Required practicles

• Eyepiece


  The part of the microscope that you look into
• Objective lenses


  The lenses on the microscope that have different magnification numbers
• Calculating magnification


  Multiply the objective lens number by the eyepiece number
• Preparing a slide


  1. Spread cells on slide

  2. Add dye (e.g. iodine)

  3. Add cover slip
• Viewing a slide


  1. Start with lowest magnification objective lens

  2. Use coarse focus wheel

  3. Use fine focus wheel

  4. Draw image without shading
• Magnification calculation


  Magnification = Image size / Real size
• Osmosis


  The movement of water from a dilute solution to a concentrated solution through a partially permeable membrane
• Osmosis practical


  1. Cut vegetable pieces of similar size

  2. Weigh pieces

  3. Place in different sugar solutions

  4. Leave for 24 hours

  5. Reweigh pieces

  6. Calculate percentage change in mass
• Osmosis graph


  • Shows percentage change in mass on y-axis
  • Shows sugar concentration on x-axis
  • Line of best fit intersects x-axis to give sugar concentration inside vegetable
• pH buffer


  A solution with an exact pH
• Enzyme activity practical


  1. Heat water bath to 37°C

  2. Add amylase and pH 3 buffer to boiling tube

  3. Add starch and start timer

  4. Every 30 seconds, take sample and add to iodine-filled well on spotting tile
• In the first stages, the spotting tile wells should go black due to the presence of starch
• Iodine test for starch


  1. Add a couple of drops of iodine into each well

  2. Iodine turns orange-brown
• Starch test


  1. Add 5 cm³ of starch to boiling tube

  2. Start stopwatch immediately
• Continuous sampling


  1. Every 30 seconds, remove a small sample from boiling tube

  2. Add a couple of drops to a well on the spotting tile
• Initial colour change in wells

  Black - indicates presence of starch
• Subsequent colour changes in wells

  Brown, light brown, orange - indicates starch being broken down by amylase
• Repeat the investigation with different pH buffers (e.g. pH 5, 8, 13)
• Repeat the whole experiment three times and calculate a mean rate of reaction
• Food tests


  • Test for carbohydrates (starch and sugar)
  • Test for protein
• Preparing food sample


  1. Crush food in pestle and mortar

  2. Mix with water to make a food solution
• Test for starch


  1. Add iodine to food solution

  2. Colour change to black indicates presence of starch
• Test for sugar


  1. Add Benedict's solution to food solution

  2. Heat in water bath

  3. Colour change to orange/red indicates presence of sugar
• Test for protein


  1. Add Biuret solution to food solution

  2. Colour change to purple indicates presence of protein
• Measuring rate of photosynthesis


  • Submerge pond weed in water
  • Count bubbles produced per minute
• Light intensity


  Affects rate of photosynthesis - higher light intensity increases rate
• Measuring effect of light intensity

  1. Measure bubbles at different distances from lamp (50 cm, 40 cm, 30 cm, 20 cm, 10 cm)

  2. Record number of bubbles per minute
• Independent variable


  Distance between lamp and pond weed
• Dependent variable


  Number of bubbles per minute
• Control variables


  • Type of pond weed, length of pond weed, power of lamp, temperature
• Inverse square law for light intensity only applies to A-level
• For foundation, just know that as distance increases, light intensity decreases
• Investigating effect of antibiotics on bacterial growth


  1. Prepare uncontaminated bacterial cultures (e.g. E. coli, Streptococcus)

  2. Seed agar plates with bacteria

  3. Place paper discs soaked in different antibiotics on plates

  4. Incubate and observe zones of inhibition
• Zone of inhibition


  Area around antibiotic disc where no bacteria are able to grow
• Measuring zones of inhibition

  1. Measure diameter or radius of zones

  2. Calculate area using πr²