Lipids

• • Lipids are non polar and insoluble in water as well as being hydrophobic , they aren’t polymers
  • Known as macromolecules
  • Made of carbon , hydrogen and oxygen
• Three main groups of lipids

  • triglycerides
  • phospholipids
  • waxes
• Roles :

  • provide flexibility in plasma membranes
  • energy source
  • provide waterproofing
  • thermal insulation
  • protection around vital organs
  • hormone production
  • buoyancy for aquatic animals
• Triglycerides made up of four parts

  • 1 glycerol
  • 3 fatty acids ( carboxyl family )

  When they join together using condensation reactions they create ester bonds COOH
• Fatty acids

  • saturated = no carbon carbon double bond ( butter )
  • mono unsaturated = has 1 carbon carbon double bond ( oil )
  • poly unsaturated = has more than one carbon carbon double bond
• Phospholipids made up of four parts

  • 1 glycerol
  • 2 fatty acids
  • phosphate group
• Phospholipids

  • fatty acids make them hydrophobic
  • phosphate molecules make them hydrophilic
  • creating a phospholipid bilayer ( important in cell and organelle membranes )
• Sterols

  • complex alcohol molecule with a hydroxyl group ( polar )
  • hydrophobic and hydrophilic end
  • e.g cholesterol
• Cholesterol

  • made in liver and intestines
  • important in cell membrane
  • hydroxyl group
  • controls fluidity of cell membrane
  • keep membrane fluid at low temperature and stops membrane becoming too fluid at high temperatures
• TESTING FOR LIPIDS - EMULSION TEST

  • place sample in test tube
  • add 1cm3 of ethanol
  • shake and adid 1cm3 water
  • positive result forms milky white emulsion