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…