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Factors Effecting Catalase Activity |
We observed how three factors influence the activity of the enzyme catalase: enzyme concentration, pH, and temperature. Below are results from three lab sections. Averages are graphed in green.
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Catalase Reactions
All of the reactions described below were run with a volume of 5 mL, including 3 mL of homogenate and/or distilled water or pH solution and 2 mL of hydrogen peroxide. Volume was a controlled variable, something which we did not allow to vary so we wouldn't have to wonder whether it would effect the outcome of our experiments. (For example, you can imagine 1/2 mL hydrogen peroxide and 1/2 mL homogenate would produce a less spectacular reaction than 10 mL of each).
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Catalase Activity and Concentration
2 ml of H2O2 was added to four solutions with varying concentrations of homogenate (H): 0% (3 mL distilled water), 33% (1 mL H, 2 mL water), 67% (2 mL H, 1 mL water), and 100% (3 mL H).
Summary: Higher enzyme concentration = faster reaction. One catalase molecule reacts with no more than 2 H2O2 molecules at a time. The H2O2 molecules in our solution far outnumber the catalase molecules in our homogenate. So, having more homogenate around means the reaction can go faster.
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Catalase Activity and pH
2 ml of H2O2 was added to five homogenate solutions with varying pHs: 1 (acidic), 3 (acidic), 7 (neutral), 9 (basic), and 12 (basic).
Summary: Reaction is fastest at neutral to basic pHs. Catalase is adapted to work best under cellular conditions. Most cells have a pH around 7, and our reaction worked well at that pH. It also worked well at higher pHs. At lower (acid) pHs, the high concentration of H+ ions damaged the enzyme and slowed (or stopped) the reaction.
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Catalase Activity and Temperature
2 ml of H2O2 was added to four homogenate solutions at various temperatures: 0' C (freezing), 25' C (room temp.), 37' C (body temp.), and 100' C (boiling).
Summary: Reaction is fastest at body temperature (37' C) . Catalase works best under cellular conditions, and beef cells have a temperature similar to yours. The reaction was slightly slower at 25' C, and even slower at freezing temperature. At 100' C, the heat destroyed (denatured) the enzyme and there was no reaction at all.
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