Introduction: Enzymes are biological catalysts that speed up chemical reactions in living organisms. The activity of enzymes is influenced by various factors, including pH, temperature, and substrate concentration. In this practical investigation, we will investigate the effect of pH on the activity of the enzyme catalase, which is found in living organisms and is responsible for breaking down hydrogen peroxide into water and oxygen.

Keywords: Enzyme activity, catalase, hydrogen peroxide, pH, biological catalysts, chemical reactions.

Equipment:

• Potato
• Blender
• 250 ml Beaker
• Hydrogen peroxide (10 vol.)
• pH solutions (1, 4, 7, 10)
• Measuring cylinder
• Gas syringe
• Stopwatch
• Spatula
• Filter paper
• Test tube rack
• Test tubes

Independent variable: pH solutions (1, 4, 7, 10) Range: pH 1-10

Dependent variable: The volume of oxygen gas produced Measurement: cm³

Method:

1. Cut a potato into small pieces and blend it in a blender with some water to make a potato extract.
2. Filter the potato extract to obtain a clear solution.
3. Pour 10 ml of hydrogen peroxide into a test tube.
4. Add 1 ml of the pH solution to the test tube, and stir gently.
5. Immediately add 5 ml of the potato extract to the test tube and start the stopwatch.
6. Record the volume of oxygen gas produced at 30-second intervals for 2 minutes using a gas syringe.
7. Repeat steps 3-6 with pH solutions of different values (4, 7, 10).
8. Record your results in a table.

Sample Data:

pH Solution	Volume of Oxygen Produced (cm³)
1	10
4	20
7	30
10	5

Calculations/Expected Findings: Calculate the average volume of oxygen produced for each pH solution. Plot a graph of pH against the average volume of oxygen produced. An increase in pH will lead to an increase in the activity of catalase up to its optimal pH range (around pH 7), after which activity will decrease.

Conclusion: The results show that the activity of the enzyme catalase is affected by the pH of the solution. As the pH increases, the activity of the enzyme also increases up to its optimal pH range, after which activity decreases. This can be explained by the fact that enzymes have an optimal pH range at which they are most active, and outside of this range, they become denatured and lose their activity.

Questions:

1. What is the enzyme used in this experiment?
2. What is the substrate of the enzyme?
3. What is the dependent variable in this experiment?
4. What is the optimal pH range for catalase?
5. How does the activity of catalase change as the pH increases?

Answers:

1. The enzyme used in this experiment is catalase.
2. The substrate of the enzyme is hydrogen peroxide.
3. The dependent variable in this experiment is the volume of oxygen gas produced.
4. The optimal pH range for catalase is around pH 7.
5. The activity of catalase increases as the pH increases up to its optimal pH range, after which activity decreases.

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