Oxidative phospho

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Oxidative Phosphorylation
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NGUYEN LE QUYEN BT060138
LAM HOANG VU
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Brief content
1.What is Oxidative Phosphorylation
2.Overview of energy transfer by chemiosmosis
3.Electron and proton transfer molecules
4.Eukaryotic electron transport chains
a.NADH-coenzyme Q oxidoreductase (complex I)…
b. Succinate-Q oxidoreductase,…






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1.What is Oxidative Phosphorylation
-Oxidative phosphorylation is a metabolic pathway that uses energy released by the oxidation of nutrients to produce adenosine triphosphate (ATP).

-This process, which takes place in mitochondria, is the major source of ATP in aerobic organisms.


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mitochondria
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2.Overview of energy transfer by chemiosmosis
-Oxidative phosphorylation works by using energy-releasing chemical reactions to drive energy-requiring reactions: The two sets of reactions are said to be coupled.
-This means one cannot occur without the other.
- The flow of electrons through the electron transport chain, from electron donors such as NADH to electron acceptors ( oxygen), is an exergonic process – it releases energy, whereas the synthesis of ATP is an endergonic (recieving the energy process, which requires an input of energy)
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3.Electron and proton transfer molecules
-The electron transport chain carries both protons and electrons, passing electrons from donors to acceptors, and transporting protons across a membrane.
-These processes use both soluble and protein-bound transfer molecules.
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-In mitochondria, electrons are transferred within the intermembrane space by the water-soluble electron transfer protein cytochrome c
-Within the inner mitochondrial membrane, the lipid-soluble electron carrier coenzyme Q10 (Q) carries both electrons and protons by a redox cycle.
-When Q accepts two electrons and two protons, it becomes reduced to the ubiquinol form (QH2);
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-When QH2 releases two electrons and two protons, it becomes oxidized back to the ubiquinone (Q) form.
-As a result, if two enzymes are arranged so that Q is reduced on one side of the membrane and QH2 oxidized on the other, ubiquinone will couple these reactions and shuttle protons across the membrane.

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-Within proteins, electrons are transferred between flavin cofactors,iron–sulfur clusters, and cytochromes.
-There are several types of iron–sulfur cluster
*The simplest kind found in the electron transfer chain consists of two iron atoms joined by two atoms of inorganic sulfur; these are called [2Fe–2S] clusters.
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*The second kind, called [4Fe–4S], contains a cube of four iron atoms and four sulfur atoms.
-Each iron atom in these clusters is coordinated by an additional amino acid, usually by the sulfur atom of cysteine
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4.Eukaryotic electron transport chains
-Many catabolic biochemical processes, such as glycolysis, the citric acid cycle, and beta oxidation, produce the reduced coenzyme NADH
-. This coenzyme contains electrons that have a high transfer potential; in other words, they will release a large amount of energy upon oxidation
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-However, the cell does not release this energy all at once, as this would be an uncontrollable reaction.
Instead, the electrons are removed from NADH and passed to oxygen through a series of enzymes that each release a small amount of the energy.
-This set of enzymes, consisting of complexes I through IV, is called the electron transport chain and is found in the inner membrane of the mitochondrion.
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-In eukaryotes, the enzymes in this electron transport system use the energy released from the oxidation of NADH to pump protons across the inner membrane of the mitochondrion.
-This causes protons to build up in the intermembrane space, and generates an electrochemical gradient across the membrane
-The energy stored in this potential is then used by ATP synthase to produce ATP
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-The energy stored in this potential is then used by ATP synthase to produce ATP.
A. NADH-coenzyme Q oxidoreductase (complex I)
-NADH-coenzyme Q oxidoreductase, also known as NADH dehydrogenase or complex I, is the first protein in the electron transport chain
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-The reaction that is catalyzed by this enzyme is the two electron reduction by NADH of coenzyme Q10 or ubiquinone (represented as Q in the equation below), a lipid-soluble quinone that is found in the mitochondrion membrane:
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-The start of the reaction, and indeed of the entire electron chain, is the binding of a NADH molecule to complex I and the donation of two electrons .
-The electrons enter complex I via a prosthetic group attached to the complex, flavin mononucleotide (FMN). The addition of electrons toFMN converts it to its reduced form, FMNH2.
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-The electrons are then transferred through a series of iron–sulfur clusters: the second kind of prosthetic group present in the complex. There are both [2Fe–2S] and [4Fe–4S] iron–sulfur clusters in complex I.
-As the electrons pass through this complex, four protons are pumped from the matrix into the intermembrane space.
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-Finally, the electrons are transferred from the chain of iron–sulfur clusters to a ubiquinone molecule in the membrane.
-Reduction of ubiquinone also contributes to the generation of a proton gradient, as two protons are taken up from the matrix as it is reduced to ubiquinol (QH2)
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B.Succinate-Q oxidoreductase (complex II)
-Succinate-Q oxidoreductase, also known as complex II or succinate dehydrogenase, is a second entry point to the electron transport chain
-it is the only enzyme that is part of both the citric acid cycle and the electrontransport chain.
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-Complex II consists of four protein subunits and contains a bound flavin adenine dinucleotide (FAD) cofactor, iron–sulfur clusters, and a heme group that does not participate in electron transfer to coenzyme Q.
-It oxidizes succinate to fumarate and reduces ubiquinone.
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C.Q-cytochrome c oxidoreductase (complex III)
-The two electron transfer steps in complex III: Q-cytochrome c oxidoreductase
-This enzyme is a dimer, with each subunit complex containing 11 protein subunits, an [2Fe-2S] iron–sulfur cluster and three cytochromes: one cytochrome c1 and two b cytochromes
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-A cytochrome is a kind of electron-transferring protein that contains at least one heme group.
-The reaction catalyzed by complex III is the oxidation of one molecule of ubiquinol and the reduction of two molecules of cytochrome c, a heme protein loosely associated with the mitochondrion.
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-Unlike coenzyme Q, which carries two electrons, cytochrome c carries only one electron.
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-In the first step, the enzyme binds three substrates, first, QH2, which is then oxidized, with one electron being passed to the second substrate, cytochrome c.
-The two protons released from QH2 pass into the intermembrane space.
-The third substrate is Q, which accepts the second electron from the QH2 and is reduced to Q.- ubisemiquinone free radical
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-In the second step, a second molecule of QH2 is bound and again passes its first electron to a cytochrome c acceptor.
-The second electron is passed to the bound ubisemiquinone, reducing it to QH2 as it gains two protons from the mitochondrial matrix.
-This QH2 is then released from the enzyme.
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D.Cytochrome c oxidase (complex IV)
-Cytochrome c oxidase, also known as complex IV, is the final protein complex in the electron transport chain
-Contains 13 subunits, two heme groups, as well as multiple metal ion cofactors – in all three atoms of copper, one of magnesium and one of zinc.
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-This enzyme mediates the final reaction in the electron transport chain and transfers electrons to oxygen.
-The final electron acceptor oxygen, which is also called the terminal electron acceptor, is reduced to water in this step.
-. The reaction catalyzed is the oxidation of cytochrome c and the reduction of oxygen:

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E.ATP synthase (complex V)
ATP synthase, also called complex V, is the final enzyme in the oxidative phosphorylation pathway
-ATP is enzyme in membrane,found in plasma membranre in plant,thylakoid membrane of chloroplast,the innermembrane mitochondia of the eukaryotic

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Components of ATPsynthase
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-is a massive protein complex with a mushroom-like shape
-2 parts
*F1: HYDROPHYLIC segment, contain of catalysing molecules, carry out the synthesize and degradation of ATP,
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-F0 is the proton channel,is also the hydrophobic segment .its function is tranporting proton
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b. The function
-synthesize ATP from ADP and Pi
-the action of electron transport chain pump H+ into the inner membrane
-Ion H+ create the potential that make the imbalance of the electronic potential

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CAC- Citric Acid Cycle
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Glycolysis
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