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AP Biology Reading Guide Name ____________________________________

Chapter 9: Cellular Respiration: Harvesting Chemical Energy Overview: Life is Work

1. Before getting involved with the details of cellular respiration and

photosynthesis, take a second to look at the big picture. Photosynthesis

and cellular respiration are key ecological concepts involved with energy

flow. The energy stored in organic molecules of food ultimately come from

the sun. However, energy and matter move through an ecosystem in very

different ways. Using the diagram to the right, explain how energy and

matter move through an ecosystem.

Concept 9.1 Catabolic pathways yield energy by oxidizing organic fuels

2. Contrast fermentation and cellular respiration. 3. Write out the equation for the catabolic degradation of glucose by cellular respiration. Include the names of the

molecules as well. 4. Both cellular respiration and photosynthesis are redox reactions. In redox reactions, pay attention to the flow of

electrons. Explain the difference between oxidation and reduction?

5. Below is a generalized formula for a redox reaction.

a. Label the formula showing which part of the reaction is oxidized and which part is reduced.

b. Circle and label the reducing agent and the oxidizing agent in the reaction.

Xe– + Y X + Ye–

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6. In cellular respiration, electrons are not transferred directly from glucose to oxygen. Each electron is coupled with a

proton to form a hydrogen atom. Following the movement of hydrogens allows you to follow the flow of electrons. Identify the name of the electron carrier molecule that temporarily holds and transports the hydrogens.

7. The molecule you named above is coenzyme. Explain why. (Don’t remember what a coenzyme is? Go back to Ch 8)

8. The molecule you named above is also an oxidizing agent during respiration. Explain why.

9. If you mix H2 and O2 and provide a spark for activation energy, the gases will combine explosively. This same reaction

using liquid H2 and O2 is used to power the main engines of the space shuttle after it is launched. The explosion represents a release of energy as the electrons of hydrogen “fall” closer to the electronegative oxygen atoms and water is produced as a waste product. Cellular respiration also brings hydrogen and oxygen together forming water but there are two important differences. Identify the 2 differences.

10. Explain how the electron transport chain “controls” the release of energy versus the combustion of hydrogen and oxygen

gases to propel a space shuttle. 11. In summary, during cellular respiration, most electrons travel the following “downhill” route:

Glucose ______________________________ ______________________________ oxygen

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12. Explain the difference between substrate-level phosphorylation and oxidative phosphorylation. Concept 9.2 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate

13. Explain what is occurring during the 2 phases of glycolysis. 14. Identify the end products of glycolysis. Concept 9.3 The citric acid cycle completes the energy-yielding oxidation of organic molecules 15. How many times does the citric acid cycle occur for each molecule of glucose? Explain.

16. Use Figure 9.11 to help you answer the following summary questions about the citric acid cycle and a molecule of

glucose. Careful - The diagram covers only one pyruvate, although two pyruvates are formed from a single glucose. You will need to double your answers to show how much is produced from a whole glucose molecule.

a. How many NADHs are formed?

b. How many total carbons are lost as pyruvate is oxidized?

c. The lost carbons helped to form which molecule?

d. How many FADH2 have been formed?

e. How many ATPs are formed?

17. What is FADH2? 18. Explain what happened to all six carbon atoms found in the original glucose molecule?

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Concept 9.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis 19. The passage on The Pathway of Electron Transport and Figure 9.13 contain an overload of information. What you should

take away from the passage is summarized below. See if you can fill it in the missing pieces.

20. Why is oxygen considered the ultimate electron acceptor?

21. In the end, oxygen collects/combines with 4 things: 2 _____________ and 2 _____________, forming ______________

22. Using Figure 9.14, explain the overall concept of how ATP synthase uses the flow of hydrogen ions to produce ATP. 23. What is the role of the electron transport chain in forming the H+ gradient across the inner mitochondrial membrane? 24. In the diagram below, use red to trace the flow of electrons and blue to trace the flow of protons (H+).

Oxidative phosphorylation involves two components: the electron transport chain and ATP synthesis. Each “downhill”

member of the electron transport chain is lower in free _________________ but has a higher ____________________

than the preceding member of the chain. The molecule at zero free energy, which is ________________________, is

the lowest of all the molecules in free energy but the highest in electronegativity.

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25. Identify how much ATP is produced in each stage of cellular respiration by filling in the dotted-lined boxes at the bottom of the diagram. Be sure you understand how each subtotal is derived from the process above it.

26. Explain what accounts for the varied amount of ATP produced during oxidative phosphorylation. Concept 9.5 Fermentation enables some cells to produce ATP without the use of oxygen 27. Fermentation allows for the production of ATP without using _______________________________

28. For aerobic respiration to continue, the cell must be supplied with oxygen—the ultimate electron acceptor. What is the

electron acceptor in fermentation?

29. Explain how alcohol fermentation starts with glucose and yields ethanol. Be sure to stress how NAD+ is recycled.

30. Explain how lactic acid fermentation starts with glucose and yields lactate. Be sure to stress how NAD+ is recycled.

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Concept 9.6 Glycolysis and the citric acid cycle connect to many other metabolic pathways 31. What three organic macromolecules are often utilized to make ATP by cellular respiration?

32. Explain the difference in energy usage between the catabolic reactions of cellular respiration and anabolic pathways of biosynthesis.