CellularRespira,onCellularRespira,onBIOL222

Ch.9

EnergyEnergy

Lightenergy

ECOSYSTEM

Photosynthesis in chloroplasts

CO2 + H2O

Cellular respirationin mitochondria

Organicmolecules +

O2

ATP powers most cellular work

Heatenergy

ATP

• Energy

• Arrivesassunlight

• Photosynthesis

• Plantscapturesunlight

• organicmoleculesandgeneratesO2

• Carbsusedincellularrespira@on

• Cellsuseenergystoredinorganicmolecules

• toregenerateATP

• Energyeventuallyleavesasheat

CatabolicPathwaysandProduc,onofATPCatabolicPathwaysandProduc,onofATP

• Thebreakdownoforganicmoleculesisexergonic

• Aerobicrespira,on

• ConsumesorganicmoleculesandO2andyieldsATP

• Typicallyglucose

• Fermenta,on

• Par@aldegrada@onofsugarsthatoccurswithoutO2

• Anaerobicrespira,on

• similartoaerobicrespira@on

• butusescompoundsotherthanO2asthefinalelectronacceptor

• Cellularrespira,on

• includesbothaerobicandanaerobicrespira@onbutisoGenusedto

refertoaerobicrespira@on

• 3of4macromoleculeclassesmaybeusedasfuel

• carbohydrates,fats,andproteins

C6H12O6+6O2→6CO2+6H2O+Energy(ATP+heat)

CellularRespira,onCellularRespira,on

ThePrincipleofRedoxThePrincipleofRedox

• oxida@on‐reduc@onreac@ons

• Chemicalreac@onsthattransferelectronsbetweenreactantsarecalled

• redoxreac,ons

• Oxida,on

• asubstanceloseselectrons

• isoxidized

• Reduc,on

• asubstancegainselectron

• isreduced(theamountofposi@vechargeisreduced)

• OIL‐RIG

becomes oxidized(loses electron)

becomes reduced(gains electron)

• Reducingagent

• electrondonor

• Oxidizingagent

• electronreceptor

• Someredoxrxnsdonot

transferelectrons

• butchangetheelectron

sharingincovalentbonds

• exampleisthereac@on

betweenmethaneandO2

ThePrincipleofRedoxThePrincipleofRedox

Reactants

becomes oxidized

becomes reduced

Products

Methane(reducing

agent)

Oxygen(oxidizing

agent)

Carbon dioxide Water

Oxida,onDuringCellularRespira,onOxida,onDuringCellularRespira,on

• Duringcellularrespira@on,thefuel(suchasglucose)isoxidized,and

O2isreduced:

becomes oxidized

becomes reduced

NADNAD++andtheElectronTransportChainandtheElectronTransportChain• Glucoseandotherorganicmolecules

• Brokendowninaseriesofsteps

• NAD+(nico@namideadeninedinucleo@de)

• Electroncarrier

• Electronsfromorganiccompoundstransferred

• func@onsasanoxidizingagentduringcellularrespira@on

• NADH

• ReducedformofNAD+

• representsstoredenergythatisusedtosynthesizeATP

Dehydrogenase

Fig.9‐4Fig.9‐4

Dehydrogenase

Reduction of NAD+

Oxidation of NADH

2 e– + 2 H+

2 e– + H+

NAD+ + 2[H]

NADH

+

H+

H+

Nicotinamide(oxidized form)

Nicotinamide(reduced form)

• NADH

• Deliverselectronstotheelectrontransportchain(ETC)

• ETCpasseselectronsinaseriesofsteps

• insteadofoneexplosivereac@on

• Slow,controlledenergyrelease

• O2receiveselectronsfromtheETC

• AGeranenergy‐yieldingtumbledownthechain

• Finalelectronacceptor

• TheenergyyieldedisusedtoregenerateATP

NAD+andtheElectronTransportChainNAD+andtheElectronTransportChain

Free

ene

rgy,

G

Free

ene

rgy,

G

(a) Uncontrolled reaction

H2O

H2 + 1 /2 O2

Explosiverelease of

heat and lightenergy

(b) Cellular respiration

Controlledrelease ofenergy for

synthesis ofATP

2 H+ + 2 e–

2 H + 1/2 O2

(from food via NADH)

ATP

ATP

ATP

1/2 O22 H+

2 e–

Electron transport

chain

H2O

TheStagesofCellularRespira,on:TheStagesofCellularRespira,on:APreviewAPreview

• Cellularrespira@onhasthreestages:

• Glycolysis

• Literally“sugarbreaking”

• breaksdownglucoseintotwomoleculesofpyruvate

• Citricacidcycle

• completesthebreakdownofglucose

• AlsocalledKrebscycle

• Oxida,vephosphoryla,on

• accountsformostoftheATPsynthesis

• IncludesElectronTransportChain

Fig.9‐6‐1Fig.9‐6‐1

Substrate-levelphosphorylation

ATP

Cytosol

Glucose Pyruvate

Glycolysis

Electronscarried

via NADH

Fig.9‐6‐2Fig.9‐6‐2

Mitochondrion

Substrate-levelphosphorylation

ATP

Cytosol

Glucose Pyruvate

Glycolysis

Electronscarried

via NADH

Substrate-levelphosphorylation

ATP

Electrons carriedvia NADH and

FADH2

Citricacidcycle

Fig.9‐6‐3Fig.9‐6‐3

Mitochondrion

Substrate-levelphosphorylation

ATP

Cytosol

Glucose Pyruvate

Glycolysis

Electronscarried

via NADH

Substrate-levelphosphorylation

ATP

Electrons carriedvia NADH and

FADH2

Oxidativephosphorylation

ATP

Citricacidcycle

Oxidativephosphorylation:electron transport

andchemiosmosis

• Oxida,vephosphoryla,on

• accountsforalmost90%oftheATPgeneratedbycellularrespira@on

• 32of36‐38total

• substrate‐levelphosphoryla,on

• ATPformedinglycolysisandthecitricacidcycle

Oxida,veOxida,vePhosphoryla,onPhosphoryla,on

Enzyme

ADP

PSubstrate

Enzyme

ATP+

Product

GlycolysisGlycolysis

• Glycolysis

• Breaksdownglucoseintotwomoleculesofpyruvate

• Occursinthecytoplasm

• Twomajorphases:

• Energyinvestmentphase

• Energypayoffphase

Fig.9‐8Fig.9‐8

Energy investment phase

Glucose

2 ADP + 2 P 2 ATP used

formed4 ATP

Energy payoff phase

4 ADP + 4 P

2 NAD+ + 4 e– + 4 H+ 2 NADH + 2 H+

2 Pyruvate + 2 H2O

2 Pyruvate + 2 H2OGlucoseNet

4 ATP formed – 2 ATP used 2 ATP

2 NAD+ + 4 e– + 4 H+ 2 NADH + 2 H+

Fig.9‐9‐1Fig.9‐9‐1

ATP

ADP

Hexokinase1

ATP

ADP

Hexokinase1

Glucose

Glucose-6-phosphate

Glucose

Glucose-6-phosphate

Fig.9‐9‐2Fig.9‐9‐2

Hexokinase

ATP

ADP

1

Phosphoglucoisomerase2

Phosphogluco-isomerase

2

Glucose

Glucose-6-phosphate

Fructose-6-phosphate

Glucose-6-phosphate

Fructose-6-phosphate

1

Fig.9‐9‐3Fig.9‐9‐3

Hexokinase

ATP

ADP

Phosphoglucoisomerase

Phosphofructokinase

ATP

ADP

2

3

ATP

ADP

Phosphofructo-kinase

Fructose-1, 6-bisphosphate

Glucose

Glucose-6-phosphate

Fructose-6-phosphate

Fructose-1, 6-bisphosphate

1

2

3

Fructose-6-phosphate

3

Fig.9‐9‐4Fig.9‐9‐4

Glucose

ATP

ADP

Hexokinase

Glucose-6-phosphate

Phosphoglucoisomerase

Fructose-6-phosphate

ATP

ADP

Phosphofructokinase

Fructose-1, 6-bisphosphate

Aldolase

Isomerase

Dihydroxyacetonephosphate

Glyceraldehyde-3-phosphate

1

2

3

4

5

Aldolase

Isomerase

Fructose-1, 6-bisphosphate

Dihydroxyacetonephosphate

Glyceraldehyde-3-phosphate

4

5

Fig.9‐9‐5Fig.9‐9‐5

2 NAD+

NADH2+ 2 H+

2

2 Pi

Triose phosphatedehydrogenase

1, 3-Bisphosphoglycerate

6

2 NAD+

Glyceraldehyde-3-phosphate

Triose phosphatedehydrogenase

NADH2+ 2 H+

2 P i

1, 3-Bisphosphoglycerate

6

2

2

Fig.9‐9‐6Fig.9‐9‐6

2 NAD+

NADH2

Triose phosphatedehydrogenase

+ 2 H+

2 P i

22 ADP

1, 3-Bisphosphoglycerate

Phosphoglycerokinase2 ATP

2 3-Phosphoglycerate

6

7

2

2 ADP

2 ATP

1, 3-Bisphosphoglycerate

3-Phosphoglycerate

Phosphoglycero-kinase

2

7

Fig.9‐9‐7Fig.9‐9‐7

3-Phosphoglycerate

Triose phosphatedehydrogenase

2 NAD+

2 NADH+ 2 H+

2 P i

22 ADP

Phosphoglycerokinase

1, 3-Bisphosphoglycerate

2 ATP

3-Phosphoglycerate2

Phosphoglyceromutase

2-Phosphoglycerate2

2-Phosphoglycerate2

2

Phosphoglycero-mutase

6

7

8

8

Fig.9‐9‐8Fig.9‐9‐8

2 NAD+

NADH2

2

2

2

2

+ 2 H+

Triose phosphatedehydrogenase

2 P i

1, 3-Bisphosphoglycerate

Phosphoglycerokinase

2 ADP

2 ATP

3-Phosphoglycerate

Phosphoglyceromutase

Enolase

2-Phosphoglycerate

2 H2O

Phosphoenolpyruvate

9

8

7

6

2 2-Phosphoglycerate

Enolase

2

2 H2O

Phosphoenolpyruvate

9

Fig.9‐9‐9Fig.9‐9‐9

Triose phosphatedehydrogenase

2 NAD+

NADH2

2

2

2

2

2

2 ADP

2 ATP

Pyruvate

Pyruvate kinase

Phosphoenolpyruvate

Enolase2 H2O

2-Phosphoglycerate

Phosphoglyceromutase

3-Phosphoglycerate

Phosphoglycerokinase

2 ATP

2 ADP

1, 3-Bisphosphoglycerate

+ 2 H+

6

7

8

9

10

22 ADP

2 ATP

Phosphoenolpyruvate

Pyruvate kinase

2 Pyruvate

10

2 P i

IntermediateIntermediateStepStep• IfO2ispresent

• pyruvateentersthe

mitochondrion

• Twoperoriginalglucose

• acetylCoA

• PyruvateaddedtocoenzymeA

• becomesacetylcoA

• Asitcrossesthemito

membranes

• YieldsfirstCO2wastes

• ReducesaNAD+toNADH

• Entersthecitricacidcycle

CYTOSOL MITOCHONDRION

NAD+ NADH + H+

2

1 3

Pyruvate

Transport protein

CO2Coenzyme A

Acetyl CoA

• Citricacidcycle

• AlsocalledtheKrebscycle

• Occursinthemitochondrial

matrix

• Cycleoxidizesorganicfuelderived

frompyruvate

• generates1ATP,3NADH,

and1FADH2perturn

• Twiceperglucose!

CitricAcidCycleCitricAcidCycle

Pyruvate

NAD+

NADH

+ H+Acetyl CoA

CO2

CoA

CoA

CoA

Citricacidcycle

FADH2

FAD

CO22

3

3 NAD+

+ 3 H+

ADP + P i

ATP

NADH

• Citricacidcycle

• Eightsteps

• Eachcatalyzedbyaspecificenzyme

• AcetylgroupofacetylCoAjoinsthecyclebycombiningwithoxaloacetate

• Formingcitrate

• CoenzymeAreturnstointermediatestep

• Thenextsevenstepsdecomposethecitratebacktooxaloacetate

• Makestheprocessacycle

• TheNADHandFADH2

• Deliverelectronstotheelectrontransportchain

CitricAcidCycleCitricAcidCycle