Lipids

• Describe how a phospholipid is formed

  1 glycerol 2 fatty acids and a phosphate group are joined together by an ester bond during a condensation reaction.
• Describe how you would test for the presence of lipids

  • small sample is dissolved in ethanol
  • added to water in another test tube and shake
  • white emulsion indicates that lipids are present
• Describe the adaptations of triglycerides for their function

  • posses a high proportion of C-H bonds therefore release twice as much energy as carbohydrates during aerobic respiration
  • High ratio of hydrogen to oxygen atoms which releases water when respired
  • Non polar so insoluble - ideal as a storage compound as they are osmotically inactive
• Describe how you would hydrolyse lipids

  • Heat with acid or alkali
  • use lipase at its optimum temperature and pH
• Describe the arrangement and function of the phospholipid bilayer

  • phospholipid molecules have a polar hydrophilic head containing the phosphate group and a non polar hydrophobic tail consisting of the long fatty acid chains
  • forms a bilayer of phospholipids due to the hydrophobic tails being attracted to each other and away from water
  • phospholipid bilayer enables lipid soluble molecules to pass quickly through cell membranes
• Describe how triglycerides are formed

  3 fatty acids combine to 1 glycerol molecule during a condensation reaction with the loss of 3 water molecules and the formation of 3 ester bonds.
• Describe the difference between saturated and unsaturated molecules

  saturates = no double bonds between carbon atoms

  unsaturated = one or more carbon carbon double bond