Deck 9: Pathways That Harvest Chemical Energy

Question 1

When a molecule loses hydrogen atoms (as opposed to hydrogen ions), it becomes

A) reduced.
B) oxidized.
C) redoxed.
D) hydrogenated.
E) hydrolyzed.

Answer 1

B

Question 2

Which of the following statements about metabolic pathways is true?

A) Complex chemical transformations in the cell occur in a single reaction.
B) Each reaction requires oxygen.
C) In eukaryotes, they occur in the cytoplasm.
D) They vary from organism to organism.
E) Each one is regulated by specific enzymes.

Answer 2

E

Question 3

The respiratory chain

A) is located in the mitochondrial matrix.
B) includes only peripheral membrane proteins.
C) always produces ATP.
D) reoxidizes reduced coenzymes.
E) operates simultaneously with fermentation.

Answer 3

D

Question 4

When NADH donates two electrons to ubiquinone during respiration, ubiquinone is

A) reduced.
B) oxidized.
C) phosphorylated.
D) aerobic.
E) hydrolyzed.

Question 5

NAD⁺ is

A) a type of organelle.
B) a protein.
C) present only in mitochondria.
D) a part of ATP.
E) formed in the reaction that produces ethanol.

Question 6

ATP is

A) a short-term energy-storage compound.
B) the cell's principal compound for energy transfers.
C) synthesized within mitochondria.
D) the molecule all living cells rely on to do work.
E) All of the above

Question 7

Which statement about oxidative phosphorylation is not true?

A) It forms ATP by the respiratory chain/ATP synthesis.
B) It is brought about by chemiosmosis.
C) It requires aerobic conditions.
D) It takes place in mitochondria.
E) Its functions can be served equally well by fermentation.

Question 8

The citric acid cycle

A) has no connection with the respiratory chain.
B) is the same thing as fermentation.
C) reduces two NAD⁺ for every glucose processed.
D) produces no ATP.
E) takes place in the mitochondrion.

Question 9

Compared with fermentation, the aerobic pathways of glucose metabolism produce

A) more ATP.
B) pyruvate.
C) fewer protons for pumping in the mitochondria.
D) less CO₂.
E) more oxidized coenzymes.

Question 10

Which of the following processes occurs when oxygen is unavailable?

A) Pyruvate oxidation
B) The citric acid cycle
C) Fermentation
D) An electron transport chain
E) All of the above

Question 11

Which of the following statements about metabolic pathways is false?

A) The product of one reaction becomes the reactant for the next reaction.
B) They are a series of enzyme-catalyzed reactions.
C) Almost all are anabolic.
D) They are similar in all organisms.
E) Many are compartmentalized in eukaryotes.

Question 12

The role of oxygen gas in our cells is to

A) catalyze reactions in glycolysis.
B) produce CO₂.
C) form ATP.
D) accept electrons from the respiratory chain.
E) react with glucose to split water.

Question 13

Glycolysis

A) takes place in the mitochondrion.
B) produces no ATP.
C) has no connection with the respiratory chain.
D) is the same thing as fermentation.
E) reduces two molecules of NAD⁺ for every glucose molecule processed.

Question 14

The oxidation of malate to oxaloacetate is coupled to the reduction of NAD⁺ to NADH + H⁺. NAD⁺ is a(n)

A) reducing agent.
B) oxidizing agent.
C) vitamin.
D) phosphate ester.
E) phosphorylating agent.

Question 15

In the conversion of succinate to fumarate, hydrogen atoms are transferred to FAD. The conversion of succinate and FAD to fumarate and FADH₂ is an example of

A) hydrolysis.
B) an allosteric reaction.
C) a metabolic pathway.
D) an aerobic reaction.
E) a redox reaction.

Question 16

In all cells, glucose metabolism begins with

A) glycolysis.
B) fermentation.
C) pyruvate oxidation.
D) the citric acid cycle.
E) chemosmosis.

Question 17

Fermentation

A) takes place in the mitochondrion.
B) takes place in all animal cells.
C) does not require O₂.
D) requires lactic acid.
E) prevents glycolysis.

Question 18

Which statement about pyruvate is not true?

A) It is the end product of glycolysis.
B) It becomes reduced during fermentation.
C) It is a precursor of acetyl CoA.
D) It is a protein.
E) It contains three carbon atoms.

Question 19

Metabolic syndrome is a disorder with several symptoms including obesity. An experimental drug, Aicar, may aid in treating this disorder. It works by

A) increasing the rate of glucose oxidation.
B) decreasing oxidative phosphorylation from ATP.
C) increasing the breakdown of fat to yield ATP.
D) stimulating production of fast-twitch muscle fibers.
E) converting slow-twitch muscle fibers into fast-twitch muscle fibers.

Question 20

Oxidation and reduction

A) entail the gain or loss of proteins.
B) are defined as the loss of electrons.
C) are both endergonic reactions.
D) always occur together.
E) proceed only under aerobic conditions.

Question 21

For glycolysis to continue, all cells require

A) a respiratory chain.
B) oxygen.
C) mitochondria.
D) chloroplasts.
E) NAD⁺.

Question 22

In the cell, the site of oxygen utilization is the

A) nucleus.
B) chloroplast.
C) endoplasmic reticulum.
D) mitochondrion.
E) cytosol.

Question 23

NAD

A) is a key electron carrier in redox reactions.
B) requires oxygen to function.
C) is found only in prokaryotes.
D) binds with an acetyl group to form acetyl CoA.
E) detoxifies hydrogen peroxide.

Question 24

Some of the free energy released by oxidation of pyruvate to acetate is stored in acetyl CoA. How does acetyl CoA store free energy?

A) Acetyl CoA has a higher free energy than acetate.
B) Acetyl CoA is an electron carrier.
C) Acetyl CoA is a phosphate donor.
D) Acetate + CoA $\to$ acetyl CoA is an exergonic reaction.
E) Reduction of acetyl CoA is coupled to ATP synthesis.

Question 25

Which of the following oxidizes other compounds by gaining free energy and hydrogen atoms and reduces other compounds by giving up free energy and hydrogen atoms?

A) Vitamins
B) Adenine
C) ATP
D) NAD
E) Riboflavin

Question 26

Glycolysis converts glucose into pyruvate, ATP, and NADH. The process requires

A) oxygen, ATP, and a series of reactions.
B) carbon dioxide, 5 enzyme-catalyzed reactions, and glucose to begin the series of reactions.
C) pyruvic acid, oxygen, and enzymes to oxidize glucose inside the mitochondria
D) the pyruvate dehydrogenase complex to catalyze the reactions.
E) 10 enzyme-catalyzed reactions, each reaction dependent on the products of the previous reaction to proceed.

Question 27

Within the cell, the pyruvate dehydrogenase complex, a multienzyme complex of the citric acid cycle, is located in the

A) thylakoids.
B) cytoplasm.
C) chloroplast.
D) mitochondrial matrix.
E) plasma membrane.

Question 28

The first five reactions of the glycolytic pathway result in

A) the addition of phosphates, modification of sugars, and formation of G3P.
B) oxidative steps, proton pumping, and reactions with oxygen.
C) the oxidation of pyruvate and formation of acetyl CoA.
D) the removal of hydrogen and protons from glucose.
E) None of the above

Question 29

The function of NAD⁺ is to

A) cause the release of energy to adjacent cells when energy is needed in aerobic conditions.
B) hasten the release of energy when the cell has been deprived of oxygen.
C) carry hydrogen atoms and free energy from compounds being oxidized and to give hydrogen atoms and free energy to compounds being reduced.
D) block the release of energy to adjacent cells.
E) None of the above

Question 30

The oxidation of pyruvate to carbon dioxide is called

A) fermentation.
B) the citric acid cycle.
C) glycolysis.
D) oxidative phosphorylation.
E) the respiratory chain.

Question 31

During glycolysis, for each mole of glucose oxidized to pyruvate,

A) 6 moles of ATP are produced.
B) 2 moles of ATP are produced.
C) 4 moles of ATP are produced.
D) 2 moles of NAD⁺ are produced.
E) no ATP is produced.

Question 32

In steps 6 through 10 of glycolysis, the conversion of 1 mole of glyceraldehyde 3-phosphate to pyruvate yields 2 moles of ATP. But the oxidation of glucose to pyruvate produces a total of 4 moles of ATP. Where do the remaining 2 moles of ATP come from?

A) One mole of glucose yields 2 moles of glyceraldehyde 3-phosphate.
B) Two moles of ATP are used during the conversion of glucose to glyceraldehyde 3-phosphate.
C) Glycolysis produces 2 moles of NADH.
D) Fermentation of pyruvate to lactic acid yields 2 moles of ATP.
E) Fermentation of pyruvate to lactic acid yields 2 moles of NAD⁺.

Question 33

ATP is used to drive the first five reactions of glycolysis because

A) nonspontaneous reactions are exergonic.
B) the breakdown of ATP to ADP is exergonic.
C) the breakdown of ATP to ADP is endergonic.
D) when ATP is broken down to ADP, P_i is released.
E) ADP possesses more free energy than ATP does.

Question 34

The end product of glycolysis is

A) pyruvate.
B) the starting point for pyruvate oxidation.
C) the starting point for the fermentation pathway.
D) Both a and b
E) All of the above

Question 35

During the energy-priming portion of glycolysis, the phosphates from ATP molecules are

A) added to the first and sixth carbons.
B) added to the second and fourth carbons.
C) wasted, as an energy investment.
D) used to make pyruvate.
E) used to make lactate.

Question 36

Substrate-level phosphorylation is the transfer of a(n)

A) phosphate to a protein.
B) phosphate to a substrate.
C) phosphate to an ADP.
D) ATP to a protein.
E) phosphate from ATP to a substrate.

Question 37

In the first reaction of glycolysis, glucose receives a phosphate group from ATP. This reaction is

A) respiration.
B) a redox reaction.
C) exergonic.
D) endergonic.
E) fermentation.

Question 38

For glucose to be used as an energy source, it is necessary that

A) glucose be formed from fructose.
B) glucose phosphate be formed from fructose phosphate.
C) glucose be degraded to carbon dioxide.
D) two ATP molecules be invested in the system.
E) None of the above

Question 39

The end result of glycolysis is the

A) creation of 38 molecules of ATP.
B) reduction of 8 molecules of NAD.
C) formation of 2 molecules of pyruvate.
D) conversion of 1 molecule of glucose to lactic acid.
E) None of the above

Question 40

The free energy released during the oxidation of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate is

A) used to oxidize NADH.
B) lost as heat.
C) used to synthesize ATP.
D) used to reduce NAD⁺.
E) stored in lactic acid.

Question 41

Which of the following is produced during the citric acid cycle?

A) FAD
B) Pyruvate
C) Reduced electron carriers
D) Lactic acid
E) Water

Question 42

The citric acid cycle begins with

A) glucose.
B) pyruvate.
C) acetyl CoA.
D) NADH + H⁺.
E) ATP synthase.

Question 43

Which process converts glucose to pyruvate, generating a small amount of ATP but no carbon dioxide?

A) Pyruvate oxidation
B) Glycolysis
C) The citric acid cycle
D) Respiratory chain
E) Gluconeogenesis

Question 44

Which of the following statements about the electron transport chain is true?

A) Electrons are received from NADH and FADH₂.
B) Electrons are passed from donor to recipient carrier molecules in a series of oxidation-reduction reactions.
C) Usually the terminal electron acceptor is oxygen.
D) Most of the enzymes are part of the inner mitochondrial membrane.
E) All of the above

Question 45

The electron transport chain contains four large protein complexes: NADH-Q reductase complex, succinate dehydrogenase, cytochrome c reductase complex, and cytochrome c oxidase complex. These proteins

A) are integral proteins.
B) change in a similar way when reduced.
C) regulate the passage of water through the respiratory chain.
D) oxidize NADH.
E) complete oxidation of pyruvate to acetate.

Question 46

The oxidizing agent at the end of the electron transport chain is

A) O₂.
B) NAD⁺.
C) ATP.
D) FAD.
E) ubiquinone.

Question 47

How does the reduction of pyruvate to lactic acid during fermentation allow glycolysis to continue in the absence of oxygen?

A) Water is formed during this reaction.
B) This reaction is a kinase reaction.
C) This reaction is coupled to the oxidation of NADH to NAD⁺.
D) This reaction is coupled to the formation of ATP.
E) This reaction is coupled to the reduction of NAD⁺ to NADH.

Question 48

Animals breathe in air containing oxygen and breathe out air with less oxygen and more carbon dioxide. The carbon dioxide comes from

A) hydrocarbons and the air.
B) the citric acid cycle.
C) glycolysis.
D) waste products.
E) All of the above

Question 49

Animals inhale air containing oxygen and exhale air with less oxygen and more carbon dioxide. After inhalation, the oxygen missing from the air will mostly be found in

A) the carbon dioxide that is exhaled.
B) water.
C) organic molecules.
D) ethanol.
E) lactate.

Question 50

The drug 2,4-dinitrophenol (DNP) destroys the proton gradient across the inner mitochondrial membrane. What would be the effect of incubating isolated mitochondria in a solution of DNP?

A) Oxygen would no longer be reduced to water.
B) No ATP would be made during transport of electrons down the respiratory chain.
C) Mitochondria would show a burst of increased ATP synthesis.
D) Glycolysis would stop.
E) Mitochondria would switch from glycolysis to fermentation.

Question 51

For the citric acid cycle to proceed, it is necessary for

A) pyruvate to bind to oxaloacetate.
B) carbon dioxide to bind to oxaloacetate.
C) an acetyl group to bind to oxaloacetate.
D) water to be oxidized.
E) None of the above

Question 52

During the citric acid cycle, energy stored in acetyl CoA is used to

A) create a proton gradient.
B) drive the reaction ADP + P_i $\to$ ATP.
C) reduce NAD⁺ to NADH.
D) drive the reaction oxaloacetate $\to$ citric acid.
E) reduce FAD to FADH₂.

Question 53

Which of the following events occurs in the electron transport chain?

A) CO₂ is released.
B) CO₂ is reduced.
C) Cytochromes, FADH, and NADH are oxidized.
D) Only NAD⁺ is reduced.
E) None of the above

Question 54

Pyruvate oxidation generates

A) acetate.
B) NADH + H⁺ from NAD⁺.
C) a change in free energy.
D) CO₂.
E) All of the above

Question 55

More free energy is released during the citric acid cycle than during glycolysis, but only 1 mole of ATP is produced for each mole of acetyl CoA that enters the cycle. Most of the remaining free energy produced during the citric acid cycle is

A) used to synthesize GTP.
B) used to reduce electron carriers.
C) lost as heat.
D) used to reduce pyruvate.
E) converted to kinetic energy.

Question 56

During the citric acid cycle, oxidative steps are coupled to

A) oxidative phosphorylation.
B) the oxidation of water.
C) the oxidation of electron carriers.
D) the hydrolysis of ATP.
E) the reduction of electron carriers.

Question 57

Electron transport within NADH-Q reductase, cytochrome reductase, and cytochrome oxidase can be coupled to proton transport from the mitochondrial matrix to the space between the inner and outer mitochondrial membranes, because those protein complexes are

A) in the mitochondrial matrix.
B) within the inner mitochondrial membrane.
C) in the space between the inner and outer mitochondrial membranes.
D) in the cytoplasm.
E) loosely attached to the inner mitochondrial membrane.

Question 58

Water is a by-product of cellular respiration. The water is produced as a result of the

A) combining of carbon dioxide with protons.
B) conversion of pyruvate to acetyl CoA.
C) degradation of glucose to pyruvate.
D) reduction of oxygen at the end of the electron transport chain.
E) None of the above

Question 59

The hydrogen ion gradient is maintained by

A) electron transport and proton pumping.
B) the splitting of water.
C) the ionization of glucose.
D) ATP synthase.
E) acetyl CoA.

Question 60

The electron transport chain contains four large protein complexes (I, II, III, and IV), cytochrome c, and ubiquinone. The function of these molecules is to

A) transport electrons.
B) ensure the production of water and oxygen.
C) regulate the passage of water through the chain.
D) oxidize NADH.
E) None of the above

Question 61

Many species derive their energy from fermentation. The function of fermentation is to

A) reduce NAD⁺.
B) oxidize CO₂.
C) oxidize NADH + H⁺, ensuring a continued supply of ATP.
D) produce acetyl CoA.
E) None of the above

Question 62

For bacteria to continue growing rapidly when they are shifted from an environment containing oxygen to an anaerobic environment, they must

A) increase the rate of the citric acid cycle.
B) produce more ATP per mole of glucose during glycolysis.
C) produce ATP during the oxidation of NADH.
D) increase the rate of transport of electrons down the respiratory chain.
E) increase the rate of the glycolytic reactions.

Question 63

The component of aerobic respiration that produces the most ATP per mole of glucose is

A) the electron transport chain.
B) the citric acid cycle.
C) glycolysis.
D) lactic acid fermentation.
E) alcoholic fermentation.

Question 64

Most ATP produced in our bodies is made

A) by glycolysis.
B) in the citric acid cycle.
C) using ATP synthase.
D) from photosynthesis.
E) by burning fat.

Question 65

During the fermentation of one molecule of glucose, the net production of ATP is _______ molecule(s).

A) one
B) two
C) three
D) six
E) eight

Question 66

When acetyl CoA builds up in the cell, it increases the activity of the enzyme that synthesizes oxaloacetate from pyruvate and carbon dioxide. Acetyl CoA is acting as a(n)

A) electron carrier.
B) substrate.
C) allosteric activator.
D) acetate donor.
E) proton pump.

Question 67

Fats are the preferred energy source in many organisms because

A) they are less dense than polysaccharides.
B) they have more C-H bonds and less C-OH bonds.
C) they are nonpolar.
D) fats do not bind to water.
E) they have essential roles as enzymes and structural elements.

Question 68

In the absence of oxygen, cells capable of fermentation

A) accumulate glucose.
B) no longer produce ATP.
C) accumulate pyruvate.
D) oxidize FAD.
E) oxidize NADH to produce NAD⁺.

Question 69

Before starch can be used for respiratory ATP production, it must be hydrolyzed to

A) pyruvate.
B) fatty acids.
C) amino acids.
D) glucose.
E) oxaloacetate.

Question 70

Regardless of the electron or hydrogen acceptor employed, fermentation always produces

A) AMP.
B) DNA.
C) P_i.
D) NAD⁺.
E) None of the above

Question 71

In alcoholic fermentation, NAD⁺ is produced during the

A) oxidation of pyruvate to acetyl CoA.
B) reduction of pyruvate to lactic acid.
C) reduction of acetaldehyde to ethanol.
D) hydrolysis of ATP to ADP.
E) oxidation of glucose.

Question 72

The chemiosmotic generation of ATP is driven by

A) osmotic movement of water into an area of high solute concentration.
B) the addition of protons to ADP and phosphate via enzymes.
C) oxidative phosphorylation.
D) the proton-motive force.
E) isocitrate dehydrogenase.

Question 73

Oxygen is used by

A) glycolysis.
B) the citric acid cycle.
C) the electron transport chain.
D) substrate-level phosphorylation.
E) ATP synthase.

Question 74

In human muscle cells, the fermentation process produces

A) lactic acid.
B) 12 moles of ATP.
C) pyruvic acid.
D) an excessive amount of energy.
E) None of the above

Question 75

In some mammals, such as newborn humans and hibernating animals, body temperature is raised by means of

A) the uncoupling of respiration by the protein thermogenin.
B) an increase in the rate of glycolysis.
C) shivering.
D) leakage of hydrogen ions across the cell's plasma membrane.
E) cytochrome reductase.

Question 76

The proton-motive force is

A) ATP synthase.
B) the proton concentration gradient and electric charge difference.
C) a metabolic pathway.
D) a redox reaction.
E) None of the above

Question 77

When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane into the intermembranous space, the result is the

A) formation of ATP.
B) reduction of NAD⁺.
C) creation of a proton gradient.
D) restoration of the Na⁺-K⁺ balance across the membrane.
E) reduction of glucose to lactic acid.

Question 78

The formation of ethanol from pyruvate is an example of

A) an exergonic reaction.
B) an extra source of energy as the result of glycolysis.
C) a fermentation process that takes place in the absence of oxygen.
D) cellular respiration.
E) None of the above

Question 79

Yeast cells tend to create anaerobic conditions because they use oxygen more quickly than it can be replaced by diffusion through the cell membrane. For this reason, yeast cells

A) exhibit a red pigment.
B) exhibit a green pigment.
C) die.
D) produce ethanol.
E) None of the above

Question 80

According to the chemiosmotic theory, the energy for the synthesis of ATP during the flow of electrons down the respiratory chain is provided directly by the

A) hydrolysis of GTP.
B) reduction of NAD⁺.
C) diffusion of protons.
D) reduction of FAD.
E) hydrolysis of ATP.