Midterms 8

• Lipids


  Water-insoluble organic biomolecules that can be extracted from cells and tissue by non-polar solvents like ether, chloroform, and benzene
• Saponifiable lipids


  Lipids that contain fatty acid components
• Non-saponifiable lipids


  Some lipids such as sterols
• Solubility test


  1. Objective: To test the solubility of oils in different solvents

  2. Principle: Fats are not dissolved in water due to their non-polar (hydrophobic) nature, but are soluble in organic solvents such as chloroform, benzene, and boiling alcohol. Different lipids have the ability to dissolve in different organic solvents.
• Solubility test method


  1. Place 1ml of Chloroform, Ethanol, Carbon tetrachloride, distilled water, and diluted NaOH

  2. Add 2 drops of olive oil and coconut oil

  3. Shake the tube thoroughly

  4. Note if it separated into two layers (oil not dissolved) or one homogenous transparent layer (oil dissolved)
• Grease spot test


  1. Objective: To see if there is an appearance of greasy spot indicating the presence of oils or fats

  2. Principle: Grease/fat have high boiling points so they are non-volatile. The spot of water can vaporize but the grease spot cannot, causing light diffraction and a translucent appearance.
• Grease spot test method


  1. Make a drop of oil and a drop of ethanol on filter paper

  2. After a few minutes, hold the paper up to the light to see which spot is translucent
• Halogenation test


  1. Principle: Unsaturated fatty acids with double bonds can take up halogens like bromine or iodine

  2. Application: Iodine number measures the amount of unsaturation in a fat
• Halogenation test method

  1. Prepare 3 test tubes with 1 drop of olive, coconut, and palmitic oil

  2. Add 1ml chloroform to each and shake well

  3. Add iodine solution dropwise until yellow color is obtained
• Emulsification of fats

  1. Objective: To determine if a substance can break down fats into smaller droplets and disperse them evenly in a liquid

  2. Principle: Fats are hydrophobic so emulsifiers can reduce surface tension and allow mixing with water-based liquids
• Emulsification test method

  First tube: 1ml water + 1 drop coconut oil

  2. Second tube: 1ml water + 1 drop coconut oil + 1 drop Na2CO3

  3. Third tube: 2ml water + 1 drop coconut oil + 2-5 drops soap solution

  Shake and allow to stand for 2 minutes