SAT Subject Biology Practice Question 23: Answer and Explanation

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Question: 23

4. Which of these is likely to reduce enzyme activity?

I. Increasing pH level

II. Decreasing temperature

III. Placing enzyme in a nonpolar liquid

A. I only
B. II only
C. III only
D. I and II
E. I, II, and III

Correct Answer: E

Explanation:

Altering temperature and pH beyond the optimal range for the enzyme is likely to reduce enzyme activity. In addition, because proteins function in an aqueous (water) solution, and water is polar, a protein will fold with its hydrophilic (water-seeking) amino acids closer to the surface and its hydrophobic (water-avoiding) amino acids closer to the center. Moving the enzyme to a nonpolar solution will alter its tertiary structure, as hydrophobic amino acids move to the surface instead.

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