62) One function of both alcohol fermentation and lactic acid fermentation is to
A) reduce NAD+ to NADH.
B) reduce FAD+ to FADH2.
C) oxidize NADH to NAD+.
D) reduce FADH2 to FAD+.
E) do none of the above.
63) An organism is discovered that thrives both in the presence and absence of oxygen in the air.
Curiously, the consumption of sugar increases as oxygen is removed from the organism’s environment,
even though the organism does not gain much weight. This organism
A) must use a molecule other than oxygen to accept electrons from the electron transport chain.
B) is a normal eukaryotic organism.
C) is photosynthetic.
D) is an anaerobic organism.
E) is a facultative anaerobe.
64) Which statement best supports the hypothesis that glycolysis is an ancient metabolic pathway that
originated before the last universal common ancestor of life on Earth?
A) Glycolysis is widespread and is found in the domains Bacteria, Archaea, and Eukarya.
B) Glycolysis neither uses nor needs O2.
C) Glycolysis is found in all eukaryotic cells.
D) The enzymes of glycolysis are found in the cytosol rather than in a membrane-enclosed organelle.
E) Ancient prokaryotic cells, the most primitive of cells, made extensive use of glycolysis long before
oxygen was present in Earth’s atmosphere.
65) Why is glycolysis considered to be one of the first metabolic pathways to have evolved?
A) It produces much less ATP than does oxidative phosphorylation.
B) It does not involve organelles or specialized structures, does not require oxygen, and is present in
most organisms.
C) It is found in prokaryotic cells but not in eukaryotic cells.
D) It relies on chemiosmosis, which is a metabolic mechanism present only in the first cells’ prokaryotic
cells.
E) It requires the presence of membrane-enclosed cell organelles found only in eukaryotic cells.
66) When an individual is exercising heavily and when the muscle becomes oxygen-deprived, muscle
cells convert pyruvate to lactate. What happens to the lactate in skeletal muscle cells?
A) It is converted to NAD+.
B) It produces CO2 and water.
C) It is taken to the liver and converted back to pyruvate.
D) It reduces FADH2 to FAD+.
E) It is converted to alcohol.
67) When skeletal muscle cells are oxygen-deprived, the heart still pumps. What must the heart muscle
cells be able to do?
A) derive sufficient energy from fermentation
B) continue aerobic metabolism when skeletal muscle cannot
C) transform lactate to pyruvate again
D) remove lactate from the blood
E) remove oxygen from lactate
68) When skeletal muscle cells undergo anaerobic respiration, they become fatigued and painful. This is
now known to be caused by
A) buildup of pyruvate.
B) buildup of lactate.
C) increase in sodium ions.
D) increase in potassium ions.
E) increase in ethanol.
69) A mutation in yeast makes it unable to convert pyruvate to ethanol. How will this mutation affect
these yeast cells?
A) The mutant yeast will be unable to grow anaerobically.
B) The mutant yeast will grow anaerobically only when given glucose.
C) The mutant yeast will be unable to metabolize glucose.
D) The mutant yeast will die because they cannot regenerate NAD+ from NAD.
E) The mutant yeast will metabolize only fatty acids.
70) You have a friend who lost 7 kg (about 15 pounds) of fat on a regimen of strict diet and exercise.
How did the fat leave her body?
A) It was released as CO2 and H2O.
B) It was converted to heat and then released.
C) It was converted to ATP, which weighs much less than fat.
D) It was broken down to amino acids and eliminated from the body.
E) It was converted to urine and eliminated from the body.
71) Phosphofructokinase is an important control enzyme in the regulation of cellular respiration. Which
of the following statements correctly describes phosphofructokinase activity?
A) It is inhibited by AMP.
B) It is activated by ATP.
C) It is activated by citrate, an intermediate of the citric acid cycle.
D) It catalyzes the conversion of fructose 1,6-bisphosphate to fructose 6-phosphate, an early step of
glycolysis.
E) It is an allosteric enzyme.
72) Phosphofructokinase is an allosteric enzyme that catalyzes the conversion of fructose 6-phosphate to
fructose 1,6-bisphosphate, an early step of glycolysis. In the presence of oxygen, an increase in the
amount of ATP in a cell would be expected to
A) inhibit the enzyme and thus slow the rates of glycolysis and the citric acid cycle.
B) activate the enzyme and thus slow the rates of glycolysis and the citric acid cycle.
C) inhibit the enzyme and thus increase the rates of glycolysis and the citric acid cycle.
D) activate the enzyme and increase the rates of glycolysis and the citric acid cycle.
E) inhibit the enzyme and thus increase the rate of glycolysis and the concentration of citrate.
73) Even though plants carry on photosynthesis, plant cells still use their mitochondria for oxidation of
pyruvate. When and where will this occur?
A) in photosynthetic cells in the light, while photosynthesis occurs concurrently
B) in nonphotosynthesizing cells only
C) in cells that are storing glucose only
D) in all cells all the time
E) in photosynthesizing cells in the light and in other tissues in the dark
74) In vertebrate animals, brown fat tissue’s color is due to abundant blood vessels and capillaries. White
fat tissue, on the other hand, is specialized for fat storage and contains relatively few blood vessels or
capillaries. Brown fat cells have a specialized protein that dissipates the proton-motive force across the
mitochondrial membranes. Which of the following might be the function of the brown fat tissue?
A) to increase the rate of oxidative phosphorylation from its few mitochondria
B) to allow the animals to regulate their metabolic rate when it is especially hot
C) to increase the production of ATP
D) to allow other membranes of the cell to perform mitochondrial functions
E) to regulate temperature by converting most of the energy from NADH oxidation to heat
75) What is the purpose of beta oxidation in respiration?
A) oxidation of glucose
B) oxidation of pyruvate
C) feedback regulation
D) control of ATP accumulation
E) breakdown of fatty acids
76) Where do the catabolic products of fatty acid breakdown enter into the citric acid cycle?
A) pyruvate
B) malate or fumarate
C) acetyl CoA
D) α-ketoglutarate
E) succinyl CoA
77) What carbon sources can yeast cells metabolize to make ATP from ADP under anaerobic
conditions?
A) glucose
B) ethanol
C) pyruvate
D) lactic acid
E) either ethanol or lactic acid
78) High levels of citric acid inhibit the enzyme phosphofructokinase, a key enzyme in glycolysis. Citric
acid binds to the enzyme at a different location from the active site. This is an example of
A) competitive inhibition.
B) allosteric regulation.
C) the specificity of enzymes for their substrates.
D) an enzyme requiring a cofactor.
E) positive feedback regulation.
79) During intense exercise, as skeletal muscle cells go into anaerobiosis, the human body will increase
its catabolism of
A) fats only.
B) carbohydrates only.
C) proteins only.
D) fats, carbohydrates, and proteins.
E) fats and proteins only.
80) Yeast cells that have defective mitochondria incapable of respiration will be able to grow by
catabolizing which of the following carbon sources for energy?
A) glucose
B) proteins
C) fatty acids
D) glucose, proteins, and fatty acids
E) Such yeast cells will not be capable of catabolizing any food molecules, and will therefore die.
Art Questions
Figure 9.1 illustrates some of the steps (reactions) of glycolysis in their proper sequence. Each step is
lettered. Use these letters to answer the questions.
Figure 9.1
81) Which step in Figure 9.1 shows a split of one molecule into two smaller molecules?
A) A
B) B
C) C
D) D
E) E
82) In which step in Figure 9.1 is an inorganic phosphate added to the reactant?
A) A
B) B
C) C
D) D
E) E
83) Which step in Figure 9.1 is a redox reaction?
A) A
B) B
C) C
D) D
E) E
84) Which portion of the pathway in Figure 9.1 involves an endergonic reaction?
A) A
B) B
C) C
D) D
E) E
85) Which portion of the pathway in Figure 9.1 contains a phosphorylation reaction in which ATP is the
phosphate source?
A) A
B) B
C) C
D) D
E) E
Figure 9.2 The citric acid cycle.
86) Starting with one molecule of isocitrate and ending with fumarate, how many ATP molecules can be
made through substrate-level phosphorylation (see Figure 9.2)?
A) 1
B) 2
C) 11
D) 12
E) 24
87) Carbon skeletons for amino acid biosynthesis are supplied by intermediates of the citric acid cycle.
Which intermediate would supply the carbon skeleton for synthesis of a five-carbon amino acid (see
Figure 9.2)?
A) succinate
B) malate
C) citrate
D) α-ketoglutarate
E) isocitrate
88) For each mole of glucose (C6H12O6) oxidized by cellular respiration, how many moles of CO2 are
released in the citric acid cycle (see Figure 9.2)?
A) 2
B) 4
C) 6
D) 12
E) 3
89) If pyruvate oxidation is blocked, what will happen to the levels of oxaloacetate and citric acid in the
citric acid cycle shown in Figure 9.2?
A) There will be no change in the levels of oxaloacetate and citric acid.
B) Oxaloacetate will decrease and citric acid will accumulate.
C) Oxaloacetate will accumulate and citric acid will decrease.
D) Both oxaloacetate and citric acid will decrease.
E) Both oxaloacetate and citric acid will accumulate.
90) Starting with citrate, which of the following combinations of products would result from three acetyl
CoA molecules entering the citric acid cycle (see Figure 9.2)?
A) 1 ATP, 2 CO2, 3 NADH, and 1 FADH2
B) 2 ATP, 2 CO2, 3 NADH, and 3 FADH2
C) 3 ATP, 3 CO2, 3 NADH, and 3 FADH2
D) 3 ATP, 6 CO2, 9 NADH, and 3 FADH2
E) 38 ATP, 6 CO2, 3 NADH, and 12 FADH2
91) For each molecule of glucose that is metabolized by glycolysis and the citric acid cycle (see Figure
9.2), what is the total number of NADH + FADH2 molecules produced?
A) 4
B) 5
C) 6
D) 10
E) 12
Figure 9.3
92) Figure 9.3 shows the electron transport chain. Which of the following is the combination of
substances that is initially added to the chain?
A) oxygen, carbon dioxide, and water
B) NAD+, FAD, and electrons
C) NADH, FADH2, and protons
D) NADH, FADH2, and O2
E) oxygen and protons
93) Which of the following most accurately describes what is happening along the electron transport
chain in Figure 9.3?
A) Chemiosmosis is coupled with electron transfer.
B) Each electron carrier alternates between being reduced and being oxidized.
C) ATP is generated at each step.
D) Energy of the electrons increases at each step.
E) Molecules in the chain give up some of their potential energy.
94) Which of the protein complexes labeled with Roman numerals in Figure 9.3 will transfer electrons
to O2?
A) complex I
B) complex II
C) complex III
D) complex IV
E) All of the complexes can transfer electrons to O2.
95) What happens at the end of the chain in Figure 9.3?
A) 2 electrons combine with a proton and a molecule of NAD+.
B) 2 electrons combine with a molecule of oxygen and two hydrogen atoms.
C) 4 electrons combine with a molecule of oxygen and 4 protons.
D) 4 electrons combine with four hydrogen and two oxygen atoms.
E) 1 electron combines with a molecule of oxygen and a hydrogen atom.
Scenario Questions
In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid
cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO2, (2) is
oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A.
96) These three steps result in the formation of
A) acetyl CoA, O2, and ATP.
B) acetyl CoA, FADH2, and CO2.
C) acetyl CoA, FAD, H2, and CO2.
D) acetyl CoA, NADH, H+, and CO2.
E) acetyl CoA, NAD+, ATP, and CO2.
97) Why is coenzyme A, a sulfur-containing molecule derived from a B vitamin, added?
A) because sulfur is needed for the molecule to enter the mitochondrion
B) in order to utilize this portion of a B vitamin which would otherwise be a waste product from another
pathway
C) to provide a relatively unstable molecule whose acetyl portion can be readily transferred to a
compound in the citric acid cycle
D) because it drives the reaction that regenerates NAD+
E) in order to remove one molecule of CO2
Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However,
the fragments will reseal “inside out.” These little vesicles that result can still transfer electrons from
NADH to oxygen and synthesize ATP. If the membranes are agitated further, however, the ability to
synthesize ATP is lost.
98) After the first disruption, when electron transfer and ATP synthesis still occur, what must be
present?
A) all of the electron transport proteins as well as ATP synthase
B) all of the electron transport system and the ability to add CoA to acetyl groups
C) the ATP synthase system
D) the electron transport system
E) plasma membranes like those bacteria use for respiration
99) After the further agitation of the membrane vesicles, what must be lost from the membrane?
A) the ability of NADH to transfer electrons to the first acceptor in the electron transport chain
B) the prosthetic groups like heme from the transport system
C) cytochromes
D) ATP synthase, in whole or in part
E) the contact required between inner and outer membrane surfaces
100) These inside-out membrane vesicles
A) will become acidic inside the vesicles when NADH is added.
B) will become alkaline inside the vesicles when NADH is added.
C) will make ATP from ADP and i if transferred to a pH 4 buffered solution after incubation in a pH 7
buffered solution.
D) will hydrolyze ATP to pump protons out of the interior of the vesicle to the exterior.
E) will reverse electron flow to generate NADH from NAD+ in the absence of oxygen.
End-of-Chapter Questions
The following questions are from the end-of–chapter “Test Your Understanding” section in Chapter 9 of
the textbook.
101) The immediate energy source that drives ATP synthesis by ATP synthase during oxidative
phosphorylation is the
A) oxidation of glucose and other organic compounds.
B) flow of electrons down the electron transport chain.
C) affinity of oxygen for electrons.
D) H+ concentration across the membrane holding ATP synthase.
E) transfer of phosphate to ADP.
102) Which metabolic pathway is common to both fermentation and cellular respiration of a glucose
molecule?
A) the citric acid cycle
B) the electron transport chain
C) glycolysis
D) synthesis of acetyl CoA from pyruvate
E) reduction of pyruvate to lactate
103) In mitochondria, exergonic redox reactions
A) are the source of energy driving prokaryotic ATP synthesis.
B) are directly coupled to substrate-level phosphorylation.
C) provide the energy that establishes the proton gradient.
D) reduce carbon atoms to carbon dioxide.
E) are coupled via phosphorylated intermediates to endergonic processes.
104) The final electron acceptor of the electron transport chain that functions in aerobic oxidative
phosphorylation is
A) oxygen.
B) water.
C) NAD+.
D) pyruvate.
E) ADP.
105) What is the oxidizing agent in the following reaction?
Pyruvate + NADH + H+ → Lactate + NAD+
A) oxygen
B) NADH
C) NAD+
D) lactate
E) pyruvate
106) When electrons flow along the electron transport chains of mitochondria, which of the following
changes occurs?
A) The pH of the matrix increases.
B) ATP synthase pumps protons by active transport.
C) The electrons gain free energy.
D) The cytochromes phosphorylate ADP to form ATP.
E) NAD+ is oxidized.
107) Most CO2 from catabolism is released during
A) glycolysis.
B) the citric acid cycle.
C) lactate fermentation.
D) electron transport.
E) oxidative phosphorylation.