lipids

• lipids

  • macromolecules
  • non-polar
  • all contain C,H and O
  • 3 types triglycerides, phospholipids and cholesterol
• Triglycerides


  1 glycerol and 3 fatty acids

  synthesised by the formation of ester bonds between each fatty acid molecule

  One triglyceride has three ester bonds (each is formed by a condensation reaction)

  To break down a triglyceride 3 water molecules are needed (hydrolysis)
• Triglycerides - fatty acids

  long 'tails' made of hydrocarbons (tails are hydrophobic) make lipids insoluble

  two kinds saturated and unsaturated

  saturated - no double bonds between carbons

  unsaturated - have at least one double bond between carbon atoms

  A) saturated

  B) unsaturated

  
• Cholesterol 


  hydrocarbon ring structure attached to hydrocarbon tail

  hydroxyl group (polar) -> HO -> hydrocarbon rings -> hydrocarbon tail
• Function of triglycerides

  mainly used as an energy storage molecules (animals & plants)

  some bacteria use to store energy and carbon

  because long hydrocarbon tails contain lots of chemical energy (lots of energy released when broken down)

  insoluble - stops water entering via osmosis
• Function of phospholipids

  Found in the cell membrane (of all eukaryotes and prokaryotes) - phospholipid

  centre of the bilayer is hydrophobic (hydrophobic tails) so water soluble molecules can't pass through easily
• Function of cholesterol


  Regulate fluidity of the cell membrane by interacting with the phospholipid bilayer

  small size and flattened shape (allowing it to fit through the phospholipid molecules into the membrane)

  at high temperature bind to hydrophobic tails ->packed close together decreasing fluidity

  at low temperatures prevents packing -> increasing fluidity