Biochemical tests

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  • Created by: Hol19
  • Created on: 12-04-16 10:17

Bieuret test

  • Test for proteins
  • Positive result is when it turns from blue to lilac or purple.
  • You add sodium hydroxide a
  • to make sure it is alkaline
  • you then add copper sulfate (detects the presence of peptide bonds)
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Iodine test

  • Test for starch
  • add iodine in potassium iodide solution
  • If it is a positive result you will see a colour change from yellow-brown to blue black.
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Emulsion test

  • Test for lipids
  • Mix the samples with ethanol in a test tube.
  • Pour the sample into a clean test tube with water.
  • If lipid is present a cloudy white emulsion will indicate the presence of lipids.
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Benedict's test

  • This is for reducing and non reducing sugars.
  • You heat the reducing sugar with benedicts solution
  • If a positive result occurs it will turn into a brick red precipitate (blue to green to yellow to orange-red)
  • If you test for non reducing sugars;
  • Test for reducing usgars first
  • take a sample and boil it with HCL to hydrolyse the sucrose to glucose and fructose
  • cool the solution and use sodium hydrogencarbonate to neutralise it.
  • Test for reducing sugars again.
  • Should form a brick red precipitate.
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