Question

Which of the following statements is incorrect regarding enzymatic activity?

• A. It increases with an increase in the substrate concentration upto the saturation point.
• B. It is highest at the optimum pH value.
• C. It initially decreases with an increase in pH value and then decreases.
• D. It initially increases with an increase in temperature and then decreases.

Answer 1

The correct option is C It initially decreases with an increase in pH value and then decreases.

Every enzyme possesses an optimum pH value, where it is most effective. Most enzymes show their maximum activity in a pH range of about 6.0 to 7.5, i.e., near neutral pH. Some digestive enzymes have their optimum pH in the acidic or the alkaline range. e.g., pepsin of gastric juice has its optimum at pH 2 (acidic), and trypsin of pancreatic juice shows its maximum activity at pH 8.8 (alkaline). Very low or high pH values reduce enzyme activity by changing the degree of ionisation of the side chains.