11 February 2026 · 9 min read
The AQA A-Level Biology required practicals: what gets examined
You are not asked to remember the lab day — you are asked about variables, controls and interpreting the data. Here is what to revise for each practical.
Practical questions are really method questions
Roughly 15% of the marks across both papers relate to practical skills. Almost none of them ask 'what did you see' — they ask you to identify the independent, dependent and control variables, justify a control experiment, evaluate reliability, or process data.
So revise each required practical as a method: what was changed, what was measured, what was kept constant, and what the expected result shows.
The ones that come up most
- Water potential of plant tissue: mass change against solute concentration; the point where the line crosses zero is the tissue's water potential.
- Membrane permeability (beetroot): pigment leakage measured by colorimeter; temperature disrupts phospholipid and protein structure.
- Enzyme rate: always name the dependent variable precisely — 'volume of oxygen collected in 60 s', not 'how fast it went'.
- Mitotic index: number of cells in mitosis divided by total cells counted, usually multiplied by 100.
- Chromatography: Rf = distance moved by spot / distance moved by solvent front; measure to the centre of the spot.
- Dissection and gas exchange: expect an application question on surface area to volume ratio.
Standard marks you can bank
- Repeats: 'repeat and calculate a mean to reduce the effect of random error'.
- Control: 'same procedure with the enzyme boiled / with distilled water, to show the change is caused by the enzyme'.
- Accuracy: name a more precise instrument and say why the smaller division reduces uncertainty.
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Revise this properly
This guide covers part of Topic 2: Cells. Inside A-Plus Biology you get 82 flashcards and 21 exam-style questions with mark schemes for this topic alone.