BMB 401 EXAM 3 SG - LECTURE 20: TCA Cycle: Reaction 1:...

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Unformatted text preview: LECTURE 20: TCA Cycle: Reaction 1: Condensation rxn driven by CoA hydrolysis Citrate Synthase : * dimer- OAA binds first causing rotation and acetyl CoA binding site to form Reaction 2: Isomerization in 2 steps: Aconitase Reaction 3: * Rate Limiting Step Isocitrate Dehydrogenase : Regulation : Negative: ATP/NADH Reaction 4: * Keto-Gluturate Dehydrogenase Complex : E1,2,3 Regulation: Negative: High Energy/ Product Inhibition Reaction 5: * GTP production from Substrate level phosphorylation by Histidyl Phosphate Succinyl CoA Synthetase *Reactions 6-8 : Rxn 6: Oxidation *Succinate Dehydrogenase : Regulation : Negative: FADH2 Flavin ring is covalently attached to enzyme itself Embedded in the inner MT membrane Also part of ETC Rxn 7: Hydration Fumarase : Fe-S in enzyme helps Stereospecific reaction- Adds H2O trans across double bond Rxn 8: Oxidation G= +7Kcal /mole (rxn must be reversible ) Malate Dehydrogenase : Regulation : Negative: High NADH/NAD + TCA Cycle Regulation: 1. Pyruvate Dehydrogenase Complex: [-] ATP/ NADH, Acetyl CoA [+] ADP, Pyruvate 2. Isocitrate Dehydrogenase: [-] ATP/ NADH 3. Ketoglutarate [-] ATP/ NADH, Succinyl CoA LECTURE 21: Glycerol 3 Phosphate Shuttle : 1. Reduction: DHAP Glycerol 3P 2. Reduction: E-FAD E-FADH 2 3. Reduction: MT e carrier Q QH 2 Malate- Aspartate Shuttle : 1) Malate Dehydrogenase CYTO : Reduction: OAA Malate (transported into MT) 3) Aspartate Aminotransferase MT : NH3 from Glu transferred to OAA. (Asp & -KG transported to Cyto) 2) Malate Dehydrogenase MT : Oxidation: Malate OAA 4) Aspartate Aminotransferase CYTO : NH3 from Asp transferred to -KG. (Glu transported into MT) Electron Transfer Potential: G = - n F n = # of electrons, F = Farradays constant (96.48kJ mol-1 V-1 ) E = change in reduction potential Standard reduction potentials Oxidant Reductant n E O (V) NAD+ NADH + H + 2- 0.32 O 2 + 2 H + H 2 O 2 + 0.82 More NEGATIVE E O : GREATER electron-transfer potential of reductant & GREATER the tendency to DONATE electrons. More POSITIVE E O : GREATER the tendency to ACCEPT electrons. Electron Carrier e- source e- carriers Ultimately reduces : Integral Membrane Proteins: Complex I : NADH-Q oxidoreductase NADH FMN Fe-S centers Ubiquinone Complex II: Succinate-Q oxidoreductase Succinate FAD Fe-S centers Ubiquinone Complex III: Q-cyt c ox red Ubiquinol 3 heme cytochromes Rieske Fe-S centers Cyt c Complex IV: Cyt c oxidase Cyt c CuA/CuA Cyt a Binuclear center: Cyt a3, CuB O2 Mobile Carriers 1. Coenzyme Q Ubiquinone (ox) Complex I Complex II G3P Shuttle Complex III 2. Cyt C Complex III Complex IV * Rieske Fe-S centers (complex III) : Central Fe coordination by Cys & His Coenzyme Q: Ubiquinone (ox) or Ubiquinol (red) Hydrophobic, travels in inner membrane Cytochrome c: Hydrophillic, travels in intermembrane space Complex IV mechanism: Cyt c transfers e (reduces) CuB & Heme a3 Reduced CuB and Fe in Heme a3 bind O2: form H2O2 bridge Addition of 2 e and 2 H cleaves bridge...
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BMB 401 EXAM 3 SG - LECTURE 20: TCA Cycle: Reaction 1:...

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