ap biology unit 3 mcq

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12-01-2025

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Unit 3 of AP Biology, focusing on cellular energetics, is a crucial section demanding a deep understanding of metabolic processes. Mastering this unit is essential for achieving a high score on the AP exam. This comprehensive guide provides practice multiple-choice questions (MCQs) mirroring the style and difficulty of the actual exam, alongside detailed explanations to solidify your understanding.

Practice MCQs: Cellular Respiration & Photosynthesis

Instructions: Choose the best answer for each multiple-choice question.

1. Which of the following is NOT a product of glycolysis?

a) ATP b) NADH c) Pyruvate d) FADH2 e) H₂O

2. The electron transport chain is located in the:

a) Cytoplasm b) Mitochondrial matrix c) Inner mitochondrial membrane d) Outer mitochondrial membrane e) Stroma of the chloroplast

3. During photosynthesis, the primary role of photosystem II is to:

a) Fix carbon dioxide b) Generate ATP c) Reduce NADP+ d) Split water molecules e) Synthesize glucose

4. What is the net ATP production from one molecule of glucose during aerobic cellular respiration?

a) 2 ATP b) 4 ATP c) 36-38 ATP d) 10 ATP e) 20 ATP

5. Which process produces the most ATP per glucose molecule?

a) Glycolysis b) Krebs cycle (Citric Acid Cycle) c) Oxidative phosphorylation (Electron Transport Chain) d) Fermentation e) Photosynthesis

6. Chemiosmosis, the process of ATP synthesis driven by a proton gradient, is crucial in both:

a) Glycolysis and fermentation b) Krebs cycle and glycolysis c) Photosynthesis and cellular respiration d) Fermentation and photosynthesis e) Only cellular respiration

7. Which of the following is a byproduct of alcoholic fermentation?

a) Lactic acid b) Ethanol c) Pyruvic acid d) Carbon dioxide e) Both b and d

8. The Calvin cycle takes place in the:

a) Thylakoid membrane b) Stroma c) Cytoplasm d) Mitochondrial matrix e) Cristae

9. What molecule acts as the final electron acceptor in the electron transport chain of cellular respiration?

a) NAD+ b) FADH2 c) Oxygen (O2) d) Water (H2O) e) Carbon dioxide (CO2)

10. Which of the following is NOT involved in the light-dependent reactions of photosynthesis?

a) Photosystems I and II b) ATP synthase c) RuBisCo d) Electron transport chain e) Water

Answer Key and Explanations

1. d) FADH2: FADH2 is produced during the Krebs cycle, not glycolysis.

2. c) Inner mitochondrial membrane: The electron transport chain is embedded within the inner mitochondrial membrane's cristae.

3. d) Split water molecules: Photosystem II uses light energy to split water molecules, releasing electrons, protons (H+), and oxygen.

4. c) 36-38 ATP: The exact number varies depending on the efficiency of the shuttle system used to transport NADH from glycolysis into the mitochondria.

5. c) Oxidative phosphorylation (Electron Transport Chain): Oxidative phosphorylation generates the vast majority of ATP during cellular respiration.

6. c) Photosynthesis and cellular respiration: Chemiosmosis is a fundamental process for ATP synthesis in both these metabolic pathways.

7. e) Both b and d: Alcoholic fermentation produces ethanol and carbon dioxide.

8. b) Stroma: The Calvin cycle, the light-independent reactions of photosynthesis, occurs in the stroma of the chloroplast.

9. c) Oxygen (O2): Oxygen is the final electron acceptor, forming water molecules.

10. c) RuBisCo: RuBisCo is an enzyme involved in the Calvin cycle (light-independent reactions).

This set of MCQs provides a taste of the types of questions you might encounter on the AP Biology exam. Remember to review all concepts thoroughly, practice more questions, and consult your textbook and other resources for a comprehensive understanding of cellular energetics. Good luck with your studies!