# A student is investigating the effect of temperature on the rate of enzyme activity using a colorimeter. Explain why the student should use a control cuvette containing the reaction mixture but with a boiled enzyme solution, and describe how this control should be used during the investigation.

> OCR A-Level Biology A (H420) — 1.2 Practical skills assessed in the practical endorsement · Explain · 4 marks

> A student sets up an experiment to measure the rate of an enzyme-controlled reaction at different temperatures. They use a colorimeter to measure the absorbance of a coloured product formed as the reaction proceeds. The student prepares several cuvettes, each containing the substrate and buffer solution at a set temperature.

## Mark scheme (4 marks)

1. The boiled enzyme is denatured and therefore inactive, so the control contains no enzyme activity
2. The control is used to zero / blank the colorimeter, accounting for any absorbance due to the reaction mixture itself rather than the enzyme-produced colour change
3. This ensures that any change in absorbance recorded in experimental cuvettes is due solely to the enzyme-catalysed reaction / product formation
4. The control cuvette should be prepared at each temperature tested so that the blank accounts for any temperature-dependent changes in absorbance of the reaction mixture

## Key terms

- [colorimeter](https://www.gradenine.co.uk/glossary/colorimeter)
- [control cuvette](https://www.gradenine.co.uk/glossary/control-cuvette)

## Related

- [Revision notes for OCR A-Level Biology A (H420)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-is-investigating-the-effect-ea597135) · Published by Druglandscape Ltd.