A student investigated the effect of temperature on the rate of respiration in yeast by measuring the volume of carbon dioxide produced each minute. The figure shows the student's results.
Figure: The rate of carbon dioxide production by a yeast culture at six different temperatures

Describe the effect of temperature on the rate of respiration in the yeast.
Explain why the rate of respiration falls above 40 °C.
Give one variable the student should have controlled.
51 exam-style questions on AQA GCSE Biology 4.2 Respiration, covering 4.2.1 Aerobic and anaerobic respiration, 4.2.2 Response to exercise, and 4.2.3 Metabolism. Each one has a worked solution and a mark scheme showing where the marks go.