A student is investigating the effect of temperature on the rate of enzyme activity using amylase and starch solution. Describe how the student should carry out this investigation safely and accurately, including how to collect valid results.

OCR A-Level Biology B — Advancing Biology (H422) — 1.2 Practical skills assessed in the practical endorsement · Describe · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Amylase is an enzyme produced in the salivary glands and pancreas. It breaks down carbohydrates into simple sugars. The student tests starch solution at different temperatures using iodine solution to detect when starch has been broken down.

Model answer (5 marks)

1. Use a water bath to keep the amylase–starch mixture at a constant temperature.
2. Keep the volume of the enzyme solution and the concentration of starch the same for every trial.
3. Add iodine solution to the mixture at regular time intervals and record the time when the blue‑black colour disappears.
4. Repeat the whole experiment at each temperature and calculate the mean time for each temperature to give a reliable rate.
5. Wear safety goggles when handling iodine and be careful with the hot water bath to avoid burns.

Examiner tips

  • Use the exact wording from the mark scheme (e.g., "water bath", "iodine solution", "mean"),
  • Show the sequence of steps clearly and link each to a mark point.
  • Mention a specific safety precaution to gain the safety mark.

Common mistakes

  • Not specifying that the water bath controls temperature,
  • Failing to state that the volume/concentration is kept constant,
  • Omitting the calculation of a mean to improve reliability.

Mark scheme (5 marks)

  1. Use a water bath to control the temperature of the amylase and starch solution
  2. Keep at least one variable constant throughout the investigation, such as the volume or concentration of amylase and starch
  3. Use iodine solution to test for the presence of starch at regular time intervals, noting when the iodine no longer turns blue-black
  4. Repeat the experiment at each temperature and calculate a mean to improve the reliability of results
  5. State an appropriate safety precaution, such as wearing safety goggles when handling iodine solution or taking care with hot water baths

Key terms in this question

amylase · enzyme

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