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32 Cards in this Set
- Front
- Back
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relationship of e- transport and oxidative phosphorylation to glycolysis and TCA cycle
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glycolysis and TCA cycle used stored energy in glu and pyruvate to pduce some ATP.
Most energy from glycolysis and TCA cycle funneled into NADH and FADH2 used in ETC/OP to generate ATP |
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electron transport
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converts energy of e- transfer into the energy of phosphoryl tranfer stored in the phosphoric anhydride bonds of ATP
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electrons carried by...
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reduced coenzymes are passed thru a chain of prot and coenzymes to drive the generation of a proton gradient across the inner mito mem
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oxidative phosphorylation
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the proton gradient runs downhill to drive the synthesis of ATP (it all happens in or at the inner mito mem)
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organization of mitochondria
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ET and OP happen here
in bacteria:plasma mem matrix:space inside inner mito mem, with most TCA cyle and FA oxidation enzymes except succinate dehydrogenase cristae:folds of inner mem,increases SA |
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electron transport 1-3
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reoxidizes coenzymes using released energy in synthesis of ATP
e-'s move from NADH & FADH2 to molecular O2 (is terminal acceptor to pduce H2O) 4 prot complexes in inner mito mem |
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electron transport 4-5
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lipid soluable coenzyme (UQ,CoQ) and a water soluable protein (cyt c) shuttle bw protein complexes
e- fall in energy thru the chain from complex I &II to IV |
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reduction potentials for components of the e- transport chain
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e- move from more neg to more pos but not in simple linar sequence.
series of redox rxns move toward more + reduction exergonic rxns creates proton pump |
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overview of complexes and pathways in ETC
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4 major protein complexes:
I&II:reduce Co-Q lipid soluable co water soluable prot 2 other flavoproteins can transfer e- to CoQ |
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COMPLEX I:NADH-CoQ reductase
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(NADH reductase)
linke bw glycolysis,TCA,FA oxidation and ETC e- from NADH to Co-Q protein w/ >30subunits (m=850kD) path:NADH->FMN->Fe-S->UQ->FeS->UQ |
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proposed structure and ET pathway for complex I
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e- from NADH thru I to CoQ
e- from NADH to FMN to multiple Fe-S centers to CoQ 4H+ transported out per 2e- |
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complex II:succinate-CoQ reductase
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includes succ dehydrog from TCA and reduces FAD to FADH2
direct link bw TCA and ET flavoprotein 2-FAD (covalent) 4 subunits, including 2Fe-S proteins |
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complex II continued
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3 types of Fe-S cluster:
4Fe-4S, 3Fe-4S, 2Fe-2S path:succ->FADH2->2Fe2+->UQH2 net rxn:succ + UQ-->fumarate + UQH2 |
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succinate dehydrogenase
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oxidation involving FAD
mechanism:hydride removal by FAD and deprotonation part of ET pathway e- from succ to FAD are passed to UQ in the ETP |
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proposed e- flow in complex II
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e- from succ to CoQ via succ-FAD multiple Fe-S centers-UQ
NO PROTONS PUMPED ACROSS MEMBRANE!! |
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Co-Q
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lipid soluable mobile e- carrier
highly lipophilic allows it to freely diffuse in hydrophobic core of inner mito mem accepts e- from I and II passes them to III |
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complex III:coQ-cytochrome reductase
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CoQ passes e- to cyt c thru III thru Q cycle (redox)
principal transmem prot is b cytochrome cytochromes like Fe in Fe-S clusters are one e- transfer agents cyt c is water soluable e- carrier passage of e- thru III drives protons across inner mem |
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typical visible spectra of cytochrome C
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top to bottom:
cyto c:reduced cyto c:oxidized cyto c:reduced minus oxidized submito:@RT, reduced minus oxidized submito:(77Kdeg) reduced minus oxidized |
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complex IV:cyto c oxidase
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mobile e- carrier
accepts e- from cyt c and are used in 4-e- reduction of O2 to produce water O2=terminal acceptor cyto c oxidase utilizes 2heme and 2Cu sites drives protons across inner mem |
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electron transfer pathway
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intermem space:P-phase
matrix:N-phase |
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model for ET in the mito inner mem
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CoQ collects e- from I and II and delivers them to III
I&III:develop H+ gradient III:transfers e- to freely moving and water soluable cyto c cyto c:delivers e- to IV which directs them to 4e- reduction of O2 (PROTON GRADIENT BY ET GENERATES ENORMOUS SOURCE OF POTENTIAL ENERGY) |
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proton gradient driven ATP synthesis:atp synthase
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proton diffusion thru ATP synthase drives synthesis:
catalyzes ATP from ADP and P-driven by H+'s across mem from gradient by ET ATP synthase:conserved 2principal complexes:F1 and F0 |
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inhibitors of oxidative phosphorylation involve direct binding to protein
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rotenone:inhibits I
from roots of plants used to catch fish cyanide,azide,CO:inhibit IV binding tight to Fe3+ oligomycin,DCCD:inhibits ATP synthase |
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uncouplers
(uncoupling ET and OP) |
dissipate gradient by disrupting tight coupling bw ET and OP
uncouplers are hydrophobic with a dissociable H+ shuttle back & forth bw mem carrying protons to dissipate gradient DOSENT INVOLVE DIRECT BINDING TO PROTEIN |
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chemical uncouplers
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dinitrophenol,dicumarol,FCCP
energy dissipated as heat happens in inner mito mem destroy tight coupling bw ET and ATP synthase rxn |
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ATP-ADP translocase
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ATP&ADP highly charged and dont cross biological mem's
ATP-ADP translocase mediates transport! ATP out is favored bc cytosol is + and matrix is - BUT ATP out and ADP in is net movement of a neg charge out(equivalent to H+ in) every ATP out costs 1 H+ one ATP synthesis cose 3H+ making/exporting:1ATP=4H+ |
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what is the P/O ratio
(how many atp made per e- pair thru the chain) |
e- thru chain from NADH yield 10H+ pumped out per e- pair from NADH to O2
4H+ back into matrix per ATP to cytosol 10/4=2.5 ATP for e- entering as NADH succ:~6H+ out per pair to O2 6/4=1.5 ATP for e- entering as FADH2 |
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shuttle systems for e-s
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most NADH used in ET is cytosolic and NADH doesnt cross the inner mito mem
shuttle systems:effect e- movement w/o carrying NADH glycero-P shuttle:stores e- in glycerol-3-P, which transfers e- to FAD malate-aspartate shuttle:uses malate to carry e- across the mem |
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glycerophosphate shuttle
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NADH in cytosol transfers its e- by reducing dihydroxyacetone-P to gly-3-P
2 diff glycero-P dehydrog, 1 in cytosol, 1 on outer face of mito mem(work together to carry e- to mito) couples cytosolic oxidation of NADH with mito reduction of FAD cell "pays" for cytosolic NADH oxidation in glycero-P shuttle since FADH2 is lower energy |
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reaction V:triose P isomerase
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near perfect enzyme
catalytic rate is limited by interaction with substrate completes the first phase of glycolysis |
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malate-aspartate shuttle
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oxaloacetate is reduced in cytosol to malate, acquiring e- from NADH
malate transported across inner mem wher eits reoxidized to regenerate NADH Oxaloacetate must be transaminated to form aspartate in order to be transported across mem into cytosol full 2.5 ATP per NADH are recovered |
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net yield of atp from glucose
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depends on which shuttle is used
30ATP per glu is gly-3-P 32ATP per glu is malate-asp in bacteria:no mito, no extra H+ used to export ATP to cytosol so: 10/3=~3ATP/NADH 6/3=~2ATP/FADH2 |
