are metabolized they yield more than twice the amount of energy per gram that carbohydrates do Fats are a form of long-term energy storage, whereas carbohydrates are a source of rapid-release energy Saponification of Triacylglycerols Basic hydrolysis of triacylglycerols yields salts of carboxylic acids and glycerol
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Chapter 23 10 Salts of long-chain carboxylic acids are called
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ch23 - Chapter 23 Lipids Introduction Lipids are compounds...

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