Require Practicals

• GCSE biology required practicals for AQA

  • Microscopy
  • Osmosis
  • Enzymes
  • Food tests
  • Photosynthesis
  • Reaction times
  • Quadrats
  • Microbiology
  • Germination
  • Decay
• Tips for answering practical questions

  • Identify the independent variable (the thing you change)
  • Identify the dependent variable (the thing that changes as a result)
  • Identify the control variables (things you keep the same)
  • Describe the equipment used for measurements
  • Discuss safety precautions like using goggles, gloves, etc.
  • Discuss ways to improve accuracy and reduce errors (e.g. taking repeat measurements, using proper techniques)
  • Use bullet point format to clearly communicate points
• Microscopy


  1. Use scalpel and tweezers to prepare thin layer of onion skin

  2. Add drop of iodine to stain cells

  3. Place cover slip on slide

  4. Start with lowest magnification objective lens

  5. Use coarse and fine focus knobs to bring specimen into focus

  6. Switch to higher magnification objective lens and refocus if needed

  7. Can use graticule to measure cell size in micrometers
• Osmosis


  1. Cut equal-sized cylinders from vegetable

  2. Dab off excess water from surface

  3. Place cylinders in test tubes with different sugar solution concentrations

  4. After set time, dab off excess water and reweigh

  5. Calculate percentage difference in mass for each cylinder

  6. Plot percentage change in mass against solution concentration
• Enzymes


  1. Measure out fixed volume of enzyme and substrate solutions

  2. Mix together and start timer

  3. Every 10 seconds, remove sample and test with iodine for presence of starch

  4. Record time until no colour change (endpoint)

  5. Repeat with different temperatures or pH values

  6. Plot time taken against temperature or pH and identify optimum
• Food tests


  1. Grind solid food and mix with distilled water to make solution

  2. Test for starch by adding iodine (turns black/purple)

  3. Test for glucose/simple sugars by adding Benedict's solution and heating

  4. Test for proteins by adding biuret reagent (turns purple)

  5. Test for lipids by adding ethanol and then water (goes cloudy)
• Photosynthesis


  1. Use pondweed submerged in water in inverted test tube or cylinder

  2. Cut stem at angle and add sodium hydrogen carbonate

  3. Measure distance from light source

  4. Wait 1 minute for photosynthesis to reach constant rate

  5. Count bubbles or measure oxygen volume in 1 minute

  6. Repeat at different distances and plot against light intensity
• Reaction times


  1. Hold ruler between partner's finger and thumb

  2. Drop ruler without warning and have partner catch it as fast as possible

  3. Calculate reaction time using equation: t = sqrt(2s/a) where s is distance and a is acceleration due to gravity

  4. Repeat and calculate mean reaction time

  5. Can test with independent variable like distraction
• Quadrats


  1. Use random number generator to choose grid positions to place quadrat

  2. Count number of organism in each quadrat

  3. Calculate mean number per square metre

  4. Multiply by total area to estimate total population

  5. Can combine with transect line to see how population varies with distance
• Microbiology


  1. Spot different bacterial cultures on agar plate and observe growth

  2. Or spread culture to make lawn and add antibiotic discs

  3. Use aseptic technique - sterilise equipment, work near Bunsen flame

  4. Incubate for days then measure colony/inhibition zone diameters
• Germination


  1. Place seeds on damp cotton wool in Petri dish

  2. Leave in dark and observe root growth (geotropism)

  3. Allow small amount of light and observe shoot growth (phototropism)
• Decay


  1. Measure volume of milk/cream in test tube

  2. Add sodium carbonate and phenolphthalein indicator

  3. Add lipase enzyme

  4. Use water bath to maintain different temperatures

  5. Time how long it takes for solution to decolourise

  6. Plot time against temperature to find optimum