Chapter 9 - Cellular Respiration: Harvesting Chemical Energy

Question 1

Fill in this summary equation for cellular respiration.

____ + 6 O₂ → ____ + 6 H₂O + ____

Answer 1

C₆H₁₂O₆; 6 CO₂; energy (ATP + heat)

Question 2

Fill in the appropriate terms in this equation.

Answer 2

a. oxidized
b. reduced
c. donates (loses)
d. oxidizing agent
e. accepts (gains)

Question 3

a. In the conversion of glucose and oxygen to carbon dioxide and water, which molecule becomes reduced?
b. Which molecule becomes oxidized?
c. What happens to the energy that is released in this redox reaction?

Answer 3

a. oxygen
b. glucose
c. Some is stored im ATP and some is released as heat.

Question 4

a. NAD⁺ is called an ____.
b. Its reduced form is ____.

Answer 4

a. electron carrier (or acceptor) or oxidizing agent
b. NADH

Question 5

Fill in the three stages of respiration (a-c).

Indicate whether ATP is produced by substrate-level or oxidative phosphorylation (d-f).

Label the arrows indicating electrons carried by NADH.

Answer 5

a. glycolysis: glucose → pyruvate (not technically considered part of cellular respiration)
b. citric acid cycle
c. oxidative phosphorylation: electron transport and chemiosmosis
d. substrate-level phosphorylation
e. substrate-level phosphorylation
f. oxidative phosphorylation

The top two arrows show electrons carried by NADH (and FADH₂, another electron carrier) to the electron transport chain.

Question 6

Fill in the blanks in this summary diagram of glycolysis.

Answer 6

a. 2 ATP
b. 2 three-carbon sugars (glyceraldehyde-3-phosphate)
c. 2 NAD⁺
d. 2 NADH + 2H⁺
e. 4 ATP
f. 2 pyruvate

Question 7

Fill in the blanks in this diagram of the citric acid cycle. Balls represent carbon atoms.

Answer 7

a. pyruvate h. NADH + H⁺
b. CO₂ i. CO₂
c. NADH + H⁺ j. CO₂
d. coenzyme A k. NADH + H⁺
e. acetyl CoA l. ATP
f. oxaloacetate m. FADH₂
g. citrate n. NADH + H⁺

Question 8

Label this diagram of oxidative phosphorylation in a mitochondrial membrane.

Answer 8

a. intermembrane space h. chemiosmosis
b. inner mitochondrial membrane i. 2 H⁺ + 1/2 O₂
c. mitochondrial matrix j. H₂O
d. electron transport chain k. ATP synthase
e. NADH + H⁺ l. ADP + ℗_i
f. NAD⁺ m. ATP
g. FADH₂

Question 9

Fill in the tally for maximum ATP yield from the oxidation of one molecule of glucose to six molecules of carbon dioxide.

Answer 9

a. -2 f. 2
b. 4 g. 6
c. citric acid cycle h. 2
d. 32 or 34 i. 2
e. 38 j. 2

Question 10

How much more ATP can be generated by respiration than by fermentation? Explain why.

Answer 10

Respiration yields up to 19 times more ATP than does fermentation. By oxidizing pyruvate to CO₂ and passing electrons from NADH (and FADH₂) through the electron transport chain, respiration can produce a maximum of 38 ATP compared to the 2 net ATP that are produced by fermentation.

Question 11

This chapter describes how the catabolic pathways of glycolysis and respiration release chemical energy and store it in ATP.

Fill in the following table to summarize the major inputs and outputs of glycolysis, the citric acid cycle, oxidative phosphorylation, and fermentation. Base inputs and outputs on one glucose molecule.

Answer 11

See Interactive Questions 9.5, 9.6, 9.7 and 9.8.

Question 12

This chapter describes how the catabolic pathways of glycolysis and respiration release chemical energy and store it in ATP.

Fill in the following table to summarize the major inputs and outputs of glycolysis, the citric acid cycle, oxidative phosphorylation, and fermentation. Base inputs and outputs on one glucose molecule.

Answer 12

See Interactive Questions 9.5, 9.6, 9.7 and 9.8.

Question 13

This chapter describes how the catabolic pathways of glycolysis and respiration release chemical energy and store it in ATP.

Fill in the following table to summarize the major inputs and outputs of glycolysis, the citric acid cycle, oxidative phosphorylation, and fermentation. Base inputs and outputs on one glucose molecule.

Answer 13

See Interactive Questions 9.5, 9.6, 9.7 and 9.8.

Question 14

This chapter describes how the catabolic pathways of glycolysis and respiration release chemical energy and store it in ATP.

Create a concept map to organize your understanding of oxidative phosphorylation.

Answer 14

Question 15

When electrons move closer to a more electronegative atom,

a. energy is released.
b. energy is consumed.
c. a proton gradient is established.
d. water is produced.
e. ATP is synthesized.

Answer 15

a. energy is released.

Question 16

In the reaction C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂0,

a. oxygen becomes reduced.
b. glucose becomes reduced.
c. oxygen becomes oxidized.
d. water is a reducing agent.
e. oxygen is a reducing agent.

Answer 16

a. oxygen becomes reduced.

Question 17

Some prokaryotes use anaerobic respiration, a process that

a. does not involve an electron transport chain.
b. produces ATP solely by substrate-level phosphorylation.
c. uses a substance other than oxygen as the final electron acceptor.
d. does not rely on chemiosmosis for the production of ATP.
e. both a and b are correct.

Answer 17

c. uses a substance other than oxygen as the final electron acceptor.

Question 18

Which of the following is not true of oxidative phosphorylation?

a. It produces approximately three ATP for every NADH that is oxidized.
b. It involves the redox reactions of the electron transport chain.
c. It involves an ATP synthase located in the inner mitochondrial membrane.
d. It uses oxygen as the initial electron donor.
e. It is an example of chemiosmosis.

Answer 18

d. It uses oxygen as the initial electron donor.

Question 19

Substrate-level phosphorylation

a. involves the shifting of a phosphate group from ATP to a substrate.
b. can use NADH or FADH₂ .
c. takes place on ly in the cytosol.
d. accounts for 10% of the ATP formed by fermentation.
e. is the energy source for facultative anaerobes under anaerobic conditions.

Answer 19

e. is the energy source for facultative anaerobes under anaerobic conditions.

Question 20

The major reason that glycolysis is not as energy-productive as respiration is that

a. NAD⁺ is regenerated by alcohol or lactate production, without the high-energy electrons passing through the electron transport chain.
b. it is the pathway common to fermentation and respiration.
c. it does not take place in a specialized membrane-bound organelle.
d. pyruvate still contains much of the energy from glucose.
e. substrate-level phosphorylation is not as energy efficient as oxidative phosphorylation.

Answer 20

d. pyruvate still contains much of the energy from glucose.

Question 21

Which of the following conversions represents a reduction reaction?

a. pyruvate → acetyl CoA + CO₂
b. C₆H₁₂O₆ → 6 CO₂
c. NADH + H⁺ → NAD⁺ + 2 H
d. glucose → pyruvate
e. acetaldehyde (C₂H₄O) → ethanol (C₂H₆O)

Answer 21

e. acetaldehyde (C2H4O) → ethanol (C2H6O)

Question 22

What is the role of oxygen in cellular respiration?

a. It is reduced in glycolysis as glucose is oxidized.
b. It provides electrons to the electron transport chain.
c. It provides the activation energy needed for oxidation to occur.
d. It is the final electron acceptor for the electron transport chain.
e. It combines with the carbon removed during the citric acid cycle to form CO₂.

Answer 22

d. It is the final electron acceptor for the electron transport chain.

Question 23

When pyruvate is converted to acetyl CoA,

a. CO₂ and ATP are released.
b. a multienzyme complex removes a carboxyl group, transfers electrons to NAD⁺, and attaches a coenzyme.
c. one turn of the citric acid cycle is completed.
d. NAD⁺ is regenerated so that glycolysis can continue to produce ATP by substrate-level phosphorylation.
e. Phosphofructokinase is activated and glycolysis continues.

Answer 23

b. a multienzyme complex removes a carboxyl group, transfers electrons to NAD+, and attaches a coenzyme.

Question 24

How many molecules of CO₂ are generated for each molecule of acetyl CoA introduced into the citric acid cycle?

a. 1
b. 2
c. 3
d. 4
e. 6

Answer 24

b. 2

Question 25

In the chemiosmotic mechanism,

a. ATP production is linked to the proton gradient established by the electron transport chain.
b. the difference in pH between the intermembrane space and the cytosol drives the formation of ATP.
c. the flow of H⁺ through ATP synthases from the matrix to the intermembrane space drives the phosphorylation of ADP.
d. the energy released by the reduction and subsequent oxidation of components of the electron transport chain is transferred as a phosphate to ADP.
e. the production of water in the matrix by the reduction of oxygen leads to a net flow of water of of a mitochondrion.

Answer 25

a. ATP production is linked to the proton gradient established by the electron transport chain.

Question 26

Which of the following reactions is incorrectly paired with its location?

a. ATP synthesis — inner membrane of the mitrochondrion, matrix and cytosol.
b. fermentation — cell cytosol
c. glycolysis — cell cytosol
d. substrate-level phosphorylation — cytosol and matrix
e. citric acid cycle — cristae of mitochondrion

Answer 26

e. citric acid cycle — cristae of mitochondrion

Question 27

When glucose is oxidized to CO₂ and water, approximately 40% of its energy is transferred to

a. heat.
b. ATP.
c. acetyl CoA.
d. water.
e. the citric acid cycle.

Answer 27

b. ATP.

Question 28

From an energetic viewpoint, what do muscle cells in oxygen deprivation gain from the reduction of pyruvate?

a. ATP
b. ATP and recycled NAD⁺
c. CO₂ and NAD⁺
d. ATP, alcohol and NAD⁺
e. ATP and CO₂

Answer 28

b. ATP and recycled NAD+

Question 29

Glucose, made from six radioactively labeled carbon atoms, is fed to yeast cells in the absence of oxygen. How many molecules of radioactive alcohol (C₂H₅OH) are formed from each molecule of glucose?

a. 0
b. 1
c. 2
d. 3
e. 6

Answer 29

c. 2

Question 30

Which of the following produces the most ATP per gram?

a. glucose, because it is the starting place for glycolysis
b. glycogen or starch, because they are polymers of glucose
c. fats, because they are highly reduced compounds
d. proteins, because of the energy stored in their tertiary structure
e. amino acids, because they can be fed directly into the citric acid cycle

Answer 30

c. fats, because they are highly reduced compounds

Question 31

Fats and proteins can be used as fuel in the cell because they

a. can be converted to glucose by enzymes.
b. can be converted to intermediates of glycolysis or the citric acid cycle.
c. can pass through the mitochondrial membrane to enter the citric acid cycle.
d. contain phosphate groups.
e. contain more energy than glucose.

Answer 31

b. can be converted to intermediates of glycolysis or the citric acid cycle.

Question 32

Which is not true of the enzymes phosphofructokinase? It is

a. an allosteric enzyme.
b. inhibited by citrate.
c. the pacemaker of glycolysis and respiration.
d. inhibited by ADP.
e. an early enzyme in the glycolytic pathway.

Answer 32

d. inhibited by ADP.

Question 33

Substrate-level phosphorylation accounts for approximately what percentage of ATP formation when glucose is oxidized to CO₂ and water?

a. 0%
b. 4%
c. 10%
d. 15%
e. 20%

Answer 33

c. 10%

Question 34

Cyanide is a poison that blocks the passage of electrons along the electron transport chain. Which of the following is a metabolic effect of the poison?

a. The pH of the intermembrane space becomes much lower than normal.
b. Electrons are passed directly to oxygen, causing cells to explode.
c. Alcohol would build up in the cells.
d. NADH supplies would be exhausted, and ATP synthesis would cease.
e. No proton gradient would be produced, and ATP synthesis would cease.

Answer 34

e. No proton gradient would be produced, and ATP synthesis would cease.

Question 35

Which enzyme would use NAD⁺ as a coenzyme?

a. phosphofructokinase
b. phosphoglucoisomerase
c. triose phosphate dehydrogenase
d. hexokinase
e. phosphoglyceromutase

Answer 35

c. triose phosphate dehydrogenase

Question 36

The metabolic function of fermentation is to

a. oxidize NADH to NAD⁺ so that glycolysis can continue in the absence of oxygen.
b. reduce NADH so that more ATP can be produced by the electron transport chain.
c. produce lactate during aerobic exercise.
d. oxidize pyruvate, thus releasing more energy.
e. make beer.

Answer 36

a. oxidize NADH to NAD+ so that glycolysis can continue in the absence of oxygen.

Question 37

Which compound will produce thae mose ATP when oxidized?

a. acetyl CoA
b. glucose
c. pyruvate
d. fructose bisphosphate
e. glyceraldehyde-3-phospate

Answer 37

d. fructose bisphosphate

Question 38

Why is glycolysis considered one of the first metabolic pathways to have evolved?

a. It relies on fermentation, which is characteristic of the archaea and bacteria.
b. It is found only in prokaryotes, whereas eukaryotes use the mitochondria to produce ATP.
c. It produces much less ATP than does the electron transport chain and chemiosmosis.
d. It relies totally on enzymes that are produced by free ribosomes, and bacteria have only free ribosomes and no bound ribosomes.
e. It is nearly universal, is located in the cytosol and does not involve O₂.

Answer 38

e. It is nearly universal, is located in the cytosol and does not involve O2.