Oxidative Phosphorylation (oxidative phosphorylation depends on electron…
is the main process that generates ATP for our body needs
the process of oxidative phosphorylation involves transferring of electrons from NADH, FADH2 to O2 by a series of electron carriers.
carbon fuels are first oxidized in the citric acid cycle to yield high-transfer-potential electrons
electrons flow through a series of large protein complexes in the inner mitochondrial membrane "respiratory chain" to reduce oxygen to water
the final phase of oxidative phosphorylation is carried out by an ATP synthase that is driven by the flow of protons back into mitochondrial matrix
the flow of electrons power the pumping of protons from the inside of the mitochondria to the outside, establishing a proton gradient
oxidative phosphorylation in eukaryotes takes place in mitochondria
like the TCA cycle, the respiratory chain and ATP synthesis take place in the MT
ATP synthesis is on inner memb.
the increase in surface area of the inner memb. provided by the cristae creates more sites for oxidative phosphorylation
the outer memb. is permeasble to most samll molecules and ions, while inner memb. is impermeable to nearly all ions and polar molec.
transporter proteins shuttle metabolites such as ATP, pyruvate and citrate across the inner memb.
the 2 faces of the memb. is referred to as the matrix side and the cytoplasmic side
oxidative phosphorylation depends on electron transfer
electrons from NADH and FADH2 flow through the components of the electron chain and ultimately resulting in the reduction of oxygen
the electron-transfer potential is measured as redox potential (E'0) which is also called "reduction potential/ oxidation-reduction potential"
the more positive E'0 means the easier for the oxidant to accept electrons ; it is good oxidizing agent.
a strong reducing agent such as NADH is poised to donate electron and has a negative reduction potential
electron flow through the electron-transport chain creates a proton gradient
the driving force of oxidative phosphorylation is the electron-transfer potential of NADH or FADH2 relative to that of O2
the electron-transfer chain is a series of coupled oxidation-reduction reactions
electrons flow down an E gradient from NADH to O2. the flow is catalyzed by the 3 protein complexes: NADH-Q oxidoreductase, Q-cytochrome c oxidase
iron is a crucial electron carriers in all complexes
all iron atoms should have the same E'0 value
the iron ion is embedded in different proteins, enabling iron to have various reduction potentials
the oxidation-reduction potential of iron ions can be altered by their environment
electron flow within these transmembrane complexs (I,III,IV) leads to the transport of protons across the inner memb. ; II does not pump protons
steps in the respiratory chain
1st: the high potential electron of NADH enter the respiratory chain at NADH-Q oxidoreductase (complex I and NADH dehydrogenase)
uniquinol is the entry point for electrons from FADH2 of flavoproteins
2nd: electrons flow from ubiquinol to cytochrome c through Q-cytochrome c oxidoreductase
the Q cycle funnels electrons from a two-electron carrier to a one-electron carrier and pumps protons
3rd: cytochrome c oxidase catalyzes the reduction of molecular oxygen to water
the last of the 3 proton-pumping assemblies of the respiratory chain is cytochrome c oxidase (complex IV)
the proton-motive force
during the electron flow, protons are pumped from the MT matrix to the outside of the inner MT memb., creating a proton gradient.
the proton gradeint is rich in E as the entropy of the proton is reduced
E of proton gradient powers the synthesis of ATP
the complex that carries out the subthesis of ATP was called ATPase or F1F0ATPase
ATP synthase is composed of a proton-conducting unit and a catalytic unit; F0 and F1 subunit
proton flow through ATP synthase leads to the release of tightly bound ATP
protons flow around the c ring powers ATP synthesis
the number of c subunits determine the efficiency with which the proton gradient is converted into ATP synthesis
the malate-aspartate shuttle
in the heart and liver, electrons from cytoplasmic NADH are brought into MT by the malate-aspartate shuttle
the total yield is about 30 ATP per glucose