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31 Cards in this Set
- Front
- Back
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What is the outer membrane of mitochondria permeable to?
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- permeable to small molecules and ions
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What is the inner membrane of mitochondria permeable to?
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- it is impermeable to small molecules and ions
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Oxidative Phosphorylation
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- energy of oxidation drives synthesis of ATP
- occurs in mitochondria - accounts for most of the ATP synthesized by the cell - oxidative phophorylation involves the reduction of O2 to H2O with electron donated by NADH and FADH2 |
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What do dehydrogenases do?
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- collect e- into electron acceptors like NADP+ or FAD
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Chemiosmotic theory
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- e- flow through a chain of membrane bound carriers
- the free energy made available by this "downhill" (exergonic) e- flow is coupled to the "uphill" transport of protons across a proton-impermeable membrane to create the transmembrane electrochemical potential - the transmembrane flow of protons "down" the gradient through specific channels provides the energy for synthesis of ATP |
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NADH dehydrogenases
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reduced substrate + NAD+ <-> oxidized substrate + NADH + H+
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Can NADH cross inner membrane?
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no
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Can e- cross inner membrane?
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yes
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What can FADH2 do that NADH can't?
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- FADH2 can do 1 or 2 e- transfers
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Electron carriers in electron transport chain
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1.) Ubiquinone (hydrophobic)
2.) cytochromes (iron containing) 3.) iron-sulfur proteins |
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Ubiquinone
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- Q
- fully oxidized |
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Semiquinone radical
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- 'QH
- 1 e- and 1 proton |
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Ubiquinol
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- QH2
- fully reduced |
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How many e- does a cytochrome carry?
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1
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How do we measure the state of cytochromes if it's oxidized or reduced?
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by spectrophotometry, they have strong absorption of visible light because of iron
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What are iron-sulfur proteins?
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- the iron is associated with sulfur atoms of Cys residues
- participate in 1 e- transfer in which 1 Fe is oxidized or reduced |
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Succinate goes to ETC through what?
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through flavoproteins
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Experiments to determine sequence of e- carriers
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1.) carriers function in order of increasing reduction potential
2.) loading w/o O2 3.) use inhibiting agents |
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Order of reducing potential
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- lower reducing potential is the least electronegative
- higher reducin potentials is the most electronegative (O2) |
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Loading without O2
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- reducing entire chain by providing an e- source but no e- acceptor (no O2)
- when O2 introduced, the rate at whcih each carrier becomes oxidized reveals order (spectroscopically) - carrier nearest O2 gives up e- first, the 2nd carrier from end is oxidized next (gives up e-) |
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Using inhibitors
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- inhibiting agents inhibit flow of e- w/ measurement of degree of oxidation of each carrier
- in presence of O2 and e- donor, carriers that function before inhibitor become fully reduced, and after are oxidized - before block: can't give e- - after block: can give e- |
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Where in the ETC does cyanide block?
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- the last step from cytochrome to O2
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e- flow to Q in 4 ways
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1.) e- from NADH pass thru a flavoprotein to Fe-S proteins in Complex I and then to Q
2.) e- from succinate pass thru a flavoprotein and Fe-S in Complex II to Q 3.) glycerol 3-phophate donates e- to a flavoprotein then to Q 4.) aCoA dehydrogenase transfers e- to flavoprotein to Q |
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Complex I: NADH:Q oxireductase
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- transfer a hydride ion to FMN where 2 e- pass thru Fe-S proteins forming QH2
- pumps 4 protons from N side to P side |
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Complex 2
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- take 2 e- from FADH to Q
- no protons pumped - succinate to Q |
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Complex III
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- Q -> cytochrome c
- transfer of e- from QH2 to cytochrome c with 4 proton transfer to intermembrane |
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How many cytochrome c needed for 1 Q?
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2 cytochrome c for 1 Q
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How many protons does 1 NADH pump?
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10 protons making 2.5 ATP
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How many protons do FADH pump?
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6 protons making 1.5 ATP
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How many protons needed to make 1 ATP?
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4 protons to make 1 ATP
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Complex IV
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- cytochrome c to O2
- 3 subunits - 2 reduced cyto c each donate 1 e- - e- pass thru heme a to Fe-Cu center - O2 binds to hema a3 and is reduced by 2 e- making O22- - delivery of 2 more e- from cyto c (4e- total) converts O22- to 2 H2O |
