Practicals

• Method

  1. Place one drop of iodine solution into each well of a spotting tile

  2. Take 3 test tubes, in one put starch solution, in another put amylase solution, and in the final one put pH 5 buffer solution. Make sure they all are equal in volume

  3. Place all 3 test tubes in a water bath at 30 degrees and leave them for 10 minutes to allow the solutions to reach the correct temperature

  4. Add all 3 solutions into one test tube and mix with a stirring rod. Return to the water bath and start a stopwatch

  5. After 30 seconds, use the stirring rod to transfer one drop of the solution to a well in the spotting tile which contains iodine

  6. The sample should turn blue black

  7. Take a sample every 30 seconds and continue until the iodine remains orange

  8. When the iodine remains orange, this tells us that starch is no longer present. Record the time for this

  9. Repeat the whole experiment with different pH buffers
• We could address this by taking samples every 10 seconds
• Method


  1. Peel off an epidermal layer on the onion using Forceps

  2. Mount onto the microscope slide with a drop of water using a pipette, making sure the tissue lies flat

  3. Add 2 drops of iodine solution to stain the cells

  4. Place the cover slip on slowly making sure no air bubbles are trapped

  5. Rotate the objective lenses so that the low power is in line with the stage

  6. Turn the course focus so that the stage is as close to the objective lens as possible

  7. Place the microscope slide in the center of the stage

  8. Focus the slide

  9. Record an image and then rotate the objectives so that the high power objective is in line with the stage