Chapter 17 Lipids

1. Chapter 17 Lipids 17.3Waxes, Fats, and Oils

2. Waxes Waxes are • esters of saturated fatty acids and long-chain alcohols • coatings that prevent loss of water from leaves of plants

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

4. Triacylglycerols In a triacylglycerol, • glycerol forms ester bonds with three fatty acids

5. Formation of a Triacylglycerol Glycerol and three stearic acid molecules form a triacylglycerol named • glyceryl tristearate • tristearin

6. Olive Oil Olive oil • contains a high percentage of oleic acid, which is a monounsaturated fatty acid with one cis double bond

7. Learning Check What are the fatty acids in the following triacylglycerol?

8. Solution Stearic acid Oleic acid Myristic acid

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

10. 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

11. Diagram of Triacylglycerol with Unsaturated Fatty Acids Unsaturated fatty acid chains have kinks that do not allow close packing.

12. Saturated and Unsaturated Fatty Acids In Fats and Oils