Transcript CH_15_3_Waxes_Fats_Oils

Chapter 15 Lipids
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15.3
Waxes, Fats, and Oils
Waxes are esters of long-chain alcohols and fatty acids.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Waxes
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Waxes are
• esters of saturated fatty acids and long-chain alcohols
• coatings that prevent loss of water by leaves of plants
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Fats and Oils: Triacylglycerols
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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
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
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Triacylglycerols
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In a triacylglycerol, glycerol forms ester bonds with three
fatty acids.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Formation of a Triacylglycerol
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In a triacylglycerol, three hydroxyl groups on a glycerol
molecule form ester bonds with the carboxyl groups of
three fatty acids.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Triacylglycerols
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Triacylglycerol may contain different fatty acids.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
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What are the fatty acids in the following triacylglycerol?
O
CH2
O
C
(CH2)16CH3
O
CH
CH2
O
O
C (CH2)7CH CH(CH2)7CH3
O
C
(CH2)12CH3
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
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What are the fatty acids in the following triacylglycerol?
O
CH2
O
C
Stearic acid
(CH2)16CH3
O
CH
CH2
O
O
C (CH2)7CH CH(CH2)7CH3
O
C
(CH2)12CH3
Oleic acid
Myristic acid
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Melting Points of Fats and Oils
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A fat
• is usually solid at room temperature
• is prevalent in meats, whole milk, butter, and cheese
An oil
• is usually liquid at room temperature
• is prevalent in plants such as olive and safflower
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Oils with Unsaturated Fatty Acids
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Oils
• have more unsaturated fats
• have cis double bonds that cause “kinks” in the fatty
acid chains
• with “kinks” in the chains do not allow the triacylglycerol
molecules to pack closely
• have lower melting points than saturated fatty acids
• are liquids at room temperature
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Diagram of Triacylglycerol with
Unsaturated Fatty Acids
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Unsaturated fatty acid chains
with kinks cannot pack closely.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Percent Saturated and Unsaturated
Fatty Acids in Fats and Oils
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Vegetable oils have low melting points because they have a
higher percentage of unsaturated fatty acids than do animal fats.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
13
Draw the condensed structural formula of glyceryl
trilinoleate (trilinolein).
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
14
Draw the condensed structural formula of glyceryl
trilinoleate (trilinolein).
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.