Passage I

Agarose, a carbohydrate composed of galactose subunits, is found in the cell wall of some types of algae. Agarose can be broken down by the enzyme agarase. A student discovered a new form of agarase, Agarase X, in a species of bacteria. The student conducted the following experiments to determine the temperature and pH at which agarase X has the greatest activity.

Experiment 1

The student added 0. 2 mL of an Agarase X solution to each of 9 test tubes (Tubes 1-9), and then added to each tube 0.8 mL of a buffer solution (a solution that maintains a stable pH) having a pH of 7 and containing 0.2% agarose. Each of the tubes was incubated at a different temperature for 30 min, and the relative activity (percent of the greatest measured activity) of the Agarase X was determined for each tube (see Table 1).

Experiment 2

The student repeated the procedures used in Experiment 1 in every respect but the following: the test tubes (Tubes 10-18) received different agarose buffer solutions, each of a different pH, and all the tubes were incubated at 40°C. Once again, the relative activity of the Agarase X was determined for each tube (see Table 2).

2. Suppose Experiment 2 had included an additional tube, which received an agarose buffer solution having a pH of 2. The relative activity of the Agarase X in that tube would most likely have been:

Answer and Explanation

Your Answer is

Correct Answer is F

Explanation

Looking at table 2, it can be found that when the pH is less than 7, the smaller the pH, the lower the relative activity;

When the pH=2, it is lower than the pH of tube 10 (pH=3) , so the relative activity should also be less than 2%, then only the F option less than 10% meets