Lipids have following characteristics:
- Carbon, hydrogen and oxygen.
- Proportion of oxygen to carbon and hydrogen smaller than in carbohydrates.
- Insoluble in water.
- Soluble in organic solvents.
Main groups = triglycerides (fats and oils), phospholipids and waxes.
Roles of lipids
Plasma membranes - phospholipids = flexibility of membranes and transfer of lipid-soluble substances across them.
- Energy source - when oxidised provide more than twice the energy of carbohydrates.
- Waterproofing - insoluble, both plants and insects have waxy cuticles, mammals produce oily secretion from sebaceous glands.
- Insulation = fats are slow conductors of heat.
- Protection - stored around delicate organs.
Fats are solid at room temp, oils are liquid.
Triglycerides = 3 fatty acids with glycerol, each fatty acid forms…