Transcript Chapter 17 Lipids 15.3 Waxes, Fats, and Oils Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings.

Chapter 17
Lipids
15.3
Waxes, Fats, and Oils
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
1
Waxes
Waxes are:
• esters of saturated fatty acids and long-chain alcohols.
• coatings that prevent loss of water by leaves of plants.
2
Fats and Oils: Triacylglycerols
Fats and oils are
• also called triacylglycerols.
• esters of glycerol.
• produced by esterification.
• fFormed when the hydroxyl
groups of glycerol react with the
carboxyl groups of fatty acids.
3
Triacylglycerols
In a triacylglycerol, glycerol forms ester bonds with
three fatty acids.
4
Formation of a Triacylglycerol
glycerol
+
three fatty acids
triacylglycerol
O
CH2
OH
CH
OH
CH2
OH
+
HO C
O
(CH2)14CH3
HO C
O
(CH2)14CH3
HO C
(CH2)14CH3
O
CH2 O C
(CH2)14CH3
O
CH O C
(CH2)14CH3 + 3H2O
O
CH2 O C
(CH2)14CH3
5
Learning Check
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
6
Solution
O
CH2
O
C
(CH2)16CH3
Stearic acid
O
CH
O
CH2
O
C (CH2)7CH CH(CH2)7CH3
O
C
(CH2)12CH3
Oleic acid
Myristic acid
7
Melting Points of Fats and Oils
A fat
• is solid at room temperature.
• is prevalent in meats, whole milk, butter, and cheese.
An oil
• is liquid at room temperature.
• is prevalent in plants such as olive and safflower.
8
Oils with Unsaturated Fatty Acids
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.
9
Diagram of Triacylglycerol with
Unsaturated Fatty Acids
Unsaturated fatty acid
chains with kinks cannot
pack closely.
10
Percent Saturated and Unsaturated
Fatty Acids In Fats and Oils
11