Question

A researcher claims that different enzymes exhibit maximal function over different pH ranges. To test the claim, the researcher carries out an experiment that includes three different enzymes: pepsin, salivary amylase, and arginase. The results of the experiment are represented in Figure 1. Which of the following actions will provide the most appropriate negative control for the experiment?

1) Using a buffer solution with a pH of 7
2) Using a buffer solution with a pH of 2
3) Using a buffer solution with a pH of 10
4) Using distilled water

Answer 1

The most appropriate negative control for an experiment testing the function of enzymes at different pH levels would be a solution that is far away from their optimal pH values. A buffer solution with a pH of 10 would serve as the best negative control since it is significantly above the optimal pH for pepsin, salivary amylase, and arginase.

Step-by-step explanation:

To determine the most appropriate negative control for an experiment testing the function of enzymes at different pH levels, it is essential to use a condition where the enzymes are expected not to function. In this scenario, we must consider the optimum pH for each enzyme involved: pepsin, salivary amylase, and arginase. Pepsin has an optimum pH of approximately 2.0, salivary amylase works best around pH 7-7.5, and arginase functions optimally at an alkaline pH, likely above 7.5. Therefore, distilled water, typically having a pH of 7, would not be a suitable negative control because it is close to the optimum pH for one of the enzymes being tested (salivary amylase). Considering that most body fluids and, by extension, most enzymes function between pH 6 and 8, a buffer solution at pH 7, corresponding to the physiological pH, would normally not serve as an ideal negative control either for testing the extremes of enzyme function. The proper negative control would be a buffer solution with a pH either well above or below these ranges to ensure that none of the enzymes function optimally, therefore, choices 2) and 3) are potential options for a negative control.

Using a buffer with a pH of 2 would not be an effective negative control for pepsin, which has an optimal pH close to 2, so it is not a good choice. On the other hand, a buffer solution with a pH of 10 would provide an environment far from the optimum for all three enzymes, making it the most appropriate negative control. This way, the experiment can validate the effect of non-optimal pH conditions on enzyme activity by showing minimal or no enzyme activity at pH 10, thereby serving as a proper benchmark for comparing the function of enzymes at their respective optimum pH values.