【生物化学】Chapter 11 Oxidative Phosphorylation

ATP: produced by mitochondria: out
ADP + Pi: into
Zhao Dandan
Chapter 11 Oxidative Phosphorylation
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Mitochondria: Power
Plants of the Cell
The inner membrane is
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Chapter 11 Oxidative Phosphorylation
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Chemiosmotic Theory (Proton-motive force)
Protons (H+) are moved into intermembrane space “pumped” byenergy from e- transfers Creates a proton gradient (pH gradient)
Convergence of degradation of Carbohydrates, Fats, AA Electrons move from intermediates to O2
Occurs in mitochondria of eukaryotes “ Fate of Electrons”
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Chapter 11 Oxidative Phosphorylation
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The Mitochondrion
Site in Eukaryotes
Demonstrated in 1948
Albert Lehninger and Eugene Kennedy
Mitochondrial transport systems
Most dehydrogenases are specific for NAD+ Location
Some: CYTOSOL Some: MITOCHONDRIA Some: two isozymes: one in each location Characteristics Water-soluble Associate reversibly with dehydrogenases Transport e- from catabolic sites to point of
Free Energy of electron transport from NADH and FADH2 O2 via Redox centers is coupled to ATP synthesis
Thermodynamics
NADH oxidation is highly exergonic
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Electron Transport
Generation (source) of hydrogen carriers: NADH and FADH2
Nicotinamide Nucleotide-linked dehydrogenases
Use either NADH or NADP
General formula
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Chapter 11 Oxidative Phosphorylation
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General points
Oxidative phosphorylation: ATP synthesis
driven by electron transfer to oxygen
Final step in energy-production of Aerobes
entry in ET
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General source of Hydrogen carriers
Flavin nucleotide dehydrogenases
Use FAD or FMN Can accept either 1 or 2 e-
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Conversion of electron-motive force to
proton-motive force
3 e- driven proton pumps NADH-Q oxidoreductase Q-cytochrome C oxidoreductase Cytochrome C oxidase
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Electron transport system (chain)
e- from glycolysis and CAC transferred
– By NADH and FADH2 – NADH 2.5 ATPs; FADH2 1.5 ATPs
e- flow through chain of intermediates to O2 to H2O
Instructor：Zhao Dandan
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Oxidative Phosphorylation
Chapter 11
Mitochondria: Power Plants of the Cell
Chapter 11 Outline
11.1 Introduction of Metabolism 11.2 The Mitochondrion 11.3 Electron Transport 11.4 Oxidative Phosporylation 11.5 Shuttles
Oxidation of NADH 2.5 ATP FADH2 Oxidation
– Requires 4th protein (II) for entrance into ET – 1.5 ATP
Zhao Dandan
Chapter 11 Oxidative Phosphorylation
Because inner membrane is impermeable to most hydrophylic molecules
Must provide transport for:
NADH: produced by glycolysis: into
Metabolites: produced by mitochondria: out
Large transmembrane complexes
* Contain multiple oxidation-reduction centers Quinones Flavins Iron-Sulfur clusters Hemes Copper ions
Last step of OP Accomplished by ATP synthase * Driven by flow of protons back into MATRIX
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Coupled: NADH oxidation to ATP synthesis
Electrons pass through 3 protein complexes with redox centers (I, III, and IV)
Transmembrane Electrochemical Potential
– Drives synthesis of ATP from ADP + Pi * Links e- movement to ATP synthesis
Peter Mitchell 1961
Zhao Dandan
Chapter 11 Oxidative Phosphorylation
– Reduced substrate + NAD+ = Ox. Sub. + NADH + H+
– Reduced substrate + NADP+ = Ox. Sub. + NADPH + H+
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Chapter 11 Oxidative Phosphorylation
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Nicotinamide dehydrogenases
Oxidation of one mole of NADH by O2 Transfer of 2e-/NADH under standard biochemical conditions Releases 218kJ of free energy
Zhao Dandan
Chapter 11 Oxidative Phosphorylation
All fuel oxidation pathways, except for glycolysis, occur in the mitochondrial matrix
Chapter 11 Oxidative Phosphorylation
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Electron Transport (ET)
General Proห้องสมุดไป่ตู้ess
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Chapter 11 Oxidative Phosphorylation
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Electron Transport
The electron transport chain: 4 protein complexes
Electrons are carried from complexes I and II To: complex III By coenzyme Q (CoQ or Ubiquinone) Complex I catalyzes oxidation of NAPH by CoQ
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Thermodynamics, cont…
ET is thermodynamically efficient
Need 30.5 kJ per mol -1 to synthesize 1 mole of ATP from ADP + Pi
Therefore can make several moles of ATP from a mole of NADH
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Chapter 11 Oxidative Phosphorylation
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What is Oxidative phosphorylation?
“Oxidative phosphorylation” is the term used to describe the synthesis of ATP, which is energetically coupled to the oxidation of reducing equivalents to water, in the mitochondria. The mechanism of the coupling of these two phenomena was elusive for many years but is now accepted to be via the “chemiosmotic model” of proton motive force.
Glucose oxidized to CO2 in glycolysis and CAC e-: move in an transfer process
– Multistep – Harnesses energy 28-30 ATP
Zhao Dandan
Chapter 11 Oxidative Phosphorylation
Each has a progressively higher affinity for e-
*** Large overall free energy change is broken into 3 packets Each packet:
– Coupled to ATP synthesis – Called OXIDATIVE PHOSPHORYLATION
an essential barrier that
carries essential machinery for both lateral and transverse translocation of substrates
The cristae, bounded by the inner membrane, invaginate deep into the matrix – why?