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4a. What was the optimum pH of catalase? Note that at other pH\'s (except for pH

ID: 198066 • Letter: 4

Question

4a. What was the optimum pH of catalase? Note that at other pH's (except for pH-3) the reaction rates were lower than those at the optimal pH, but that the enzyme clearly was still intact, as the H202 was still converted into H20 and O2. Explain the mechanism(s) of how nonoptimal pH's cause enzymes to have lower reaction rates. 4b. Some enzymes are highly resistant to pH changes-i.e., their reaction rates do not change much when pH is changed. Refer to your answer to the 4a and propose structural characteristics that might make enzymes pH resistant.

Explanation / Answer

4a. Catalase: It catalyzes the decomposition of hydrogen peroxide into water and oxygen. If other condition held constant and the concentration of substance is raised, the rate of reaction should increase rapidly. Eventually the rate will level off when the maximum rate is achieved. (for catalase it's the presence hydrogen peroxide). Temperature can affect catalase ability because as the temperature is raised the reacting molecules have more kinetic energy to undergo reaction. The reaction will go faster until the optimum temperature is reached. pH can affect catalyze activity because as the pH goes more acidic (1-7), the enzyme gains hydrogen ions from the solution.  

4b. Different enzymes have different optimum pH values. This is the pH value at which the bonds within them influenced by H+ and OH- ions in such a way that the shape of their active site is the most complementary to the shape of their substrate. At the optimum pH, the rate of reaction is at an optimum.

Any change in pH above or below the optimum will quickly cause a decrease in the rate of reaction, since more of the enzyme molecules will have active sites whose shapes are not complementary to the shape of their substrate.

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