Lesson 4.2: Photosynthesis: Sugar as Food



Chapter 26. CK-12 Biology Workbook Answers

Lesson 4.2: Photosynthesis: Sugar as Food

Lesson 4.2: True or False

1. true 2. true 3. false 4. false 5. true 6. false 7. true 8. true 9. true 10. false 11. false 12. true 13. false 14. true 15. false

Lesson 4.2: Critical Reading

1. During the light reactions, light is absorbed and transformed to chemical energy in the bonds of NADPH and ATP. 2. Light is absorbed in steps 1 and 4. 3. Water is split to produce the electrons needed to replace the two electrons that were lost from the chlorophyll molecule in Step 1. 4. An electron transport chain is a series of electron-transport molecules. During the light reactions, as electrons are passed down the electron transport chain, their energy is captured and used to pump hydrogen ions into the thylakoid interior space. At the end of the second electron transport chain, the electrons are transferred to NADP+ to produce the energy-carrying molecule NADPH. 5. ATP is made by ATP synthase. Towards the end of the light reactions, there is a greater concentration of hydrogen ions in the thylakoid interior space, forming a chemiosmotic gradient. This gradient causes hydrogen ions to flow back across the thylakoid membrane to the stroma, where their concentration is lower. The enzyme ATP synthase acts as a channel protein and helps the ions cross the membrane. ATP synthase also uses their energy to add a phosphate group (Pi) to a molecule of ADP, producing a molecule of ATP.

Lesson 4.2: Multiple Choice

1. d 2. b 3. c 4. a 5. a 6. b 7. d 8. b

Lesson 4.2: Vocabulary I

1. c 2. f 3. b 4. i 5. l 6. d 7. k 8. h 9. e 10. j 11. g 12. a

Lesson 4.2: Vocabulary II

1. Chloroplasts 2. light reactions 3. Calvin cycle 4. oxygen 5. chemosynthesis 6. grana, thylakoid 7. autotrophs 8. chlorophyll 9. electrons 10. two, glucose 11. ATP, NADPH 12. glucose

Lesson 4.2: Critical Writing

Sample answer The two stages of photosynthesis are the light reactions and the Calvin cycle. During the light reactions, water and light energy from the sun are changed into chemical energy that is stored in ATP and NADPH. This stage also releases oxygen as a waste product. The Calvin cycle combines carbon from carbon dioxide in the air and uses the chemical energy in ATP and NADPH - from the light reactions - to make glucose.

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26.4. Chapter 4: Photosynthesis and Cellular Respiration



Lesson 4.3: Powering the Cell: Cellular Respiration

Lesson 4.3: True or False

1. false 2. true 3. false 4. true 5. true 6. false 7. true 8. false 9. false 10. true 11. true 12. true 13. true 14. false 15. false

Lesson 4.3: Critical Reading

1. Electron transport is stage III of cellular respiration --it occurs at the end of the process. 2. As high-energy electrons are transported along the electron transport chain, some of their energy is used to pump hydrogen ions (from NADH and FADH2) across the inner membrane, from the matrix into the intermembrane space. These hydrogen ions are used to make ATP as they flow through ATP synthase. 3. Oxygen is the final electron acceptor at the end of the electron transport chain. Electrons combine with hydrogen ions and oxygen to form water. Without oxygen, this process cannot occur. 4. ATP synthase is a channel protein and an enzyme. It acts as a channel protein, helping the hydrogen ions cross the membrane, and as an enzyme, forming ATP from ADP and inorganic phosphate. 5. Glycolysis produces 2 ATP molecules, and the Krebs cycle produces 2 more. Electron transport begins with several molecules of NADH and FADH2 from the Krebs cycle and transfers their energy into as many as 34 more ATP molecules.

Lesson 4.3: Multiple Choice

1. b 2. c 3. c 4. a 5. b 6. d 7. a 8. c

Lesson 4.3: Vocabulary I

1. c 2. e 3. h 4. l 5. b 6. k 7. d 8. j 9. f 10. i 11. g 12. a

Lesson 4.3: Vocabulary II

1. glycolysis, Krebs 2. anaerobic 3. mitochondria 4. III 5. oxygen 6. pyruvate 7. cellular respiration 8. NADH, ATP 9. Acetyl-CoA 10. 2, 4 11. ATP synthase 12. 38

Lesson 4.3: Critical Writing

Cellular respiration and photosynthesis form a cycle as cellular respiration uses the products of photosynthesis and photosynthesis uses the products of cellular respiration. Specifically, photosynthesis makes glucose and oxygen, which are the reactants of cellular respiration. Cellular respiration then uses the glucose and oxygen to make carbon dioxide and water, which are released to the environment. The plants then take up water through their roots and carbon dioxide through their leave, and together with energy from the sun, photosynthesis begins again.

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Chapter 26. CK-12 Biology Workbook Answers

Lesson 4.4: Anaerobic Respiration

Lesson 4.4: True or False

1. false 2. true 3. true 4. true 5. false 6. false 7. true 8. true 9. false 10. false 11. true 12. false 13. true 14. true 15. false

Lesson 4.4: Critical Reading

1. Fermentation is a way of making ATP without oxygen. 2. NAD+ allows glycolysis to continue to make ATP. So NAD+ must continually be recycled from NADH during fermentation. Without this recycling, glycolysis cannot continue. 3. Both lactic acid fermentation and alcoholic fermentation begin with pyruvate (or pyruvic acid), the product of glycolysis. 4. Yeasts in bread dough use alcoholic fermentation. During this process, they produce carbon dioxide gas, which is released as pyruvic acid is reduced to ethanol. The gas forms bubbles in the dough, which cause the dough to expand. The bubbles leave small holes in the bread after it bakes, making the bread light and fluffy. 5. Your muscles get sore because your muscle cells used lactic acid fermentation for energy when oxygen cannot reach these cells quickly enough for aerobic respiration, such as during intense activity. This causes lactic acid to build up in the muscles. It is the buildup of lactic acid that makes the muscles feel tired and sore.

Lesson 4.4: Multiple Choice

1. a 2. c 3. d 4. a 5. a 6. d 7. b 8. d

Lesson 4.4: Vocabulary I

1. e 2. c 3. g 4. j 5. a 6. i 7. l 8. f 9. k 10. d 11. h 12. b

Lesson 4.4: Vocabulary II

1. ATP 2. glycolysis 3. glycolysis 4. oxygen 5. alcoholic 6. fungi 7. lactic acid 8. carbon dioxide 9. two 10. Yeasts 11. ATP 12. ATP

Lesson 4.4: Critical Writing

Sample answer Aerobic respiration only occurs in the presence of oxygen, whereas anaerobic respiration occurs in the absence of oxygen. Aerobic respiration produces much more ATP per glucose than anaerobic respiration, but anaerobic respiration allows the cell to survive in the absence of oxygen by recycling NAD+ and allowing glycolysis to continue.

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