ch. 9 cellular respira,on
TRANSCRIPT
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