Practicals

• Microscopy

  1. Place onion tissue onto a slide using tweezers
  2. Add a drop of iodine (stain)
  3. Put on cover slip
  4. Use the clip to secure the slide to the microscope stage
  5. Use the coarse adjustment know then the fine knob to move the stage until the image is clean
  6. Calculate magnification
• Osmosis

  1. Cut up potatoes into identical cylinders
  2. Get beakers with different sugar solutions
  3. Measure the mass of each potato and leave in beakers for 24 hours
  4. Dry potatoes and measure the mass

  Results:

  If water has drawn out by osmosis, the potato will decrease in mass
• Food Tests

  Sugars

  • Benedicts solution
  • If sugar is present, will turn from blue to red

  Starch

  • Iodine solution
  • If starch is present, will turn from brown/orange to blue/black

  Proteins

  • Buiret solution
  • If protein is present, will turn from blue to purple
• Enzymes

  1. Mix the same volume of starch solution with amylase solution at 20°C
  2. After 30 seconds, add a drop of the starch and amylase mixture to a drop of iodine solution in one well of a spotting tile
  3. Repeat every 30 seconds until the iodine solution no longer changes colour
  4. Repeat the experiment at 40°C, 60°C and 80°C
• Photosynthesis

  1. Cut a 10cm peice of pondweed
  2. Place in a beaker of water covered with a filter funnel
  3. Fill a measuring cylinder with water and place over the filter funnel
  4. Position a lamp 10cm away then turn on and leave for 2 minutes for acclimatisation
  5. Start a stopwatch and record the bubbles for 3 minutes
  6. Record the volume of gas from the 3 minutes
  7. Repeat the experiment but each time moving the lamp away every 10cm