Chapter 9 Practice Questions

1) In which reactions of cellular respiration does substrate-level phosphorylation occur?
A) only in glycolysis
B) only in the citric acid cycle
C) only in the electron transport chain
D) in both glycolysis and the citric acid cycle

D

2) Which of the summary statements below best describes the results of the following reaction?
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
A) C6H12O6 is oxidized and O2 is reduced.
B) O2 is oxidized and H2O is reduced.
C) CO2 is reduced and O2 is oxidized.
D) O2 is reduced and CO2 is oxidized.

A

3) When a glucose molecule loses a hydrogen atom in an oxidation-reduction reaction, the
glucose molecule is ________.
A) hydrolyzed
B) an oxidizing agent
C) oxidized
D) reduced

C

4) Which of the following statements best describes what happens to a molecule of NAD+
(nicotinamide adenine dinucleotide) when it gains a hydrogen atom?
A) NAD+ becomes dehydrogenated.
B) NAD+ becomes oxidized.
C) NAD+ becomes reduced.
D) NAD+ becomes ionized.

C

5) Which of the following statements best explains why carbohydrates and fats may be
considered high-energy foods?
A) They contain many protons associated with oxygen atoms.
B) They contain no low-energy nitrogen atoms.
C) They contain many electrons associated with hydrogen atoms.
D) They are strong oxidizing molecules

C

6) Substrate-level phosphorylation accounts for approximately what percent of the ATP formed
by the reactions of glycolysis?
A) 0%
B) 2%
C) 38%

D) 100%

D

7) Glycolysis results in the net production of which of the following sets of molecules per
glucose molecule?
A) 2 NAD+, 2 pyruvate, and 2 ATP
B) 2 NADH, 2 pyruvate, and 2 ATP
C) 4 NADH, 2 pyruvate, and 4 ATP
D) 6 CO2, 2 pyruvate, and 2 ATP

B

8) Which of the following statements best summarizes ATP use and production in the catabolism
of each glucose molecule in glycolysis?
A) two molecules of ATP are used, and two molecules of ATP are produced
B) two molecules of ATP are used, and four molecules of ATP are produced
C) four molecules of ATP are used, and two molecules of ATP are produced
D) four molecules of ATP are used, and four molecules of ATP are produced

B

9) Which of the following reactions produces the majority of the CO2 released by the complete
oxidation of glucose?
A) glycolysis
B) electron transport
C) oxidation of pyruvate to acetyl-CoA
D) the citric acid cycle

D

10) Upon completion of the citric acid cycle, most of the energy originally stored in each glucose
molecule catabolized by cellular respiration is stored in which of the following molecules?
A) acetyl-CoA
B) ATP
C) CO2
D) NADH

D

(11) Which of the following is the most likely effect on the rates of ATP and CO2 production if yeast
cells growing in minimal medium lacking glucose are provided with supplemental acetyl-CoA?
A) There would be no change in ATP production, but the rate of carbon dioxide production
would increase.
B) The rates of ATP production and carbon dioxide production would both increase.
C) The rate of ATP production would increase, but the rate of carbon dioxide production would
decrease.
D) The rates of ATP and carbon dioxide production would both decrease.

B

12) Inhibition of which of the following metabolic pathways would result in decreased rates of
CO2 production?
A) glycolysis and the oxidation of pyruvate to acetyl CoA
B) oxidation of pyruvate to acetyl CoA and the citric acid cycle
C) oxidative phosphorylation and fermentation
D) fermentation and glycolysis

B

13) If glucose is the sole energy source for cellular respiration in an animal, what proportion of
the carbon dioxide exhaled is derived from oxidation of pyruvate to acetyl CoA?
A) 1/6
B) 1/3
C) 2/3

D) 100%

B

For each mole of glucose (C6H12O6) oxidized by cellular respiration, how many moles of CO2
are released in the citric acid cycle (see the accompanying figure)?
A) 2
B) 4
C) 6
D) 32

B

(15) If pyruvate oxidation is blocked, what is the most likely effect on the levels of oxaloacetate and
citrate in the citric acid cycle shown in the accompanying figure?
A) Oxaloacetate will decrease and citrate will accumulate.
B) Oxaloacetate will accumulate and citrate will decrease.
C) Both oxaloacetate and citrate will decrease.
D) Both oxaloacetate and citrate will accumulate.

B

16) Which of the following events takes place in the electron transport chain?
A) the breakdown of glucose into six carbon dioxide molecules
B) the breakdown of an acetyl group to carbon dioxide
C) the harnessing of energy from redox reactions to generate a proton gradient
D) substrate-level phosphorylation

C

17) Which of the following statements best describes the electron transport chain?
A) It is driven by ATP hydrolysis.
B) It includes a series of hydrolysis reactions associated with mitochondrial membranes.
C) It consists of a series of redox reactions.
D) It occurs in the cytoplasm of both prokaryotic and eukaryotic cells.

C

18) Which of the following processes is driven by chemiosmosis?
A) substrate-level phosphorylation
B) oxidative phosphorylation
C) ATP hydrolysis
D) reduction of NAD+ to NADH

B

19) Which of the following sequences describes the path by which electrons move from high-
energy to lower-energy molecules in aerobic respiration?
A) glucose → NADH → electron transport chain → oxygen
B) glucose → pyruvate → ATP → oxygen
C) glucose → pyruvate → electron transport chain → NADH → ATP
D) food → glycolysis → citric acid cycle → NADH → ATP

A

20) Which of the following statements best describes the primary role played by oxygen in
cellular respiration?
A) It yields energy in the form of ATP as it is passed down the electron transport chain.
B) It oxidizes glucose to form two molecules of pyruvate.
C) It serves as an acceptor for carbon, forming CO2 in the citric acid cycle.
D) It serves as the final acceptor for electrons from the electron transport chain.

D

21) Assume that it is possible to label each of the molecules below with 18O a heavy isotope of
oxygen. As a result of cellular respiration, water containing 18O would most quickly be detected
if cells are provided with which one of the following molecules labeled with 18O?
A) carbon dioxide (CO2)
B) glucose (C6H12O6)
C) molecular oxygen (O2)
D) pyruvate (C3H3O3)

C

22) In chemiosmosis, the most direct source of energy used to convert ADP + i to ATP is
energy released ________.
A) as electrons flow through the electron transport chain
B) from substrate-level phosphorylation
C) from movement of protons through ATP synthase, down their electrochemical gradient
D) as electrons are transported across the inner mitochondrial membrane

C

23) Approximately how many molecules of ATP are produced from the complete oxidation of
one molecule of glucose (C6H12O6) in aerobic cellular respiration?
A) 2
B) 4
C) 18-24
D) 30-32

D

24) The synthesis of ATP by oxidative phosphorylation is an example of which of the following
processes?
A) active transport
B) allosteric regulation
C) a reaction with a positive ΔG
D) coupling of an endergonic reaction to an exergonic reaction

D

25) If a cell produces on average 30 ATP molecules for each molecule of glucose that is
completely oxidized to carbon dioxide and water, how many ATP molecules on average can the
cell synthesize for each molecule of pyruvate oxidized to carbon dioxide and water?
A) 8
B) 12.5
C) 14
D) 25

B

26) When a cell is deprived of oxygen, which of the following processes will be inhibited first?
A) glycolysis
B) the electron transport chain
C) the citric acid cycle
D) the oxidation of pyruvate to acetyl CoA

B

27) A person on a strict diet and exercise regimen lost 7 kg (about 15 pounds) of body fat in just
two weeks. In which of the following forms did the lost fat most likely leave the body?
A) released as CO2 and H2O
B) converted to heat and then released
C) converted to ATP, which weighs much less than fat
D) eliminated from the body as feces

A

28) Which of the following metabolic processes normally occurs in most cells regardless of
oxygen (O2) availability?
A) citric acid cycle
B) glycolysis
C) lactate fermentation
D) oxidative phosphorylation

B

29) Which of the following metabolic processes take place in the cytosol of a eukaryotic cell?
A) glycolysis and fermentation
B) fermentation and chemiosmosis
C) oxidation of pyruvate to acetyl CoA
D) citric acid cycle

A

30) In the absence of oxygen, yeast cells can obtain energy by fermentation, which results in the

net production of which of the following sets of molecules?
A) ATP, CO2, and ethanol
B) ATP, CO2, and lactate
C) ATP, NADH, and ethanol
D) ATP, CO2, and acetyl CoA

A

31) Which of the following statements describes a primary function of both alcohol fermentation
and lactic acid fermentation?
A) reduction of NAD+ to NADH
B) reduction of FAD to FADH2
C) oxidation of NADH to NAD+
D) hydrolysis of ATP to ADP + i

C

32) Which of the following best predicts the effect of removal of oxygen from a facultative
anaerobic organism's environment?
A) glucose consumption increases, while the growth rate decreases
B) glucose consumption and the growth rate both increase
C) glucose consumption decreases, while the growth rate increases
D) glucose consumption decreases, while the growth rate remains unchanged

A

33) New biosensors, applied like a temporary tattoo to the skin, can alert endurance athletes that
they are about to "hit the wall" and will find it difficult to continue exercising. These biosensors
monitor lactate present in sweat during strenuous exercise. Which of the statements below best
explains the use of lactate as an indicator of exercise capacity?
A) During aerobic respiration, muscle cells cannot produce enough lactate to fuel muscle cell
contractions, and muscles begin to cramp, thus athletic performance suffers.
B) During anaerobic respiration, lactate levels increase when muscles cells need more energy;
however, muscles cells eventually fatigue, thus athletes should modify their activities to increase
aerobic respiration.
C) During aerobic respiration, muscles cells produce too much lactate, which causes a rise in the
pH of the muscle cells, thus athletes must consume increased amounts of sports drinks, high in
electrolytes, to buffer the pH.
D) During anaerobic respiration, muscle cells receive too little oxygen and begin to convert
lactate to pyruvate (pyruvic acid), thus athletes experience cramping and fatigue

B

34) A 3-year old dog has never been able to tolerate much physical activity. A veterinarian
discovers that the dog's mitochondria can use only fatty acids and amino acids for cellular
respiration, and its muscle cells produce elevated levels of lactate. Which of the following
statements best explains the dog's condition?
A) Its cells cannot transport pyruvate from the cytosol into the mitochondria.
B) Its cells cannot transport NADH from glycolysis into the mitochondria.
C) Its cells cannot complete glycolysis.
D) Its cells have a defective electron transport chain, so glucose is metabolized to lactate instead

of to acetyl CoA

A