AS Biology Practical Skills

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  • AS Biology Practical Skills
    • Biological molecules
      • Reducing Sugars: Add equal volume of Benedicts, heat to gently boil. Positive Result= Red
        • Non-Reducing SugarsAdd hydrochloric acid, gently boil, add sodium hydrocarbonate, add Benedicts.
      • Non-Reducing SugarsAdd hydrochloric acid, gently boil, add sodium hydrocarbonate, add Benedicts.
      • Lipids: Add 5cm^3 of ethanol to 2cm^3 sample, shake tube, add 5cm^3 water. Positive Result=cloudy.
      • Proteins: Add equal volume of sodium hydroxide, add a few drops of very dilute copper(II) sulfate solution and mix. Positive Result= Purple
      • Enzymes
        • Temperature: Increases movement and collisions but too high it can denature enzymes.
        • Concentration
          • Enzyme: an increase only increases ror when it does not exceed the concentration of substrate after this point the ror remains constant.
          • Substrate: an increase in concentration means alll active sites are working at their maximum rate. Lowering it means it is a limiting factor and will not reach max.
        • pH: Any change in pH affects Enzymes and in extremes denatures them.
        • Investigation into effect of temperature on ror of enzyme reaction.
      • Semi-Conservative Replication: using two different isotopes of Nitrogen they could track where each one went.
      • ATP: Energy Source, unstable bonds between phosphates.
      • Water: Dipolar, hydrogen bonds, Cohesion, Tension.
    • Cells
      • Studying cells
        • Fractionation: Cold, isotonic buffer solution. Homogenise. Ultracentrifugate.
      • Immunisation: Ethics- side effects? testing? Compulsory? Cost vs. need? MMR vaccine vs. Autism.
        • ELISA Test
        • Aseptic Techniques
      • Effect of alcohol on permeability of cell membranes, leakage of pigment from beetroot.
      • Root tip Squash & Mitotic Index
      • Creating a calibration curve to help determine the water potential of potato tubers.
    • Exchange
      • Surface Area to Volume Ratio
      • Dissection:
      • Oxygen Dissociation curves
      • Potometer: Stem cut in water, potometer filled with water (no bubbles), stem put into water and potometer, remove everything fromwater and sealed with jelly, air bubble introduced to capillary tube, the bubble moving shows transpiration.
      • Transport in Plants
        • Ringing: when bark is removed from the tree the phloem is cut meaning the tree swells above the cut proving that phloem flows downwards.
        • Tracers
    • Genetics
      • Sampling
        • Random Sanpling: careful with Bias,chance.
        • Mean
        • Mode
        • Median
        • Standard Deviation
      • Index of Diversity


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