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Oxidative Phosphorylation - Coggle Diagram
Oxidative Phosphorylation
Structure of a Mitochondrion
Outer membrane
多孔的
allows passage of metabolites
Intermembrane space (IMS)
similar environment to cytosol
higher proton concentration (lower pH)
Inner membrane
impermeable
proton gradient across it
location of electron transport chain complexes
有皺褶增加面積
Matrix
location of the citric acid cycle and parts of lipid and amino acid metabolism
lower proton concentration (higher pH)
Cytochromes
One-electron carriers
Iron coordinating porphoryin ring
a, b, or c differ by ring additions
Iron-Sulfur Clusters
One-electron carriers
Coordinating by cysteines
Containing equal number of iron and sulfur atoms
Coenzyme Q or Ubiquinone
lipid-soluble
Upon accepting two electrons, it picks up two protons to give an alcohol, ubiquinol.
Ubiquinol can freely diffuse in the membrane, carrying
electrons with protons from one side of the membrane to another side.
a mobile electron carrier transporting
electrons from Complexes I and II to Complex III
Complex I
NADH:Ubiquinone Oxidoreductase
NADH binding site in the matrix side
flavin mononucleotide (FMN) accepts two electrons from NADH
Several iron-sulfur centers pass one electron at a time toward the ubiquinone binding site
Is a Proton Pump
transfer of protons from the matrix (N) to
the intermembrane space (P) .
four protons are transported per one NADH
Reduced coenzyme Q picks up two protons
Complex II
Succinate Dehydrogenase
FAD accepts two electrons from succinate
Does not transport protons
a single enzyme with dual roles
convert succinate to fumarate in the citric acid cycle
capture and donate electrons in the electron transport chain
Complex III
Ubiquinone:Cytochrome c Oxidoreductase
Uses two electrons from QH2 to reduce two molecules of cytochrome c
Additionally contains iron-sulfur clusters, cytochrome b, and cytochrome c
The Q Cycle
Cytochrome c
The second mobile electron carrier
Ubiquinone
through the membrane
Cytochrome c
through the intermembrane space
A soluble heme-containing protein in the intermembrane space
carries a single electron from the cytochrome bc1 complex to cytochrome oxidase.
Complex IV
a membrane protein with 13 subunits
Contains two heme groups: a and a3
Contains copper ions
CuA
two ions that accept electrons from cyt c
CuB
bonded to heme a3, forming a binuclear center that transfers four electrons to oxygen
Electron Flow Through Complex IV
Summary of Electron Transport
Complex I ->Complex IV
Complex II-> Complex IV
Reactive Oxygen Species Can Damage Biological Macromolecules
Ubiquinone is naturally “leaky” and facilitates partial reduction of non Complex III targets
production of reduced glutathione can correct freeradical
Chemiosmotic Model for ATP Synthesis
Electron transport sets up a proton-motive force.
• Energy of proton-motive force drives synthesis of ATP
Relationship of ETC and ATP Synthesis
ATP synthesis requires electron transport.
electron transport does not requires ATP synthesis.
Dinitrophenol (DNP) is an uncoupler, allowing respiration to continue without ATP synthesis.
Mitochondrial ATP Synthase Complex
F1
soluble complex in the matrix
individually catalyzes the hydrolysis of ATP
catalyzes ADP + Pi-> ATP
Hexamer arranged in three αβ dimers
three different conformations
open: empty
loose: binding ADP and Pi
tight: catalyzes ATP formation and binds product
F0
integral membrane complex
transports protons from IMS to matrix
energy transferred to F1
to catalyze phosphorylation of ADP
Net Production of ATP by Oxidation of
Glucose (and Other Fuels) Varies
Two methods are used to feed the electrons from NADH from the cytosol into the mitochondria
malate-aspartate shuttle
glycerol-3-phosphate shuttle
Regulation of Oxidative Phosphorylation
Primarily regulated by substrate availability
NADH and ADP/Pi
Inhibitor of F1 (IF1)
prevents hydrolysis of ATP during low oxygen
only active at lower pH
Inhibition of OxPhos leads to accumulation of NADH
feedback inhibition cascade up to PFK-1 in glycoysis
