Key facts

  • Used as an energy reserve for respiration 
  • Soluble 
  • Can exits fats, oils and waxes 
  • Consists of two molecules, glycerol and fatty acids 
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  • Contain carbon, hydrogen and oxygen 
  • the proportion of oxygen through is way smaller than in carbohydrates 
  • infact unlike carbohydrates, lipids are not even polymers 
  • they are made of a glycerol, molecule and a new fatty acids.
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Role of lipids

They form Plasma membranes 

other uses = 

Energy source 

Water proofting 



Cell membrane 

Other (scented oils in plants attract insects)

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Are composed of a glycogen molecule and 3 fatty acids 

the glycerol and fatty acids are combined in a condensation 

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Fatty acids in more detail

There are about 70 different fatty acids 

They all have a carboxyl group which is what makes them an acid 

one double bond = mono-unsaturated and more than one double bond = poly-unsaturated 

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Saturated fat = A fat that contains only saturated fatty acids is a solid at room temperature 

unsaturated fat = A fat that is a liquid at room temperature and comes from a plant such as oil 

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The emulsions test

1. Grab a clean dry test - tube 

2. To around 2cm cubed of the sample add around 5cm cubed of ethanol 

3. Shake violently to dissolve the lipid in the sample 

4. Add 5cm cubed of water and shake less violently

5. If the content of the tube turens cloudy-white a lipid is present 

6. As a control, use water as a sample  

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