1. Lipids are complex organic compounds that made up of carbon, hydrogen and oxygen. Some lipids contain the elements nitrogen and phosphorus.
  2. The ratio of hydrogen atoms to oxygen atoms in a lipid molecule is higher than the 2 : 1 ratio in carbohydrates.
  3. Lipids are insoluble in water. However, they are soluble in other lipids and organic solvents such as alcohol and acetone.
  4. The basic units of lipids are fatty acids and glycerol. A lipid molecule is made up of one molecule of glycerol and three molecules of fatty acid.
(Formation of molecule of lipid)

Types of Lipids
  1. Examples of lipids include
    1. fats and oils (triglycerides), 
    2. waxes, 
    3. phospholipids
    4. steroids.
  2. Fats and oils (triglycerides)
    1. A triglyceride is formed from glycerol and three molecules of fatty acids through condensation.
    2. Triglycerides can be broken down into fatty acids and glycerol by hydrolysis.
    3. There are two types of fats.
      1. Saturated fats
        1. Fats containing saturated fatty acids
        2. are solids at room temperature.
      2. Unsaturated fats
        1. Fats containing unsaturated fatty acids
        2. usually Iiquid at room temperature
        3. it is called oil 
  3. Waxes
    1. Waxes are long chain esters.
    2. They are found in the cuticle of leaves.
    3. They are waterproof
    4. They can prevents entry of microorganisms and evaporation of water
  4. Phospholipids
    1. Phospholipids are component of plasma membrane.
    2. Example of phospholipid is lecithin. It is a type of triglyceride, which is the main constituent of the plasma membrane.
  5. Steroids
    1. Steroids include cholesterol and hormones such as testosterone, oestrogen and progesterone.
    2. Steroids have a basic structure which consists of four interconnected rings of carbon atoms. Attached to this basic structure are side chains of different lengths.