MODULE 5 - LIPIDS

• Lipids


  aka "fats"
• Lipids


  • Insoluble in water
  • Soluble in non-polar inorganic compounds such as Chloroform, Hexane, etc.
• Polar solvents (Hydrophilic)


  • Water
  • Acetic acid
  • Methanol
  • Ethanol
  • N-propanol
• Non-polar solvents (Lipophilic)


  • Chloroform
  • Carbon Tetrachloride
  • Methylene chloride
  • Diethyl ether
  • Benzene
• Classification of lipids according to biochemical functions

  • Energy-storage lipids
  • Membrane lipids
  • Emulsification lipids
  • Messenger lipids
  • Protective-coating lipids
• Burning fats produces more than twice as much energy than carbohydrates
• Membrane lipids


  • Amphipathic and complex (both hydrophilic and hydrophobic)
  • Two groups: Phospholipids and Glycolipids
• Fatty acids


  Basic unit of lipids, their building blocks
• Types of fatty acids

  • Saturated - all C-C bonds are single bonds
  • Monounsaturated - one C=C bond
  • Polyunsaturated - 2 or more C=C bonds present, up to six double bonds
• Fats and oils


  Naturally occurring mixed triglycerides
• Fats


  • Predominantly saturated
  • Solids/semisolids at room temperature
  • Predominantly obtained from animals
  • Tasteless, odorless, colorless
• Oils


  • Predominantly unsaturated
  • Liquids at room temperature
  • Obtained from plants and fish oil
  • Odorless, colorless
• Spotting Effect Test


  1. Samples: Ethyl Alcohol (Negative), Acetic acid (Negative), Coconut oil (Positive), Margarine (Positive)

  2. Interpretation: Lipids have higher boiling points than other substances, thus they evaporate slower, leaving a stain on the filter paper
• Solubility test


  Samples: Coconut Oil (Miscible in Hexane, Immiscible in Water, Ethanol, HCl, NaOH), Margarine (Soluble in Hexane, Insoluble in Water, Ethanol, HCl, NaOH)
• Test for Unsaturated Glycerides

  Halogenation (reaction with alcoholic Iodine): Coconut Oil (Orange-brown coloration, less unsaturation), Cottonseed oil (Lighter color change, more unsaturation)
• Saponifiable lipids


  Can be hydrolyzed to form fatty acid salts (soaps)
• Saponification


  1. First test tube (with heat) - Formation of bubbles, indication that soap was formed

  2. Second tube (without heat) - Less to no bubbles formed
• Cholesterol


  Most important and abundant steroid, Plasma membrane component (animal cells), Precursor for other steroid based lipids
• Salkowski Test


  1. Test for cholesterol: Chloroform (extracting solvent), Conc. Sulfuric Acid (dehydrating agent)

  2. Positive result: Red/Pink color, the solution becomes bluish red and slowly changes to a violet red, and the sulfuric acid becomes red with a green fluorescence
• Liebermann-Burchard Test


  1. Test for unsaturated steroids & cholesterol: Chloroform (extracting solvent), Conc. Sulfuric Acid (dehydrating agent), Acetic Anhydride

  2. Positive result: Pink to Green to Blue to Green