Biology – Mode of action of enzymes | e-Consult

Equipment Required:

• Test tubes (at least 5)
• Beakers (various sizes)
• Pipettes (various volumes)
• Starch solution (e.g., 1% w/v)
• Amylase solution (at varying concentrations – e.g., 0.1%, 0.2%, 0.3%, 0.4%, 0.5%)
• Distilled water
• Thermometer
• Stopwatch
• Graduated cylinders
• Forceps

Procedure:

1. Prepare starch solution and amylase solutions of varying concentrations.
2. In each test tube, add an equal volume of starch solution.
3. Add a fixed volume of amylase solution to each test tube.
4. Start the stopwatch immediately after adding the amylase.
5. At regular time intervals (e.g., every 30 seconds) remove a small aliquot of the mixture from each test tube and add it to a separate beaker containing iodine solution.
6. Observe the colour change. The iodine solution will turn blue-black in the presence of starch. The time taken for the colour to disappear indicates the rate of starch hydrolysis.
7. Repeat the experiment at a constant temperature (e.g., 37°C) to ensure consistent reaction conditions.
8. Repeat the experiment multiple times (at least three) for each amylase concentration to ensure reliable results.

Rate Measurement: The rate of reaction can be determined by measuring the time taken for the blue-black colour to disappear in the iodine solution. A shorter time indicates a faster rate of reaction.

Potential Sources of Error and Minimisation:

• Temperature variations: Maintain a constant temperature using a water bath.
• Inconsistent mixing: Ensure thorough and consistent mixing of the starch and amylase solutions.
• Inaccurate volume measurements: Use calibrated pipettes and graduated cylinders.
• Subjectivity in colour observation: Use a standardized colour chart or a spectrophotometer to objectively measure the absorbance of the iodine solution.
• Starch degradation: Use fresh starch solution and avoid prolonged exposure to light.