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OCR Categories Archives: Module 1: Development of Practical Skills in Biology

Practical Biochemistry Tests

Practical Biochemistry Tests

STARCH:

  • Add a solution of iodine to sample
  • If starch is present, iodine changes colour from yellow-brown to blue-black

REDUCING SUGARS:

  • Add Benedicts solution (alkaline copper sulphate) to sample
  • Heat in a water bath of 80oc
  • If reducing sugar is present it turns brick-red – if not present no change
  • Compare sample to know sugar contents in a colorimeter
  • If not present – do non-reducing sugar test
  • If present – compare on a graph to the know sugar contents solutions

NON-REDUCING SUGARS:

  • Make sure no reducing sugars in sample
  • Boil the sample with Hydrochloric acid
  • Cool solution and neutralise by adding sodium hydrogen carbonate solution
  • Repeat reducing sugar test again

BIURET TEST (TESTING FOR PROTEINS):

  • Add biuret reagent to sample
  • If colour changes to lilac proteins are present

ETHANOL EMULSION TEST (TESTING FOR LIPIDS):

  • Mix sample with ethanol – dissolves any present lipid
  • Then pour liquid into water contained in another clean test tube
  • If lipid present – cloudy white emulsion with form near top of water

 

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