General, Organic & Biological Chemistry, 5e (Timberlake)Chapter 23 Metabolism and Energy Production

23.1 Multiple-Choice Questions

1) When combined with electron transport, one turn of the citric acid cycle produces ________ ATP.A) 24B) 12C) 10D) 14E) 2Answer: CObjective: 23.1Global Outcomes: GO2

2) Which coenzyme is the electron acceptor in the following reaction?

H H| |

- C - C - → - C =C -| | | |

A) FADB) NAD+C) FMND) NADHE) FADH2 Answer: AObjective: 23.1Global Outcomes: GO2

3) Which coenzyme is the electron acceptor in the following reaction?

OH O|

- C - → - C -|H

A) FADB) NAD+C) FMND) NADHE) FADH2 Answer: BObjective: 23.1Global Outcomes: GO2

4) NAD+ participates in reactions that produceA) a CH2 group.B) a C=O bond.C) phosphorylation.D) ADP from ATP.

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E) a C-C bond.Answer: BObjective: 23.1Global Outcomes: GO2

5) FAD is a coenzyme which usually participates inA) oxidation of alcohols to aldehydes.B) formation of carbon-carbon double bonds.C) decarboxylation reactions.D) phosphorylation reactions.E) β-oxidation reactions.Answer: BObjective: 23.1Global Outcomes: GO2

6) In order to enter the citric acid cycle, pyruvate is first converted to A) ate.B) acetaldehyde.C) citrate.D) acetyl CoA.E) ethanol.Answer: DObjective: 23.1Global Outcomes: GO2

7) The citric acid cycle is used in the oxidation ofA) glucose only.B) glucose and fatty acids only.C) fatty acids only.D) glucose, fatty acids, and proteins.E) proteins only.Answer: DObjective: 23.1Global Outcomes: GO2

8) What electron acceptor(s) is(are) used in the citric acid cycle?A) FAD onlyB) NAD+ onlyC) NADH + FADH2 + HS - CoAD) FMNE) NAD+ + FADAnswer: EObjective: 23.1Global Outcomes: GO2

9) Which of the following compounds in the citric acid cycle undergoes oxidative decarboxylation?A) citrateB) isocitrateC) succinateD) fumarateE) succinyl CoAAnswer: BObjective: 23.1Global Outcomes: GO2

10) Which of the following is the net reaction for one turn of the citric acid cycle?2

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A) Acetyl CoA + 3 NAD+ + FAD + GDP + Pi + 2H2O → 2CO2 + 3 NADH + 3 H+ + FADH2 + HS - CoA + GTPB) Pyruvate + 3 NAD+ + FAD + GDP + Pi + 2H2O → 3 CO2 + 3 NADH + 3 H+ + FADH2 + GTPC) Acetyl CoA + NAD+ + FAD + GDP + Pi → 2 CO2 + NADH + H+ + FADH2 + HS - CoA + GTPD) Glucose + 2 NAD+ + 2GDP + 2 Pi + 2H2O → 2Pyruvate + 2 NADH + 2 H+ + GTPE) Glucose + 2GDP + 2 Pi → 2Lactate + 2GTPAnswer: AObjective: 23.1Global Outcomes: GO2

11) The citric acid cycle operates only under aerobic conditions becauseA) oxygen is a reactant in the citric acid cycle.B) oxygen is a product of the citric acid cycle.C) CO2 is a product of the citric acid cycle.D) the NADH and FADH2 produced by the citric acid cycle can only be reoxidized by the electron transport chain.E) the NAD+ and FAD produced by the citric acid cycle can only be reduced by the electron transport chain.Answer: DObjective: 23.1Global Outcomes: GO2

12) When oxygen is in plentiful supply in the cell, pyruvate is converted toA) CoA.B) acetyl CoA.C) glucose.D) lactate.E) fructose.Answer: BObjective: 23.1Global Outcomes: GO2

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13) Which of the three major stages of metabolism includes the citric acid cycle?A) Stage oneB) Stage twoC) Stage threeAnswer: CObjective: 23.1Global Outcomes: GO2

14) The citric acid cycle takes place in theA) mitochondria.B) cytosol.C) cytoplasm.D) Golgi apparatus.E) endoplasmic reticulum.Answer: AObjective: 23.1Global Outcomes: GO7

15) Most of the energy released in the citric acid cycle is used to produceA) glucose.B) acetyl CoA.C) NADH and FADH2.D) carbon dioxide and water.E) citric acid.Answer: CObjective: 23.1Global Outcomes: GO2

16) Another name for the citric acid cycle isA) electron transport.B) glycolysis.C) the tricarboxylic acid (TCA) cycle.D) glucolysis.E) the transamination pathway.Answer: CObjective: 23.1Global Outcomes: GO7

17) Another name for the citric acid cycle isA) the Krebs cycle.B) gluconeogenesis.C) glucose hydrolysis.D) oxidative phosphorylation.E) the chemiosmotic pump. Answer: AObjective: 23.1Global Outcomes: GO7

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18) In the first reaction of the citric acid cycleA) glucose becomes pyruvate.B) ATP is produced.C) NADH is produced.D) acetyl CoA reacts with oxaloacetate to give citrate.E) pyruvate becomes CO2 and H2O.Answer: DObjective: 23.1Global Outcomes: GO2

19) During the first reaction in the citric acid cycle,A) HS- CoA is released.B) acetyl CoA is made.C) a decarboxylation occurs.D) a decomposition occurs.E) ATP is synthesized.Answer: AObjective: 23.1Global Outcomes: GO2

20) The transformation of citrate to isocitrate in the citric acid cycle requires two ________ reactions.A) oxidationB) reductionC) hydrolysisD) decarboxylationE) dehydration-hydrationAnswer: EObjective: 23.1Global Outcomes: GO2

21) The citric acid cycle step that removes the first CO2 molecule is a(n)A) oxidative decarboxylation.B) reduction.C) carbonylation.D) hydrolysis.E) combination.Answer: AObjective: 23.1Global Outcomes: GO2

22) In the third major step of the citric acid cycle, NAD+ is converted toA) NAS-.B) NAD2+.C) NADH2.D) NAD.E) NADH.Answer: EObjective: 23.1Global Outcomes: GO2

23) Step 5 of the citric acid cycle is the hydrolysis of succinyl CoA. In this reactionA) the energy released is used to make GTP.B) the energy released is used to make ATP.C) carbon dioxide is released.D) α-ketoglutarate is released.

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E) the enzyme aconitase is needed.Answer: AObjective: 23.1Global Outcomes: GO2

24) In the hydrolysis of succinyl CoA in step 5 of the citric acid cycle, CoA is released asA) HS-CoA.B) HO-CoA.C) CoA-O-.D) CoA-S-.E) CoA-COO-.Answer: AObjective: 23.1Global Outcomes: GO2

25) The GTP formed in step 5 of the citric acid cycle is used to makeA) carbon dioxide.B) oxygen.C) water.D) CoA.E) ATP.Answer: EObjective: 23.1Global Outcomes: GO2

26) In the dehydration of succinate to fumarate in the citric acid cycle, the coenzyme used isA) CoA.B) acetyl CoA.C) NAD+.D) NADH.E) FAD.Answer: EObjective: 23.1Global Outcomes: GO2

27) In step 7 of the citric acid cycle, fumarate is converted to malate by a ________ reaction.A) hydrolysisB) dehydrogenationC) hydrogenationD) hydrationE) dehydrationAnswer: DObjective: 23.1Global Outcomes: GO2

28) The last step in the citric acid cycle converts malate toA) citrate.B) isocitrate.C) succinate.D) fumarate.E) oxaloacetate.Answer: EObjective: 23.1Global Outcomes: GO2

29) One method of regulation of the citric acid cycle is6

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A) allosteric control.B) osmosis.C) temperature control.D) carbon dioxide production.E) water concentration.Answer: AObjective: 23.1Global Outcomes: GO2

30) The process which requires oxygen to produce carbon dioxide and water is calledA) fermentation.B) reduction.C) decomposition.D) oxidation.E) respiration.Answer: EObjective: 23.2Global Outcomes: GO2

31) Which of the following metabolic pathways can occur in the absence of oxygen?A) electron transportB) oxidative phosphorylationC) citric acid cycleD) glycolysisE) β-oxidationAnswer: DObjective: 23.2Global Outcomes: GO2

32) Under anaerobic conditions, there is a net production of ________ ATP during glycolysis.A) zeroB) twoC) fourD) sixE) eightAnswer: BObjective: 23.2Global Outcomes: GO4

33) Cyanide ion and carbon monoxide inhibitA) cytochrome c oxidase.B) ATP production.C) antibiotic activity.D) CoQ formation.E) CoA formation.Answer: AObjective: 23.2Global Outcomes: GO2

34) In the chemiosmotic model, protons circulate through a protein complex calledA) Cyt c.B) FMN.C) Complex III.D) CoQ.E) ATP synthase.Answer: EObjective: 23.2

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Global Outcomes: GO2

35) The components of the electron transport chain do NOT includeA) oxygen (O2).B) Cyt c.C) Complex III.D) CoQ.E) acetyl CoA.Answer: EObjective: 23.2Global Outcomes: GO2

36) In the chemiosmotic model of oxidative phosphorylation, ATP is synthesized asA) OH- flows through ATP synthase.B) electrons flow through ATP synthase.C) Ca2+ flows through ATP synthase.D) H+ flows through ATP synthase.E) Na+ flows through ATP synthase.Answer: DObjective: 23.2Global Outcomes: GO2

37) In electron transport, the synthesis of ATP from ADP + Pi is calledA) glycolysis.B) fermentation.C) oxidative phosphorylation.D) isomerization.E) hydrolysis.Answer: CObjective: 23.2Global Outcomes: GO2

38) In electron transport, the three protein complexes (I, III, and IV)A) act as proton pumps, which generate a proton gradient.B) transfer electrons from NAD+ to O2. C) transfer electrons from FAD to O2. D) act as electron pumps, which generate an electron gradient.E) act as Ca2+ pumps, which generate a Ca2+ gradient.Answer: AObjective: 23.2Global Outcomes: GO2

39) In electron transport, the oxidized product from the reaction of CoQ + NADH + H+ isA) CoQ.B) CoQH2.C) FADH.D) FAD.E) NAD+.Answer: EObjective: 23.2Global Outcomes: GO2

40) The electron carrier ________ provides 1.5 ATP via electron transport.A) FADH2B) NADH

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C) NADPHD) HS-CoAE) acetyl CoAAnswer: AObjective: 23.2Global Outcomes: GO2

41) Electron transport is also calledA) the citric acid cycle.B) β-oxidation.C) transamination.D) the respiratory chain.E) fermentation.Answer: DObjective: 23.2Global Outcomes: GO2

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42) In electron transport, NADH and FADH2 are used to provideA) oxygen.B) electrons and hydrogen ions.C) carbon atoms.D) water and carbon dioxide.E) thiol groups.Answer: BObjective: 23.2Global Outcomes: GO2

43) The energy released during electron transport is used to produceA) glucose.B) citric acid.C) carbon dioxide.D) ATP.E) NADH.Answer: DObjective: 23.2Global Outcomes: GO2

44) The compounds in the respiratory chain that remove hydrogen ions and electrons from NADH are classified asA) oxidative transporters.B) osmotic carriers.C) electron carriers.D) phosphorylators.E) citrates.Answer: CObjective: 23.2Global Outcomes: GO2

45) One example of an electron carrier in the respiratory chain isA) ATP.B) GTP.C) coenzyme Q.D) citrate.E) water.Answer: CObjective: 23.2Global Outcomes: GO2

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46) Which is the best choice for the box labeled "Answer" in the illustration below?

A) oxidized carrier BB) carbon dioxideC) OH-D) reduced carrier BH2E) energyAnswer: DObjective: 23.2Global Outcomes: GO2

47) What is the correct coefficient for ATP in the complete combustion of glucose?

C6H12O6 + 6O2 → 6CO2 + ________ ATP + 6H2O

A) 6B) 12C) 18D) 24E) 32Answer: EObjective: 23.3Global Outcomes: GO4

48) Which of the following is NOT a possible product of pyruvate under anaerobic conditions?A) lactateB) acetaldehydeC) fumarateD) ethanolE) CO2Answer: CObjective: 23.3Global Outcomes: GO2

49) In stage three of metabolism, the overall result is to releaseA) glucose and water.B) lactate and acetyl CoA.C) lactate and glucose.D) glycogen and water.E) carbon dioxide and energy.Answer: EObjective: 23.3Global Outcomes: GO2

50) Overall, one turn of the citric acid cycle producesA) three CO2 molecules.B) three NADH molecules.C) two FADH2 molecules.

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D) 6 ATP.E) 2 GTP.Answer: BObjective: 23.3Global Outcomes: GO2

51) In glycolysis, glucose produces 2 pyruvate ions and a total of ________ ATP molecules.A) 2B) 4C) 7D) 8E) 12Answer: CObjective: 23.3Global Outcomes: GO4

52) The complete oxidation of glucose produces ________ ATP molecules.A) 2B) 8C) 12D) 24E) 32Answer: EObjective: 23.3Global Outcomes: GO4

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23.2 Short Answer Questions

In this figure depicting the Stages of Metabolism taken from your text, identify the metabolic substance numbered.

1) Substance 1Answer: proteinsObjective: 23.1Global Outcomes: GO2

2) Substance 2Answer: carbohydrates or polysaccharidesObjective: 23.1Global Outcomes: GO2

3) Substance 3Answer: lipidsObjective: 23.1Global Outcomes: GO2

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4) Substance 4Answer: pyruvateObjective: 23.1Global Outcomes: GO2

5) Substance 5Answer: acetyl CoAObjective: 23.1Global Outcomes: GO2

6) Substance 6 Answer: carbon dioxideObjective: 23.1Global Outcomes: GO2

7) Substance 7Answer: ATPObjective: 23.1Global Outcomes: GO2

8) Substance 8Answer: oxygenObjective: 23.1Global Outcomes: GO2

9) Process 9Answer: citric acid cycle or Krebs cycle or tricarboxylic acid cycleObjective: 23.1Global Outcomes: GO2

10) Process 10Answer: electron transportObjective: 23.1Global Outcomes: GO2

11) Process 11Answer: oxidative phosphorylationObjective: 23.1Global Outcomes: GO2

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In this figure, depicting part 1 of the Citric Acid Cycle, taken from your text, identify the substances numbered.

12) Substance 12Answer: acetyl CoAObjective: 23.1Global Outcomes: GO2

13) Substance 13Answer: citrateObjective: 23.1Global Outcomes: GO2

14) Substance 14Answer: carbon dioxideObjective: 23.1Global Outcomes: GO2

15) Substance 15Answer: α-ketoglutarateObjective: 23.1Global Outcomes: GO2

16) Substance 16Answer: carbon dioxideObjective: 23.1Global Outcomes: GO2

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17) Substance 17Answer: succinyl CoAObjective: 23.1Global Outcomes: GO2

18) Substance 18Answer: oxaloacetateObjective: 23.1Global Outcomes: GO2

23.3 True/False Questions

1) In reaction 4 of the citric acid cycle, α-ketoglutarase, a five-carbon keto acid, is decarboxylated.Answer: TRUEObjective: 23.1Global Outcomes: GO2

2) In reaction 1 of the citric acid cycle, acetyl CoA reacts with oxaloacetate.Answer: TRUEObjective: 23.1Global Outcomes: GO2

3) Citrate is one of the products of the citric acid cycle.Answer: FALSEObjective: 23.1Global Outcomes: GO2

4) NAD+ acts as a hydrogen acceptor in metabolic reactions.Answer: TRUEObjective: 23.1Global Outcomes: GO2

5) FADH2 is the oxidized form of FAD.Answer: FALSEObjective: 23.1Global Outcomes: GO2

6) Cyt c is a component of complex IV.Answer: FALSEObjective: 23.2Global Outcomes: GO2

7) The energy levels of complexes decrease as electron transport progresses.Answer: TRUEObjective: 23.2Global Outcomes: GO2

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8) 12 ATP are produced when glucose is oxidized to CO2 and H2O.Answer: FALSEObjective: 23.3Global Outcomes: GO4

9) The conversion of ATP to ADP and inorganic phosphate produces 7.3 kcal/mole of energy.Answer: TRUEObjective: 23.3Global Outcomes: GO4

10) The oxidation of NADH yields 2.5 ATP.Answer: TRUEObjective: 23.3Global Outcomes: GO4

11) The oxidation of FADH2 yields 1.5 ATP.Answer: TRUEObjective: 23.3Global Outcomes: GO4

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23.4 Matching Questions

Indicate the amount of ATP produced when each of the following reactions occurs.

A) 7 ATPB) 2 ATPC) 32 ATPD) 2.5 ATPE) 10 ATP

1) complete oxidation of glucoseObjective: 23.3Global Outcomes: GO4

2) acetyl CoA → 2CO2Objective: 23.3Global Outcomes: GO4

3) glucose → 2 pyruvate under aerobic conditionsObjective: 23.3Global Outcomes: GO4

4) glucose → 2 lactateObjective: 23.3Global Outcomes: GO4

5) pyruvate → acetyl CoA + CO2Objective: 23.3Global Outcomes: GO4

Answers: 1) C 2) E 3) A 4) B 5) D

Match the terms with the following descriptions.

A) oxidative phosphorylationB) coenzyme A

6) the process that makes ATP using energy from the electron transport chainObjective: 23.3Global Outcomes: GO2

7) the carrier of acetyl (two-carbon) groupsObjective: 23.1Global Outcomes: GO2

Answers: 6) A 7) B

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Identify each of the following metabolic pathways.

A) glycolysisB) electron transportC) citric acid cycle

8) the conversion of glucose to pyruvic acidObjective: 23.1Global Outcomes: GO2

9) the series of reactions that converts acetyl CoA to carbon dioxide and waterObjective: 23.1Global Outcomes: GO2

10) the series of reactions that produces waterObjective: 23.2Global Outcomes: GO2

11) the series of reactions that uses electron carriersObjective: 23.2Global Outcomes: GO2

Answers: 8) A 9) C 10) B 11) B

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