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Unit 3 revision
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  • 1. Unit 3 Revision
  • 2. The effect of Caffeine of Heart Rate
  • 3. Independent variable?
    Why it is important to use equal-sized cylinders of beetroot?
    So that same amount of pigment will be present in each disc.
    So that the number of cells in each disc can be controlled.
    So that the surface area of the disc can be made uniform.
    The Effect of Temperature on Membrane
  • 4. The dependent variable?
    Degree of redness
    Describe how the degree of redness could be measured.
    Shake the water in the boiling tube before measuring.
    Select the blue filter in colorimeter
    Keep an empty cuvette with wiped edges and make the reading zero.
    Care should be taken to keep the transparent side of the cuvette facing the light or colorimeter.
    Keep the cuvette with water from each repetition in the practical, inside the colorimeter holder.
    Record absorbance from the colorimeter screen.
    The Effect of Temperature on Membrane
  • 5. Variables that need to be controlled
    Volume of water in the boiling tube.
    Uniform rinsing of beetroot discs.
    Similar variety of beetroot must be used for the experiment.
    The Effect of Temperature on Membrane
  • 6. Antimicrobial Properties of Plants
    Weigh 10g of the plant material to be tested for antimicrobial properties.
    Grind the plant material in a pestle and mortar with 10ml of ethanol as the medium.
    Collect the plant extract in a test tube.
    Take 1ml of the extract into a cavity slide.
    Prepare paper discs of 1cm diameter from filter paper.
    Place these filter paper with a sterilised forceps into the extract in cavity slide.
    Take 1ml of ethanol alone in another cavity slide.
    Place another disc of the same diameter in this slide.
    This will act as the control.
  • 7. Antimicrobial Properties of Plants
    Prepare agar medium in a Petri dish.
    Pour a drop of bacterial culture on top of the agar medium.
    Spread the bacteria all over the medium using a sterilized spreader.
    Put the paper discs from plant extract and the control disc into the agar medium.
    Place them well apart and cover the petri dish and close the lid with transparent tape.
    Keep the petri dish upside down and incubate in an incubator for 24 hours at 24O C.
    After incubation, observe clear areas around the discs.
    If the plant is having antimicrobial properties, the clear area around the disc will be larger.
  • 8. Sterilizing methods.
    Disinfectants can be used to sterilize the area where the practical is being done.
    Autoclave is used to sterilize the equipments used in the practical.
    Flaming the forceps and glass apparatus before and after transferring bacteria is another aseptic method.
    Antimicrobial Properties of Plants
  • 9. Measuring the clear area around disc.
    Keep a graph paper over the petri dish and trace the clear area on the graph paper.
    Count the number of squares in the traced area.
    Calculate the area of the trace from this.
    Subtract the area of the disc from this value.
    The result will show the size of the clear zone around the disc.
    Antimicrobial Properties of Plants
  • 10. Variables that need to be controlled
    Volume of enzyme
    Enzyme Concentration and Rate of Reaction
  • 11. Independent variable?
    the deficient mineral solution
    Why it was important to make sure all the seeds were about the same mass?
    To make valid comparison between seeds later.
    Any differences between seedling masses later should be caused by treatment and not by their differences in the beginning.
    Investigating Plant Mineral Deficiencies
  • 12. Variables that need to be controlled
    Light intensity
    wavelength of light
    carbon dioxide level
    wind speed
    Variety of seed or age of seed
    Same concentration and volume of other nutrients in the solution
    Investigating Plant Mineral Deficiencies
  • 13. The strength of Plant Fibres
  • 14. Totipotency and Plant Tissue Culture
  • 15. Name of the stain?
    Toluedene blue
    Why heating the slide?
    Increases intake of stain by cells
    Why adding HCl?
    Softening the cell wall and helps in individual cells separately
    Observing Mitosis
  • 16. The Vitamin C content of Fruit Juices