Biology Pratical Work

  • Created by: Vss2017
  • Created on: 24-11-17 10:10
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  • Biology Pratical Work
    • Qualitative tests
      • Benedict's Test- used to detect Reducing sugars
        • Heated in a water bath, wiht Benedict's Solution
          • blue, green, yellow, orange, brick red precipitate.
        • Non-reducing suagrs
          • 1.Negative result with benedict's
            • 2. Hydrolise sample by heating with Dilute Hydrochloric Acid in a water bath.
              • 3. Once cooled Neutrilise with Sodium Hydrogencarbonate
                • 4. Test with benedict's solution- Positive test
      • Iodine test- starch
        • yellow- brown to blue-black
      • Glucose-Specific tests
        • Cllinistix strips change colour in glucose only
        • used to test for the presence of glucose in urine which is a symptom of diabetes
      • Biuret Test- detects the presence of peptide links in PROTEIN
        • adding equal volumes of sodium hydroxide solution then testing wiht a few drops of dilute copper sulfate solution
          • shake gently
            • blue to lilac if protein is present
    • Identifying amino acids through the use of chromotography paper
      • preparing the chromatogram
        • chromatogram cut to fit the tank. allowed to attach to the lid and drop to just above the base of the tank
        • horizontial line drawn in pencil. BASE LINE
        • Solution containing amino acids needs to be SPOTTED onto the pencil line using a MICRO-PIPETTE.After each drp the solution is DRIEDout before process is REPEATEDto increase CONCENTRATION
        • Avoid contmination1. hold chomatogram at the edges2.dont set on lab benches- range of other chemicals could contaminate.
        • before placing the prepared chromatogram into the tank, the solvent should be added and the lip placed on top to allow the stmosphere to become saturated.
      • Running the chromatogram
        • 1.ensure the base line does not make contact with the solvent- suspended above2.securely attached to the lid3.not suspended at an angle
      • developing the chromatogram
        • Mark the solvent front wiht a pencil.spray chromatogram with NINHYDRIN in a fume cupboard
        • After being re-dried the amino acids appear as purple spots.The spots should be encircled wiht a pencil as they will fade
      • Calculating the Rf value
        • The distance moved by the solute (amino acid) X divided by the distance moved by the solvent front Y.
          • measuring the distance from the origin to the position of the solvent front. and hen from the origin to the position of the amino acids.
        • Rf value is always less than 1.Rf value = X/Y


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