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  • Created by: JasmineR
  • Created on: 25-10-15 17:59

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

  • They contain cabon, 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 and acetone.

The main groups of lipids are triglycerides and phospholipids.

Roles of lipids:

  • Source of energy - when oxidised, lipids provide more than twice the energy as the same mass of carbohydrate and release valuable water. 
  • Waterproofing - lipids are insoluable in water and therefore useful as a waterproofing. Both plants and insects have waxy, lipid cuticles that conserve water, while mammals produce an oily secretion from the sabaceous glands in the skin. 
  • Insulaiton - fats are slow conductors of heat and when stored beneath the body surface help to retain body heat. They also act as electrical insulators. 
  • Protection - fat is often stored around delicate organs, such as the kidney. 


  • They get their name because they have three (tri) fatty acids and one glycerol (glyceride) molecule. 
  • Each fatty acid forms an ester bond with glycerol in a condensation reaction. (Hydrolysis therefore produces one glycerol molecule and three fatty acids).
  • The glycerol molecule in all triglycerides is the same, the difference in properties of different fats and oils comes from variations in the fatty acids. 
  • There are over 70 different fatty acids and all have a carboxyl ( -COOH) group with a hydrocarbon chain attached. 
  • A saturated triglyceride has no double bonds between carbon atoms.
  • A mono-unsaturated triglyceride has one double bound between carbon atoms. 
  • A poly-unsaturated triglyceride…


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