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Lipids: a large and varied group of organic compounds.
Lipids include:
Triglycerides
Phospholipids
Waxes
Cholesterol and Steroids
Lipids are all non-polar and do not dissolve in water
Triglycerides are one of the most common types of lipids
Triglycerides consist of one molecule of glycerol bonded to three fatty acid molecules
Each fatty acid is linked to the glycerol molecule by an ester bond
C C C
H
OH
H
H H
H
OH OH
Glycerol
Hydroxyl groups
Fatty Acids:
General Formula: CH3 (CH2)n C
O
OH
Carboxyl group
H C C C
H
H
H H
H H
C C C
H
H
H H
H H
C
O
OH
CH3 CH2
H C C C
H
H
H H
H H
C C C
H
H
H H
H H
C
O
OH
Can be drawn as:
C
O
OH
Forming a monoglyceride:
C
C
C
H OH
H
H
H
H
OH
OH
C
O
OH
C
C
C
H OH
H
H
H
H
OH
O C
O
+ H2O
Ester bond
Hydroxyl group and carboxyl group react
This is a condensation reaction
C
C
C
H O
H
H
H
H
O
O C
O
C
O
C
O
A triglyceride:
Can be drawn as:G
lyce
rol
Fatty acid
Fatty acid
Fatty acid
Ester bond
To split these ester bonds and separate a fatty acid from glycerol we need to add a molecule of water
C
C
C
H OH
H
H
H
H
OH
O C
O
+ H2O
C
C
C
H OH
H
H
H
H
OH
OH
C
O
OH
This is a hydrolysis reaction
Uses of Lipids in Living Things
1. Long-term energy stores
Human Adipose Tissue Plant Oils
2. Buoyancy for marine animals: lipids are less dense than water so help animals float
3. Insulation: a layer of fat beneath the skin cuts down heat loss
4. Production of water: fatty acids produce a lot of metabolic water when they are oxidised during respiration
e.g. C17H35COOH + 26 O2 18 CO2 + 18 H2O (a typical fatty acid)
Camels’ humps are made of fat
Homework:
Compare the relative advantages and disadvantages to an organism of using carbohydrates and lipids as energy stores
To be handed in on a separate sheet of paper.