This section covers measuring enzyme-controlled reaction rates using product formation or substrate disappearance.
The progress of an enzyme-controlled reaction can be followed by measuring how quickly a product appears or how quickly a substrate disappears.
Approach
Example
Measurement
Product formation
Catalase breaks down hydrogen peroxide and oxygen is produced.
Measure the volume of oxygen collected over time.
Substrate disappearance
Amylase breaks down starch.
Test samples at intervals to determine when starch is no longer detected.
Reaction rate describes how much change occurs during a known period. Depending on the investigation, this can be measured from product accumulation or substrate loss.
rate=timechangeinproductorsubstrate
Measurements taken at several time points can also show how the rate changes as the reaction progresses.
Exam Tip: When asked how enzyme activity could be measured, identify a measurable change and include time. Suitable answers may use either product formation or substrate disappearance.