Required 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)
  • State the equipment used for each measurement
  • Discuss safety precautions like using goggles, gloves, etc.
  • Discuss the accuracy of measurements and how to reduce errors/uncertainties
  • Discuss taking multiple/repeat measurements to calculate a mean
• Microscopy

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

  2. Add a drop of iodine to stain the cells

  3. Place a cover slip on top

  4. Place the slide on the microscope stage

  5. Start with the shortest objective lens and use the coarse and fine focus knobs to bring the specimen into focus

  6. Change to a higher magnification objective lens and refocus if needed

  7. You can use a graticule (tiny ruler) to measure cell size in micrometers
• Osmosis

  1. Cut equal-sized cylinders from the same vegetable using a cork borer

  2. Dab off excess water and weigh the cylinders

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

  4. After a set time, remove the cylinders, dab off excess water, and reweigh

  5. Calculate the percentage difference in mass for each cylinder

  6. Plot the percentage change in mass against solution concentration to find the concentration with no osmosis
• Enzymes

  1. Measure out a set volume of the enzyme (amylase) and substrate (starch) solutions

  2. Mix them together and start a timer

  3. Every 10 seconds, remove a sample and test it with iodine to see if the starch has been broken down

  4. Record the time taken for all the starch to be broken down

  5. Repeat this using different temperatures or pH values

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

  1. Grind solid food samples and add distilled water to create a solution

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

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

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

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

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

  2. Cut the stem at an angle and add sodium hydrogen carbonate to the water

  3. Measure the distance between the light source and the pondweed

  4. Count the bubbles of oxygen released or measure the volume of oxygen made in a minute

  5. Repeat at different distances and plot the results against distance
• Reaction timespractical

  1. Hold a ruler between your lab partner's finger and thumb with the zero mark in line with them

  2. Drop the ruler without warning and have your partner catch it as fast as they can

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

  4. Repeat multiple times and calculate the mean reaction time
• Quadrats

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

  2. Count the number of the chosen organism inside each quadrat

  3. Calculate the mean number per square meter

  4. Multiply the mean by the total area to estimate the total population

  5. You can also use a transect line to see how population density varies with distance
• Microbiology

  1. Spot different bacterial cultures on agar in a petri dish and observe how they grow

  2. Spread a culture over the agar to make a lawn and then add antibiotic discs

  3. Use aseptic technique - sterilize equipment, work near a Bunsen flame, etc.

  4. Incubate for days and then measure the diameters of colonies or areas with no bacteria
• Germination

  1. Place seeds on damp cotton wool in a Petri dish

  2. Leave the dish upright in the dark and observe the roots growing downwards (geotropism)

  3. Allow a small amount of light in and observe the shoot growing towards the light (phototropism)
• Decay

  1. Measure out a volume of milk or cream and add sodium carbonate and phenolphthalein indicator

  2. Add the enzyme lipase and use a water bath to control the temperature

  3. Time how long it takes for the solution to decolorize as the milk decays

  4. Plot the time taken against temperature and identify the optimum temperature
• Dab off excess water and weigh the cylinders


  Necessary to determine the initial mass of the cylinders before they are placed in the sugar solutions.