3.1.3 Lipids

• Test for lipid

  Crush + grind food in ethanol

  Filter + collect filtrate

  Add water, bung and shake

  Positive result = white emulsion
• Bond in a lipid

  Ester bond

  
• Triglycerides

  Main function - energy storage molecules, insulation

  most common lipids in nature

  1 glycerol + 3 fatty acids (hydrocarbon tails)

  
• Fatty acids - long chain hydrocarbons with a carboxyl group at one end

  • Saturated - contains only single bonds between carbon atoms
  • Unsaturated - contains at least one double carbon bond

  
• Phospholipids

  • Main function is to make cell membranes
  • Contains a phosphate group
  • Only two hydrocarbon tails
  • Hydrophilic head - polar, will react with water - faces outwards
  • Hydrophobic tail - non-polar, won't react with water - faces inwards