讲义说明共享presentation

1、Cellular Respiration and FermentationChapter 9Overview: Life Is WorkLiving cells require energy from outside sourcesSome animals, such as the chimpanzee, obtain energy by eating plants, and some animals feed on other organisms that eat plants 2011 Pearson Education, Inc.Figure 9.1Energy flows into a

2、n ecosystem as sunlight and leaves as heatPhotosynthesis generates O2 and organic molecules, which are used in cellular respirationCells use chemical energy stored in organic molecules to regenerate ATP, which powers work 2011 Pearson Education, Inc.Figure 9.2LightenergyECOSYSTEMPhotosynthesisin chl

3、oroplastsCellular respirationin mitochondriaCO2 H2O O2OrganicmoleculesATP powersmost cellular workATPHeatenergyConcept 9.1: Catabolic pathways yield energy by oxidizing organic fuelsSeveral processes are central to cellular respiration and related pathways 2011 Pearson Education, Inc.Catabolic Pathw

4、ays and Production of ATPThe breakdown of organic molecules is exergonicFermentation is a partial degradation of sugars that occurs without O2Aerobic respiration consumes organic molecules and O2 and yields ATPAnaerobic respiration is similar to aerobic respiration but consumes compounds other than

5、O2 2011 Pearson Education, Inc.Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respirationAlthough carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose C6H12O6 + 6 O2

6、6 CO2 + 6 H2O + Energy (ATP + heat) 2011 Pearson Education, Inc.Redox Reactions: Oxidation and ReductionThe transfer of electrons during chemical reactions releases energy stored in organic moleculesThis released energy is ultimately used to synthesize ATP 2011 Pearson Education, Inc.The Principle o

7、f RedoxChemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactionsIn oxidation, a substance loses electrons, or is oxidizedIn reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced) 2011 Pearson Ed

8、ucation, Inc.Figure 9.UN01 es oxidized(loses electron) es reduced(gains electron)Figure 9.UN02 es oxidized es reducedThe electron donor is called the reducing agentThe electron receptor is called the oxidizing agentSome redox reactions do not transfer electrons but change the electron sharing in cov

9、alent bondsAn example is the reaction between methane and O2 2011 Pearson Education, Inc.Figure 9.3ReactantsProductsEnergyWaterCarbon dioxideMethane(reducingagent)Oxygen(oxidizingagent) es oxidized es reducedOxidation of Organic Fuel Molecules During Cellular RespirationDuring cellular respiration,

10、the fuel (such as glucose) is oxidized, and O2 is reduced 2011 Pearson Education, Inc.Figure 9.UN03 es oxidized es reducedStepwise Energy Harvest via NAD+ and the Electron Transport ChainIn cellular respiration, glucose and other organic molecules are broken down in a series of stepsElectrons from o

11、rganic compounds are usually first transferred to NAD+, a coenzymeAs an electron acceptor, NAD+ functions as an oxidizing agent during cellular respirationEach NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATP 2011 Pearson Education, Inc.Figure 9.4Nicotinamide

12、(oxidized form)NAD(from food)DehydrogenaseReduction of NADOxidation of NADHNicotinamide(reduced form)NADHFigure 9.UN04DehydrogenaseNADH passes the electrons to the electron transport chainUnlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of o

13、ne explosive reactionO2 pulls electrons down the chain in an energy-yielding tumbleThe energy yielded is used to regenerate ATP 2011 Pearson Education, Inc.Figure 9.5(a) Uncontrolled reaction(b) Cellular respirationExplosiverelease ofheat and lightenergyControlledrelease ofenergy forsynthesis ofATPF

14、ree energy, GFree energy, GH2 1/2 O22 H1/2 O21/2 O2H2OH2O2 H+ 2 e2 e2 H+ATPATPATPElectron transportchain(from food via NADH)The Stages of Cellular Respiration: A PreviewHarvesting of energy from glucose has three stagesGlycolysis (breaks down glucose into two molecules of pyruvate)The citric acid cy

15、cle (completes the breakdown of glucose)Oxidative phosphorylation (accounts for most of the ATP synthesis) 2011 Pearson Education, Inc.Figure 9.UN05Glycolysis (color-coded teal throughout the chapter)1.Pyruvate oxidation and the citric acid cycle(color-coded salmon)2.Oxidative phosphorylation: elect

16、ron transport andchemiosmosis (color-coded violet)3.Figure 9.6-1Electronscarriedvia NADHGlycolysisGlucosePyruvateCYTOSOLMITOCHONDRIONATPSubstrate-levelphosphorylationFigure 9.6-2Electronscarriedvia NADHElectrons carriedvia NADH andFADH2CitricacidcyclePyruvateoxidationAcetyl CoAGlycolysisGlucosePyruv

17、ateCYTOSOLMITOCHONDRIONATPATPSubstrate-levelphosphorylationSubstrate-levelphosphorylationFigure 9.6-3Electronscarriedvia NADHElectrons carriedvia NADH andFADH2CitricacidcyclePyruvateoxidationAcetyl CoAGlycolysisGlucosePyruvateOxidativephosphorylation:electron transportandchemiosmosisCYTOSOLMITOCHOND

18、RIONATPATPATPSubstrate-levelphosphorylationSubstrate-levelphosphorylationOxidative phosphorylationThe process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions 2011 Pearson Education, Inc.BioFlix: Cellular RespirationOxidative phosphorylation

19、 accounts for almost 90% of the ATP generated by cellular respirationA smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylationFor each molecule of glucose degraded to CO2 and water by respiration, the cell makes up to 32 molecules of ATP 2011 Pearso

20、n Education, Inc.Figure 9.7SubstrateProductADPPATPEnzymeEnzymeConcept 9.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvateGlycolysis (“splitting of sugar”) breaks down glucose into two molecules of pyruvateGlycolysis occurs in the cytoplasm and has two major phasesEnergy investm

21、ent phaseEnergy payoff phaseGlycolysis occurs whether or not O2 is present 2011 Pearson Education, Inc.Figure 9.8Energy Investment PhaseGlucose2 ADP 2 P4 ADP 4 PEnergy Payoff Phase2 NAD+ 4 e 4 H+ 2 Pyruvate 2 H2O 2 ATP used4 ATP formed2 NADH 2 H+ NetGlucose2 Pyruvate 2 H2O 2 ATP2 NADH 2 H+ 2 NAD+ 4

22、e 4 H+ 4 ATP formed 2 ATP usedFigure 9.9-1Glycolysis: Energy Investment PhaseATPGlucoseGlucose 6-phosphateADPHexokinase1Figure 9.9-2Glycolysis: Energy Investment PhaseATPGlucoseGlucose 6-phosphateFructose 6-phosphateADPHexokinasePhosphogluco-isomerase12Figure 9.9-3Glycolysis: Energy Investment Phase

23、ATPATPGlucoseGlucose 6-phosphateFructose 6-phosphateFructose 1,6-bisphosphateADPADPHexokinasePhosphogluco-isomerasePhospho-fructokinase123Figure 9.9-4Glycolysis: Energy Investment PhaseATPATPGlucoseGlucose 6-phosphateFructose 6-phosphateFructose 1,6-bisphosphateDihydroxyacetonephosphateGlyceraldehyd

24、e3-phosphateTostep 6ADPADPHexokinasePhosphogluco-isomerasePhospho-fructokinaseAldolaseIsomerase12345Figure 9.9-5Glycolysis: Energy Payoff Phase2 NADH2 NAD+ 2 H 2 P i1,3-Bisphospho-glycerate6TriosephosphatedehydrogenaseFigure 9.9-6Glycolysis: Energy Payoff Phase2 ATP2 NADH2 NAD+ 2 H 2 P i2 ADP1,3-Bis

25、phospho-glycerate3-Phospho-glycerate2Phospho-glycerokinase67TriosephosphatedehydrogenaseFigure 9.9-7Glycolysis: Energy Payoff Phase2 ATP2 NADH2 NAD+ 2 H 2 P i2 ADP1,3-Bisphospho-glycerate3-Phospho-glycerate2-Phospho-glycerate22Phospho-glycerokinasePhospho-glyceromutase678Triosephosphatedehydrogenase

26、Figure 9.9-8Glycolysis: Energy Payoff Phase2 ATP2 NADH2 NAD+ 2 H 2 P i2 ADP1,3-Bisphospho-glycerate3-Phospho-glycerate2-Phospho-glyceratePhosphoenol-pyruvate (PEP)2222 H2OPhospho-glycerokinasePhospho-glyceromutaseEnolase6789TriosephosphatedehydrogenaseFigure 9.9-9Glycolysis: Energy Payoff Phase2 ATP

27、2 ATP2 NADH2 NAD+ 2 H 2 P i2 ADP1,3-Bisphospho-glycerate3-Phospho-glycerate2-Phospho-glyceratePhosphoenol-pyruvate (PEP)Pyruvate2 ADP2222 H2OPhospho-glycerokinasePhospho-glyceromutaseEnolasePyruvatekinase678910TriosephosphatedehydrogenaseFigure 9.9aGlycolysis: Energy Investment PhaseATPGlucoseGlucos

28、e 6-phosphateADPHexokinase1Fructose 6-phosphatePhosphogluco-isomerase2Figure 9.9bGlycolysis: Energy Investment PhaseATPFructose 6-phosphateADP3Fructose 1,6-bisphosphatePhospho-fructokinase45AldolaseDihydroxyacetonephosphateGlyceraldehyde3-phosphateTostep 6IsomeraseFigure 9.9cGlycolysis: Energy Payof

29、f Phase2 NADH2 ATP2 ADP222 NAD+ 2 H2 P i3-Phospho-glycerate1,3-Bisphospho-glycerateTriosephosphatedehydrogenasePhospho-glycerokinase67Figure 9.9dGlycolysis: Energy Payoff Phase2 ATP2 ADP22222 H2OPyruvatePhosphoenol-pyruvate (PEP)2-Phospho-glycerate3-Phospho-glycerate8910Phospho-glyceromutaseEnolaseP

30、yruvatekinaseConcept 9.3: After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic moleculesIn the presence of O2, pyruvate enters the mitochondrion (in eukaryotic cells) where the oxidation of glucose is completed 2011 Pearson Education, Inc.Oxidation of

31、Pyruvate to Acetyl CoABefore the citric acid cycle can begin, pyruvate must be converted to acetyl Coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycleThis step is carried out by a multienzyme complex that catalyses three reactions 2011 Pearson Education, Inc.Figure 9.10PyruvateT

32、ransport proteinCYTOSOLMITOCHONDRIONCO2Coenzyme ANAD+ HNADHAcetyl CoA123The citric acid cycle, also called the Krebs cycle, completes the break down of pyruvate to CO2The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn 2011 Pearson Education, Inc.The

33、 Citric Acid CycleFigure 9.11PyruvateNADNADH+ HAcetyl CoACO2CoACoACoA2 CO2ADP + P iFADH2FADATP3 NADH3 NADCitricacidcycle+ 3 HThe citric acid cycle has eight steps, each catalyzed by a specific enzymeThe acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrateThe nex

34、t seven steps pose the citrate back to oxaloacetate, making the process a cycleThe NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain 2011 Pearson Education, Inc.Figure 9.12-11Acetyl CoACitrateCitricacidcycleCoA-SHOxaloacetateFigure 9.12-21Acetyl

35、 CoACitrateIsocitrateCitricacidcycleH2O2CoA-SHOxaloacetateFigure 9.12-31Acetyl CoACitrateIsocitrate-KetoglutarateCitricacidcycleNADH+ HNADH2O32CoA-SHCO2OxaloacetateFigure 9.12-41Acetyl CoACitrateIsocitrate-KetoglutarateSuccinylCoACitricacidcycleNADHNADH+ H+ HNADNADH2O324CoA-SHCO2CoA-SHCO2Oxaloacetat

36、eFigure 9.12-51Acetyl CoACitrateIsocitrate-KetoglutarateSuccinylCoASuccinateCitricacidcycleNADHNADHATP+ H+ HNADNADH2OADPGTPGDPP i3245CoA-SHCO2CoA-SHCoA-SHCO2OxaloacetateFigure 9.12-61Acetyl CoACitrateIsocitrate-KetoglutarateSuccinylCoASuccinateFumarateCitricacidcycleNADHNADHFADH2ATP+ H+ HNADNADH2OAD

37、PGTPGDPP iFAD32456CoA-SHCO2CoA-SHCoA-SHCO2OxaloacetateFigure 9.12-71Acetyl CoACitrateIsocitrate-KetoglutarateSuccinylCoASuccinateFumarateMalateCitricacidcycleNADHNADHFADH2ATP+ H+ HNADNADH2OH2OADPGTPGDPP iFAD324567CoA-SHCO2CoA-SHCoA-SHCO2OxaloacetateFigure 9.12-8NADH1Acetyl CoACitrateIsocitrate-Ketog

38、lutarateSuccinylCoASuccinateFumarateMalateCitricacidcycleNADNADHNADHFADH2ATP+ H+ H+ HNADNADH2OH2OADPGTPGDPP iFAD3245678CoA-SHCO2CoA-SHCoA-SHCO2OxaloacetateFigure 9.12aAcetyl CoAOxaloacetateCitrateIsocitrateH2OCoA-SH12Figure 9.12bIsocitrate-KetoglutarateSuccinylCoANADHNADHNADNAD+ HCoA-SHCO2CO234+ HFi

39、gure 9.12cFumarateFADH2CoA-SH6SuccinateSuccinylCoAFADADPGTPGDPP iATP5Figure 9.12dOxaloacetate8MalateFumarateH2ONADHNAD+ H7Concept 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesisFollowing glycolysis and the citric acid cycle, NADH and FADH2 account for

40、most of the energy extracted from foodThese two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation 2011 Pearson Education, Inc.The Pathway of Electron TransportThe electron transport chain is in the inner membrane (cristae) of

41、 the mitochondrionMost of the chains components are proteins, which exist in multiprotein complexesThe carriers alternate reduced and oxidized states as they accept and donate electronsElectrons drop in free energy as they go down the chain and are finally passed to O2, forming H2O 2011 Pearson Educ

42、ation, Inc.Figure 9.13NADHFADH22 H + 1/2 O22 e2 e2 eH2ONADMultiproteincomplexes(originally from NADH or FADH2) IIIIIIIV50403020100Free energy (G) relative to O2 (kcal/mol)FMNFeSFeSFADQCyt bCyt c1Cyt cCyt aCyt a3FeSElectrons are transferred from NADH or FADH2 to the electron transport chainElectrons

43、are passed through a number of proteins including cytochromes (each with an iron atom) to O2The electron transport chain generates no ATP directlyIt breaks the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts 2011 Pearson Education, Inc.Chemiosmosis

44、: The Energy-Coupling MechanismElectron transfer in the electron transport chain causes proteins to pump H+ from the mitochondrial matrix to the intermembrane spaceH+ then moves back across the membrane, passing through the proton, ATP synthase ATP synthase uses the exergonic flow of H+ to drive pho

45、sphorylation of ATPThis is an example of chemiosmosis, the use of energy in a H+ gradient to drive cellular work 2011 Pearson Education, Inc.Figure 9.14INTERMEMBRANE SPACERotorStatorHInternalrodCatalyticknobADP+P iATPMITOCHONDRIAL MATRIXFigure 9.15Proteincomplexof electroncarriers(carrying electrons

46、from food)Electron transport chainOxidative phosphorylationChemiosmosisATPsynth-aseIIIIIIIVQCyt cFADFADH2NADHADP P iNADH2 H + 1/2O2HHH21HH2OATPThe energy stored in a H+ gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesisThe H+ gradient is referred

47、to as a proton-motive force, emphasizing its capacity to do work 2011 Pearson Education, Inc.An Accounting of ATP Production by Cellular RespirationDuring cellular respiration, most energy flows in this sequence: glucose NADH electron transport chain proton-motive force ATPAbout 34% of the energy in

48、 a glucose molecule is transferred to ATP during cellular respiration, making about 32 ATPThere are several reasons why the number of ATP is not known exactly 2011 Pearson Education, Inc.Figure 9.16Electron shuttlesspan membraneMITOCHONDRION2 NADH2 NADH2 NADH6 NADH2 FADH22 FADH2or 2 ATP 2 ATP about

49、26 or 28 ATPGlycolysisGlucose2 PyruvatePyruvate oxidation2 Acetyl CoACitricacidcycleOxidativephosphorylation:electron transportandchemiosmosisCYTOSOLMaximum per glucose:About30 or 32 ATPAnimation Concept 9.5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxyge

50、nMost cellular respiration requires O2 to produce ATPWithout O2, the electron transport chain will cease to operateIn that case, glycolysis couples with fermentation or anaerobic respiration to produce ATP 2011 Pearson Education, Inc.Anaerobic respiration uses an electron transport chain with a fina

51、l electron acceptor other than O2, for example sulfateFermentation uses substrate-level phosphorylation instead of an electron transport chain to generate ATP 2011 Pearson Education, Inc.Types of FermentationFermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused

52、 by glycolysisTwo common types are alcohol fermentation and lactic acid fermentation 2011 Pearson Education, Inc.In alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO2Alcohol fermentation by yeast is used in brewing, winemaking, and baking 2011 Pearson E

53、ducation, Inc.Animation: Fermentation OverviewFigure 9.172 ADP2 ATPGlucoseGlycolysis2 Pyruvate2 CO222 NADH2 Ethanol2 Acetaldehyde(a) Alcohol fermentation(b) Lactic acid fermentation2 Lactate2 Pyruvate2 NADHGlucoseGlycolysis2 ATP2 ADP2PiNAD2 H2Pi2NAD2 H2 ADP 2 P i2 ATPGlucoseGlycolysis2 Pyruvate2 CO2

54、2 NAD2 NADH2 Ethanol2 Acetaldehyde(a) Alcohol fermentation2 HFigure 9.17aIn lactic acid fermentation, pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO2Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurtHuman muscle cells use lact

55、ic acid fermentation to generate ATP when O2 is scarce 2011 Pearson Education, Inc.(b) Lactic acid fermentation2 Lactate2 Pyruvate2 NADHGlucoseGlycolysis2 ADP 2 P i2 ATP2 NAD2 HFigure 9.17bComparing Fermentation with Anaerobic and Aerobic RespirationAll use glycolysis (net ATP = 2) to oxidize glucos

56、e and harvest chemical energy of foodIn all three, NAD+ is the oxidizing agent that accepts electrons during glycolysisThe processes have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O2 in cellular respirationCellular respiration prod

57、uces 32 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule 2011 Pearson Education, Inc.Obligate anaerobes carry out fermentation or anaerobic respiration and cannot survive in the presence of O2Yeast and many bacteria are facultative anaerobes, meaning that they can survive u

58、sing either fermentation or cellular respirationIn a facultative anaerobe, pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes 2011 Pearson Education, Inc.Figure 9.18GlucoseCYTOSOLGlycolysisPyruvateNo O2 present:FermentationO2 present: Aerobic cellular respiration

59、Ethanol,lactate, orother productsAcetyl CoAMITOCHONDRIONCitricacidcycleThe Evolutionary Significance of GlycolysisAncient prokaryotes are thought to have used glycolysis long before there was oxygen in the atmosphereVery little O2 was available in the atmosphere until about 2.7 billion years ago, so

60、 early prokaryotes likely used only glycolysis to generate ATPGlycolysis is a very ancient process 2011 Pearson Education, Inc.Concept 9.6: Glycolysis and the citric acid cycle connect to many other metabolic pathwaysGycolysis and the citric acid cycle are major intersections to various catabolic an