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).
3. Based on the results of Experiments 1 and 2, the optimal temperature and pH for the greatest Agarase X activity are closest to which of the following?
Your Answer is
Correct Answer is B
Explanation
Look at table 1, when the temperature is 40°C, the relative activity is the largest;
Look at table 2 again, when the pH=7, the relative activity is the largest