Chapter 9: Cell Respiration

Front 1

1) What is the term for metabolic pathways that release stored energy by breaking down complex molecules?
A) anabolic pathways
B) catabolic pathways
C) fermentation pathways
D) thermodynamic pathways
E) bioenergetic pathways

Back 1

B) catabolic pathways

Front 2

2) The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction
A) gains electrons and gains energy.
B) loses electrons and loses energy.
C) gains electrons and loses energy.
D) loses electrons and gains energy.
E) neither gains nor loses electrons, but gains or loses energy

Back 2

B) loses electrons and loses energy

Front 3

3) When electrons move closer to a more electronegative atom, what happens?
A) Energy is released.
B) Energy is consumed.
C) The more electronegative atom is reduced.
D) The more electronegative atom is oxidized.
E) A and C are correct.

Back 3

E) A and C are correct.

Front 4

4) Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free
energy?
A) The covalent bonds in organic molecules are higher energy bonds than those in water and carbon dioxide.
B) Electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with a
higher affinity for electrons (such as O).
C) The oxidation of organic compounds can be used to make ATP.
D) The electrons have a higher potential energy when associated with water and CO2 than they do in
organic compounds.
E) The covalent bond in O2 is unstable and easily broken by electrons from organic molecules.

Back 4

B) Electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with a
higher affinity for electrons (such as O).

Front 5

5) Which of the following statements describes the results of this reaction?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 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) C6H12O6 is reduced and CO2 is oxidized.
E) O2 is reduced and CO2 is oxidized.

Back 5

A) C6H12O6 is oxidized and O2 is reduced

Front 6

7) When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a hydrogen ion)
the molecule becomes
A) hydrogenated.
B) oxidized.
C) reduced.
D) redoxed.
E) a reducing agent

Back 6

C) reduced.

Front 7

8) Which of the following statements describes NAD+?
A) NAD+ is reduced to NADH during both glycolysis and the citric acid cycle.
B) NAD+ has more chemical energy than NADH.
C) NAD+ is reduced by the action of hydrogenases.
D) NAD+ can donate electrons for use in oxidative phosphorylation.
E) In the absence of NAD+, glycolysis can still function.

Back 7

A) NAD+ is reduced to NADH during both glycolysis and the citric acid cycle.

Front 8

9) Where does glycolysis takes place?
A) mitochondrial matrix
B) mitochondrial outer membrane
C) mitochondrial inner membrane
D) mitochondrial intermembrane space
E) cytosol

Back 8

E) cytosol

Front 9

10) The ATP made during glycolysis is generated by
A) substrate-level phosphorylation.
B) electron transport.
C) photophosphorylation.
D) chemiosmosis.
E) oxidation of NADH to NAD+.

Back 9

A) substrate-level phosphorylation.

Front 10

11) The oxygen consumed during cellular respiration is involved directly in which process or event?
A) glycolysis
B) accepting electrons at the end of the electron transport chain
C) the citric acid cycle
D) the oxidation of pyruvate to acetyl CoA
E) the phosphorylation of ADP to form ATP

Back 10

B) accepting electrons at the end of the electron transport chain

Front 11

12) Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent?
A) electron transport
B) glycolysis
C) the citric acid cycle
D) oxidative phosphorylation
E) chemiosmosis

Back 11

B) glycolysis

Front 12

13) An electron loses potential energy when it
A) shifts to a less electronegative atom.
B) shifts to a more electronegative atom.
C) increases its kinetic energy.
D) increases its activity as an oxidizing agent.
E) attaches itself to NAD+.

Back 12

B) shifts to a more electronegative atom

Front 13

14) Why are carbohydrates and fats considered high energy foods?
A) They have a lot of oxygen atoms.
B) They have no nitrogen in their makeup.
C) They can have very long carbon skeletons.
D) They have a lot of electrons associated with hydrogen.
E) They are easily reduced.

Back 13

D) They have a lot of electrons associated with hydrogen.

Front 14

20) Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed during
glycolysis?
A) 0%
B) 2%
C) 10%
D) 38%
E) 100%

Back 14

E) 100%

Front 15

21) During glycolysis, when glucose is catabolized to pyruvate, most of the energy of glucose is
A) transferred to ADP, forming ATP.
B) transferred directly to ATP.
C) retained in the pyruvate.
D) stored in the NADH produced.
E) used to phosphorylate fructose to form fructose-6-phosphate

Back 15

C) retained in the pyruvate.

Front 16

22) In addition to ATP, what are the end products of glycolysis?
A) CO2 and H2O
B) CO2 and pyruvate
C) NADH and pyruvate
D) CO2 and NADH
E) H2O, FADH2, and citrate

Back 16

C) NADH and pyruvate

Front 17

24) Starting with one molecule of glucose, the ʺnetʺ products of glycolysis are
A) 2 NAD+, 2 H+, 2 pyruvate, 2 ATP, and 2 H2O.
B) 2 NADH, 2 H+, 2 pyruvate, 2 ATP, and 2 H2O.
C) 2 FADH2, 2 pyruvate, 4 ATP, and 2 H2O.
D) 6 CO2, 6 H2O, 2 ATP, and 2 pyruvate.
E) 6 CO2, 6 H2O, 36 ATP, and 2 citrate

Back 17

B) 2 NADH, 2 H+, 2 pyruvate, 2 ATP, and 2 H2O

Front 18

25) In glycolysis, for each molecule of glucose oxidized to pyruvate
A) 2 molecules of ATP are used and 2 molecules of ATP are produced.
B) 2 molecules of ATP are used and 4 molecules of ATP are produced.
C) 4 molecules of ATP are used and 2 molecules of ATP are produced.
D) 2 molecules of ATP are used and 6 molecules of ATP are produced.
E) 6 molecules of ATP are used and 6 molecules of ATP are produced

Back 18

B) 2 molecules of ATP are used and 4 molecules of ATP are produced

Front 19

26) A molecule that is phosphorylated
A) has been reduced as a result of a redox reaction involving the loss of an inorganic phosphate.
B) has a decreased chemical reactivity; it is less likely to provide energy for cellular work.
C) has been oxidized as a result of a redox reaction involving the gain of an inorganic phosphate.
D) has an increased chemical reactivity; it is primed to do cellular work.
E) has less energy than before its phosphorylation and therefore less energy for cellular work.

Back 19

D) has an increased chemical reactivity; it is primed to do cellular work

Front 20

27) Which kind of metabolic poison would most directly interfere with glycolysis?
A) an agent that reacts with oxygen and depletes its concentration in the cell
B) an agent that binds to pyruvate and inactivates it
C) an agent that closely mimics the structure of glucose but is not metabolized
D) an agent that reacts with NADH and oxidizes it to NAD+
E) an agent that blocks the passage of electrons along the electron transport chain

Back 20

C) an agent that closely mimics the structure of glucose but is not metabolized

Front 21

28) Why is glycolysis described as having an investment phase and a payoff phase?
A) It both splits molecules and assembles molecules.
B) It attaches and detaches phosphate groups.
C) It uses glucose and generates pyruvate.
D) It shifts molecules from cytosol to mitochondrion.
E) It uses stored ATP and then forms a net increase in ATP.

Back 21

E) It uses stored ATP and then forms a net increase in ATP.

Front 22

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.
29) 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.

Back 22

D) acetyl CoA, NADH, H+, and CO2.

Front 23

31) How does pyruvate enter the mitochondrion?
A) active transport
B) diffusion
C) facilitated diffusion
D) through a channel
E) through a pore

Back 23

A) active transport

Front 24

32) Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the
removal of a carbon (CO2) from one molecule of pyruvate?
A) lactate
B) glyceraldehydes-3-phosphate
C) oxaloacetate
D) acetyl CoA
E) citrate

Back 24

D) acetyl CoA

Front 25

33) During cellular respiration, acetyl CoA accumulates in which location?
A) cytosol
B) mitochondrial outer membrane
C) mitochondrial inner membrane
D) mitochondrial intermembrane space
E) mitochondrial matrix

Back 25

E) mitochondrial matrix

Front 26

34) How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of
pyruvate?
A) 2
B) 4
C) 6
D) 8
E) 10

Back 26

A) 2

Front 27

35) Starting with one molecule of isocitrate and ending with fumarate, what is the maximum number of ATP
molecules that could be made through substrate-level phosphorylation?
A) 1
B) 2
C) 11
D) 12
E) 24

Back 27

A) 1

Front 28

36) 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?
A) succinate
B) malate
C) citrate
D) α-ketoglutarate
E) isocitrate

Back 28

D) α-ketoglutarate

Front 29

37) How many molecules of carbon dioxide (CO2) would be produced by five turns of the citric acid cycle?
A) 2
B) 5
C) 10
D) 12
E) 60

Back 29

C) 10

Front 30

38) How many reduced dinucleotides would be produced with four turns of the citric acid cycle?
A) 1 FADH2 and 4 NADH
B) 2 FADH2 and 8 NADH
C) 4 FADH2 and 12 NADH
D) 1 FAD and 4 NAD+
E) 4 FAD+ and 12 NAD+

Back 30

C) 4 FADH2 and 12 NADH

Front 31

39) Starting with citrate, which of the following combinations of products would result from three turns of the
citric acid cycle?
A) 1 ATP, 2 CO2, 3 NADH, and 1 FADH2
B) 2 ATP, 2 CO2, 1 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

Back 31

D) 3 ATP, 6 CO2, 9 NADH, and 3 FADH2

Front 32

40) Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?
A) glycolysis and the oxidation of pyruvate to acetyl CoA
B) oxidation of pyruvate to acetyl CoA and the citric acid cycle
C) the citric acid cycle and oxidative phosphorylation
D) oxidative phosphorylation and fermentation
E) fermentation and glycolysis

Back 32

B) oxidation of pyruvate to acetyl CoA and the citric acid cycle

Front 33

41) For each molecule of glucose that is metabolized by glycolysis and the citric acid cycle, what is the total number
of NADH + FADH2 molecules produced?
A) 4
B) 5
C) 6
D) 10
E) 12

Back 33

E) 12

Front 34

42) A young animal has never had much energy. He is brought to a veterinarian for help and is sent to the animal
hospital for some tests. There they discover his mitochondria can use only fatty acids and amino acids for
respiration, and his cells produce more lactate than normal. Of the following, which is the best explanation of
his condition?
A) His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial
membrane.
B) His cells cannot move NADH from glycolysis into the mitochondria.
C) His cells contain something that inhibits oxygen use in his mitochondria.
D) His cells lack the enzyme in glycolysis that forms pyruvate.
E) His cells have a defective electron transport chain, so glucose goes to lactate instead of to acetyl CoA.

Back 34

A) His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial
membrane

Front 35

43) Cellular respiration harvests the most chemical energy from which of the following?
A) substrate-level phosphorylation
B) chemiosmotic phosphorylation
C) converting oxygen to ATP
D) transferring electrons from organic molecules to pyruvate
E) generating carbon dioxide and oxygen in the electron transport chain

Back 35

B) chemiosmotic phosphorylation

Front 36

44) During aerobic respiration, electrons travel downhill in which sequence?
A) food → citric acid cycle → ATP → NAD+
B) food → NADH → electron transport chain → oxygen
C) glucose → pyruvate → ATP → oxygen
D) glucose → ATP → electron transport chain → NADH
E) food → glycolysis → citric acid cycle → NADH → ATP

Back 36

B) food → NADH → electron transport chain → oxygen

Front 37

45) Where are the proteins of the electron transport chain located?
A) cytosol
B) mitochondrial outer membrane
C) mitochondrial inner membrane
D) mitochondrial intermembrane space
E) mitochondrial matrix

Back 37

C) mitochondrial inner membrane

Front 38

46) Which of the following describes the sequence of electron carriers in the electron transport chain, starting with
the least electronegative?
A) ubiquinone (Q), cytochromes (Cyt), FMN, Fe•S
B) cytochromes (Cyt), FMN, ubiquinone, Fe•S
C) Fe•S, FMN, cytochromes (Cyt), ubiquinone
D) FMN, Fe•S, ubiquinone, cytochromes (Cyt)
E) cytochromes (Cyt), Fe•S, ubiquinone, FMN

Back 38

D) FMN, Fe•S, ubiquinone, cytochromes (Cyt)

Front 39

47) During aerobic respiration, which of the following directly donates electrons to the electron transport chain at
the lowest energy level?
A) NAD+
B) NADH
C) ATP
D) ADP + Pi
E) FADH2

Back 39

E) FADH2

Front 40

49) Inside an active mitochondrion, most electrons follow which pathway?
A) glycolysis → NADH → oxidative phosphorylation → ATP → oxygen
B) citric acid cycle → FADH2 → electron transport chain → ATP
C) electron transport chain → citric acid cycle → ATP → oxygen
D) pyruvate → citric acid cycle → ATP → NADH → oxygen
E) citric acid cycle → NADH → electron transport chain → oxygen

Back 40

E) citric acid cycle → NADH → electron transport chain → oxygen

Front 41

50) During oxidative phosphorylation, H2O is formed. Where does the oxygen for the synthesis of the water come
from?
A) carbon dioxide (CO2)
B) glucose (C6H12O6)
C) molecular oxygen (O2)
D) pyruvate (C3H3O3-)
E) lactate (C3H5O3-)

Back 41

C) molecular oxygen (O2)

Front 42

51) In chemiosmotic phosphorylation, what is the most direct source of energy that is used to convert ADP + Pi to
ATP?
A) energy released as electrons flow through the electron transport system
B) energy released from substrate-level phosphorylation
C) energy released from ATP synthase pumping hydrogen ions from the mitochondrial matrix
D) energy released from movement of protons through ATP synthase
E) No external source of energy is required because the reaction is exergonic

Back 42

D) energy released from movement of protons through ATP synthase

Front 43

52) Energy released by the electron transport chain is used to pump H+ ions into which location?
A) cytosol
B) mitochondrial outer membrane
C) mitochondrial inner membrane
D) mitochondrial intermembrane space
E) mitochondrial matrix

Back 43

D) mitochondrial intermembrane space

Front 44

53) The direct energy source that drives ATP synthesis during respiratory oxidative phosphorylation is
A) oxidation of glucose to CO2 and water.
B) the thermodynamically favorable flow of electrons from NADH to the mitochondrial electron transport
carriers.
C) the final transfer of electrons to oxygen.
D) the difference in H+ concentrations on opposite sides of the inner mitochondrial membrane.
E) the thermodynamically favorable transfer of phosphate from glycolysis and the citric acid cycle
intermediate molecules of ADP.

Back 44

D) the difference in H+ concentrations on opposite sides of the inner mitochondrial membrane

Front 45

54) When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the
intermembrane space, the result is the
A) formation of ATP.
B) reduction of NAD+.
C) restoration of the Na+/K+ balance across the membrane.
D) creation of a proton gradient.
E) lowering of pH in the mitochondrial matrix.

Back 45

D) creation of a proton gradient.

Front 46

55) Where is ATP synthase located in the mitochondrion?
A) cytosol
B) electron transport chain
C) outer membrane
D) inner membrane
E) mitochondrial matrix

Back 46

D) inner membrane

Front 47

56) It is possible to prepare vesicles from portions of the inner membrane of the mitochondrial components. Which
one of the following processes could still be carried on by this isolated inner membrane?
A) the citric acid cycle
B) oxidative phosphorylation
C) glycolysis and fermentation
D) reduction of NAD+
E) both the citric acid cycle and oxidative phosphorylation

Back 47

B) oxidative phosphorylation

Front 48

57) Each time a molecule of glucose (C6H12O6) is completely oxidized via aerobic respiration, how many oxygen
molecules (O2) are required?
A) 1
B) 2
C) 6
D) 12
E) 38

Back 48

C) 6

Front 49

58) Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon
dioxide (CO2) and water?
A) glycolysis
B) fermentation
C) oxidation of pyruvate to acetyl CoA
D) citric acid cycle
E) oxidative phosphorylation (chemiosmosis)

Back 49

E) oxidative phosphorylation (chemiosmosis)

Front 50

59) Approximately how many molecules of ATP are produced from the complete oxidation of two molecules of
glucose (C6H12O6) in cellular respiration?
A) 2
B) 4
C) 15
D) 38
E) 76

Back 50

E) 76

Front 51

60) Assume a mitochondrion contains 58 NADH and 19 FADH2. If each of the 77 dinucleotides were used,
approximately how many ATP molecules could be generated as a result of oxidative phosphorylation
(chemiosmosis)?
A) 36
B) 77
C) 173
D) 212
E) 1102

Back 51

D) 212

Front 52

61) Approximately what percentage of the energy of glucose (C6H12O6) is transferred to storage in ATP as a result
of the complete oxidation of glucose to CO2 and water in cellular respiration?
A) 2%
B) 4%
C) 10%
D) 25%
E) 40%

Back 52

E) 40%

Front 53

62) Recall that the complete oxidation of a mole of glucose releases 686 kcal of energy (ΔG = -686 kcal/mol). The
phosphorylation of ADP to form ATP stores approximately 7.3 kcal per mole of ATP. What is the approximate
efficiency of cellular respiration for a ʺmutantʺ organism that produces only 29 moles of ATP for every mole of
glucose oxidized, rather than the usual 36-38 moles of ATP?
A) 0.4%
B) 25%
C) 30%
D) 40%
E) 60%

Back 53

C) 30%

Front 54

63) What is proton-motive force?
A) the force required to remove an electron from hydrogen
B) the transmembrane proton concentration gradient
C) movement of hydrogen into the intermembrane space
D) movement of hydrogen into the mitochondrion
E) the addition of hydrogen to NAD+

Back 54

B) the transmembrane proton concentration gradient

Front 55

64) In liver cells, the inner mitochondrial membranes are about 5 X the area of the outer mitochondrial membranes,
and about 17 X that of the cellʹs plasma membrane. What purpose must this serve?
A) It allows for increased rate of glycolysis.
B) It allows for increased rate of the citric acid cycle.
C) It increases the surface for oxidative phosphoryation.
D) It increases the surface for substrate-level phosphorylation.
E) It allows the liver cell to have fewer mitochondria.

Back 55

C) It increases the surface for oxidative phosphoryation.

Front 56

Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will
reseal ʺinside out.ʺ These little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. If
the membranes are agitated still further however, the ability to synthesize ATP is lost.
65) After the first disruption, when electron transfer and ATP synthesize 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 is sufficient
D) the electron transport system is sufficient
E) plasma membranes like those bacteria use for respiration

Back 56

A) all of the electron transport proteins as well as ATP synthase

Front 57

Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will
reseal ʺinside out.ʺ These little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. If
the membranes are agitated still further however, the ability to synthesize ATP is lost.
66) After the second 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

Back 57

D) ATP synthase, in whole or in part

Front 58

Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will
reseal ʺinside out.ʺ These little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. If
the membranes are agitated still further however, the ability to synthesize ATP is lost.
67) It should be possible to reconstitute the abilities of the vesicles if which of the following is added?
A) cytochromes
B) extra NADH
C) a second membrane surface
D) more electrons
E) intact ATP synthase

Back 58

E) intact ATP synthase

Front 59

72) Which of the following couples chemiosmosis to energy storage?
A) NADH
B) FADH2
C) cytochromes
D) electron transport
E) ATP synthase

Back 59

E) ATP synthase

Front 60

73) Which of the following describes ubiquinone?
A) a protein in the electron transport chain
B) a small hydrophobic coenzyme
C) a substrate for synthesis of FADH
D) a vitamin needed for efficient glycolysis
E) an essential amino acid

Back 60

B) a small hydrophobic coenzyme

Front 61

74) Which of the following normally occurs whether or not oxygen (O2) is present?
A) glycolysis
B) fermentation
C) oxidation of pyruvate to acetyl CoA
D) citric acid cycle
E) oxidative phosphorylation (chemiosmosis)

Back 61

A) glycolysis

Front 62

78) In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of
A) ATP, CO2, and ethanol (ethyl alcohol).
B) ATP, CO2, and lactate.
C) ATP, NADH, and pyruvate.
D) ATP, pyruvate, and oxygen.
E) ATP, pyruvate, and acetyl CoA.

Back 62

A) ATP, CO2, and ethanol (ethyl alcohol).

Front 63

79) In alcohol fermentation, NAD+ is regenerated from NADH during which of the following?
A) reduction of acetaldehyde to ethanol (ethyl alcohol)
B) oxidation of pyruvate to acetyl CoA
C) reduction of pyruvate to form lactate
D) oxidation of NAD+ in the citric acid cycle
E) phosphorylation of ADP to form ATP

Back 63

A) reduction of acetaldehyde to ethanol (ethyl alcohol)

Front 64

80) 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) none of the above

Back 64

C) oxidize NADH to NAD+.

Front 65

83) 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 is found in the cytosol, does not involve 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.

Back 65

B) It is found in the cytosol, does not involve oxygen, and is present in most organisms.

Front 66

84) Muscle cells, when an individual is exercising heavily and when the muscle becomes oxygen deprived, 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.

Back 66

C) It is taken to the liver and converted back to pyruvate.

Front 67

85) When muscle cells are oxygen deprived, the heart still pumps. What must the heart 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

Back 67

B) continue aerobic metabolism when skeletal muscle cannot

Front 68

86) When 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.

Back 68

D) increase in potassium ions.

Front 69

87) You have a friend who lost 7 kg (about 15 pounds) of fat on a ʺlow carbʺ diet. How did the fat leave her body?
A) It was released as CO2 and H2O.
B) Chemical energy 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

Back 69

A) It was released as CO2 and H2O.

Front 70

88) Phosphofructokinase is an important control enzyme in the regulation of cellular respiration. Which of the
following statements describes a function of phosphofructokinase?
A) It is activated by AMP (derived from ADP).
B) It is activated by ATP.
C) It is inhibited 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.

Back 70

E) It is an allosteric enzyme

Front 71

89) 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
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.

Back 71

A) inhibit the enzyme and thus slow the rates of glycolysis and the citric acid cycle

Front 72

90) 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 non-photosynthesizing cells only
C) in cells that are storing glucose only
D) in photosynthesizing cells in dark periods and in other tissues all the time
E) in photosynthesizing cells in the light and in other tissues in the dark

Back 72

D) in photosynthesizing cells in dark periods and in other tissues all the time

Front 73

91) In vertebrate animals, brown fat tissueʹs color is due to abundant mitochondria. White fat tissue, on the other
hand, is specialized for fat storage and contains relatively few mitochondria. 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 synthase
D) to allow other membranes of the cell to perform mitochondrial function
E) to regulate temperature by converting energy from NADH oxidation to heat

Back 73

E) to regulate temperature by converting energy from NADH oxidation to heat

Front 74

92) 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

Back 74

E) breakdown of fatty acids

Front 75

93) 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

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C) acetyl CoA