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Lipids are a varied group of substances that share the following characteristics:

- They contain carbon, hydrogen and oxygen
- The proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates
- They are insoluble in water
- They are soluble in organic solvents such as alcohols…

Page 2

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The main group of lipids are triglycerides (fats and oils), phospholipids and waxes.

Triglycerides are so called because they have 3 fatty acids combined with glycerol

Tri = 3
Glyceride = glycerol molecules
Glycerol is an alcohol containing 3 carbon atoms with an ­OH group.

A fatty acid is…

Page 3

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A phospholipid is a lipid in which one of the fatty acids is replaced by a phosphate

The phosphate is hydrophilic ­ it attracts water

The phosphate group ionise which gives it a negative charge making it polar and so
attracts the water.

The fatty acid chain carries…

Page 4

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Test for Lipids
1. Clean test tube
2. Place sample in test tube
3. Add 5cm³ of ethanol
4. Shake tube until dissolved
5. Add 5cm³ of water
6. Shake gently

Results: cloudy ­ white suspension
The cloudy colour is due to any lipid in the sample being finely dispersed…


Sadam Hussain



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