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Chapter 17 Lipids. 17.3 Waxes, Fats, and Oils. Waxes. Waxes are esters of saturated fatty acids and long-chain alcohols coatings that prevent loss of water from leaves of plants. Fats and Oils: Triacylglycerols. Fats and oils are also called triacylglycerols esters of glycerol
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Chapter 17 Lipids 17.3Waxes, Fats, and Oils
Waxes Waxes are • esters of saturated fatty acids and long-chain alcohols • coatings that prevent loss of water from leaves of plants
Fats and Oils: Triacylglycerols Fats and oils are • also called triacylglycerols • esters of glycerol • produced by esterification • formed when the hydroxyl groups of glycerol react with the carboxyl groups of fatty acids
Triacylglycerols In a triacylglycerol, • glycerol forms ester bonds with three fatty acids
Formation of a Triacylglycerol Glycerol and three stearic acid molecules form a triacylglycerol named • glyceryl tristearate • tristearin
Olive Oil Olive oil • contains a high percentage of oleic acid, which is a monounsaturated fatty acid with one cis double bond
Learning Check What are the fatty acids in the following triacylglycerol?
Solution Stearic acid Oleic acid Myristic acid
Melting Points of Fats and Oils A triacylglycerol that is usually called a fat • is solid at room temperature • is prevalent in meats, whole milk, butter, and cheese A triacylglycerol that is usually called an oil • is liquid at room temperature • is prevalent in plants such as olive and safflower
Oils with Unsaturated Fatty Acids Oils • have more unsaturated fats • have cisdouble bonds that cause “kinks” in the fatty acid chains • cannot pack triacylglycerol molecules as close together as in fats • have lower melting points than do saturated fats • are liquids at room temperature
Diagram of Triacylglycerol with Unsaturated Fatty Acids Unsaturated fatty acid chains have kinks that do not allow close packing.
