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7
ENERGY
FOR
CELLS
CHAPTER REVIEW
Cellular respiration is the breakdown of glucose and other
metabolites, along with the capture of energy for the
buildup of ATP molecules. Of four phases, only one occurs outside the mitochondria. This chapter considers
each phase of cellular respiration in some detail. It also
considers fermentation, which provides a burst of ATP
when oxygen is not available. Fermentation cannot
occur long term because it leads to cramping and a
lower pH than normal.
CHAPTER KEY TERMS
After studying the key terms of this chapter, match the phrases below with the alphabetized list of terms.
acetyl-CoA
glycolysis
citric acid cycle
intermembrane space
electron transport chain
oxygen deficit
fermentation
preparatory (prep) reaction
a. space between the outer and inner membrane of a mitochondrion _______________________
b. passage of electrons from one carrier to the next with the capture of energy for ATP production
_______________________
c. produces acetyl groups, which enter the citric acid cycle _______________________
d. series of reactions that begin and end with the same molecule; releases carbon dioxide _______________________
e. breakdown of glucose to two pyruvic acid molecules _______________________
f. molecule that transports acetyl groups to the citric acid cycle _______________________
g. breakdown of glucose to lactic acid (or alcohol and CO 2 ) _______________________
h. metabolic state in need of oxygen to restore homeostatic conditions in cells _______________________
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S T U DY E X E R C I S E S
Study the text section by section as you answer the questions that follow.
7.1 CELLULAR RESPIRATION (PP. 98–99)
• The breakdown of glucose to CO 2 and H 2 O during cellular respiration drives the synthesis of ATP.
• The complete breakdown of glucose requires four phases: three metabolic pathways and one individual
enzymatic reaction.
1. Study the overall equation for cellular respiration and then answer the questions:
C6H12O6
glucose
+
6 O2
6 CO2
+
6 H2O
+
energy
a. What are the reactants for cellular respiration? _____________________________________________________
b. How do your cells acquire these reactants? ________________________________________________________
c. How does your body rid itself of the end products of cellular respiration? _____________________________
d. What is the purpose of cellular respiration? ________________________________________________________
e. What form of energy do cells use? ________________________________________________________________
2. From the list of terms on page 53, list the four phases of cellular respiration which are a-d in the diagram:
a. _______________________________________________________________________________________________
b. _______________________________________________________________________________________________
c. _______________________________________________________________________________________________
d. _______________________________________________________________________________________________
Cytoplasm
e–
glucose
pyruvate
b.
a.
c.
ATP
d.
ATP
ATP
3. Cellular respiration results in 38 ATP. Glycolysis and the citric acid cycle produce 2 ATP per glucose
molecule:
a. Write the number of ATP produced next to the ATP bursts in the diagram above.
b. Which phase of cellular respiration accounts for most of the ATP produced?
__________________________
7.2 OUTSIDE THE MITOCHONDRIA: GLYCOLYSIS(P. 101)
• Glycolysis is a metabolic pathway that partially breaks down glucose outside the mitochondria.
4. a. Where does glycolysis occur? ______________
b. Does it require oxygen? ______________
c. Glycolysis begins with ______________.
d. Glycolysis ends with ______________.
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e. How many ATP are produced per glucose molecule as a direct result of glycolysis? ______________
f. What coenzyme carries out oxidation of substrates during glycolysis? ______________
g. Considering your answers to these questions, what is the output of glycolysis? ______________,
______________, and ______________.
7.3 INSIDE THE MITOCHONDRIA (PP. 102–106)
• The preparatory reaction and the citric acid cycle, which occur inside the mitochondria, continue the
breakdown of glucose products until carbon dioxide and water result.
• The electron transport chain, which receives electrons from NADH and FADH 2 , produces most of the ATP
during cellular respiration.
• Other nutrients in addition to glucose can be broken down to drive ATP synthesis.
5. Label the following diagram of a mitochondrion using the terms:
cristae
inner membrane
intermembrane space
matrix
outer membrane
a.
b.
c.
d.
e.
6. Using three of your labels from question 5, where does each of the following processes occur?
a. glycolysis ______________
b. citric acid cycle ______________
c. electron transport chain ______________
7. a. The citric acid cycle begins and ends with what molecule? ______________
b. A two-carbon molecule acetyl group enters the citric acid cycle. What gas leaves the citric acid
cycle? ______________
c. How many ATP are produced per glucose molecule as a direct result of the citric acid cycle? _____________
d. What coenzymes carry out oxidation of substrates in the citric acid cycle? ______________
e. Considering your answers to these questions, what are the outputs of the citric acid cycle? ______________,
______________, ______________, and ______________
The Electron Transport Chain ( PP . 104–105)
8. What coenzymes bring hydrogen atoms (H + + e – ) to the electron transport chain?
a. ______________
What happens to the electrons? b. ______________
What happens to the hydrogen ions?
c. ______________
What molecule is the final acceptor of electrons from the electron transport chain?
d. ______________
Each pair of electrons carried by NADH from the citric acid cycle that passes down the electron transport
chain accounts for the buildup of how many ATP?
e. ______________
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9. As a result of electron transport chain activity, H + build up in the
a. ______________
flow b. ______________ their concentration gradient into the matrix,
ADP + P .
space. When these H +
c. ______________
is produced from
Energy Yield from Glucose Metabolism ( P . 106)
10. After studying the following calculation of the ATP yield per glucose molecule, answer the questions:
Phase
NADH
FADH2
ATP Yield
Glycolysis
2
–
2
Prep reaction
2
–
–
Citric acid
cycle
6
2
2
2
30
4
Electron
transport chain
10
Total ATP
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a. What is the only phase of cellular respiration that doesn’t produce some ATP directly? _________________
b. The formation of what reduced coenzyme accounts for most of the ATP production during cellular
respiration? ____________________________________________________________________________________
Alternative Metabolic Pathways ( P . 106)
Study the diagram and then answer these questions.
11. The carbon skeleton of amino acids can be respired if the amino acid first undergoes _________________________.
12. When fats are respired, glycerol enters a. ______________,
fatty acids are converted to the molecule
b. ______________,
and the acetyl group enters
the citric acid cycle.
Proteins
Carbohydrates
amino acids
glucose
Fats and oils
13. Explain why the consumption of carbohydrates
makes us fat. _________________________________
glycerol
______________________________________________
NH3
Glycolysis
ATP
pyruvate
Acetyl-CoA
Citric
acid
cycle
ATP
ATP
Electron
transport
chain
H 2O
O2
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fatty acids
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7.4 FERMENTATION (P. 107)
• Fermentation is a metabolic pathway that partially breaks down glucose under anaerobic conditions.
14. a. What happens to pyruvate during fermentation in humans? _______________________________________________
b. Why is fermentation wasteful? __________________________________________________________________________
c. What is its advantage? __________________________________________________________________________________
d. What is oxygen deficit in humans? _______________________________________________________________________
glucose
NAD+
I
NADH
DH
II
acetyl group
III
+
D
NA
NA
DH
NA
D+
pyruvate
NA
15. Label the following processes I, II, and/or III, based on this diagram:
a.
occurs under anaerobic conditions
b.
fermentation
c.
glycolysis
d.
prep reaction
e.
occurs in cytoplasm
f.
occurs in mitochondria
lactate
Concerning microorganisms and fermentation, answer the following questions.
16. a. What happens to pyruvate during fermentation in yeast? __________________________________________________
b. When yeast is used to leaven bread, what makes the bread rise? __________________________________________
c. When yeast is used to ferment grapes, which end product of fermentation is desired? _____________________
17. Considering your answers to the questions about fermentation, what are the outputs of fermentation? In
humans, a. ________________________, and b. ________________________ . In yeasts, c. ________________________, and
d. ________________________.
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K E Y WO R D C RO S S WO R D
Review key terms by completing this crossword puzzle using the following alphabetized list of terms:
1
2
3
4
5
6
acetyl-CoA
citric acid cycle
coenzyme A
electron transport
fermentation
glycolysis
intermembrane space
oxygen deficit
7
8
–
Across
1 occurs between the outer and inner membrane of a
mitochondrion (two words)
4 molecule that carries acetyl group to the citric acid
cycle
5 anaerobic breakdown of glucose that results in two
ATP and products such as alcohol and lactate
8 pathway of metabolism converting glucose to pyruvate; resulting in a net gain of two ATP and two
NADH molecules
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Down
2 type of chain whereby electrons are passed along a
series of carrier molecules, storing energy for the
synthesis of ATP (two words)
3 reactions in mitochondria that connect acetyl groups
to carbon dioxide (three words)
6 molecule made up of an acetyl group attached to
coenzyme A (two words)
7 occurs due to fermentation that results in lactate
buildup (two words)
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CHAPTER TEST
OBJECTIVE QUESTIONS
Do not refer to the text when taking this test.
1. Fermentation is
a. glycolysis and the citric acid cycle.
b. glycolysis and the reduction of pyruvate.
c. glycolysis only.
d. the reduction of pyruvate only.
2. Each of the following is a product of cellular
respiration EXCEPT
a. ATP.
b. carbon dioxide.
c. oxygen.
d. water.
3. Per glucose molecule, the net gain of ATP molecules from glycolysis per substrate phosphor–
ylation is
a. two.
b. four.
c. six.
d. eight.
4. Fermentation supplies
a. glycolysis with free NAD + .
b. hydrogen to the prep reaction.
c. oxygen as an electron acceptor.
d. the citric acid cycle with oxygen.
5. Which is NOT an event of the prep reaction?
a. breaks down pyruvate
b. converts a citric acid molecule
c. oxidizes pyruvate
d. transfers an acetyl group
6. Select the incorrect association.
a. electron transport chain—cristae
b. fermentation—plasma membrane
c. glycolysis—cytoplasm
d. citric acid cycle—matrix
7. Select the process with the greatest yield of
NADH per glucose molecule.
a. glycolysis
b. citric acid cycle
c. substrate-level phosphorylation
d. prep reaction
8. Which of the following do not result in NADH?
a. glycolysis
b. citric acid cycle
c. electron transport chain
d. prep reaction
e. fermentation
9. The coenzyme that carries acetyl groups is
a. ATP.
b. NAD + .
c. NADH.
d. coenzyme A.
e. RuBP.
10. The carbon dioxide given off by cellular respiration is produced by
a. glycolysis.
b. the prep reaction.
c. the citric acid cycle.
d. the electron transport chain.
e. Both b and c are correct.
11. The final acceptor for electrons in cellular respiration is
a. ATP.
b. NAD + .
c. FAD.
d. oxygen.
e. carbon dioxide.
12. Which of the following reactions occurs in the
cristae of the mitochondria?
a. the citric acid cycle
b. the prep reaction
c. the electron transport chain
d. glycolysis
e. the Calvin cycle
13. The coenzymes NAD + and FAD carry hydrogen
atoms (H + + e – ) to the
a. glycolysis reactions.
b. prep reaction.
c. citric acid cycle.
d. Calvin cycle.
e. electron transport chain.
14. Which of the following statements is NOT true
about fermentation?
a. It is an anaerobic process.
b. The products are toxic to cells.
c. It results in two ATPs per glucose molecule.
d. In the absence of O 2 , muscle cells form CO 2
and alcohol.
e. It can be used to make bread rise.
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CRITICAL THINKING QUESTIONS
The introduction to this chapter is about weight loss and cellular respiration.
15. Which section in the chapter discusses how you can gain weight regardless of the particular type of food you
eat? ________________________________________________________________________________________________________
16. Suppose your diet consisted of nothing but fruits, but at the end of the week, you consumed many more
calories than usual. Would you gain weight? ________________________________________________________________
Explain. ____________________________________________________________________________________________________
17. Why does exercise help you lose weight? ___________________________________________________________________
18. Which organelle is working overtime when we exercise? ____________________________________________________
19. What gas does mitochondria need to break down nutrient molecules and where does this gas come from? _____
____________________________________________________________________________________________________________
20. What do mitochondria specifically do with oxygen? _________________________________________________________
Test Results: ______ number correct ÷ 20 = ______ × 100 = ______ %
EXPLORING
THE
INTERNET
ARIS, the Essentials of Biology website: http://www.mhhe.com/maderessentials
ARIS, the website for Essentials of Biology, offers access to a wide variety of tools to help students learn biological
concepts and to reinforce their knowledge. Online study aids such as practice quizzes, interactive activities, animations, labeling exercises, flashcards, and much more are organized according to the major sections of each chapter.
There is even an online tutorial service!
ANSWER KEY
CHAPTER KEY TERMS
a. intermembrane space b. electron transport chain
c. preparatory (prep) reaction d. citric acid cycle e. glycolysis f. acetyl-CoA g. fermentation h. oxygen deficit
STUDY EXERCISES
1. a. glucose and oxygen b. Glucose is in the food we eat
and oxygen is in the air we breathe. c. Breathing out CO 2
and urination rids the body of excess water. d. to acquire chemical energy in a form cells can use e. ATP
molecules 2. a. glycolysis b. preparatory reaction
c. citric acid cycle d. electron transport chain 3. a. 2,
2, 34 b. electron transport chain 4. a. cytoplasm b. no
c. glucose d. pyruvate e. two ATP f. NAD g. pyruvate, NADPH, ATP 5. a. cristae b. matrix c. outer
membrane d. intermembrane space e. inner membrane
f. cytoplasm 6. a. cytoplasm b. matrix c. cristae
7. a. citrate b. CO 2 c. two ATP d. NAD and FAD
e. NADH, FADH 2 , ATP, and CO 2 8. a. NADH and
FADH 2 b. pass down the system c. pumped into intermembrane space d. O 2 e. three ATP 9. a. intermembrane b. down c. ATP 10. a. prep reaction b. NADH
11. removal of amino groups 12. a. glycolysis b. acetylCoA 13. Carbohydrates are metabolized to glycerol
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and fatty acids, which join to form fat. 14. a. reduced
to lactate b. produces only two ATP c. does not require
oxygen d. O 2 needed to metabolize lactate 15. a. I and
III b. I and III c. I d. II e. I and III f. II 16. a. reduced
to alcohol and CO 2 b. release of CO 2 c. alcohol
17. a. two lactate b. two ATP net c. two alcohol d. two
CO 2 and two ATP net
KEYWORD CROSSWORD
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CHAPTER TEST
1. b 2. c 3. a 4. a 5. b 6. b 7. b 8. c 9. d
10. e 11. d 12. c 13. e 14. d 15. alternative metabolic pathways 16. yes, because all nutrient molecules
in excess can be converted to fat 17. You need more
ATP molecules to perform exercise, and your body breaks
down many more nutrients to build up the number of ATP
molecules needed. 18. mitochondrion 19. We breathe
in oxygen from the atmosphere; oxygen was put there by
plants. 20. Oxygen is the final acceptor for electrons at
the end of the electron transport chain.
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