Lipids

• lipids contain carbon, hydrogen and oxygen
• lipids are insoluble in water, theyre “water-hating” molecules (water is

  polar and is attracted more strongly to itself or other polar molecules than it is to non-polar lipids).
• lipids are non polar as they dont have a charge
• 
  

  lipids are said to be hydrophobic. They can however, be

  dissolved in organic solvents such as alcohol, propanone and ether

  
  

  this is bc alcohol dissolves membrane
• fats/oils are compounds called triglyceride.

  formed by condensation reaction

  this is between fatty acids and glycerol(alcohol)
• fatty acids in triglycerides have long hydrocarbon tails
• Fatty acids are acids because their functional group

  (-COOH) tends to ionise slightly to produce hydrogen ions, which is the

  property of an acid –
• -COOH ---------------------> -COO - + H +

  h+ GIVES ACIDIC CONDITIONS
• The –COOH functional group of these three organic acids react with the three -COH functional groups of glycerol to form a triglyceride.

  The bonds formed are known as ester bonds.

  Fats and oils are formed in this way and they have the same chemical structure. The only chemical difference between them is that at about 20C oils are liquids and fats are solids.
• fats and oils that are saturated have no double bonds (-C=C-) between the carbon atoms in their hydrocarbon tails,

  whereas unsaturated fats and oils have one or more.
• Fats containing several double bonds are called polyunsaturated.
• Fats with unsaturated fatty acids melt at a lower temperature than those with saturated fatty acids because their unsaturated hydrocarbon tails do not pack so closely together.

  This difference between saturated and polyunsaturated fats is important in the manufacture of margarine/butter spreads, since polyunsaturates perform better from the fridge.
• The roles of fats and oils in living things include:

  Energy Store – because of the hydrocarbon chain, lipids are energy

  rich, when broken down. When respired they provide double the energy

  Protection and Insulation –

  ● Protection of internal organs

  ● bark of trees

  ● Thermal insulation

  ● Electrical insulation – myelin sheath around nerve cells

  Waterproofing – wax is a form of structural lipid and is found on skin

  Water Storage
• Phospholipids have almost the same chemical structure  to triglycerides. EXCEPT,that one of the fatty acid groups is replaced by a phosphate group. Thephosphate group is ionised, having a negative charge, so water molecules areattracted to this part of the molecule. So phospholipids combine thehydrophobic properties of the hydrocarbon chain with the water-loving(water-loving properties) of the phosphate group.
• Phospholipids - have a very almost the same chemical structure to triglycerides, exceptthat one of the fatty acid groups is replaced by a phosphate group. The phosphate group is ionised, having a negative charge, so the H20 molecules attracted to this part of the molecule. So phospholipids combine

   the hydrophobic properties of the hydrocarbon chain with the 

  water-loving (water-loving properties) of the phosphate group.

   
• Cell membranes are made

  almost entirely of protein and lipid, together with a small and variable amount

  of carbohydrate. The lipids in cell membranes are phospholipids.