2 22 15 Biochemistry 401 Lecture 21 Transporting Reducing Equivalents into the Mitochondrial Matrix Cytochrome c Complex IV Oxidative Phosphorylation Overview Electron Transport Chain ETC Integral membrane electron carriers Mobile electron carriers Following electrons through the electron transport chain How do reducing equivalents get from the cytoplasm into the mitochondrial matrix Glycerol 3 phosphate Shuttle 1 Reduction of DHAP to Glycerol 3P 2 Reduction of FAD to FADH2 3 Reduction of MT e carrier Q to QH Mobile inner mitochondrial membrane e carrier Q Ubiquinone oxidixed QH2 Ubiquinol reduced 1 2 22 15 Malate Aspartate Shuttle Malate dehydrogenaseC Aspartate amino transferaseC Aspartate amino transferaseMT Malate dehydrogenaseMT 1 6 NOTES to Help you no audio 2 5 5 6 1 IN Cyto OAA reduced to Malate Malate Dehydrogenasecyto 2 Malate transported into MT 3 4 3 IN MT Malate oxidized to OAA Malate DehydrogenaseMT 4 IN MT Glu is deaminated to make KG NH3 group from Glu is transferred to OAA to make Asp Aspartate AminotransferaseMT 5 Aspartate KG transported to Cyto 6 IN Cyto Asp deaminated makes OAA NH3 group from Asp is transferred to KG to make Glu Aspartate AminotransferaseCyto Glu transported into MT Aspartate Amino Transferase NH NH3 3 Ketoglutarate Glutamate Oxaloacetate Aspartate 2 2 22 15 4C 3C 5C Amination changes these alpha keto acids to alpha amino acids Can you name these amino acids 3C 4C O 5C O NADH FADH2 Glycolysis Fatty Acid Catabolism TCA Cycle NADH and FADH2 carriers of electrons with high transfer potential Electrons are transferred and energy released during this transfer can be used to do work energy NADH FADH2 Highest electron transfer potential energy energy eCarrier 2eOther ecarriers 1 2O2 Lowest electron transfer potential 3 2 22 15 Highest NADH FADH2 energy eCarrier Other ecarriers energy 2e1 2O2 Lowest electron transfer potential Electron transfer potential can be quantified through the use of the expression E 0 This term refers to a molecule s reduction potential These two terms are interrelated this way G nF 0 n number of electrons F Farraday s constant 96 48 kJ mol 1 V 1 The more negative the E o the greater the electron transfer potential of the reductant and the greater the tendency to donate electrons The more positive the greater the tendency to accept electrons 3 2 1 1 2 O2 NADH H H2O NAD 2 1 2 O2 2H 2e H2O 0 0 82V 3 NAD H 2e NADH 0 0 32V 4 NADH NAD H 2e 0 0 32V Solve for G for each half reaction G nF 0 Flipped so flip sign Rxn 2 G 2 96 48kJmol 1 V 1 0 82 V 158 23 kJmol 1 Rxn 4 G 2 96 48kJmol 1 V 1 0 32 V 61 8 kJ mol 1 Sum 2 4 G 158 23 kJmol 1 61 80 kJmol 1 220 03 kJmol 1 4 2 22 15 3 Electron carriers in ETC Complex I FADH FADH Glycerol 3 phosphate Shuttle Complex II Complex III Complex IV H H Cytochrome c H e 1 2O2 H 2O 5 2 22 15 Coenzyme Q10 Fully oxidized Fully reduced Which one is this Ubiquinone or ubiquinol Ubiquinone ubiquinol have a long hydrocarbon tail H H Cytochrome c H e 1 2O2 H 2O 6 2 22 15 Oxygen is held in place as a peroxide bridge between an iron and copper metal ion Histdine with a tyrosine adduct Addition of 2 protons 2 electrons Yields 2 hydroxyl groups Additional 2 protons 2 electrons releases 2 H2O Complex I NADH Q oxidoreductase NADH dehydrogenase Accepts e from NADH passes e to ubiquinone Pumps protons into intermembrane space Complex II Succinate Q reductase succinate dehydrogenase same enzyme as in TCA cycle Accepts e from FADH2 passes e to ubiquinone to form ubiquinol Does NOT pump protons into intermembrane space Complex III Q cytochrome c oxidoreductase Accepts e from ubiquinol Passes e to cytochrome c Pumps protons into intermembrane space Complex IV Cytochrome c oxidase accepts e from cytochrome c Passes e to molecular oxygen Pumps protons into intermembrane space Integral membrane Electron carriers Mobile electron carriers Ubiquinone fully oxidized ubiquinol fully reduced Co Enzyme Q Hydrophobic travels within the inner membrane Accepts e from Complex I Q NADH oxidoreductase Complex II Succinate Q reductase Glycerol 3 Phosphate Shuttle carries e to Complex III Q cytochrome c oxidoreductase Cytochrome c Hydrophilic travels in the intermembrane space Accepts electrons from Complex III Q cytochrome c oxidoreductase Carries e to Complex IV Cytochrome c oxidase 7 2 22 15 Iron sulfur centers Copper containing centers FMN Iron sulfur centers Iron containing cytochromes Coper containing cytochromes Copper containing centers Iron and copper containing cytochromes This is the end of Lecture 21 Have a great day 8
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