Required practicals

• Food samples:

  1. Take food sample and grind with distilled water using a mortar and pestle to make a paste
  2. Transfer paste to beaker and add more water, stir so chemicals in food are dissolved in water
  3. Filter to remove food particles

  Now test
• Test for starch: 2cm^3 solution,

  Positive iodine = blue/black

  Negative iodine = brown/orange
• Test for sugars: 2cm^3 solution

  10 drops Benedict -> positive = green for a little, yellow for more, brick red loads

  Place test tube in beaker of hot water

  Only works for reducing sugars such as glucose
• Test for protein: Biurets solution

  Blue -> purple/lilac
• Test for lipids:

  Grind with water but don’t filter because lipid molecules stick to paper

  Few drops of ethanol and distilled water

  Shake

  Positive = white cloudy emulsion forms
• Microscopy

  1. Peel off a thin sheet of epidermal tissue using forceps
  2. Place on slide using a pipette to flatten it
  3. Add two Drops of iodine
  4. Place a cover slip on top ensuring there are no air bubbles
  5. Remove excess stain with paper towel
  6. Place slide on stage
  7. Turn nosepiece to select a low power objective
  8. Raise the stage so the cover slip is touching objective lense
  9. look into eyepiece and move stage away until image is focused
  10. Turn nose piece to select a higher objective power
  11. Repeat
• Osmosis

  1. Use cork borer to cut 5 pieces of potato cylinders
  2. Make sure they‘re the Same length
  3. Measure and record the mass of each cylinder
  4. Measure 10cm^3 of 1.0M sugar solution and transfer to first boiling tube and label
  5. Repeat steps 1-4 with different concentrations of distilled water and sugar solution
  6. Add one potato cylinder to each cylinder
  7. Draw-a table
  8. Leave cylinders overnight
  9. Remove cylinders and blot them dry with paper towel
  10. Record new measurements
  11. Calculate percentage change
  12. Plot a graph
• Enzyme experiment


  1. Label each well on spotting tile with time starting from 0

  2. Place a drop of iodine in each well

  3. Add 2cm^3 of buffer solution to labelled test tubes using a syringe starting from pH3 - pH7

  4. Immerse starch solution, amylase solution and the test tubes into a water bath for 25 minutes

  5. Allow a few minutes for temperature to equilibrate

  6. Use a syringe to add 2cm^3 starch solution to buffer tube

  7. Then add 2cm^3 amylase to same tube and start timing immediately

  8. Use a glass rod to transfer a drop of iodine solution from the first well

  9. Repeat steps with different well until iodine stays orange and doesn't turn blue/black

  10. Repeat with different buffer solutions with diff pH values

  11. Plot a graph