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32 Cards in this Set

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relationship of e- transport and oxidative phosphorylation to glycolysis and TCA cycle
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
electron transport
converts energy of e- transfer into the energy of phosphoryl tranfer stored in the phosphoric anhydride bonds of ATP
electrons carried by...
reduced coenzymes are passed thru a chain of prot and coenzymes to drive the generation of a proton gradient across the inner mito mem
oxidative phosphorylation
the proton gradient runs downhill to drive the synthesis of ATP (it all happens in or at the inner mito mem)
organization of mitochondria
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
electron transport 1-3
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
electron transport 4-5
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
reduction potentials for components of the e- transport chain
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
overview of complexes and pathways in ETC
4 major protein complexes:
I&II:reduce
Co-Q
lipid soluable co
water soluable prot
2 other flavoproteins can transfer e- to CoQ
COMPLEX I:NADH-CoQ reductase
(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
proposed structure and ET pathway for complex I
e- from NADH thru I to CoQ
e- from NADH to FMN to multiple Fe-S centers to CoQ
4H+ transported out per 2e-
complex II:succinate-CoQ reductase
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
complex II continued
3 types of Fe-S cluster:
4Fe-4S, 3Fe-4S, 2Fe-2S
path:succ->FADH2->2Fe2+->UQH2
net rxn:succ + UQ-->fumarate + UQH2
succinate dehydrogenase
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
proposed e- flow in complex II
e- from succ to CoQ via succ-FAD multiple Fe-S centers-UQ

NO PROTONS PUMPED ACROSS MEMBRANE!!
Co-Q
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
complex III:coQ-cytochrome reductase
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
typical visible spectra of cytochrome C
top to bottom:
cyto c:reduced
cyto c:oxidized
cyto c:reduced minus oxidized
submito:@RT, reduced minus oxidized
submito:(77Kdeg) reduced minus oxidized
complex IV:cyto c oxidase
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
electron transfer pathway
intermem space:P-phase
matrix:N-phase
model for ET in the mito inner mem
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)
proton gradient driven ATP synthesis:atp synthase
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
inhibitors of oxidative phosphorylation involve direct binding to protein
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
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
chemical uncouplers
dinitrophenol,dicumarol,FCCP
energy dissipated as heat
happens in inner mito mem
destroy tight coupling bw ET and ATP synthase rxn
ATP-ADP translocase
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+
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
shuttle systems for e-s
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
glycerophosphate shuttle
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
reaction V:triose P isomerase
near perfect enzyme
catalytic rate is limited by interaction with substrate
completes the first phase of glycolysis
malate-aspartate shuttle
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
net yield of atp from glucose
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