AP Biology
AP Bio Unit 3: Enzymes and Cellular Energy (3.1–3.3)
Shared by ashtont · Oct 29, 2026 · 0 plays
16 AP-style multiple-choice questions on enzyme structure, how temperature, pH and inhibitors affect enzymes, and free energy and energy coupling. Most come with a lab passage, data table or graph shown beside the question, like the real exam.
16 questions across 3 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.
What is the dependent variable in this experiment?
- A. The time it took each disk to rise to the surface ✓
- B. The temperature the liver extract was kept at
- C. The concentration of hydrogen peroxide
- D. The volume of liver extract on each disk
Correct answer: A. Right. Rise time is what the class measured, and it depends on how fast catalase makes oxygen.
Which explanation best accounts for the results of Trial 3?
- A. Boiling destroyed the hydrogen peroxide, so there was no substrate left
- B. Boiling raised the activation energy of the breakdown of hydrogen peroxide
- C. Heat broke the weak bonds holding catalase's shape, so the active site no longer fit hydrogen peroxide ✓
- D. Boiling used up the ATP that catalase needs to work
Correct answer: C. Right. Heat breaks the hydrogen bonds and other weak interactions in the protein (denaturation), and the active site loses its shape. Cooling it back to 22 °C didn't bring the activity back.
Disks in Trial 2 (2 °C) rose more slowly than in Trial 1, but they did rise. What best explains this?
- A. At 2 °C, catalase was denatured, but only partly
- B. Cold temperatures make the reaction endergonic
- C. Cold temperatures change the shape of hydrogen peroxide so it fits the active site less well
- D. At 2 °C, molecules move more slowly, so catalase and hydrogen peroxide collide less often ✓
Correct answer: D. Right. Less kinetic energy means fewer enzyme-substrate collisions per second, so oxygen is made more slowly.
What is the main purpose of Trial 4?
- A. It shows that water is the enzyme's substrate
- B. It shows that the paper disks alone don't make oxygen with hydrogen peroxide ✓
- C. It tests the effect of temperature on catalase
- D. It shows that catalase can't work in water
Correct answer: B. Right. It's a negative control: with no enzyme, nothing happens, so the bubbles in other trials came from catalase.
Which statement is best supported by the data?
- A. Enzyme Q works faster than enzyme P at every temperature
- B. Both enzymes have the same optimum temperature
- C. Enzyme Q is denatured at temperatures below 50 °C
- D. Enzyme P's optimum temperature is near 37 °C, and it is likely denatured by 70 °C ✓
Correct answer: D. Right. P peaks at 37 °C (30) and drops to 0 by 70 °C, which fits a human enzyme losing its shape at high heat.