Effect of pH on Catalase Enzyme Activity

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★☆ Some safety precautions required to perform safely

Categories: Catalysts, Enzymes and Digestion

Alternative titles: Catalase pH

Summary

This demonstration investigates how the pH of a solution affects the activity of the enzyme catalase, obtained from yeast. The enzyme breaks down hydrogen peroxide into water and oxygen, and the rate of reaction is measured by the height of foam produced as oxygen gas is trapped by detergent.

Procedure

Label five test tubes with the pH values 1, 4, 7, 8, and 12.
Add 5 ml of hydrogen peroxide to each test tube.
Adjust the pH of each tube by adding suitable acid or alkali solutions to reach the target pH levels.
Add a few drops of universal indicator to confirm the pH of each tube.
Add a few drops of detergent to each tube to trap oxygen gas as foam.
Add 1 ml of yeast solution (a source of catalase enzyme) to each tube.
Allow the reactions to proceed for 5 minutes at room temperature.
Measure and record the height of foam produced in each tube as an indicator of enzyme activity.

Links

How pH effects enzyme activity - Milne’s Science Tech:

Variations

Test additional pH values between 5 and 9 to more precisely determine the optimum pH.
Use catalase from different sources such as potato or liver.
Repeat the experiment at different temperatures to see combined effects of pH and temperature.

Safety Precautions

Wear safety goggles and gloves when handling acids, alkalis, and hydrogen peroxide.
Avoid skin contact with hydrogen peroxide and strong pH solutions.
Work in a well-ventilated area or fume hood if possible.
Dispose of chemical mixtures safely according to local regulations.

Questions to Consider

What is the function of catalase in this experiment? (It breaks down hydrogen peroxide into water and oxygen.)
Why is detergent added to the test tubes? (It traps the oxygen gas released, forming foam that can be measured.)
At which pH was enzyme activity highest? (The highest foam production occurred at pH 8, suggesting this is near the enzyme’s optimum pH.)
Why does enzyme activity decrease at very high or low pH values? (Extreme pH levels alter the enzyme’s shape and denature the active site, reducing activity.)