electron transport chain

introduction>what is ETC>location of ECT>component of ETC>end of ETC

1. ELECTRON TRANSPORT CHAIN Presented by :- Prajapati Jinal V . CBO :- 501 M.Sc Sem :- 3 Department of life sciences , H.N.G.U., Patan

2. CONTENT Introduction What is ETC ? Location of ETC Component of ETC End of ETC

3. Introduction An electron transport chain is a series of complex that transfer electron from electron donors to electron acceptors via redox reaction and couples this electron transfer with the transfer of protons across a membrane . This creates an electrochemical proton gradient that drives the synthesis of ATP, a molecule that stores energy chemically in the form of highly strained bonds . The molecules of the chain include peptides ,enzymes and others .

4. The final acceptor of electrons in the electron transport chain during aerobic respiration is molecular oxygen although a variety of acceptors other than oxygen such as sulfate exist in anaerobic respiration . ETC is the 4ᵗ ᵸ and final stage of aerobic respiration . ETC is series of highly organized oxidation – reduction enzymes . The direction of energy flow level in the ETC is form a higher to a lower energy level .

5. What is ETC ? ETC is a process in which the NADH and FADH₂ produced during glycolysis , ᵦ - oxidation and other catabolic processes are oxidized thus releasing energy in the form of ATP . The metabolic Pathway through which the electron passes from one carrier to another is called ELECTRON TRANSPORT CHAIN .

6. Location of ETC This chain is located in the inner mitochondria membrane of cell. Protons are transported from the matrix of the mitochondria across the inner mitochondrial membrane to the intermembrane space located between the inner and outer mitochondrial membrane . The process takes place in units arranged on the cristae membrane of mitochondria .

7. Components of ETC The various components of the respiratory chain occur within the mitochondria . Complex are formed by Proteins . Each of the 4 complexes contain up to 40 individual polypeptide chains . They perform several functions such as enzymatic activities and trans – membrane pumps .

8. The large trans- membrane complexes are called I , II , III and IV and are formed by intergal proteins . There are 4 complex used in electron transport chain . 1 . Complex I ( NADH dehydrogenase ) 2 . Complex II ( Succinate dehydrogenase ) 3 . Complex III ( Cytochrome bc₁ complex ) 4 . Complex IV ( Cytochrome c oxidase )

9. 1 . Complex I (NADH dehydrogenase) :- There are four steps in Krebs cycle in which hydrogen is taken up by NADᶧ to from NADH . The electrons of NADH are oxidized by NADH dehydrogenase of complex I which contains tightly bound cofactors FMN and iron sulphur centers . The electron passed to the next carrier CoQ of ubiquinone which is similar to plastoquinone of the thylakoids of chloroplasts . For every pair of electrons 4 protons are pumped from the matrix to the intermembrane space .

10. 2 . COMPLEX II (Succinate dehydrogenase) :- Succinic acid is the only substance in Krebs cycle which is oxidized by FAD of the enzyme Succinate dehydrogenase of complex II to form FADH₂ . The hydrogen of FADH₂ enters the ubiquinone pool . it does not any proton during transport of electron across the inner mitochondrial membrane .

11. 3 . Complex III ( Cytochrome bc₁ complex ) :- The Ubiquinone is oxidized by this complex . Four protons are out for every 2 electrons transferred to the next carrier . The electron are transferred to cytochrome c via an iron – sulphur center . Two b type cytocromes , cyt b₅₆₅ and cyt b₅₆ₒ and a membrane bound cytochrome c₁.

12. 4 . Complex IV (Cytochrome c oxidase ) :- It has two copper centers – CuA and CuB and cytochrome a and a₃ . The cytochrome a₃ transfer 4 electrons to oxygen which tacks up protons to form two molecules of H₂O . This complex is known as also terminal oxidase . For transfer of 2 electrons 2 protons are pumped into the intermembrane space . Ubiquinone transfer electron between complex I and II wheres cytochrome c transfer eletrons from complex III to IV .

13. End of ETC The protons are shuttled to the outside of the membrane . Inside of the cell membrane as it accepts electrons . At the end of the electron transport chain the electrons are given to oxygen .at the same time oxygen accepts hydrogen to form water . Released in this process to the phosphorylation of ADP to from ATP . ⅟₂O₂ + 2Hᶧ + 2e˗→ H₂O

14. REFERENCES Textbook of PLANT PHYSIOLOGY BY : - V . Verma Plant Physiology by :- LINCOLN TAIZ EDUARDO ZEIGER Principle of biochemistry by :- Albert Leningher

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