Oxidative phosphorylation From Wikipedia the free encyclopedia The electron transport chain in the cell is the site of oxidative phosphorylation in prokaryotes The NADH and succinate generated in the citric acid cycle are oxidized releasing energy to power the ATP synthase Oxidative phosphorylation UK ɒ k ˈ s ɪ d ə t ɪ v US ˈ ɑː k s ɪ ˌ d eɪ t ɪ v is the metabolic pathway in which cells use enzymes to oxidize nutrients thereby releasing energy which is used to produce adenosine triphosphate ATP In most eukaryotes this takes place inside mitochondria Almost all aerobic organisms carry out oxidative phosphorylation This pathway is probably so pervasive because it is a highly efficient way of releasing energy compared to alternative fermentation processes such as anaerobic glycolysis During oxidative phosphorylation electrons are transferred from electron donors to electron acceptors such as oxygen in redox reactions These redox reactions release energy which is used to form ATP In eukaryotes these redox reactions are carried out by a series of protein complexes within the inner membrane of the cells mitochondria whereas in prokaryotes these proteins are located in the cells intermembrane space These linked sets of proteins are called electron transport chains In eukaryotes five main protein complexes are involved whereas in prokaryotes many different enzymes are present using a variety of electron donors and acceptors The energy released by electrons flowing through this electron transport chain is used to transport protons across the inner mitochondrial membrane in a process called electron transport This generates potential energy in the form of a pH gradient and an electrical potential across this membrane This store of energy is tapped when protons flow back across the membrane and down the potential energy gradient through a large enzyme called ATP synthase this process is known as chemiosmosis The ATP synthase uses the energy to transform adenosine diphosphate ADP into adenosine triphosphate in a phosphorylation reaction The reaction is driven by the proton flow which forces the rotation of a part of the enzyme the ATP synthase is a rotary mechanical motor Although oxidative phosphorylation is a vital part of metabolism it produces reactive oxygen species such as superoxide and hydrogen peroxide which lead to propagation of free radicals damaging cells and contributing to disease and possibly aging senescence The enzymes carrying out this metabolic pathway are also the target of many drugs and poisons that inhibit their activities It is the terminal process of cellular respiration in eukaryotes and accounts for high ATP yield Contents 1 Chemiosmosis 2 Electron and proton transfer molecules 3 Eukaryotic electron transport chains 31 NADHcoenzyme Q oxidoreductase complex I 32 SuccinateQ oxidoreductase complex II 33 Electron transfer flavoproteinQ oxidoreductase 34 Qcytochrome c oxidoreductase complex III 35 Cytochrome c oxidase complex IV 36 Alternative reductases and oxidases 37 Organization of complexes 4 Prokaryotic electron transport chains 5 ATP synthase complex V 6 Reactive oxygen species 7 Inhibitors 8 History 9 See also 10 Notes 11 12 121 Introductory 122 Advanced 123 General resources 124 Structural resources Chemiosmosis Further information Chemiosmosis and Bioenergetics Oxidative phosphorylation works by using energy releasing chemical reactions to drive energyrequiring reactions The two sets of reactions are said to be coupled This means one can not occur without the other The flow of electrons through the electron transport chain from electron donors such as NADH to electron acceptors such as oxygen is an exergonic process it releases energy whereas the synthesis of ATP is an endergonic process which requires an input of energy Both the electron transport chain and the ATP synthase are embedded in a membrane and energy is transferred from electron transport chain to the ATP synthase by movements of protons across this membrane in a process called chemiosmosis In practice this is like a simple electric circuit with a current of protons being driven from the negative Nside of the membrane to the positive Pside by the protonpumping enzymes of the electron transport chain These enzymes are like a battery as they perform work to drive current through the circuit The movement of protons creates an electrochemical gradient across the membrane which is often called the protonmotive force It has two components a difference in proton concentration a H gradient Δ pH and a difference in electric potential with the Nside having a negative charge ATP synthase releases this stored energy by completing the circuit and allowing protons to flow down the electrochemical gradient back to the Nside of the membrane The electrochemical gradient drives the rotation of part of the enzymes structure and couples this motion to the synthesis of ATP The two components of the protonmotive force are thermodynamically equivalent In mitochondria the largest part of energy is provided by the potential in alkaliphile bacteria the electrical energy even has to compensate for a counteracting inverse pH difference Inversely chloroplasts operate mainly on ΔpH However they also require a small membrane potential for the kinetics of ATP synthesis In the case of the fusobacterium Propionigenium modestum it drives the counterrotation of subunits a and c of the F O motor of ATP synthase The amount of energy released by oxidative phosphorylation is high compared with the amount produced by anaerobic fermentation Glycolysis produces only 2 ATP molecules but somewhere between 30 and 36 ATPs are produced by the oxidative phosphorylation of the 10 NADH and 2 succinate molecules made by converting one molecule of glucose to carbon dioxide and water while each cycle of beta oxidation of a fatty acid yields about 14 ATPs These ATP yields are theoretical maximum values in practice some protons leak across the membrane lowering the yield of ATP Electron and proton transfer molecules Further information Coenzyme and Cofactor biochemistry Reduction of coenzyme Q from its ubiquinone form Q to the reduced ubiquinol form QH 2 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 proteinbound transfer molecules In mitochondria electrons are transferred within the intermembrane space by the water soluble electron transfer protein cytochrome c This carries only electrons and these are transferred by the reduction and oxidation of an iron atom that the protein holds within a heme group in its structure Cytochrome c is also found in some bacteria where it is located within the periplasmic space Within the inner mitochondrial membrane the lipid soluble electron carrier coenzyme Q10 Q carries both electrons and protons by a redox cycle This small benzoquinone molecule is very hydrophobic so it diffuses freely within the membrane When Q accepts two electrons and two protons it becomes reduced to the ubiquinol form QH 2 when QH 2 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 QH 2 oxidized on the other ubiquinone will couple these reactions and shuttle protons across the membrane Some bacterial electron transport chains use different quinones such as menaquinone in addition to ubiquinone Within proteins electrons are transferred between flavin cofactors ironsulfur clusters and cytochromes There are several types of ironsulfur 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 2Fe2S clusters The second kind called 4Fe4S 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 Metal ion cofactors undergo redox reactions without binding or releasing protons so in the electron transport chain they serve solely to transport electrons through proteins Electrons move quite long distances through proteins by hopping along chains of these cofactors This occurs by quantum tunnelling which is rapid over distances of less than 14 10 9 m Eukaryotic electron transport chains Further information Electron transport chain and Chemiosmosis 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 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 Succinate is also oxidized by the electron transport chain but feeds into the pathway at a different point 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 Oxidative phosphorylation in the eukaryotic mitochondrion is the bestunderstood example of this process The mitochondrion is present in almost all eukaryotes with the exception of anaerobic protozoa such as Trichomonas vaginalis that instead reduce protons to hydrogen in a remnant mitochondrion called a hydrogenosome Typical respiratory enzymes and substrates in eukaryotes Respiratory enzyme Redox pair Midpoint potential Volts NADH dehydrogenase NAD NADH 032 Succinate dehydrogenase FMN or FAD FMNH 2 or FADH 2 020 Cytochrome bc 1 complex Coenzyme Q10 ox Coenzyme Q10 red 006 Cytochrome bc 1 complex Cytochrome b ox Cytochrome b red 012 Complex IV Cytochrome c ox Cytochrome c red 022 Complex IV Cytochrome a ox Cytochrome a red 029 Complex IV O 2 HO 082 Conditions pH 7 NADHcoenzyme Q oxidoreductase complex I Complex I or NADHQ oxidoreductase The abbreviations are discussed in the text In all diagrams of respiratory complexes in this article the matrix is at the bottom with the intermembrane space above NADHcoenzyme Q oxidoreductase also known as NADH dehydrogenase or complex I is the first protein in the electron transport chain Complex I is a giant enzyme with the mammalian complex I having 46 subunits and a molecular mass of about 1000 kilodaltons kDa The structure is known in detail only from a bacterium in most organisms the complex resembles a boot with a large ball poking out from the membrane into the mitochondrion The genes that encode the individual proteins are contained in both the cell nucleus and the mitochondrial genome as is the case for many enzymes present in the mitochondrion The reaction that is catalyzed by this enzyme is the two electron oxidation of NADH by coenzyme Q10 or ubiquinone represented as Q in the equation below a lipidsoluble quinone that is found in the mitochondrion membrane 1 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 to FMN converts it to its reduced form FMNH 2 The electrons are then transferred through a series of ironsulfur clusters the second kind of prosthetic group present in the complex There are both 2Fe2S and 4Fe4S ironsulfur clusters in complex I As the electrons pass through this complex four protons are pumped from the matrix into the intermembrane space Exactly how this occurs is unclear but it seems to involve conformational changes in complex I that cause the protein to bind protons on the Nside of the membrane and release them on the Pside of the membrane Finally the electrons are transferred from the chain of ironsulfur 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 QH 2 SuccinateQ oxidoreductase complex II Complex II SuccinateQ oxidoreductase SuccinateQ oxidoreductase also known as complex II or succinate dehydrogenase is a second entry point to the electron transport chain It is unusual because it is the only enzyme that is part of both the citric acid cycle and the electron transport chain Complex II consists of four protein subunits and contains a bound flavin adenine dinucleotide FAD cofactor ironsulfur clusters and a heme group that does not participate in electron transfer to coenzyme Q but is believed to be important in decreasing production of reactive oxygen species It oxidizes succinate to fumarate and reduces ubiquinone As this reaction releases less energy than the oxidation of NADH complex II does not transport protons across the membrane and does not contribute to the proton gradient 2 In some eukaryotes such as the parasitic worm Ascaris suum an enzyme similar to complex II fumarate reductase menaquinolfumarate oxidoreductase or QFR operates in reverse to oxidize ubiquinol and reduce fumarate This allows the worm to survive in the anaerobic environment of the large intestine carrying out anaerobic oxidative phosphorylation with fumarate as the electron acceptor Another unconventional function of complex II is seen in the malaria parasite Plasmodium falciparum Here the reversed action of complex II as an oxidase is important in regenerating ubiquinol which the parasite uses in an unusual form of pyrimidine biosynthesis Electron transfer flavoproteinQ oxidoreductase Electron transfer flavoproteinubiquinone oxidoreductase ETFQ oxidoreductase also known as electron transferringflavoprotein dehydrogenase is a third entry point to the electron transport chain It is an enzyme that accepts electrons from electrontransferring flavoprotein in the mitochondrial matrix and uses these electrons to reduce ubiquinone This enzyme contains a flavin and a 4Fe4S cluster but unlike the other respiratory complexes it attaches to the surface of the membrane and does not cross the lipid bilayer 3 In mammals this metabolic pathway is important in beta oxidation of fatty acids and catabolism of amino acids and choline as it accepts electrons from multiple acetylCoA dehydrogenases In plants ETFQ oxidoreductase is also important in the metabolic responses that allow survival in extended periods of darkness Qcytochrome c oxidoreductase complex III The two electron transfer steps in complex III Qcytochrome c oxidoreductase After each step Q in the upper part of the figure leaves the enzyme Qcytochrome c oxidoreductase is also known as cytochrome c reductase cytochrome bc 1 complex or simply complex III In mammals this enzyme is a dimer with each subunit complex containing 11 protein subunits an 2Fe2S ironsulfur cluster and three cytochromes one cytochrome c 1 and two b cytochromes A cytochrome is a kind of electrontransferring protein that contains at least one heme group The iron atoms inside complex IIIs heme groups alternate between a reduced ferrous 2 and oxidized ferric 3 state as the electrons are transferred through the protein 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 Unlike coenzyme Q which carries two electrons cytochrome c carries only one electron 4 As only one of the electrons can be transferred from the QH 2 donor to a cytochrome c acceptor at a time the reaction mechanism of complex III is more elaborate than those of the other respiratory complexes and occurs in two steps called the Q cycle In the first step the enzyme binds three substrates first QH 2 which is then oxidized with one electron being passed to the second substrate cytochrome c The two protons released from QH 2 pass into the intermembrane space The third substrate is Q which accepts the second electron from the QH 2 and is reduced to Q which is the ubisemiquinone free radical The first two substrates are released but this ubisemiquinone intermediate remains bound In the second step a second molecule of QH 2 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 QH 2 as it gains two protons from the mitochondrial matrix This QH 2 is then released from the enzyme As coenzyme Q is reduced to ubiquinol on the inner side of the membrane and oxidized to ubiquinone on the other a net transfer of protons across the membrane occurs adding to the proton gradient The rather complex twostep mechanism by which this occurs is important as it increases the efficiency of proton transfer If instead of the Q cycle one molecule of QH 2 were used to directly reduce two molecules of cytochrome c the efficiency would be halved with only one proton transferred per cytochrome c reduced Cytochrome c oxidase complex IV Further information cytochrome c oxidase Complex IV cytochrome c oxidase Cytochrome c oxidase also known as complex IV is the final protein complex in the electron transport chain The mammalian enzyme has an extremely complicated structure and 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 This enzyme mediates the final reaction in the electron transport chain and transfers electrons to oxygen while pumping protons across the membrane The final electron acceptor oxygen which is also called the terminal electron acceptor is reduced to water in this step Both the direct pumping of protons and the consumption of matrix protons in the reduction of oxygen contribute to the proton gradient The reaction catalyzed is the oxidation of cytochrome c and the reduction of oxygen 5 Alternative reductases and oxidases Many eukaryotic organisms have electron transport chains that differ from the muchstudied mammalian enzymes described above For example plants have alternative NADH oxidases which oxidize NADH in the cytosol rather than in the mitochondrial matrix and pass these electrons to the ubiquinone pool These enzymes do not transport protons and therefore reduce ubiquinone without altering the electrochemical gradient across the inner membrane Another example of a divergent electron transport chain is the alternative oxidase which is found in plants as well as some fungi protists and possibly some animals This enzyme transfers electrons directly from ubiquinol to oxygen The electron transport pathways produced by these alternative NADH and ubiquinone oxidases have lower ATP yields than the full pathway The advantages produced by a shortened pathway are not entirely clear However the alternative oxidase is produced in response to stresses such as cold reactive oxygen species and infection by pathogens as well as other factors that inhibit the full electron transport chain Alternative pathways might therefore enhance an organisms resistance to injury by reducing oxidative stress Organization of complexes The original model for how the respiratory chain complexes are organized was that they diffuse freely and independently in the mitochondrial membrane However recent data suggest that the complexes might form higherorder structures called supercomplexes or respirasomes In this model the various complexes exist as organized sets of interacting enzymes These associations might allow channeling of substrates between the various enzyme complexes increasing the rate and efficiency of electron transfer Within such mammalian supercomplexes some components would be present in higher amounts than others with some data suggesting a ratio between complexes IIIIIIIV and the ATP synthase of approximately 11374 However the debate over this supercomplex hypothesis is not completely resolved as some data do not appear to fit with this model Prokaryotic electron transport chains Further information Microbial metabolism In contrast to the general similarity in structure and function of the electron transport chains in eukaryotes bacteria and archaea possess a large variety of electrontransfer enzymes These use an equally wide set of chemicals as substrates In common with eukaryotes prokaryotic electron transport uses the energy released from the oxidation of a substrate to pump ions across a membrane and generate an electrochemical gradient In the bacteria oxidative phosphorylation in Escherichia coli is understood in most detail while archaeal systems are at present poorly understood The main difference between eukaryotic and prokaryotic oxidative phosphorylation is that bacteria and archaea use many different substances to donate or accept electrons This allows prokaryotes to grow under a wide variety of environmental conditions In E coli for example oxidative phosphorylation can be driven by a large number of pairs of reducing agents and oxidizing agents which are listed below The midpoint potential of a chemical measures how much energy is released when it is oxidized or reduced with reducing agents having negative potentials and oxidizing agents positive potentials Respiratory enzymes and substrates in E coli Respiratory enzyme Redox pair Midpoint potential Volts Formate dehydrogenase Bicarbonate Formate 043 Hydrogenase Proton Hydrogen 042 NADH dehydrogenase NAD NADH 032 Glycerol3phosphate dehydrogenase DHAP Gly3P 019 Pyruvate oxidase Acetate Carbon dioxide Pyruvate Lactate dehydrogenase Pyruvate Lactate 019 D amino acid dehydrogenase 2oxoacid ammonia D amino acid Glucose dehydrogenase Gluconate Glucose 014 Succinate dehydrogenase Fumarate Succinate 003 Ubiquinol oxidase Oxygen Water 082 Nitrate reductase Nitrate Nitrite 042 Nitrite reductase Nitrite Ammonia 036 Dimethyl sulfoxide reductase DMSO DMS 016 Trimethylamine N oxide reductase TMAO TMA 013 Fumarate reductase Fumarate Succinate 003 As shown above E coli can grow with reducing agents such as formate hydrogen or lactate as electron donors and nitrate DMSO or oxygen as acceptors The larger the difference in midpoint potential between an oxidizing and reducing agent the more energy is released when they react Out of these compounds the succinatefumarate pair is unusual as its midpoint potential is close to zero Succinate can therefore be oxidized to fumarate if a strong oxidizing agent such as oxygen is available or fumarate can be reduced to succinate using a strong reducing agent such as formate These alternative reactions are catalyzed by succinate dehydrogenase and fumarate reductase respectively Some prokaryotes use redox pairs that have only a small difference in midpoint potential For example nitrifying bacteria such as Nitrobacter oxidize nitrite to nitrate donating the electrons to oxygen The small amount of energy released in this reaction is enough to pump protons and generate ATP but not enough to produce NADH or NADPH directly for use in anabolism This problem is solved by using a nitrite oxidoreductase to produce enough protonmotive force to run part of the electron transport chain in reverse causing complex I to generate NADH Prokaryotes control their use of these electron donors and acceptors by varying which enzymes are produced in response to environmental conditions This flexibility is possible because different oxidases and reductases use the same ubiquinone pool This allows many combinations of enzymes to function together linked by the common ubiquinol intermediate These respiratory chains therefore have a modular design with easily interchangeable sets of enzyme systems In addition to this metabolic diversity prokaryotes also possess a range of isozymes different enzymes that catalyze the same reaction For example in E coli there are two different types of ubiquinol oxidase using oxygen as an electron acceptor Under highly aerobic conditions the cell uses an oxidase with a low affinity for oxygen that can transport two protons per electron However if levels of oxygen fall they switch to an oxidase that transfers only one proton per electron but has a high affinity for oxygen ATP synthase complex V Further information ATP synthase ATP synthase also called complex V is the final enzyme in the oxidative phosphorylation pathway This enzyme is found in all forms of life and functions in the same way in both prokaryotes and eukaryotes The enzyme uses the energy stored in a proton gradient across a membrane to drive the synthesis of ATP from ADP and phosphate P Estimates of the number of protons required to synthesize one ATP have ranged from three to four with some suggesting cells can vary this ratio to suit different conditions 6 This phosphorylation reaction is an equilibrium which can be shifted by altering the protonmotive force In the absence of a protonmotive force the ATP synthase reaction will run from right to left hydrolyzing ATP and pumping protons out of the matrix across the membrane However when the protonmotive force is high the reaction is forced to run in the opposite direction it proceeds from left to right allowing protons to flow down their concentration gradient and turning ADP into ATP Indeed in the closely related vacuolar type HATPases the hydrolysis reaction is used to acidify cellular compartments by pumping protons and hydrolysing ATP ATP synthase is a massive protein complex with a mushroomlike shape The mammalian enzyme complex contains 16 subunits and has a mass of approximately 600 kilodaltons The portion embedded within the membrane is called F O and contains a ring of c subunits and the proton channel The stalk and the ballshaped headpiece is called F 1 and is the site of ATP synthesis The ballshaped complex at the end of the F 1 portion contains six proteins of two different kinds three α subunits and three β subunits whereas the stalk consists of one protein the γ subunit with the tip of the stalk extending into the ball of α and β subunits Both the α and β subunits bind nucleotides but only the β subunits catalyze the ATP synthesis reaction Reaching along the side of the F 1 portion and back into the membrane is a long rodlike subunit that anchors the α and β subunits into the base of the enzyme As protons cross the membrane through the channel in the base of ATP synthase the F O protondriven motor rotates Rotation might be caused by changes in the ionization of amino acids in the ring of c subunits causing electrostatic interactions that propel the ring of c subunits past the proton channel This rotating ring in turn drives the rotation of the central axle the γ subunit stalk within the α and β subunits The α and β subunits are prevented from rotating themselves by the sidearm which acts as a stator This movement of the tip of the γ subunit within the ball of α and β subunits provides the energy for the active sites in the β subunits to undergo a cycle of movements that produces and then releases ATP Mechanism of ATP synthase ATP is shown in red ADP and phosphate in pink and the rotating γ subunit in black This ATP synthesis reaction is called the binding change mechanism and involves the active site of a β subunit cycling between three states In the open state ADP and phosphate enter the active site shown in brown in the diagram The protein then closes up around the molecules and binds them loosely the loose state shown in red The enzyme then changes shape again and forces these molecules together with the active site in the resulting tight state shown in pink binding the newly produced ATP molecule with very high affinity Finally the active site cycles back to the open state releasing ATP and binding more ADP and phosphate ready for the next cycle In some bacteria and archaea ATP synthesis is driven by the movement of sodium ions through the cell membrane rather than the movement of protons Archaea such as Methanococcus also contain the A 1 A o synthase a form of the enzyme that contains additional proteins with little similarity in sequence to other bacterial and eukaryotic ATP synthase subunits It is possible that in some species the A 1 A o form of the enzyme is a specialized sodiumdriven ATP synthase but this might not be true in all cases Reactive oxygen species Further information Oxidative stress and Antioxidant Molecular oxygen is an ideal terminal electron acceptor because it is a strong oxidizing agent The reduction of oxygen does involve potentially harmful intermediates Although the transfer of four electrons and four protons reduces oxygen to water which is harmless transfer of one or two electrons produces superoxide or peroxide anions which are dangerously reactive 7 These reactive oxygen species and their reaction products such as the hydroxyl radical are very harmful to cells as they oxidize proteins and cause mutations in DNA This cellular damage might contribute to disease and is proposed as one cause of aging The cytochrome c oxidase complex is highly efficient at reducing oxygen to water and it releases very few partly reduced intermediates however small amounts of superoxide anion and peroxide are produced by the electron transport chain Particularly important is the reduction of coenzyme Q in complex III as a highly reactive ubisemiquinone free radical is formed as an intermediate in the Q cycle This unstable species can lead to electron leakage when electrons transfer directly to oxygen forming superoxide As the production of reactive oxygen species by these protonpumping complexes is greatest at high membrane potentials it has been proposed that mitochondria regulate their activity to maintain the membrane potential within a narrow range that balances ATP production against oxidant generation For instance oxidants can activate uncoupling proteins that reduce membrane potential To counteract these reactive oxygen species cells contain numerous antioxidant systems including antioxidant vitamins such as vitamin C and vitamin E and antioxidant enzymes such as superoxide dismutase catalase and peroxidases which detoxify the reactive species limiting damage to the cell Inhibitors There are several wellknown drugs and toxins that inhibit oxidative phosphorylation Although any one of these toxins inhibits only one enzyme in the electron transport chain inhibition of any step in this process will halt the rest of the process For example if oligomycin inhibits ATP synthase protons can not pass back into the mitochondrion As a result the proton pumps are unable to operate as the gradient becomes too strong for them to overcome NADH is then no longer oxidized and the citric acid cycle ceases to operate because the concentration of NAD falls below the concentration that these enzymes can use Compounds Use Site of action Effect on oxidative phosphorylation Cyanide Carbon monoxide Azide Hydrogen sulfide Poisons Complex IV Inhibit the electron transport chain by binding more strongly than oxygen to the Fe Cu center in cytochrome c oxidase preventing the reduction of oxygen Oligomycin Antibiotic Complex V Inhibits ATP synthase by blocking the flow of protons through the F o subunit CCCP 24Dinitrophenol Poisons weightloss Inner membrane Ionophores that disrupt the proton gradient by carrying protons across a membrane This ionophore uncouples proton pumping from ATP synthesis because it carries protons across the inner mitochondrial membrane Rotenone Pesticide Complex I Prevents the transfer of electrons from complex I to ubiquinone by blocking the ubiquinonebinding site Malonate and oxaloacetate Poisons Complex II Competitive inhibitors of succinate dehydrogenase complex II Antimycin A Piscicide Complex III Binds to the Qi site of cytochrome c reductase thereby inhibiting the oxidation of ubiquinol Not all inhibitors of oxidative phosphorylation are toxins In brown adipose tissue regulated proton channels called uncoupling proteins can uncouple respiration from ATP synthesis This rapid respiration produces heat and is particularly important as a way of maintaining body temperature for hibernating animals although these proteins may also have a more general function in cells responses to stress History Further information History of biochemistry and History of molecular biology The field of oxidative phosphorylation began with the report in 1906 by Arthur Harden of a vital role for phosphate in cellular fermentation but initially only sugar phosphates were known to be involved However in the early 1940s the link between the oxidation of sugars and the generation of ATP was firmly established by Herman Kalckar confirming the central role of ATP in energy transfer that had been proposed by Fritz Albert Lipmann in 1941 Later in 1949 Morris Friedkin and Albert L Lehninger proved that the coenzyme NADH linked metabolic pathways such as the citric acid cycle and the synthesis of ATP The term oxidative phosphorylation was coined by Volodymyr Belitser uk in 1939 For another twenty years the mechanism by which ATP is generated remained mysterious with scientists searching for an elusive highenergy intermediate that would link oxidation and phosphorylation reactions This puzzle was solved by Peter D Mitchell with the publication of the chemiosmotic theory in 1961 At first this proposal was highly controversial but it was slowly accepted and Mitchell was awarded a Nobel prize in 1978 Subsequent research concentrated on purifying and characterizing the enzymes involved with major contributions being made by David E Green on the complexes of the electrontransport chain as well as Efraim Racker on the ATP synthase A critical step towards solving the mechanism of the ATP synthase was provided by Paul D Boyer by his development in 1973 of the binding change mechanism followed by his radical proposal of rotational catalysis in 1982 More recent work has included structural studies on the enzymes involved in oxidative phosphorylation by John E Walker with Walker and Boyer being awarded a Nobel Prize in 1997 See also Respirometry TIMTOM Complex Notes DNP was extensively used as an antiobesity medication in the 1930s but was ultimately discontinued due to its dangerous side effects However illicit use of the drug for this purpose continues today See 24DinitrophenolDieting aid for more information References oxidative Meaning in the Cambridge English Dictionary 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O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O 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O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O 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O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O

oxidative phosphorylation
metabolic pathway
adenosine triphosphate


Oystercatcher From Wikipedia the free encyclopedia Oystercatchers Pied oystercatcher Haematopus longirostris Scientific classification Kingdom Animalia Phylum Chordata Class Aves Order Charadriiformes Suborder Charadrii Family Haematopodidae Bonaparte 1838 Genus Haematopus Linnaeus 1758 Species See text American oystercatcher Juvenile The oystercatchers are a group of waders forming the family Haematopodidae which has a single genus Haematopus They are found on coasts worldwide apart from the polar regions and some tropical regions of Africa and South East Asia The exception to this is the Eurasian oystercatcher and the South Island oystercatcher both of which breed inland far inland in some cases In the past there has been a great deal of confusion as to the species limits with discrete populations of all black oystercatchers being afforded specific status but pied oystercatchers being considered one single species The name oystercatcher was coined by Mark Catesby in 1731 as a common name for the North American species H palliatus described as eating oysters Yarrell in 1843 established this as the preferred term replacing the older name sea pie or seapie The genus name Haematopus comes from the Greek haima αἳμα blood pous πούς foot Contents 1 Description 2 Feeding 3 Breeding 4 Conservation 5 Species 6 7 External links Description The different species of oystercatcher show little variation in shape or appearance They range from 3950 cm 1520 in in length and 7291 cm 2836 in in wingspan The Eurasian oystercatcher is the lightest on average at 526 g 1160 lb while the sooty oystercatcher is the heaviest at 819 g 1806 lb The plumage of all species is either allblack or black or dark brown on top and white underneath The variable oystercatcher is slightly exceptional in being either allblack or pied They are large obvious and noisy plover like birds with massive long orange or red bills used for smashing or prying open molluscs The bill shape varies between species according to the diet Those birds with bladelike bill tips pry open or smash mollusc shells and those with pointed bill tips tend to probe for annelid worms They show sexual dimorphism with females being longerbilled and heavier than males Feeding The diet of oystercatchers varies with location Species occurring inland feed upon earthworms and insect larvae The diet of coastal oystercatchers is more varied although dependent upon coast type on estuaries bivalves gastropods and polychaete worms are the most important part of the diet whereas rocky shore oystercatchers prey upon limpets mussels gastropods and chitons Other prey items include echinoderms fish and crabs Breeding Nearly all species of oystercatcher are monogamous although there are reports of polygamy in the Eurasian oystercatcher They are territorial during the breeding season with a few species defending territories year round There is strong mate and site fidelity in the species that have been studied with one record of a pair defending the same site for 20 years A single nesting attempt is made per breeding season which is timed over the summer months The nests of oystercatchers are simple affairs scrapes in the ground which may be lined and placed in a spot with good visibility The eggs of oystercatchers are spotted and cryptic Between one and four eggs are laid with three being typical in the Northern Hemisphere and two in the south Incubation is shared but not proportionally females tend to take more incubation and males engage in more territory defence Incubation varies by species lasting between 2439 days Oystercatchers are also known to practice egg dumping Like the cuckoo they sometimes lay their eggs in the nests of other species such as seagulls abandoning them to be raised by those birds Conservation The Canary Islands oystercatcher became extinct during the 20th century The Chatham oystercatcher is endemic to the Chatham Islands of New Zealand but is listed as endangered by the IUCN while both the African and Eurasian oystercatchers are considered near threatened There has been conflict with commercial shellfish farmers but studies have found that the impact of oystercatchers is much smaller than that of shore crabs Species Species in taxonomic order Common name Binomial Image Magellanic oystercatcher H leucopodus Blackish oystercatcher H ater Black oystercatcher H bachmani American oystercatcher H palliatus Canary Islands oystercatcher H meadewaldoi African oystercatcher H moquini Eurasian oystercatcher or Palaearctic oystercatcher H ostralegus Pied oystercatcher H longirostris South Island oystercatcher H finschi Chatham oystercatcher H chathamensis Variable oystercatcher H unicolor Sooty oystercatcher H fuliginosus One fossil species is known Haematopus sulcatus Brodkorb 1955 from the early Pliocene of Florida References a b c Hockey P 1996 Family Haematopodidae Oystercatchers in del Hoyo J Elliot A Sargatal J editors 1996 Handbook of the Birds of the World Volume 3 Hoatzin to Auks Lynx Edicions 8487334202 a b Lockwood W B 1993 The Oxford Dictionary of British Bird Names OUP 9780198661962 Jobling James A 2010 The Helm Dictionary of Scientific Bird Names London Christopher Helm pp 184 286 9781408125014 Selous Edmund 1905 The Bird Watcher in the Shetlands London JM Dent Wikisource p 218 Jobling James A 2010 The Helm Dictionary of Scientific Bird Names London Christopher Helm p 184 9781408125014 John B Dunning Jr 1992 CRC Handbook of Avian Body Masses CRC Press p 98 9780849342585 Birds Dumping Eggs on the Neighbors Sciencedailycom 20110603 Retrieved 20121220 Wikispecies has information related to Haematopodidae External links ARKive images and movies of the oystercatcher Haematopus ostralegus Oystercatcher videos on the Internet Bird Collection LIVE webcam at the seashore in Namsos Norway 2013 Taxon identifiers Wikidata Q27515 Wikispecies Haematopus EoL 19930 Fauna Europaea 96894 Fauna Europaea new 96576e7d6e69468eb2ba20a57230a328 Fossilworks 39586 GBIF 2480260 iNaturalist 4837 IRMNG 1395435 ITIS 176468 NBN NBNSYS0000188685 NCBI 32635 NZOR f8618f3996c540398aa2d7179d27fcff WoRMS 147435 Categories Haematopus Birds by common name Shorebirds Haematopodidae

B O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O B O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O B O O O B O O O B O O O O B O O O B O O O B O O B O O O B O O O O B O O O B O O O B O O O B O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B

oystercatcher
haematopodidae
single genus


P B Jayasundera From Wikipedia the free encyclopedia Punchi Banda Jayasundera is a Sri Lankan economist He was the former Permanent Secretary of the Ministry of Finance Treasury on multiple occasions Contents 1 Education 2 Career 21 Central Bank 22 Ministry of Finance 23 Removal from public office 24 Flight 3 See also 4 Education Jayasundera graduated from University of Sri Lanka Colombo in 1973 with a BA in Economics he also gained Masters in Development Economics from Williams College in 1980 and a PhD in Economics from Boston University in 1984 Career Central Bank He joined the Central Bank of Sri Lanka as an economist in the 1974 and was later promoted to senior economist in the 1980s following his postgraduate studies in the United States Ministry of Finance In 1990 he was seconded to the Treasury Ministry of Finance as an Economic Advisor in 1990 on secondment In 1995 he was appointed as Director General Department of Fiscal Policy and Economic Affairs in the Ministry of Finance and from 1997 to 1999 he served as the Deputy Secretary to the Treasury He served as Secretary to the Treasury and Permanent Secretary of the Ministry of Finance from 1999 to 2001 He then served as Chairman Public Enterprises Reform Commission Senior Policy Advisor Ernst Young Sri Lanka and as consultant to the IMF and the World Bank in Sri Lankan assignments Jayasundera was reappointed as Secretary to the Treasury and Ministry of Finance in 2004 Removal from public office In 2008 he was found guilty by the Supreme Court of Sri Lanka of a violation of procedure in the awarding of a large contract for the expansion of the Port of Colombo The court barred him from holding any public office As a result he resigned from all public offices he held at the time In 2009 on invitation by then President Mahinda Rajapaksa to PB Jayasundera to once again take up the post of treasury secretary he submitted a fundamental rights petition protesting the original decision to the Supreme Court which was heard by the newly appointed Chief Judge who overturned the previous decision and allowed Jayasundera to be reinstated as secretary of the treasury Flight On the day before the 2015 presidential election at which Mahinda Rajapaksa was defeated Jayasundera left the country to Singapore He was replaced the day after the election by Dr R H S Samaratunga as secretary of the treasury See also List of Sri Lankan noncareer Permanent Secretaries References LMSL controversy heats up a b c Dr P B Jayasundera and the Sri Lankan Economy Jayasundara steps down from public office wants to read books Transparency and Public Accountability Fiscal Mismanagement Lack of Public Accountability Case Study Sri Lanka a Country Under the Purview of IMF World Bank and ADB Constitution and Social Contract Rule of Law Attorney General and the Judiciary Nivard Dilan Nalaka resign PB overseas Categories Living people Sri Lankan economists Sri Lankan bankers Alumni of the University of Sri Lanka Williams College alumni Boston University alumni Sinhalese civil servants Permanent secretaries of Sri Lanka

O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O B I O O O O O O O O O O O O O O O O O O O O O O

p . b . jayasundera
ministry of finance & treasury