9/25/2009
Lipids
Types of Lipids
Types of Lipids
Fatty Acids
Fats, and Oils
Chemical Properties of Triglycerides
• Lipids with fatty acids
Waxes
Fats and oils (triglycerides)
Phospholipids
Sphingolipids
• Lipids without fatty acids
Steroids
1
Saturated and Unsaturated
Fatty Acids
Fatty Acids
• Long-chain carboxylic acids
• Insoluble in water
• Typically 12-18 carbon atoms (even
number)
• Some contain double bonds
corn oil contains 86%
unsaturated fatty
acids
and 14%
saturated fatty
acids
Saturated = C–C bonds
Unsaturated = one or more C=C bonds
COOH
palmitic acid, a saturated acid
COOH
palmitoleic acid, an unsaturated fatty acid
3
• Contain only single C–C bonds
Saturated fatty acids
• Fit closely in regular pattern
• Closely packed
COOH
COOH
COOH
• Strong attractions between chains
• High melting points
H
• Solids at room temperature
C C
cis double bond
4
Properties of Saturated
Fatty Acids
Structures
Unsaturated fatty acids H
• Cis double bonds
2
COOH
5
6
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9/25/2009
Properties of Unsaturated
Fatty Acids
Learning Check
• Contain one or more double C=C bonds
• Nonlinear chains do not allow molecules
to pack closely
• Few interactions between chains
• Low melting points
• Liquids at room temperature
How would the melting point of stearic
acid compare to the melting points of oleic
acid and linoleic acid? Assign the melting
points of –17°C, 13°C, and 69°C to the
correct fatty acid. Explain.
stearic acid (18 C) saturated
oleic acid (18 C) one double bond
linoleic acid (18 C) two double bonds
7
Fats and Oils
8
Triglycerides (triacylglcerols)
Formed from glycerol and fatty acids
Esters of glycerol and fatty acids
O
CH2 OH
HO C
O
+
CH
OH
CH2
OH
glycerol
ester bonds
(CH2)14CH3
O
CH2
HO C (CH2)14CH3
O
HO C
O
C
(CH2)14CH3 + H2O
O
CH
(CH2)14CH3
palmitic acid (a fatty acid)
CH2
O
O
C (CH2)14CH3
O
C
+ H 2O
(CH2)14CH3 +
H2O
10
Learning Check
Properties of Triglycerides
Hydrogenation
What are the fatty acids in the following
triglyceride?
• Unsaturated compounds react with H2
• Ni or Pt catalyst
• C=C bonds
C–C bonds
O
CH2
O
C
(CH2)16CH3
O
CH
CH2
O
O
C (CH2)7CH CH(CH2)7CH3
O
C
(CH2)12CH3
11
12
Hydrolysis
• Split by water and acid or enzyme
catalyst
• Produce glycerol and 3 fatty acids
14
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9/25/2009
Hydrogenation
Product of Hydrogenation
O
CH 2
O
CH2
O
CH
O
C
O
O
C
(CH2)5CH CH(CH2)7CH3
CH
Ni
+ 3 H2
CH 2
(CH2)5CH CH(CH2)7CH3
15
Hydrolysis
C
(CH2)14CH3
O
CH
O
CH2
H+
C (CH2)14CH3
O
O
C
O
O
C (CH 2)14CH 3
O
C
(CH2)14CH 3
Hydrogenation converts double bonds in oils
to single bonds. The solid products are used
to make margarine and other hydrogenated
items.
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• Hydrolysis with a strong base
• Triglycerides split into glycerol and the
salts of fatty acids
• The salts of fatty acids are “soaps”
• KOH gives softer soaps
O
O
(CH 2)14CH 3
Saponification and Soap
Triglycerides split into glycerol and
three fatty acids (H+ or enzyme
catalyst)
CH2
C
O
(CH2)5CH CH(CH2)7CH3
C
O
CH2
O
+3 H2O
(CH2)14CH3
CH2 OH
CH
OH
CH2
OH
O
+
3 HO C
(CH2)14CH3
17
Saponification
Learning Check
O
CH2
O
C
What are the products obtained from the
complete hydrogenation of glyceryl
trioleate?
(CH2)16CH3
O
CH
CH2
O
O
C
O
C
(CH2)16CH3 + 3 NaOH
(CH2)16CH3
CH2 OH
CH
CH2
18
O
+OH + 3 Na O C (CH2)14CH3
salts of fatty acids (soaps)
OH
19
(1) Glycerol and 3 oleic acids
(2) Glyceryltristearate
(3) Glycerol and 3 stearic acids
20
3