Lipids (fats and oils) |
Key Concepts
- A lipid is a fat, oil or wax.
- A lipid contains carbon, hydrogen and some oxygen atoms.
- Lipids are mixtures of glycerides, mostly triglycerides.
- Triglyceride means tri-esters of glycerol, and so lipids contain ester functional groups
- Triglycerides are formed in a condensation reaction between glycerol and fatty acids.
- A fatty acid is a long chain carboxylic acid.
- Fats are classified as saturated or unsaturated.
- A saturated fat contains only single bonds between the carbon atoms in the fatty acid componenet.
- An unsaturated fat contains 1 or more double bonds between the carbon atoms in the fatty acid component.
- An unsaturated fat can be classified as either monounsaturated or polyunsaturated.
- A monounsaturated fat contains only 1 double bond between the carbon atoms in the fatty acid component.
- A polyunsaturated fat contains more than 1 double bond between the carbon atoms in the fatty acid component.
Fatty Acids
Fatty acids are long chain carboxylic acids.
Fatty acids can be classified as:
- Unsaturated: only single bonds are present between the carbon atoms.
- Unsaturated: more than one double bond in the chain.
Unsaturated fatty acids can be classified as either:
- Monounsaturated: only 1 double bond between carbon atoms in the chain.
- Polyunsaturated: more than 1 double bond between carbon atoms in the chain.
| Type |
General Formula |
Example |
Properties |
|---|
Saturated
(no double bonds) |
CnH2n+1COOH |
CH3(CH2)14COOH
palmitic acidCH3(CH2)16COOH
stearic acid |
solids
unreactive
relatively non-polar
insoluble in water
more in animal fats |
|
Monounsaturated
(1 double bond) |
CnH2n-1COOH |
CH3(CH2)7CH=CH(CH2)7COOH
oleic acid |
softer than saturated fats
reactive
relatively non-polar
insoluble in water |
|
Polyunsaturated
(> 1 double bond) |
CnH2n-3COOH
(2 double bonds)CnH2n-5COOH
(3 double bonds) |
CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH
linoleic acid |
likely to be oils
reactive
relatively non-polar
insoluble in water
more in vegetable oils |
Formation of Trigylcerides (lipids)
A triglyceride is formed by the condensation reaction between glycerol and 3 fatty acid molecules. The products are a triglyceride (containing 3 ester functional groups) and water.
| glycerol |
+ |
fatty acids |
-----> |
triglyceride |
+ water |
| |
H
| |
|
| H- |
C |
-OH |
| |
| |
|
| H- |
C |
-OH |
| |
| |
|
| H- |
C |
-OH |
| |
|
H |
|
|
|
|
|
| |
H
| |
|
O
|| |
|
| H- |
C |
- O- |
C |
-(CH2)n-CH3 |
| |
| |
|
O
|| |
|
| H- |
C |
- O- |
C |
-(CH2)n-CH3 |
| |
| |
|
O
|| |
|
| H- |
C |
- O- |
C |
-(CH2)n-CH3 |
| |
|
H |
|
|
|
|
H2O |
| + |
|
-----> |
+ H2O |
| |
|
|
H2O |
|
|
|
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