Lipids

• What are the 3 types of lipid?

  Triglyceride

  Phospholipid

  Steroid
• What are the common properties of these lipids?


  All contain carbon, hydrogen and oxygen.

  All are non-polar.

  All are insoluble in water, but soluble in organic solvents.
• What are triglycerides made of?


  3 molecules of fatty acids and 1 molecule of glycerol.

  Formed via a condensation reaction.

  Bonds formed are called ester bonds.
• How do you change what fatty acid is being made?


  Different number of carbon atoms

  or

  Double bonds between carbon atoms.
• What do fatty acids look like?


  A carboxyl group and a hydrocarbon tail with differing numbers of carbon atoms depending on the fatty acid.
• How many water molecules are formed when a triglyceride is formed?


  3
• When forming a triglyceride, which atoms are removed to form the water molecules?


  The OH group on the glycerol molecule (that was originally bonded to the C chain) and the H atom from the carboxyl group in the fatty acid.
• What can the structure of a triglyceride be written as when the hydrocarbon tail of the fatty acid is labelled as R?


  H This is because the OH has been replaced by the

  | carboxyl group (minus the H as this is now part of

  H-C-COOR the water molecule) from the fatty acid.

  H-C-COOR

  H-C-COOR

  |

  H
• What are the two types of fat?

  Saturated and unsaturated.
• What does it mean for a fat to be saturated?


  It has the maximum number of hydrogen atoms that it can.
• What does it mean for a fat to be unsaturated?


  It does not have the maximum number of hydrogen atoms possible, due to a C=C bond somewhere in the chain.
• Which type of fat is a solid at room temperature?

  Saturated fat.
• What do saturated fats contribute to?


  Coronary heart disease.
• Which type of fat is made by plants, and which by animals?

  Plants: Unsaturated fats Animals: Saturated fats.
• What is the structural difference between triglycerides and phospholipids?


  Phospholipids have a phosphate group and two fatty acid chains, while triglycerides have three fatty acid chains.
• Which part of the phospholipid is hydrophobic?


  The tail (fatty acids)
• Which part of the phospholipid is hydrophilic?


  The head (phosphate and glycerol)
• What are the functions of lipids?


  Waterproofing outside layers of organisms - e.g. skin or leaves

  Energy store - twice as much energy/gram than glucose

  Heat insulator - blubber

  Hormones - testosterone

  Protection of organs

  Membranes - formed from a phospholipid bilayer
• What is the positive result for the emulsion test?


  Formation of a milky white emulsion.
• How does the emulsion test for lipids work?


  The ethanol dissolves the lipids (which are insoluble in water) and so the droplets collect to form the white emulsion layer.