General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.1 Chapter 17 Lipids 17.3 Waxes, Fats, and Oils

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.2 Waxes Waxes are  esters of saturated fatty acids and long-chain alcohols  coatings that prevent loss of water from leaves of plants

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.3 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

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.4 In a triacylglycerol,  glycerol forms ester bonds with three fatty acids Triacylglycerols

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.5 Formation of a Triacylglycerol Glycerol and three stearic acid molecules form a triacylglycerol named  glyceryl tristearate  tristearin

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.6 Olive Oil Olive oil  contains a high percentage of oleic acid, which is a monounsaturated fatty acid with one cis double bond

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.7 Learning Check What are the fatty acids in the following triacylglycerol?

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.8 Solution Stearic acid Oleic acid Myristic acid

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.9 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

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.10 Oils with Unsaturated Fatty Acids Oils  have more unsaturated fats  have cis double 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

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.11 Diagram of Triacylglycerol with Unsaturated Fatty Acids Unsaturated fatty acid chains have kinks that do not allow close packing.

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.12 Saturated and Unsaturated Fatty Acids In Fats and Oils