Enzyme Experiments

ninja icon


•  Design of experiments to test the effect of temperature, pH and substrate concentration on the

   activity of enzymes

When designing an experiment to test the effect of factors affecting enzyme activity, the three key decisions to be made are:

  • Which factor to investigate (i.e. the independent variable)
  • Which enzyme / substrate reaction to use
  • How to measure the enzyme activity (i.e. the dependent variable)

Choosing the Independent Variable

The main factors which will affect the activity of an enzyme on a given substrate are:

  • Temperature (use water baths to minimise fluctuations)
  • pH (acidic or alkaline solutions)
  • Substrate concentration (choose range to avoid saturation)
  • Presence of inhibitor (type of inhibitor will be enzyme-specific)

Selecting an Enzyme and Substrate

Selection will depend on availability within the school, however certain enzymes can be extracted from common food sources

Examples of common enzyme-catalysed reactions include:

enzyme table 1

Measuring Enzyme Activity

The method of data collection will depend on the reaction occurring – typically most reactions are measured according to:

  • The amount / rate of substrate decomposition (e.g. breakdown of starch)
  • The amount / rate of product formation (e.g. formation of maltose)
enzyme table 2

ninja icon


•  Experimental investigation of a factor affecting enzyme activity

Key things to consider when conducting an experimental investigation into a factor affecting enzyme activity include:

  • What is an appropriate range of values to select for your independent variable?
  • Have you chosen a sufficient time period for the reaction to proceed?
  • Have you identified, and controlled, all relevant extraneous variables?
  • Can you include a negative control condition (no enzyme) to establish baseline readings?
  • Can you include a positive control condition to confirm enzyme activity?
  • Is it possible to treat the enzyme with the independent variable before mixing with the substrate?
  • Does the data collection method allow for sufficient precision in detecting changes to levels of product / substrate?
  • Have all appropriate safety precautions been taken when handling relevant substances?