Lipids

Lipids

Test for Lipids
1. Emulsion Test
  1. Add ethanol to sample in a test tube
    1. Shake test tube
      1. Add to water and any lipid shows as a milky emulsion
        More lipid equals more noticeable milky colour
Intro
1. Main groups are triglycerides and phospholipids
2. Insoluble in water
3. Soluble in alcohols and acetone
Triglycerides
1. Structure
  1. Triglycerides are molecule of glycerol and three fatty acids
    1. Fatty acid "tail" of triglyceride are hydrophobic - repel water molecules
      1. This makes lipids insoluble in water
2. Formation
  1. Glycerol and fatty acids combine by condensation reactions
    1. Forms an ester bond
    2. Hydrolysis therefore produces glycerol and three fatty acids
  2. Fatty acid chains can be saturated / unsaturated
    1. Saturated, no double C-C bonds
      1. Mono-unsaturated, one double bond
        Polyunsaturated, more than one double bond
        Unsaturated causes chain to bend
        Bend in the chain means they can not pack closely together
        Causes them to be liquid at room temp e.g. they are oils
3. Function
  1. Mainly used for energy storage
    1. Long tails contain many bonds that release chemical energy when broken down
      1. Contain more energy than carbohydrates
Phospholipids
1. Structure
  1. Phospholipids similar to triglycerides as one fatty acid is replaced by a phoshate group
    1. Polar molecule, phosphate end attacts water and fatty acids repel water
2. Function
  1. Forms a bilayer for cell membranes forming a hydrophobic barrier between outside and inside a cell
    1. Water soluble substances cant pass through
  2. Helps form glycolipids by combining phosphate group on membrane with carbs
    1. Important for cell recognition

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	Created by Dominic Weston almost 7 years ago