biol 222 ch 9 cellular respiration part 2...

1

Fig.9-12-2

Acetyl CoA

Oxaloacetate

Citrate

CoA—SH

Citric acid cycle

1

2

H2O

Isocitrate

Fig.9-12-3

Acetyl CoACoA—SH

Oxaloacetate

Citrate

H2O

Citric acid cycle

Isocitrate

1

2

3

NAD+

NADH+ H+

α-Keto- glutarate

CO2

Fig.9-12-4

Acetyl CoACoA—SH

Oxaloacetate

Citrate

H2O

IsocitrateNAD+

NADH+ H+

Citric acid cycle

α-Keto- glutarate

CoA—SH

1

2

3

4

NAD+

NADH+ H+Succinyl

CoA

CO2

CO2

2

Fig.9-12-5

Acetyl CoACoA—SH

Oxaloacetate

Citrate

H2O

IsocitrateNAD+

NADH+ H+

CO2

Citric acid cycle

CoA—SH

α-Keto- glutarate

CO2NAD+

NADH+ H+Succinyl

CoA

1

2

3

4

5

CoA—SH

GTP GDP

ADP

P iSuccinate

ATP

Fig.9-12-6

Acetyl CoACoA—SH

Oxaloacetate

H2O

CitrateIsocitrate

NAD+

NADH+ H+

CO2

Citric acid cycle

CoA—SH

α-Keto- glutarate

CO2NAD+

NADH+ H+

CoA—SH

PSuccinyl

CoA

iGTP GDP

ADP

ATP

SuccinateFAD

FADH2

Fumarate

1

2

3

4

5

6

Fig.9-12-7

Acetyl CoACoA—SH

Oxaloacetate

Citrate

H2O

IsocitrateNAD+

NADH+ H+

CO2

α-Keto- glutarate

CoA—SH

NAD+

NADHSuccinyl

CoA

CoA—SH

PP

GDPGTP

ADP

ATP

SuccinateFAD

FADH2

Fumarate

Citric acid cycleH2O

Malate

1

2

5

6

7

i

CO2

+ H+

3

4

3

Fig.9-12-8

Acetyl CoACoA—SH

Citrate

H2O

IsocitrateNAD+

NADH+ H+

CO2

α-Keto- glutarate

CoA—SH

CO2NAD+

NADH+ H+Succinyl

CoA

CoA—SH

P iGTP GDP

ADP

ATP

SuccinateFAD

FADH2

Fumarate

Citric acid cycleH2O

Malate

Oxaloacetate

NADH+H+

NAD+

1

2

3

4

5

6

7

8

ElectronTransport•  Electrontransportchain

•  Ontheinnermembrane(cristae)ofthemitochondrion

•  MostlyinmulFproteincomplexes

•  Carriersalternatereducedandoxidizedstates

•  astheyacceptanddonateelectrons

•  Electronbucketbrigade

•  Electrons

•  Dropinfreeenergyastheygodownthechain

•  FinallypassedtoO2,formingH2O

NADH

NAD+2FADH2

2 FADMultiprotein complexesFAD

Fe•SFMN Fe•S

Q

Fe•S

Ι

Cyt b

ΙΙ

ΙΙΙ

Cyt c1

Cyt cCyt a

Cyt a3

IV

Free

ene

rgy

(G) r

elat

ive

to O

2 (kc

al/m

ol)

50

40

30

20

10 2(from NADH

or FADH2)

0 2 H+ + 1/2 O2

H2O

e–

e–

e–

•  Electrontransportchain

•  generatesnoATP(directly)

•  ButcreatesH+gradient

•  Concentratedinthe

intermembranespace

•  breaksthelargefree-energydrop

fromglucosetoO2

•  intosmallerstepsthatrelease

energyinmanageableamounts

ElectronTransportChain

4

Chemiosmosis:TheEnergy-CouplingMechanism•  H+intheintermembranespace

•  thenmovebackacrossthemembrane

•  DownconcentraFongradient

•  passingthroughchannelsinATP

synthase

•  ATPsynthase

•  usestheexergonicflowofH+todrive

phosphorylaFonofATP

•  ThisisChemiosmosis

•  TheuseofenergyinaH+gradienttodrive

cellularwork

INTERMEMBRANE SPACE

Rotor

H+

Stator

Internal rod

Cata- lytic knob

ADP+P ATP

i

MITOCHONDRIAL MATRIX

•  TheenergystoredinaH+gradient

•  CouplestheredoxreacFonsoftheelectrontransportchaintoATP

synthesis

•  Proton-mo:veforce

•  PotenFalenergyintheH+gradient

•  Representsitscapacitytodowork

ThePathwayofElectronTransport

Fig.9-16

Protein complex of electron carriers

H+

H+H+

Cyt c

Q

Ι

ΙΙ

ΙΙΙ

ΙV

FADH2 FAD

NAD+NADH(carrying electrons from food)

Electron transport chain

2 H+ + 1/2O2 H2O

ADP + P i

Chemiosmosis

Oxidative phosphorylation

H+

H+

ATP synthase

ATP

21

PLAY

5

AerobicRespira:onSummary

•  Energyflowsinthissequence:

glucose→NADH →electrontransportchain→proton-moFveforce→ATP

•  About37%oftheenergyinaglucosemoleculeistransferredtoATPduring

cellularrespiraFon

•  Makesabout38ATP

•  36net!(inprokaryotes)

•  Actuallyabout30inEukaryotes

•  Roughly3ATPperreducedelectroncarrier

•  InaddiFontoATPformedbysubstratelevelphosphorylaFon

Fig.9-17

Maximum per glucose: About 36 or 38 ATP

+ 2 ATP+ 2 ATP + about 32 or 34 ATP

Oxidative phosphorylation: electron transport

and chemiosmosis

Citric acid cycle

2 Acetyl CoA

Glycolysis

Glucose2

Pyruvate

2 NADH 2 NADH 6 NADH 2 FADH2

2 FADH2

2 NADHCYTOSOL Electron shuttles

span membraneor

MITOCHONDRION

Fermenta:onandanaerobicrespira:on•  AerobiccellularrespiraFonrequiresO2to

produceATP

•  Glycolysis

•  canproduceATPwithorwithoutO2

•  inaerobicoranaerobiccondiFons

•  WithoutO2

•  Electrontransportchaincan’treleaseelectrons

•  Systembacksupandshutsdown

•  Glycolysiscoupleswithfermenta:onoranaerobicrespira:ontoproduceATP

NADH

NAD+2FADH2

2 FADMultiprotein complexes

FADFe•S

FMN Fe•

S Q

Fe•S

Ι

Cyt b

ΙΙ

ΙΙΙ

Cyt c1

Cyt cCyt a

Cyt a3

IV

Free

ene

rgy

(G) r

elat

ive

to O

2 (kc

al/

mol

)

50

40

30

20

10 2(from

NADH or FADH2)

0 2 H+ + 1/2 O2

H2O

e–

e–

e–

6

•  AnaerobicrespiraFon

•  usesETCwithanelectron

acceptorotherthanO2

•  sulfate

•  FermentaFon

•  usessubstratelevel

phosphorylaFon

•  insteadofanelectron

transportchainto

generateATP

Fermenta:onandanaerobicrespira:on

TypesofFermenta:on•  FermentaFon

•  Consistsofglycolysisplus

reacFonsthatregenerateNAD+

•  Tobereusedbyglycolysis

•  Twocommontypes

•  alcoholfermentaFon

•  Plants,fungi,bacteria

•  lacFcacidfermentaFon

•  Animalsandafewbacteria

andfungi

•  Alcoholfermenta:on

•  Pyruvateis

convertedto

ethanolintwosteps

•  firstreleases

CO2

•  Usedbyyeastinbrewing,

winemaking,andbaking

Fermenta:on

2 ADP + 2 P i 2 ATP

Glucose Glycolysis

2 Pyruvate

2 NADH2 NAD+

+ 2 H+CO2

2 Acetaldehyde2 Ethanol

(a) Alcohol fermentation

2

7

•  Lac:cacidfermenta:on

•  PyruvateisreducedbyNADH

•  formslactateasanendproduct

•  noreleaseofCO2

•  Usedbysomefungiandbacteriatomakecheeseandyogurt

•  Humanmusclecells

•  usetogenerateATPwhenO2isscarceorabsent

•  Earlyinstrenuousexerciseassugarcatabolismoutpacesoxygendelivery


Glucose

2 ADP + 2 P i 2 ATP

Glycolysis

2 NAD+ 2 NADH+ 2 H+

2 Pyruvate

2 Lactate

(b) Lactic acid fermentation

Fermenta:onandAerobicRespira:onCompared•  Bothprocesses

•  Useglycolysistooxidizeglucoseandotherorganicfuelstopyruvate

•  Havedifferentfinalelectronacceptors:

•  FermentaFon

•  anorganicmolecule

•  pyruvateoracetaldehyde

•  AerobicCellularrespiraFon

•  O2

•  CellularrespiraFon

•  Produces36(or30(38))ATPperglucosemolecule

•  FermentaFon

•  Produces2(4)ATPperglucosemolecule

•  Obligateanaerobes

•  carryoutfermentaFonoranaerobic

respiraFon

•  cannotsurviveinthepresenceofO2

•  Faculta:veanaerobes

•  Yeastandmanybacteria

•  cansurviveusingeitherfermentaFon

orcellularrespiraFon

•  pyruvateisaforkinthemetabolicroad

•  thatleadstotwoalternaFvecatabolic

routes


8

Fig.9-19

Glucose

Glycolysis

Pyruvate

CYTOSOL

No O2 present: Fermentation

O2 present: Aerobic cellular respiration

MITOCHONDRIONAcetyl CoAEthanol

or lactate

Citric acid cycle

TheVersa:lityofCatabolism•  Catabolicpathways

•  funnelelectronsfrommanykindsoforganicmoleculesintocellular

respiraFon

•  Glycolysis

•  acceptsawiderangeofcarbohydrates

•  Notjustglucoseorpolymersofglucose

•  Proteins

•  mustbedigestedtoaminoacids

•  aminoacidscanfeedglycolysisorthecitricacidcycle

•  Mustbedeaminatedfirst

•  Fatsdigestedto

•  glycerol(usedinglycolysis)

•  convertedtoG3P

•  fafyacids(usedingeneraFngacetylCoA)

•  Fafyacids

•  brokendownbybetaoxida:on

•  yield2-carbonfragments

•  becomesacetylCoA

•  AlsoyieldssomeNADHandFADH2

•  AnoxidizedgramoffatproducesmorethantwiceasmuchATPasanoxidizedgramofcarbohydrate

TheVersa:lityofCatabolismProteins Carbohydrates

Amino acids

Sugars

Fats

Glycerol Fatty acids

Glycolysis

Glucose

Glyceraldehyde-3-

Pyruvate

P

NH3

Acetyl CoA

Citric acid cycle


9

Regula:onofCellularRespira:on

•  FeedbackinhibiFon

•  Mostcommonmechanismforcontrol

•  ATPconcentraFon

•  beginstodrop,respiraFonspeedsup

•  plentyofATP,respiraFonslowsdown

•  Controlofcatabolism

•  basedmainlyonregulaFngtheacFvityofenzymes

•  Atstrategicpointsinthecatabolicpathway

Glucose

GlycolysisFructose-6-phosphate

Phosphofructokinase

Fructose-1,6-bisphosphateInhibits

AMP

Stimulates

Inhibits

Pyruvate

CitrateAcetyl CoA

Citric acid cycle


ATP

+

––

Regula:onofCellularRespira:onviaFeedbackMechanisms

•  Phosphofructokinase

•  Majorswitchinglycolysis

•  Substratenowcommifedto

glycolysis

•  PacemakerofrespiraFon

•  Allostericenzyme

•  InhibitedbyATP,citrate

•  SFmulatedbyAMP

Youshouldnowbeableto:

1.  ExplainingeneraltermshowredoxreacFonsareinvolvedinenergyexchanges

2.  NamethethreestagesofcellularrespiraFon;foreach,statethe

regionoftheeukaryoFccellwhereitoccursandtheproductsthatresult

3.  Ingeneralterms,explaintheroleoftheelectrontransportchainincellularrespiraFon

4.  Explainwhereandhowtherespiratoryelectrontransportchain

createsaprotongradient

5.  DisFnguishbetweenfermentaFonandanaerobicrespiraFon

biol 222 ch 9 cellular respiration part 2...

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