Final answer:
The statement about enzyme activity decreasing as pH moves away from the optimal value is true. Changes in pH can alter enzyme structure and reduce the rate of reaction, with extreme deviations potentially causing permanent denaturation.
Step-by-step explanation:
The statement 'As pH is changed away from the optimum pH for the enzyme, the reaction rate will decrease' is indeed true.
Enzymes are proteins that have an optimal pH at which they function most effectively. Adjusting the pH level above or below this optimum value can lead to a change in the enzyme's structure, specifically impacting the secondary, tertiary, and quaternary structures. This alteration can reduce the efficiency of the enzyme's active site in catalyzing reactions. At extreme pH levels, enzymes may become permanently denatured, resulting in a significant decrease or complete cessation of enzyme activity.
Denaturation of enzymes due to pH changes can disrupt the delicate balance of hydrogen bonds and other interactions within the protein, leading to a loss of its unique three-dimensional structure that is essential for its function. This is particularly crucial in biological systems where most enzymes perform within a narrow and specific pH range, typically around the pH of 7.4, aligning with the average biological pH. However, certain enzymes, like pepsin and alkaline phosphatase, have different optimal pH values, 1.5 and 9.8 respectively, and perform best in those conditions.