lipids

• lipids are

  made up of C,H and O
• 3 main types of lipids:

  • triglycerides= three fatty acids and glycerol
  • phospholipids = 2 fatty acids, glycerol and a phosphate group
  • steroids= 4 fused rings
• each fatty acid consists of

  • a carboxylic acid group (COOH)
  • a long hydrocarbon chain
  • a methyl group (CH3)
• fatty acids can be

  • saturated - no double bonds
  • monosaturated - one double bond between 2 carbon atoms
  • polyunsaturated - more than one double bond between carbon atoms
• Unsaturated fatty acids can be 


  • Cis - hydrogen atoms are on the same side of a double bond
  • Trans - hydrogen atoms are on opposite sides of a double bond
• Triglycerides


  • 3 fatty acid molecules bonded to a glycerol
  • fatty acids are bonded to glycerol by ester bonds formed during condensation reactions
• what is the test for lipids


  emulsion test
• structure and properties of phospholipids


  • 2 fatty acids bonded to the glycerol molecule on a phospholipid as one has been replaced by a phosphate ion
  • as the phosphate is polar and therefore insoluble in water
  • phospholipids are amphipathic (both hydrophobic/philic)
  • as a result phospholipids form monolayers or bilayers in water
• function of lipids


  • store energy
  • insulation
  • protection of vital organs
  • component of cell membranes
  • form the myelin sheath around some neurones
  • prevent evaporation in plants and animals
• structure and properties of phospholipids


  • 2 fatty acid bonded to glycerol molecule
  • phosphate is soluble in water (hydrophilic)
  • fatty acid tails non-polar and insoluble in water (hydrophobic)
  • phospholipids are amphipathic (both polar and non-polar)
  • form monolayers or bilayers
• function of phospholipids


  • building block of cell membranes
  • hydrophobic core created when phospholipid bilayer forms and acts as barrier to water molecules
  • hydrophilic heads form h-bonds with water allowing the cell membrane to be used to compartmentalise enabling the cells to organise specific roles into organelles helping with efficiency
• functions of phospholipids


  • composition of phospholipids contributes to the fluidity of cell membrane if mainly saturated then membrane less fluid, if more non-saturated then membrane is more fluid
  • phospholipids control membrane protein orientation and weak hydrophobic interactions between the phospholipids and membrane proteins hold the proteins within the membrane but still allow movement within the layer
• triglycerids vs phospholipids

  .

  A) 2

  B) yes

  C) no

  D) non-polar

  E) 3

  F) 3

  G) cell membrane component

  H) energy storage