REQUIRED PRACTICALS

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Created by
Sadia

Cards (15)

  • aspetic techniques?
    1. sterilise all equipement by sterlising the agar, putting a bunsen burner on the bench to kill airborne microrganisms, passing the inocculating loop through the flame
    2. tape a lid on the petri dish
    3. incubate upside down to avoid condensation of bacteria dripping on the bacteria
    4. place the filter disks on the bacteria culture and wait for it to grow
    5. let them incubate for a few days
    6. calculate average area of inubation zone and calculate mean area
    7. compare results
  • Osmosis - potato R.P.
    1. Peel potato skin
    2. Use cork borer to produce 3 cylinders of potato
    3. Use scalpel to cut the cylinder to the same length using ruler
    4. Use top pan balance to measure the initial mass
    5. Place each cylinder into a test tube
    6. Add the given concentration of sugar solution into each test tube
    7. Add distilled water to the last one
    8. Leave potatoes overnight
    9. Gently pat them dry to remove excess water from surface
    10. Measure final mass using top pan and record in a table
    11. Calculate % change in mass using final mass-initial/initial x 100
    12. Repeat and calculate mean
  • light intensity of temp- pondweed R.P:
    1. cut the pondweed so bubbles escape~
    2. control CO2 in H20 by placing pondweed in sodium hydrogen carbonate
    3. set the lamp at a distance of 10cm from the pondweed using a ruler ensuring it is in the dark
    4. allow pondweed to equilibrate
    5. in 1 min count the no of bubbles released. these are O2 bubbles released from photosynthesis
    6. use same pondweed and same length of pondweed repeat test at 20cm, 30cm...
    7. repeat 3 times
    8. calculate mean of number of bubbles at each length
  • Effect on pH on amylase- spotting tile
    1. Place 1 drop of iodine solution into each well of a spotting tile
    2. Label test tube starch amylase and buffer pH
    3. Pour 2cm^3 starch/amylase solution into the test tube and add 2cm^3 pH 5 buffer solution - control pH
    4. Place all test tube in water bath at 30 and leave for 10mins
    5. Combine 3 solutions into 1 test tube and mix with stirring rod
    6. Place it back into water bath and start stopwatch
    7. After 30secs use stirring rod to transfer one drop of solution into a well in the spotting tile that contains iodine
    8. Should turn blue/black - starch is present
    9. Every 30 secs add a drop until iodine remains orange- starch no longer present
    10. Record time and repeat 4 times with diff pH buffer
  • Amylase is an enzyme that breaks down starch
  • Iodine solution is used to test for the presence of starch
  • A spotting tile is used to hold small amounts of liquid for testing
  • A buffer solution is used to control the pH of the reaction
  • A water bath is used to maintain a constant temperature for the reaction
  • Stirring the solution helps to mix the components
  • The time taken for the starch to be broken down by the amylase is recorded
  • The experiment is repeated with different pH buffers to see the effect on the amylase activity
  • problems with the amylase r.p:
    1. only taking samples every 30 secs so just an approximate time could address it every 10 secs
    2. might see colour change and diff times by others
  • Using a light microscope to draw and label a cell with a magnification scale

    1. Use clips to hold the slide in place
    2. Select lowest power objective lens (usually 4x)
    3. Position the objective lens so it almost touches the microscope slide by slowly turning coarse focusing dial
    4. Look at microscope from the side while we adjust the position of the objective lens
    5. When objective lens almost touches the slide, stop turning the dial
    6. Look down through the eyepiece
    7. Slowly turn coarse focusing dial = increases distance between objective lens & slide= do until focus
    8. Use fine focusing dial to bring cells into clear focus
    9. Calculate total magnification = magnification of eyepiece lens(10x) x magnification of objective lens(4x)
    10. Select higher power objective lens e.g. 10x
    11. Adjust fine focusing dial= bring focus
    12. Use pencil = make a clear labelled drawing of some cells
    13. Magnification scale= clear plastic ruler over stage = measure diameter in mm = scale bar = write magnification
  • Microscope

    • R.P