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AP Biology
AP Bio Unit 3 MCQ Set B Data and Experiments
Shared by Ashton · Nov 12, 2026 · 0 plays
15 questions across 4 sections. After every answer you’ll see why each choice is right or wrong, not just the one you picked.
Sample questions
Open a question to see the answer choices and the correct answer.
Based on the data, at about what pH does this amylase work best?
- A. pH 9
- B. pH 6
- C. pH 7 ✓
- D. pH 8
Correct answer: C. The highest rate (4.6 mg/min) is at pH 7.
By about what percentage does the rate decrease when pH changes from 7 to 9?
- A. About 410%
- B. About 3.7%
- C. About 80% ✓
- D. About 20%
Correct answer: C. (0.9 − 4.6) ÷ 4.6 × 100 ≈ −80%.
Which explanation best accounts for the low rate at pH 9?
- A. The starch is denatured at pH 9, so it can't enter the active site
- B. Fewer collisions happen because molecules move more slowly at high pH
- C. Disrupted R-group bonds change the active site's shape ✓
- D. Basic solutions supply hydroxide that acts as a competitive inhibitor
Correct answer: C. PH outside the optimum disrupts H-bonds and ionic interactions, changing the structure (3.2.A.1).
Which would be the most appropriate negative control for this experiment?
- A. Twice as much amylase in each pH buffer with the starch
- B. Starch in each pH buffer with no amylase added ✓
- C. Amylase and starch in water instead of buffer
- D. Amylase and starch at pH 7 only, since that's the optimum
Correct answer: B. It shows whether starch breaks down by itself at each pH, so the loss can be credited to amylase.
Which conclusion about Inhibitor Z is best supported by the data?
- A. It denatures the enzyme, since the rate at 1 mM drops by 65%
- B. It's noncompetitive: it lowers the rate at every substrate level
- C. It's an activator, because the rate increases with more substrate
- D. It's competitive: high substrate brings the rate close to normal ✓
Correct answer: D. At 20 mM, Z's rate (78) is close to the uninhibited rate (83). Extra substrate outcompetes it at the active site.