AS Biological Tests

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  • Created by: Closey
  • Created on: 19-09-16 11:49
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  • Biological AS Tests
    • Test for lipids
      • 1. Take a completely dry and grease-free test tube
      • 2. To 2cm^3 of sample, add 5cm^3 of ethanol
      • 3. Shake the tube thoroughly (to dissolve any lipid in the sample)
      • 4. Add 5cm^3 of water and shake gently
      • 5. A cloudy-white colour indicates the presence of a lipid
    • Test for proteins (Biuret test)
      • 1. Place a sample of the solution to be tested in a test tube and add an equal volume of sodium hydroxide solution
      • 2. Add a few drops of very dilute copper (II) sulphate solution and mix gently
      • 3. If a protien is present, the solution will go a  purple colour. If not, it will remain blue
    • Test for reducing sugars (Benedict's test)
      • 1. Add 2cm^3 of sample to a test tube (if it is not already liquid, first grind it in water)
      • 2. Add an equal volume of Benedict's
      • 3. Heat the mixture in a gently boiling water bath for five minutes
      • 4. A red colour shows the presence of a reducing sugar
    • Test for starch
      • 1. Place 2cm^3 of sample into a test tube
      • 2. Add two drops of iodine solution and shake or stir
      • 3. A blue-black colour indicates the presence of starch
    • Test for non-reducing sugars
      • 1. Carry out Benedict's test to confirm it is not a reducing sugar
      • 2. Add 2cm^3 to 2cm^3 of dilute HCl acid, and leave in a boiling water bath for five minutes
      • 3. Slowly add sodium hydrogencarbonate to neutralise the acid. Check the solution is alkaline
      • 4. Repeat Benedict's


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