Stir the yeast, seal the tube, collect every bubble. Then turn the volumes into a rate.
Yeast respiration comes up again and again in 0610 Paper 6. Here yeast and 5 % glucose solution respire under a layer of oil in a thermostatic water bath, and the carbon dioxide made in 5.0 minutes is collected over water in an upturned measuring cylinder at five temperatures. Watch the set-up built step by step, then build it yourself and check it against the points the examiners look for.
Past-paper referenceOriginal experiment, wording and figures, written in the style of Cambridge IGCSE Biology 0610 Paper 6 (Alternative to Practical). It is not copied from a past paper. The “what the examiners said” notes are our paraphrase of the Principal Examiner Reports for Teachers.
Practise next: 0610/61 May/June 2023, (counting bubbles from yeast in hot and cold water, equilibration, drawing gas collection over water) · official past papers
Practise next: 0610/62 February/March 2024, (yeast with glucose under oil, stirring the suspension, anomalous results, collecting carbon dioxide) · official past papers
Practise next: 0610/63 October/November 2025, (rate of bubble production against temperature, sources of error, testing for carbon dioxide) · official past papers
Examiner reports used: 0610 June 2023 (Paper 61), March 2024 (Paper 62), November 2023 (Paper 63) and November 2025 (Papers 62 and 63), with points from the March 2024 Paper 62 mark scheme.
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What a full-mark diagram shows
Collect and measure
A sealed boiling tube with a delivery tube leading under an upturned measuring cylinder full of water in a trough, all labelled; the volume read after a set time.
Control variables, in detail
The volume of stirred yeast suspension, the glucose, the oil layer, the time to equilibrate and the time to collect gas, each stated with its value.
Results table
Quantity and unit in every heading, numbers only in the body, the same number of decimal places, and a mean that leaves out an anomalous run.
Graph and conclusion
Rate (not number of bubbles) against temperature, a smooth curve through the points with no extrapolation, and a conclusion about the rate of respiration.
Habits the examiner reports keep asking for
The 5 minute wait is for equilibration: the yeast reaches the temperature of its water bath. Yeast does not need time to start respiring.
Stir the yeast suspension so every sample has the same number of cells. Yeast is living and does not dissolve.
Counting bubbles is not accurate because bubbles differ in size and are easy to miscount; measure the volume instead.
Leave an anomalous result out of the mean and divide by the number of values you actually used.
Your conclusion must mention the rate of respiration, not just the bubbles or the volume of gas.