Lipids

• What are the two types of lipids 


  triglycerides and phospholipids
• Triglyceride Structure 


  Non polar

  monomer is one glycerol head connected to 3 fatty acid chains
• chemical formula group for fatty acid 


  RCOOH
• how can fatty acids vary

  Length f hydrocarbon chain (R group )

  or if saturated or unsaturated
• what are saturated and unsaturated fatty acids

  Saturated =no double bonds between carbon atoms

  Unsaturated = contain carbon to carbon double bond
• what are cis fatty acids 


  H atoms on same side of double bond in unsaturated fatty acid and can me metabolised by enzymes
• what are trans fatty acids 


  H atoms on opposite side of double bond in unsaturated fatty acid and can not be hydrolysed - linked to coronary heart disease
• which bonds to lipids form 


  form ester bonds when hydroxyl (-OH) group ln glycerol bonds with carboxyl (-COOH) group of fatty acid in a condensation reaction and a molecule of water removed
• how are triglycerides formed 


  By esterification 3 fatty acids join to one glycerol molecule by condensation reactions and 3 molecules of water released
• Functions of triglycerides 


  Energy storage - long hydrocarbon chains release energy when oxidised

  Hydrophobic so do not cause osmotic water uptake so more can be stored

  Oxidation of carbon hydrogen bonds release large number of water molecules
• functions of triglycerides Pt2


  insulation- part of myelin sheath that surrounds nerve fibres increases speed of transmission and can sit under skin to reduce heat loss

  buoyancy - low density increases animals ability to float

  protection -adipose tissue in mammals contains stored tri glycerides and helps protect organs from damage
• structure of phospholipids 


  monomers: contains one phosphate group which is bonded to a glycerol molecule that is bonded to two fatty acid chains
• phospholipid polarity 


  phosphate head is hydrophilic and polar and soluble

  fatty acid tails are non polar , hydrophobic and insoluble
• Role of phospholipids 


  Main component is cell membranes

  hydrophilic head faces outwards of cell and hydrophobic tails face inwards creating phospholipid bilayer
• How do phospholipids contribute to fluidity of cell membrane

  If manly saturated fatty acid tails membrane less fluid

  If there are mainly unsaturated fatty acid tails then the membrane will be more fluid
• how do phospholipids control membrane protein orientation

  Weak hydrophobic interactions between the phospholipids and membrane proteins hold the proteins within the membrane but still allow movement within the layer
• test for lipids 


  Emulsion test - qualitative test

  add ethanol to sample and shake to mix , then add water to test tube and shake if lipid present milky emulsion will form ( appears cloudy )