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UIUC MCB 450 - Lecture 18 MCB450-F15 RF

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PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Cytochrome c StructureSlide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Lecture 18 – (Ch 20) The Electron Transport ChainOxidation-Reduction reactionsDefinition of ξ° (standard reduction potential)′Organization of the ETC is according to increasing ξ′ values.The components of the mitochondrial ETC The path of e- flow and concomitant H+ transfer in the ETC.ROS1How do cells oxidize NADH and FADH2 and convert their reducing potential into the chemical energy of ATP?Overview of the process of complete oxidation of glucose under aerobic conditions (Glycolyis + TCA Cycle + Oxidative Phosphorylation)Cellular Respiration: generation of High-transfer potential electron by TCA, their flow through respiratory chain, and synthesis of ATP.2pyruvate Mitochondrial functions are localized in specific compartments (eukaryotes)Results from Endosymbiotic events, most likely from Rickettsia prowazekii3Cellular RespirationIIIIIIIV45Reduction of NAD+6Oxidation --- Loss of e-B is getting oxidized  B is a Reducing Agent (RA). A strong reducing agent readily donates electrons and has a negative redox potential (E0’)A is getting reduced  A is an Oxidizing Agent (OA). A strong oxidizing agent readily accepts electrons and has a positive redox potential (E0)′The reduction potential E0 (′ ξ° )′ , or redox potential, is a measure of a molecule’s tendency to donate or accept electrons.7 Aox + Bred Ared + BoxMeasuring Redox Potential (electromotive force)oxidizedreducedTogether the oxidized and the reduced forms of the substance are referred to as a ‘redox couple’1 M Fumarate1 M Succinate8E’o (Standard Reduction Potential) values can be used to predict the direction of redox reactionsThe E o (std state reduction potential), refers to the partial reactions writen as ′Oxidant + e- -> Reductant.9pH 7.0E°= +0.77 VAn Electrochemical CellE°cell = Ered + Eox 1. Cu+ + Fe3+ Cu2+ +Fe2+ E°cell = (-0.16) + 0.77oxoxred redE°= -0.16 VE°= +0.77 VAn Electrochemical CellE°cell = Ered + Eox 1. Cu+ + Fe3+ Cu2+ +Fe2+ E°cell = (-0.16) + 0.77oxoxred redE°= -0.16 VFe2+  e- + Fe3+Cu2++ e-  Cu+Predict the direction of redox reactionsConsider the oxidation of NADH during Oxidative Phosphorylation: NADH + H+ + ½O2  NAD+ + H2O red ox ox redThis involves the following two half reactions:(1) NAD(1) NAD++ + 2e + 2e-- + 2H + 2H++  NADH + H NADH + H+ + E’°° = - 0.32 V (from table) = - 0.32 V (from table)(2) ½ O(2) ½ O22 + 2H + 2H++ + 2e + 2e- -  H H22O O E’°° = +0.816 V (from table) = +0.816 V (from table)Since we are looking for oxidation of NADH, reverse reaction 1 so that it is writen as oxidation, [Note: E’° (2) > E’° (1)](3) NADH + H+  NAD+ + 2H+ + 2e- E’° = +0.32 VNow, add reactions 2 and 3 to get the overall reaction as writen above:NADH + H+ + O2  NAD+ + H2O ΔE’° (whole reaction) = E’° (2) + E’°(3) = (+0.816 + 0.32) V = +1.136 V12Relation between E° (Std Reduction Potential) and ΔG°′ (Std State Free Energy) of a redox reaction ΔG°′ = -nFΔE’°ΔG°’ is the standard state free energy change of the whole reactionΔE’° is the standard state reduction potential difference between the two half cells n is the number of e- transferred F is Faraday’s constant. F = 96,500 Coulomb/ mol or 96500 JV-1mol-1 (since, 1C = 1 JV-1) = 96.5 kJV-1mol-1Should be able to calculate ΔG° from self-calculated / given ′ ΔE’° of a whole redox reaction13E° (Std Reduction Potential) values can be used to predict the direction of redox reactionsConsider the oxidation of NADH during Oxidative Phosphorylation:NADH + H+ + ½O2  NAD+ + H2O red ox ox redΔE’° (whole reaction) = +1.136 VΔ°G = -nF′ ΔE’° = -(2)(96.5 kJV-1mol-1)(+1.136 V) = -219.3 kJ/mol  large –ve value  Reaction very spontaneous14The Electron Transport Chain424Correction: Cyt c Is soluble in the intermembrane space NOT the matrixalso to QH2 poolDoes NOT go through IICyt cX15Electrons flow down an energy gradient16FMN = oxidized flavin mononucleotideComplex I – NADH-Q reductase complexmatrix17NADH + Q + 5 H+(Matrix)  NAD+ + QH2 + 4 H+ (intermembrane)Iron–sulfur clusters 2Fe-2S cluster 4Fe-4S cluster18FMN = oxidized flavin mononucleotideComplex I – NADH-Q reductase complexmatrix19NADH + Q + 5 H+(Matrix)  NAD+ + QH2 + 4 H+ (intermembrane)Coenzyme Q is derived from isoprene20Coenzyme Q/Ubiquinone (UQ)/ Q10•A mobile e- carrier•Highly hydrophobic•Freely diffuses in the hydrophobic core of the inner mitochondrial membrane.21CoQ can exist in one of three oxidation statesComplex II – Succinate-Q Reductase complexSuccinate dehydrogenaseSuccinate + Q -- > Fumarate + QH223Complex III – Q-Cytochrome C Oxidoreductase(Ubiquinone)Q pool(Q/QH2)matrixcytochrome C (Cyt C)Q pool(Q/QH2)24Complex III – Q-Cytochrome C Oxidoreductase25Q pool(Q/QH2)matrixQ pool(Q/QH2)cytochrome C (Cyt C)2H+Complex III – Q-Cytochrome C OxidoreductaseQ pool(Q/QH2)Q pool(Q/QH2)26QH2 + 2 Cyt-Cox + 2 H+ (Matrix)  Q + 2 Cyt-Cred + 4 H+ (Intermembrane)Q pool(Q/QH2)Cytochrome c Structure27Oxidized (Fe3+)Reduced (Fe2+)Complex IV (Cytochrome c Oxidase) - Overview 28Complex IV Mechanism29Complex IV (Cytochrome c Oxidase) - Summary ∆G°’ = -231.8 kJ mol-1304 Cyt cred + O2 + 8 H+ (matrix)  4 Cyt cox + 2 H2O + 4 H+ (intermembrane)Oxidative Phosphorylation4x4x2x31The Dangerous side to Cellular RespirationReactive Oxygen Species (ROS) & Free Radicals2%-4% of oxygen molecules consumed by mitochondria are converted into superoxide ions.32Bad side of ROS-Lipid peroxidation (membrane damage) Polyunsaturated fat only -DNA damage ( 10,000 oxidative hits/day)-Protein oxidation33•ROS-damaged proteins and lipids become reactive radical species themselves and help spread the damage•The mutation rate for Mitochondial DNA is 10-20 fold higher than nuclear DNA- Due in large part to ROS produced during oxidative phosphorylation•Heart’s


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UIUC MCB 450 - Lecture 18 MCB450-F15 RF

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