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  • Lipids
    • Characteristics
      • Contain carbon, hydrogen, oxygen
      • Insoluble in water
      • Soluble in organic solvents e.g. alcohols/acetone
    • Roles
      • Source of energy
      • Waterproofing
      • Insulation
      • Protection
    • Triglycerides
      • Three fatty acids combined with glycerol
      • Each fatty acid forms ester bond with glycerol in condensation reaction
      • Large, non-polar, insoluble: their storage does not affect water potential
      • Release water when oxidised
      • Low mass to energy ratio, lots stored in small space.
    • Phospholipids
      • Hydrophillic head, hydrophobic tail.
      • Polar, form a bilayer within cell surface membrane (barrier)
      • Heads help hold them at surface of membrane
      • Structure allows them to form glycolipids by combining with carbohydrates. Glycolipids aid cell recognition.
    • Test for lipids
      • Take a dry, grease free test tube.
      • Add 5cm3 ethanol to 2cm3 sample.
      • Shake to dissolve lipid
      • Add 5cm3 water, shake gently
      • Cloudy white colour indicates presence of lipid
      • CONTROL: Repeat using water instead of sample- solution should remain clear


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