Ap Bio Unit 2 Practice Test

AP Bio Unit 2 Practice Test: Mastering Cellular Energetics and Cell Communication

Unit 2 of the AP Biology curriculum delves into the fascinating worlds of cellular energetics and cell communication. These fundamental processes are crucial for all living organisms, and a strong understanding is essential for success on the AP exam. This comprehensive guide provides a practice test, detailed explanations, and valuable study tips to help you master this unit.

Section 1: Cellular Energetics (Multiple Choice)

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 Krebs cycle takes place in the:

(a) Cytoplasm (b) Mitochondria (c) Nucleus (d) Golgi Apparatus (e) Chloroplast

3. What is the primary role of oxygen in cellular respiration?

(a) To donate electrons to the electron transport chain. (b) To act as the final electron acceptor in the electron transport chain. (c) To directly produce ATP. (d) To break down glucose. (e) To generate CO2.

4. What is the net ATP yield from oxidative phosphorylation (electron transport chain and chemiosmosis)?

(a) 2 ATP (b) 4 ATP (c) 34 ATP (approximately) (d) 36 ATP (approximately) (e) 38 ATP (approximately)

5. Fermentation produces significantly less ATP than cellular respiration because:

(a) It does not require oxygen. (b) It only uses glycolysis. (c) It does not utilize the electron transport chain. (d) It produces ethanol or lactic acid as a byproduct. (e) Both (b) and (c).

6. Which process directly uses light energy to excite electrons?

(a) Glycolysis (b) Krebs Cycle (c) Photosynthesis (d) Fermentation (e) Chemiosmosis

7. The Calvin cycle occurs in the:

(a) Thylakoid membrane (b) Stroma (c) Cytoplasm (d) Mitochondria (e) Nucleus

8. What is the primary role of Rubisco in the Calvin cycle?

(a) To split water molecules. (b) To capture light energy. (c) To fix carbon dioxide. (d) To produce ATP. (e) To produce NADPH.

9. Which molecule acts as both an electron carrier and a proton carrier in photosynthesis and cellular respiration?

(a) ATP (b) NAD+ (c) FAD (d) NADP+ (e) ADP

10. Photorespiration reduces the efficiency of photosynthesis because:

(a) It consumes ATP. (b) It releases oxygen. (c) It uses rubisco to fix oxygen instead of carbon dioxide. (d) It generates more ATP. (e) It reduces the amount of light absorbed.

Section 2: Cell Communication (Multiple Choice)

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

11. Which of the following is NOT a type of cell signaling?

(a) Direct contact (b) Paracrine signaling (c) Endocrine signaling (d) Synaptic signaling (e) Exocytosis

12. A ligand is:

(a) A type of receptor protein. (b) A molecule that binds to a receptor. (c) A second messenger molecule. (d) An enzyme that catalyzes phosphorylation. (e) A type of transmembrane protein.

13. Which type of receptor is directly involved in the opening or closing of ion channels?

(a) G protein-coupled receptors (b) Receptor tyrosine kinases (c) Ligand-gated ion channels (d) Intracellular receptors (e) Steroid hormone receptors

14. Second messenger molecules:

(a) Are always proteins. (b) Amplify the signal from a first messenger. (c) Directly bind to the ligand. (d) Are located on the cell membrane. (e) Only function in plant cells.

15. Which of the following is a common second messenger molecule?

(a) ATP (b) cAMP (c) Glucose (d) Pyruvate (e) FADH2

16. Apoptosis is:

(a) Cell division. (b) Programmed cell death. (c) Uncontrolled cell growth. (d) Cell differentiation. (e) Cell migration.

17. Which type of signaling involves the release of hormones into the bloodstream?

(a) Paracrine signaling (b) Autocrine signaling (c) Endocrine signaling (d) Direct contact signaling (e) Synaptic signaling

18. Signal transduction pathways are important because they:

(a) Convert extracellular signals into intracellular responses. (b) Store genetic information. (c) Produce ATP. (d) Synthesize proteins. (e) Transport molecules across the cell membrane.

19. What is the role of protein kinases in signal transduction pathways?

(a) To dephosphorylate proteins. (b) To phosphorylate proteins. (c) To act as second messengers. (d) To transport ions across the membrane. (e) To bind to ligands.

20. What is the general role of protein phosphatases in signal transduction pathways?

(a) Amplify the signal (b) Activate target proteins (c) Turn off signaling pathways (d) Act as second messengers (e) Transcribe genes

Section 3: Free Response Question

Question: Compare and contrast cellular respiration and photosynthesis, focusing on the following aspects:

(a) The overall goal of each process. (b) The location within the cell where each process occurs. (c) The key reactants and products of each process. (d) The similarities and differences in the electron transport chains used in each process. (e) The importance of each process for maintaining life on Earth.

Answer Key and Explanations

Section 1: Cellular Energetics

1. (d) FADH2: FADH2 is a product of the Krebs cycle, not glycolysis.
2. (b) Mitochondria: The Krebs cycle occurs in the mitochondrial matrix.
3. (b) To act as the final electron acceptor in the electron transport chain: Oxygen is essential for the electron transport chain to function properly.
4. (c) 34 ATP (approximately): The exact number can vary slightly depending on the shuttle system used.
5. (e) Both (b) and (c): Fermentation only uses glycolysis and does not involve the electron transport chain.
6. (c) Photosynthesis: Light energy is directly used to excite electrons in photosystem II.
7. (b) Stroma: The Calvin cycle occurs in the stroma of the chloroplast.
8. (c) To fix carbon dioxide: Rubisco catalyzes the reaction that fixes CO2 into an organic molecule.
9. (d) NADP+: NADP+ is reduced to NADPH in photosynthesis and oxidized in the Calvin cycle.
10. (c) It uses rubisco to fix oxygen instead of carbon dioxide: Photorespiration wastes energy and reduces the efficiency of carbon fixation.

Section 2: Cell Communication

11. (e) Exocytosis: Exocytosis is a process of vesicle secretion, not a type of cell signaling.
12. (b) A molecule that binds to a receptor: Ligands initiate signaling cascades by binding to specific receptors.
13. (c) Ligand-gated ion channels: These channels open or close in response to the binding of a ligand.
14. (b) Amplify the signal from a first messenger: Second messengers help relay the signal and enhance its effect.
15. (b) cAMP: cAMP is a widely used second messenger in many signaling pathways.
16. (b) Programmed cell death: Apoptosis is a controlled process of cell death.
17. (c) Endocrine signaling: Endocrine signaling uses hormones released into the bloodstream to reach distant targets.
18. (a) Convert extracellular signals into intracellular responses: Signal transduction pathways translate signals from outside the cell to inside the cell.
19. (b) To phosphorylate proteins: Protein kinases add phosphate groups to proteins, often activating them.
20. (c) Turn off signaling pathways: Protein phosphatases remove phosphate groups, deactivating proteins and terminating the signal.

Section 3: Free Response Question (Example Response)

(a) Overall Goal: Cellular respiration breaks down glucose to generate ATP, the cell's energy currency. Photosynthesis converts light energy into chemical energy in the form of glucose.

(b) Location: Cellular respiration primarily occurs in the mitochondria (Krebs cycle and electron transport chain), with glycolysis in the cytoplasm. Photosynthesis takes place in chloroplasts, with the light-dependent reactions in the thylakoid membranes and the Calvin cycle in the stroma.

(c) Reactants and Products: Cellular respiration: Reactants – glucose and oxygen; Products – ATP, carbon dioxide, and water. Photosynthesis: Reactants – carbon dioxide and water (plus light energy); Products – glucose and oxygen.

(d) Electron Transport Chains: Both processes utilize electron transport chains embedded in membranes to generate a proton gradient, which drives ATP synthesis through chemiosmosis. However, the electron donors and acceptors differ. In cellular respiration, electrons are donated from NADH and FADH2 and the final electron acceptor is oxygen. In photosynthesis, electrons are donated from water, and the final electron acceptors are NADP+. The flow of electrons is also reversed, from water to NADP+ in photosynthesis, versus from NADH/FADH2 to O2 in respiration.

(e) Importance: Cellular respiration provides the energy required for virtually all life processes. Photosynthesis is crucial for producing the organic molecules (glucose) that serve as the foundation of most food chains on Earth and releases oxygen, essential for aerobic respiration. The two processes are intimately linked, with the products of one serving as the reactants for the other, maintaining a crucial balance in the biosphere.

This practice test and its explanations should provide a solid foundation for your preparation for the AP Biology Unit 2 exam. Remember to review the relevant chapters in your textbook, utilize additional resources like online quizzes and practice questions, and consult with your teacher or classmates if you need further assistance. Good luck!