Lecture'18'*'Chapters'20'The'Electron'Transport'Chain!“In$all$things$in$nature,$there$is$something$of$the$marvelous.”$Aristotle$(384;322$B.C.)$''''Wall'Piece'#IV'(1985),'a'kineCc'sculpture'by'George'Rhoads.'1'EssenCal'QuesCon'How'do'cells'oxidize'NADH'and'FADH2'and'convert'their'reducing'potenCal'into'the'chemical'energy'of'ATP?'2'Outline'§ OxidaCon*ReducCon'reacCons'§ DefiniCon'of'ξ°ʹ′'(standard'reducCon'potenCal)'§ OrganizaCon'of'the'ETC'is'according'to'increasing'ξʹ′'values.'§ The'components'of'the'mitochondrial'ETC'§ 'The'path'of'e*'flow'and'concomitant'H+'transfer'in'the'ETC.'§ ROS'3'Overview'of'the'process'of'complete'oxidaCon'of'glucose'under'aerobic'condiCons'''''''''''(Glycolyis'+'TCA'Cycle'+'OxidaCve'PhosphorylaCon)'Cellular'RespiraCon:'generaCon'of'High*transfer'potenCal'electron'by'TCA,'their'flow'through'respiratory'chain,'and'synthesis'of'ATP.'4'pyruvate''Mitochondrial'funcCons'are'localized'in'specific'compartments''''''''''''''''''''''''''''''''''''''''''''''''(eukaryotes)'Results'from'EndosymbioCc'events,'most'likely'from'RickeCsia$prowazekii$5'Cellular'RespiraCon'I!II!III!IV!Proton*moCve'force'6'hep://classes.midlandstech.edu/carterp/courses/bio225/chap05/lecture3.htm'ReducCon'of'NAD+'7'''''Aox'''+''''Bred''''''''''''''''''''''''Ared''''+''''''Box'ReducCon'***''Gain'of'e*'OxidaCon'***''Loss'of'e*'B'is'geing'oxidized'à'B'is'a'Reducing'Agent'(RA).'''A'strong'reducing'agent'readily'donates'electrons'and'has'a'nega&ve'redox'potenCal'(E0’)'A'is'geing'reduced'à'A'is'an'Oxidizing'Agent'(OA).'''A'strong'oxidizing'agent'readily'accepts'electrons'and'has'a'posi&ve!redox'potenCal'(E0ʹ′)'The'reducCon'potenCal'E0'ʹ′(ξ°ʹ′),'or'redox'potenCal,'is'a'measure'of'a'molecule’s'tendency'to'donate'or'accept'electrons.'8'Measuring'Redox'PotenCal'(electromoCve'force)'oxidized'reduced'Voltmeter'Together'the'oxidized'and'the'reduced'forms'of'the'substance'are'referred'to'as'a'‘redox'couple’'1'M'Fumarate'1'M'Succinate'9'ξ’o'(Standard'ReducCon'PotenCal)'values'can'be'used'to'predict'the'direcCon'of'redox'reacCons'The'ξʹ′o'(std'state'reducCon'potenCal),'refers'to'the'parCal'reacCons'wrieen'as'Oxidant'+'e*'*>''Reductant.'pH'7.0'Fe'3+''''''''''''''''''''''''Fe'2+'''''''''''''''''''''''''1''''''''''''''''''''''''Cu'2+'''''''''''''''''''''''' Cu'+'''''''''''''''''''''''''1'''''''''''''''''''''''''+0.77'''''''''''''''''''''''''+0.16''''''''''''''''''''''''10'E°='+0.77'V'An'Electrochemical'Cell'E°cell'='Ered'+'Eox'E°='*0.16'V''1.'Cu+'+'Fe3+'èCu2+'+Fe2+'''''E°cell'=''(*0.16)'+'0.77''ox'ox'red' red'E°='*0.16'V'An'Electrochemical'Cell'E°cell'='Ered'+'Eox'Fe2+''è''e*'+''Fe3+'E°='*0.77'V'2.'Cu2+'+Fe2+'è'Cu+'+'Fe3+'''''E°cell'=''0.16'+'(*0.77)''ox'ox' red' red'Cu2++'e*''è'Cu+'E°='+0.16'V'12'Predict'the'direcCon'of'redox'reacCons'Consider!the!oxida&on!of!NADH!during!Oxida&ve!!Phosphoryla&on:!''''''''''''''''NADH'+'H+'+'½O2'à'NAD+'+'H2O'''''''''''''''''''''red'''''''''''''''''ox''''''''ox''''''''red'This'involves'the'following'two'half'reacCons:'(1)'NAD+'+'2e*'+'2H+'à'NADH'+'H+''''''''''''''''ξ°ʹ′'='*'0.32'V'(from'table)'(2)'½'O2'+'2H+'+'2e*'à'H2O'''''''''''''''''''''''''ξ°ʹ′'='+0.816'V'(from'table)''Since'we'are'looking'for'oxidaCon'of'NADH,'reverse'reacCon'1'so'that'it'is'wrieen'as'oxidaJon,''[Note:''ξ°ʹ′'(2)'>'ξ°ʹ′'(1)]''(3)'NADH'+'H+'à'NAD+'+'2H+'+'2e*'''''''''''''''ξ°ʹ′'='+0.32'V''Now,'add'reacCons'2'and'3'to'get'the'overall'reacCon'as'wrieen'above:''NADH'+'H+'+'O2'à'NAD+'+'H2O''''''''Δξ°ʹ′'(whole'reacCon)'='ξ°ʹ′'(2)'+'ξ°ʹ′(3)''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''='(+0.816'+'0.32)'V'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''='+1.136'V'''13'RelaCon'between'ξ°'(Std'ReducCon'PotenCal)'and'ΔG°ʹ′'(Std'State'Free'Energy)'of'a'redox'reacCon' ΔG°′ = -nFΔξ°′ ΔG°ʹ′''is'the'standard'state'free'energy'change'of'the'whole'reacCon'Δξ°ʹ′'''is'the'standard'state'reducCon'potenCal'difference'between'the'two'half'cells''n''''''''is'the'number'of'e*'transferred''F''''''''is'Faraday’s'constant.''F'='96500'Coulomb'/'mol'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''or'''''''''''''''''''''''''''''''''''''''''''''''''''''''''96500'JV*1mol*1'(since,'1C'='1'JV*1)'''''''''''''''''''''''''''''''''''''''''''''''''''''''='96.5'kJV*1mol*1'Should'be'able'to'calculate'ΔG°ʹ′'from'self*calculated'/'given'Δξ°ʹ′'of'a'whole'redox'reacCon'14'ξ° (Std Reduction Potential) values can be used to predict the direction of redox reactions Consider the oxidation of NADH during Oxidative Phosphorylation: NADH + H+ + ½O2 NAD+ + H2O red ox ox red Δξ°′ (whole reaction) = +1.136 V Δ°Gʹ′'='*nFΔξ°ʹ′'='*(2)(96.5'kJV*1mol*1)(+1.136'V)'='*219.3'kJ/mol'''''''''''''à'large'–ve'value''à'ReacCon'very'spontaneous'15'The'Electron'Transport'Chain'4'2'4'CorrecCon:'Cyt'c'Is'soluble'in'the'intermembrane'space'NOT'the'matrix'also'to'QH2'pool'Does'NOT'go'through'II'Cyt!c!X'16'Electrons'flow'down'an'energy'gradient'+0.82'17'FMN'='oxidized'flavin'mononucleoCde'Complex'I'–'NADH*Q'reductase'complex'matrix'18'Iron–sulfur'clusters''2Fe-2S cluster '4Fe-4S cluster'19'FMN'='oxidized'flavin'mononucleoCde'Complex'I'–'NADH*Q'reductase'complex'matrix'20'Coenzyme'Q'is'derived'from'isoprene.''21'Coenzyme'Q/Ubiquinone'(UQ)/'Q10'It'is'a'mobile'e*'carrier.'It'is'highly'hydrophobic'and'freely'diffuses'in'the'hydrophobic'core'of'the'inner'mitochondrial'membrane.'22'e*'+'H+'2e*'+'2H+''e*'+'2H+'e*''2e*'+'2H+'CoQ'can'exist'in'one'of''three'oxidaCon'states'/UQ)!/UQH2)!23'Complex'II'–'Succinate*Q'Reductase'complex'Succinate'dehydrogenase'Succinate'+'Q'èFumarate'+'QH2'24'Complex'III'–'Q*Cytochrome'C'Oxidoreductase'(Ubiquinone)'Q._!Q'pool'(Q/QH2)'matrix'cytochrome'C'(Cyt'C)'Q'pool'(Q/QH2)'25'Complex'III'–'Q*Cytochrome'C'Oxidoreductase'(Ubiquinone)'Q._!Q'pool'(Q/QH2)'matrix'cytochrome'C'(Cyt'C)'Q'pool'(Q/QH2)'26'Complex'III'–'Q*Cytochrome'C'Oxidoreductase'matrix'Q'pool'(Q/QH2)'Q'pool'(Q/QH2)'Q'pool'(Q/QH2)'27'Cytochrome'c'Structure'Heme'A'Iron'λ=550'nm'28'Complex'IV'(Cytochrome'c'Oxidase)'*'Overview''29'2'Reduced'Cytochrome'c'1' 2'
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