17. biological oxidation

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17. biological oxidation

  1. 1. BIOLOGICAL OXIDATION
  2. 2. Biological oxidation is the process in which substances (carbohydrate, Lipid, AAs) are oxidized in living organism.
  3. 3. Oxidation types: Dehydrogenation Electron lost Oxygenation
  4. 4. Nature of biological oxidation : 1. 37℃ , pH 7.4, enzymatic reaction. 2. Energy released gradually. 3. Formation of H2O. 4. Formation of CO2 by decarboxylation.
  5. 5. General situation of biological oxidation glycogen cytosol Mit. 1/2 O2 G lipids proteins glycerol, FAs AAs 2H first phase second phase acetyl CoA Pyr CoASH ATP ADP + Pi 2H oxidative H2O phosphorylation third phase TCAC CO2
  6. 6. §1 Respiratory Chain §2 Oxidative Phosphorylation §3 ATP §4 Shuttle Systems
  7. 7. § 1 Respiratory Chain
  8. 8. A chain in the mitochondria consists of a number of redox carriers for transferring hydrogens removed from the substrate to oxygen to form water. The chain is termed a respiratory chain, also called electron transport chain (ETC).
  9. 9. COMPOSITION OF RESPIRATORY CHAIN COMPLEXES Prosthetic Groups Complexes Name Complex I NADH-CoQ Reductase Complex II Succinate-CoQ FAD, Fe-S Reductase Complex III CoQ-Cyt c Reductase iron-porphyrine Fe-S Complex IV Cytochrome Oxidase iron-porphyrine Cu FMN, Fe-S
  10. 10. Position of Respiratory Chain Complexes
  11. 11. Order of Respiratory Chain Complexes NADH succinate FMN £¨ Fe-S£© compex I FAD £¨ Fe-S£© compex II CoQ Cyt b, c1 £¨ Fe-S£© compex III Cyt c Cyt aa3 compex IV O2
  12. 12. Composition of ETC    Hydrogen carrier :                         NAD + FMN FAD CoQ    electron carrier : Fe-S                 Cyt
  13. 13. 1. Nicotinamide coenzymes  NAD+/NADH (Nicotinamide Adenine Dinucleotide, CoⅠ )  NADP+/NADPH (Nicotinamide Adenine Dinucleotide Phosphate, CoⅡ ) The nicotinamide is the vitamin Niacin B3
  14. 14. NAD+ NH2 CONH2 N H OH H N O H CH2 OH O H N O P OH O O P N N O CH2 OH H O H H H OH OH
  15. 15. NADP+ NH2 CONH2 N H H CH2 OH OH H O H N N O O P OH O O P N N O CH2 OH O H H H H OH O O P OH OH
  16. 16. H H CONH2 H CONH2 + H + H++ e N N R +H+ R NAD +/NADP + NADH/NADPH
  17. 17. 2. Flavin prosthetic groups FMN: Flavin Mononucleotide FAD: Flavin Adenine Dinucleotide They contain the riboflavin (Vit B2).
  18. 18. FMN O Isoalloxazine H3C H3C N 5 8 4 NH 10 9 1 N H C H ribitol O N C OH H H C OH H C OH CH2 O O P OH OH
  19. 19. O H3C H3C N 5 4 NH 10 8 9 1 N H FAD N O NH2 C H H C OH N H C OH H C OH CH2 O N O P O O OH OH P N N O CH2 H O H H H OH OH
  20. 20. O H3C H3C N 5 10 8 9 N 4 NH 1 N R FMN/FAD O H3C + 2H H3C H N 5 10 8 9 N R O 4 NH 1 N H FMNH2/FADH2 O
  21. 21.  NAD+ is a coenzyme, that reversibly binds to enzymes.  FAD is a prosthetic group, that remains tightly bound at the active site of an enzyme.
  22. 22. 3. Fe-S Iron-sulfur centers (Ironsulfur protein, Fe-S) are prosthetic groups containing 2, 3, 4 or 8 nonheme iron atoms complexed to elemental and cysteine S.
  23. 23. Cys S S S Cys Cys Fe Fe Fe S S S Cys S S Fe Cys S S Fe Cys S S Cys S Cys Fe S Iron-sulfur centers
  24. 24. 2 Fe iron-sulfur center of ferredoxin. 2 Fe colored orange; elemental & Cys S yellow.
  25. 25. Different types of iron-sulfur centers
  26. 26. Iron-sulfur centers transfer only one electron. Fe3+ + e- Fe2+
  27. 27. 4. CoQ Coenzyme Q (CoQ, ubiquinone) is very hydrophobic. It dissolves in the membrane. Coenzyme Q functions as a mobile e- carrier within the mitochondrial inner membrane.
  28. 28. O H3CO CH3 (CH2 H3CO O CoQ CH3 C H C CH2)nH CH3 H2C C C H isoprene CH2
  29. 29. O CH3O OH CH3 CH3O CH3 CH3O R + 2H CH3O R O ubiquinone OH ubiquinol
  30. 30. 5. Cytochromes Cytochromes (Cyt) are proteins with heme prosthetic groups. They absorb light at characteristic wavelengths.  Hemes in the 3 classes of cytochrome (a, b, c) differ slightly in substituents on the porphyrin ring system.
  31. 31.  Hemes a & a3 are often referred to as cytochromes aa3.  Cytochrome c is a small, watersoluble protein with a single heme group.
  32. 32. CH2 Heme b CH3 O N HC N − OOC CH2 CH2 CH Fe CH3 N CH N CH2 CH2 COO− CH3 CH2
  33. 33. Heme c CH3 CH3 HC S N H3C N Fe CH3 N − OOC CH2 CH2 CH N CH2 CH2 COO− CH2 protein CH3 CH3 S CH2 protein
  34. 34. Heme c
  35. 35. Cytochrome c heme Lys13 complex IV _ _ ++ _ + cyt. c Lys 72
  36. 36. CH3 Heme a CH2 CH3 O N OOC CH2 CH2 Fe CH2 COO− C CH3 N CH N CH2 CH OH N HC − HC CH2 CH3 CH2 CH2 3 H
  37. 37. The heme iron can undergo an electron transition between ferric and ferrous states: Fe3+ + e- Fe2+
  38. 38. The sequence of the components in the respiratory chain has been deduced in several ways. 1. Inhibitor. 2. O2 is suddenly introduced into the system. 3. Standard redox potential.
  39. 39. INHIBITOR
  40. 40. 1. NADH respiratory chain : 2. Succinate respiratory chain : CoQ succinate £¨ FAD Fe-S£© Cyt b c1 c aa3 O2
  41. 41. succinate malate -glycerophosphate ¦Â -hydroxy fatty acyl CoA ¦Á ¦Â -hydroxybutyrate isocitrite FAD Glu £¨ Fe-S£© NADH FMN CoQ £¨ Fe-S£© Cyt b c1 FAD FAD lipoic acid pyruvate ¦Á -ketoglutarate fatty acyl CoA c aa3 O2

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