Brent Cornell

    
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:

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)

    
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?