Enzyme Activity and pH
Test Tube pH Height of foam (cm)
1 3.0 4.5
2 5.5 5.5
3 7.0 10.0
4 10.0 4.0
5 13.0 0


Students in biology class wanted to test the specificity of the enzyme catalase. Catalase, present in all living cells, breaks down hydrogen peroxide into water and oxygen gas.
Procedure:
1. 2 mL of hydrogen peroxide was added to five clean test tubes.
2. The pH of each test tube was manipulated using 1M HCl (an acid) and/or 1M NaOH (a base). By adding HCl or NaOH drop by drop, the pH was manipulated to reach the following:
Test tube 1 – pH 3
Test tube 2 – pH 5
Test tube 3 – pH 7
Test tube 4 – pH 10
Test tube 5 – pH 13

3. 1 mL of liver puree was added to each test tube. Observations were made. If there was evidence of gas production (foam), the level of foam was measured in centimeters and recorded. Student data can be seen in the table above.
Certain environmental changes can denature proteins. Denatured proteins lose their three dimensional structure and when the protein is an enzyme, they lose their ability to function. pH is just one factor that can change the effectiveness of an enzyme. What other factor might the students test regarding catalase specificity?
A) Students could test various other enzymes to see if all enzymes were denatured in a basic environment (pH = 13).
B) After determining the optimum pH, they could vary the temperature of the environment to see if catalase is temperature specific.
C) After determining the optimum pH, the students could vary the amount of catalase used while keeping the amount of substrate constant.
D) Students could test an assortment of food items besides liver, raw potato, apple, crackers, to see if catalase is consistently pH specific.