In short
AQA GCSE Biology has 10 required practicals; AQA Combined Science has 7 of them. The Triple-only ones are antiseptics and antibiotics, light and gravity on seedlings, and the decay of milk. Written papers test them, and AQA says practical questions are at least 15% of the marks. Each practical below links to a free full sheet.
AQA GCSE Biology (8461) has 10 required practicals, and AQA GCSE Combined Science: Trilogy (8464) has 7 biology required practicals, which are 7 of the 10. The three Triple-only ones are antiseptics and antibiotics, light and gravity on seedlings, and the decay of milk. You are not assessed while doing the practicals, but the written papers include questions on them, and AQA says these questions count for at least 15% of the overall marks.
Below is the full list, then each practical in turn: the aim, what you measure, the typical exam question and the most common mistake. Every one links to our free practical sheet with the full method, results table, errors and exam-style questions with mark schemes. This is your AQA GCSE Biology required practicals list, and the AQA Combined Science version is the same list without the Triple-only ones.
AQA GCSE Biology required practicals list (summary table)
| Triple no. | Practical | Spec point | Combined? | Combined no. |
|---|---|---|---|---|
| 1 | Using a light microscope | 4.1.1.2 | Yes | 1 |
| 2 | Antiseptics and antibiotics on bacterial growth | 4.1.1.6 | Triple only | - |
| 3 | Osmosis in potato cylinders | 4.1.3.2 | Yes | 2 |
| 4 | Food tests | 4.2.2.1 | Yes | 3 |
| 5 | The effect of pH on amylase | 4.2.2.1 | Yes | 4 |
| 6 | Light intensity and the rate of photosynthesis | 4.4.1.2 | Yes | 5 |
| 7 | Reaction time | 4.5.2.1 | Yes | 6 |
| 8 | Light, gravity and the growth of seedlings | 4.5.4.1 | Triple only | - |
| 9 | Field investigations: quadrats and transects | 4.7.2.1 | Yes | 7 |
| 10 | Temperature and the rate of decay of milk | 4.7.2.3 | Triple only | - |
The numbers differ because the Triple-only practicals are missing from Combined: osmosis is practical 3 in Triple but 2 in Combined. Exam questions name the activity, so learn them by name.
Which required practicals are in Combined Science biology?
If you take Combined Science: Trilogy, you need these seven: using a light microscope, osmosis in potato cylinders, food tests, the effect of pH on amylase, light intensity and photosynthesis, reaction time, and field investigations with quadrats and transects. Our AQA Combined Science course has the same practical sheets, numbered the Combined way.
The 10 AQA biology required practicals, one by one
Required practical 1: Using a light microscope
Aim: Prepare slides of plant and animal cells (onion and cheek cells), focus a light microscope, make a labelled drawing and work out its magnification.
What you measure: There is no independent or dependent variable here, because it is a technique practical. You measure the length of a cell in your drawing and in real life, then use ==magnification = image size ÷ real size==.
Typical exam question: "A drawing is 36 mm long and the real cell is 90 µm long. Calculate the magnification." (3 marks), or "Explain why you start on the lowest-power objective lens."
Mixing up mm and µm. 1 mm = 1000 µm, so convert before you divide. Drawings also lose marks for shading, crossing label lines and no magnification or scale bar.
Revise it with the full practical sheet (spec 4.1.1.2), and read the matching revision notes. For Combined Science (practical 1) use the Combined version.
Required practical 2: Antiseptics and antibiotics on bacterial growth (Triple only)
Aim: Grow bacteria on agar, add discs soaked in different antiseptics and compare the sizes of the clear zones of inhibition.
What you measure: Independent variable: the type of antiseptic (or antibiotic) on the disc. Dependent variable: the size of the zone of inhibition, measured as a diameter and turned into an area with ==area = πr²==. Controls include the bacterial culture, the agar, the disc size and the incubation temperature and time.
Typical exam question: "A disc soaked in sterile water is used as a control. Explain why." or "Plates are incubated at 25 °C, not 37 °C. Explain why." (dangerous pathogens grow best at body temperature).
Putting the diameter into πr². Halve it to get the radius first. The other classic slip is saying antibiotics kill viruses: they only act on bacteria.
Revise it with the full practical sheet (spec 4.1.1.6), and read the matching revision notes. It is not in Combined Science.
Required practical 3: Osmosis in potato cylinders
Aim: Place potato cylinders in sugar (or salt) solutions of different concentrations and find how the mass of the tissue changes.
What you measure: Independent variable: the concentration of the solution. Dependent variable: the percentage change in mass. Controls include the size and type of potato, the volume of solution, the temperature and the time in the solution.
Typical exam question: "A potato cylinder goes from 2.50 g to 2.15 g. Calculate the percentage change in mass." (answer −14%), or "Use the graph to estimate the concentration inside the potato cells", which is where the line crosses zero.
Dividing by the final mass instead of the starting mass, and dropping the minus sign for a loss. Also leaving out "partially permeable" when defining osmosis.
Revise it with the full practical sheet (spec 4.1.3.2), and read the matching revision notes. For Combined Science (practical 2) use the Combined version.
Required practical 4: Food tests
Aim: Use qualitative reagents to test foods for sugars (Benedict's), starch (iodine), protein (Biuret) and lipids (Sudan III).
What you measure: Nothing is measured. These tests are qualitative: they show whether a molecule is present, not how much. You record the colour change for each test.
Typical exam question: "Describe how you would test a food for sugar and say what you would see if sugar is present." (3 marks), often followed by a 6-mark question on testing an unknown powder for all four molecules.
Forgetting to heat Benedict's solution in a hot water bath, or giving a vague colour. Iodine goes from orange-brown to blue-black, not "blue", and Biuret goes from blue to purple.
Revise it with the full practical sheet (spec 4.2.2.1), and read the matching revision notes. For Combined Science (practical 3) use the Combined version.
Required practical 5: The effect of pH on amylase
Aim: Mix amylase with starch and buffers of different pH, test samples with iodine every 30 seconds and find the pH at which starch disappears fastest.
What you measure: Independent variable: the pH of the buffer. Dependent variable: the time for the starch to be digested, with ==rate = 1 ÷ time==. Controls include temperature (water bath at about 35 °C), and the volume and concentration of starch and amylase.
Typical exam question: "State the optimum pH from the table and give a reason", "Calculate the rate if the starch is digested in 50 seconds" (0.020 per second), or "Explain why a buffer is used."
Saying the enzyme is "killed" at the wrong pH. Enzymes are not alive: they are denatured because the active site changes shape. And the end point is iodine staying orange-brown, not "going clear".
Revise it with the full practical sheet (spec 4.2.2.1), and read the matching revision notes. For Combined Science (practical 4) use the Combined version.
Required practical 6: Light intensity and the rate of photosynthesis
Aim: Move a lamp to different distances from pondweed and count the oxygen bubbles released, to see how light intensity affects the rate of photosynthesis.
What you measure: Independent variable: the distance of the lamp (which changes the light intensity). Dependent variable: the number of bubbles per minute, or the volume of gas collected in a set time. Controls include temperature, carbon dioxide concentration (sodium hydrogencarbonate solution) and the piece of pondweed.
Typical exam question: "Counting bubbles is not very accurate. Explain why and suggest a better method" (bubble size varies, so collect and measure the gas), plus a Higher tier calculation using the inverse square law: moving the lamp from 10 cm to 20 cm makes the light intensity four times lower.
Writing "it has reached its maximum" when the rate levels off. Name the limiting factor instead, for example carbon dioxide concentration or temperature.
Revise it with the full practical sheet (spec 4.4.1.2), and read the matching revision notes. For Combined Science (practical 5) use the Combined version.
Required practical 7: Reaction time
Aim: Plan and carry out an investigation into how a factor, such as a distraction, affects human reaction time using the ruler-drop test.
What you measure: Independent variable: the factor you choose, such as distracted or not. Dependent variable: the distance the ruler falls, converted to a reaction time in seconds. Controls: same volunteer, same hand, same ruler, same drop height and the same way of reading the result.
Typical exam question: "Explain why the partner drops the ruler without warning", "Identify the anomalous result and calculate the mean of the rest", or a 6-mark plan to test whether caffeine shortens reaction time.
Vague control variables such as "keep it fair". Say "same hand" or "same height of drop". Also, this is a voluntary response, so do not call it a reflex.
Revise it with the full practical sheet (spec 4.5.2.1), and read the matching revision notes. For Combined Science (practical 6) use the Combined version.
Required practical 8: Light, gravity and the growth of seedlings (Triple only)
Aim: Grow cress seedlings with light from one side, or on their side in the dark, and record how the shoots and roots grow.
What you measure: Independent variable: the direction of light or the position of the seedlings. Dependent variable: the direction of growth (angle of bend) and shoot length. The spec asks for results as both measurements and labelled biological drawings.
Typical exam question: "Explain why the shoots bent towards the light" (3 marks) or "Explain why the roots bent downwards", answered using auxin.
Saying "auxin makes the shoot bend". Say that auxin is unequally distributed, more builds up on the shaded side, and cells there elongate more. In a root the lower side grows slower, the opposite of a shoot.
Revise it with the full practical sheet (spec 4.5.4.1), and read the matching revision notes. It is not in Combined Science.
Required practical 9: Field investigations: quadrats and transects
Aim: Use random quadrats to estimate the population size of a common plant, and a transect to find how a factor such as light affects its distribution.
What you measure: You count the number of organisms in each quadrat. In the transect part, the independent variable is the distance along the line (which changes a factor such as light intensity) and the dependent variable is the number of plants per quadrat.
Typical exam question: "Explain why quadrats are placed at random" (to avoid bias), "Calculate the mean number per quadrat" and then "Estimate the population in a 400 m² field."
Mixing up units. Work out the number per m² first, then multiply by the area of the habitat. Also claiming a correlation "proves" a cause: say "suggests" and name another factor that could be involved.
Revise it with the full practical sheet (spec 4.7.2.1), and read the matching revision notes. For Combined Science (practical 7) use the Combined version.
Required practical 10: Temperature and the rate of decay of milk (Triple only)
Aim: Mix milk, lipase, sodium carbonate and phenolphthalein at different temperatures and time how long the pink colour takes to disappear, as a model of decay.
What you measure: Independent variable: the temperature of the water bath. Dependent variable: the time for the pink colour to vanish, giving ==rate = 1 ÷ time==. Controls include the volume of milk, lipase and sodium carbonate, and the number of drops of indicator.
Typical exam question: "Explain why the pink colour disappears" (lipase makes fatty acids, so the pH falls), or "Milk goes off more slowly in a fridge than on a table. Explain why."
Saying "the rate decreased" when the time decreased. A shorter time means a faster rate. Another is forgetting that a colour-change end point is subjective, so a pH probe or colorimeter would improve it.
Revise it with the full practical sheet (spec 4.7.2.3), and read the matching revision notes. It is not in Combined Science.
How to revise the AQA required practicals
- Learn the aim and the variables for each one: independent, dependent and at least two controls, named specifically.
- Learn the exact results: colour changes for food tests, the units for each measurement and the calculation, such as percentage change, rate = 1 ÷ time, magnification or area = πr².
- Practise the 6-mark "describe a method" question. Every practical sheet has one with a level-based mark scheme.
- Practise evaluation: why repeat and take a mean, what an anomalous result is, and one realistic improvement.
- Test yourself with exam questions and flashcards, and tick off the practicals on the specification checklist.
Required practical questions reward specific wording. Say "same hand" not "keep it fair", "denatured" not "killed", and "from orange-brown to blue-black" not "it changed colour".
If you want help turning these into confident exam answers, we offer 1-to-1 tutoring online and in Dubai.