Download 3. Wax, Fats, and Oils

Chapter 17 Lipids
17.3
Waxes, Fats, and Oils
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
1
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.
2
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.
3
Triacylglycerols
In a triacylglycerol,
 glycerol forms ester bonds with three fatty acids
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
4
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.
5
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.
6
Learning Check
What are the fatty acids in the following triacylglycerol?
O
CH2 O C
(CH2)16
CH3
O
CH O C
(CH2)7
CH CH
(CH2)7 CH3
O
CH2 O C
(CH2)12 CH3
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
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Solution
O
CH2 O C
(CH2)16
CH3
Stearic acid
O
CH O C
(CH2)7
CH CH
(CH2)7 CH3
Oleic acid
O
CH2 O C
(CH2)12 CH3
General, Organic, and Biological Chemistry
Myristic acid
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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.
9
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.
10
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.
11
Saturated and Unsaturated Fatty
Acids In Fats and Oils
General, Organic, and Biological Chemistry
Copyright © 2010 Pearson Education, Inc.
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