Biology Paper 1 practicals

• Required practical 1: Microscopes?

  • Peel of an epidermal layer on the onion via forceps and place on slide
  • Add 2 drops of iodine solution to stain the cells
  • Place slide on stage, use clips to hold slide in place
  • Cover the slide by placing a cover slip slowly on top using forceps to prevent air bubbles
  • Select lowest power objective lens, usually 4x
  • Position objective lens so it almost touches slide
  • Slowly turn coarse focusing dial
  • When objective lens almost touches, stop turning dial
• Required practical 2: Culturing Microorganisms?

  • Clean work bench via disinfectant to prevent contaminations
  • Sterilise inoculating loop via bunsen burner flame
  • Open sterile agar gel plate near bunsen burner flame to kill any bacteria in the air
  • Use loop to spread chosen bacteria
  • Place sterile filter paper discs containing antibiotics onto plate
  • Incubate at 25 degrees celcius
• Why incubate at 25?

  To prevent growth of harmful bacteria
• Required practical 3: Osmosis?

  • Ensure all 3 potato pieces are the same length
  • Place each piece into a test tube
  • Add 10cm^3 of 0.5 molar sugar solution to first test tube
  • Add 10cm^3 of 0.25 molar sugar solution to second test tube
  • Add 10cm^3 of distilled water to final test tube
  • Leave overnight for osmosis to take place
  • Remove the potato pieces and roll on paper towel to remove any surface moisture
• Required practical 4: Food tests?

  Make solution of the food via grinding with pestle and mortar, and adding distilled water

  • Starch: turns iodine from orange to black
  • Sugars: when heated turns benedict's solution from blue to brick red
  • Protein: turns biuret's reagent from blue to purple
  • Lipids(fats): add cold ethanol, then mix with water. When shook it should turn cloudy
• Required practical 5: Enzymes

  • Measure out enzyme and substrate(e.g starch & amylase)
  • Place separately in water bath, along with buffer solution if changing the pH
  • Prepare a spotting tile with iodine drops
  • Mix the reactants together & start timer
  • Every 10 seconds, remove a drop of the mixture & put in a dimple of iodine
  • If it changes colour, starch is still present
  • Once all starch is broken down, it will not change colour
  • Repeat this process for different temperatures or different pH buffer solutions
• Microscopes part 2?

  • Look down eye piece while adjusting coarse focusing lens until cells come into focus
  • Use fine focusing dial to bring cells into clear focus
  • Make labelled drawing of the cells you can see
• Required practical 6: Photosynthesis?

  • Cut pondweed stem
  • put in inverted measuring cylinder filled with water (add sodium hydrogen carbonate to provide CO2)
  • measure distance from light source
  • let acclimate first, then measure volume of oxygen made in 1 minute or count bubbles
  • repeat at different distances from light sources
• What is the inverse square law?


  1/distance^2