Term
| Oxidative Phosphorylation- what is it? |
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Definition
- all oxidative steps in degradation of carbs, fats and amino acids converge at this final stage of cellular respiration
- energy of oxidation drives the synthesis of ATP
- mitochondria and chloroplasts
- involves the reduction of O2 to H2O with electrons donated by NADH and FADH2
- oxidative and photophosphorylation both:involve the flow of electrons through membrane bound carriers, the free energy made available by this exergonic electron flow is coupled to uphill transport of protons against a membrane, and the transport of the protons down their [] gradients thru specific channels provides free energy for ATP synthesis
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Term
| What Occur where in the Mitochondria? |
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Definition
- Mitochondrial matrix contains all oxidative pathways except glycolysis (cytosol)
- specific transporters carry pyruvate, fatty acids, and amino acids or their a-keto derivatives from the inner membrane into the matrix for access into the citric acid cycle
- [image]
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Term
| Electrons are Funneled to Universal Electron Acceptors: NAD(+) |
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Definition
- dehydrogenases collect electrons in catabolic pathways and funnel them to electron acceptors-NAD/P(+) or FAD/FMN
- nicotinamine linked dehydrogenases catalyze: reduced substrate + NAD/P(+) <--> oxidized substrate + NADH + H(+)
- NAD linked dehydrogenases romove 2 hydrogens from substrate, one H:(-) goes to NAD(+) and one is released at H(+)
- these are water soluble and associate reversibly with dehydrogenases
- NADH carries electrons from catabolic reactions into resp. chain (NADH dehydrogenase complex)
- NADPH supplies electrons to anabolic reactions
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Term
| Electrons are Funneled to Universal Electron Acceptors: FAD |
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Definition
- dehydrogenases collect electrons in catabolic pathways and funnel them to electron acceptors-NAD/P(+) or FAD/FMN
- flavoproteins contain tightly bound FMN or FAD
- Oxidized flavin nucleotide can accept one electron(semiquinine) or two (FADH2)
- electron transfer occurs because the flavoprotein has higher reduction potential than the compound oxidized
- the std reduction potential of the flavin nucleotide, unlike NAD, depends on the protein with which it is associated(entire flavoprotein)- local interactions with functional groups in the protein distort electron orbits in flavin and relative stabilities of oxidized/reduced forms are changed
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Term
| Electrons Pass Through Membrane Bound Carriers |
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Definition
- Mitochondrial respiratory chain consists of sequentially acting electron carriers, most of whihc are integral proteins with prosthetic groups which accept/donate one or two electrons
- Three types of electron transfers occur in ox. phosphorylation: direct transfer of electrons, transfer as hydrogen atom(H(+) and e(-)) and transfer as two electron hydride ion (:H(-))
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Term
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Definition
- designates a single eectron equivalent transferred in a redox reaction
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Term
| Types of Electron Carrying Molecules in Respiratory Chain |
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Definition
- NAD, Flavoproteins, hydrophobic quinone, cytochromes and iron-sulfur proteins
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Term
| Types of Electron Carrying Molecules in Respiratory Chain: Ubiquinone |
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Definition
- Called Q
- lipid soluble
- can accept one or two electrons and can act at the junction between a two electron donor and a one electron acceptor (like flavoprotein carriers)
- because small and can freely diffuse within the inner mitochondrial membrane, it can shuttle electrons between other less mobile electron carriers
- carries bothe protons and electrons and couples electron flow to proton movement
- [image]
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Term
| Types of Electron Carrying Molecules in Respiratory Chain: Cytochromes |
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Definition
- Strong absorption of visible light
- three types: a,b,c
- prosthetic groups have porphyrin with central Fe atom
- std reduction potential depends on interaction w/ protein side chains
- mostly inner mitochondrial membrane proteins
- [image]
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Term
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Definition
- participate in one-electron transfers in which one iron atom of iron-sulfur cluster is oxidized or reduced
- [image]
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Term
| Sequence of Electron Carriers |
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Definition
- standard reducton potentials of individual electron carriers are known, and those with lower reduction potential transfer their electrons to those with higher electron potentials
- order is: NADH-->Q-->cytochrome b-->cytochrome c1-->cytochrome c-->cytochome a-->cytochrome a3-->O2
- this may/may not be cellular order because cells have varying [oxidzed]:[reduced] carriers
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Term
| Electron Carriers Function in Multienzyme Complexes |
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Definition
- A membrane embedded supromelecular complex of all electron carriers can be separated into four complexes
- complexes I and II transfer electrons to ubiquinone from two different electron donors: NADH(complexI) and Succinate (complex II)
- complex III carries electrons from reduced ubiquinone to cytochrome c
- complex IVtransfers electrons from cytochrome c to O2
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Term
| Complex I: NADH to Ubiquinone |
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Definition
- also called NADH dehydrogenase
- catalyzes two simultaneous and coupled processes: 1) exergonic transfer to ubiquinone of a hydride ion from NADH and a proton from the matrix
- NADH + H(+) + Q--> NAD(+) + QH2
- and 2)endergonic transfer of four protons from the matrix to the intermembrane space
- complex I is a proton pump driven by electron transfer( and intermembrane space becomes positively charged)
- QH2(ubiquinol) diffuses from complex I to III where it is oxidized to Q in a process that involves the outward movement of H(+)
- [image]
- [image]
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Term
| Complex II: Succinate to Ubiquinone |
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Definition
- succinate dehydrogenase
- A transmembrane complex with 5 prosthetic groups and four subunits
- [image]
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Term
| Complex III: Ubiquinone to Cytochrome C |
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Definition
- couples transfer of electrons from QH2 to cytochrome C while transporting protons from the matrix to the intermembrane space
- add Q cycle and complex III pictures
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Term
| Complex IV: Cytochrome C to O2 |
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Definition
- in the final step of the respiratory chain, complex IV carries electrons from cytochrome c to O2, forming water
- for every four electrons passing through this complex, the enzme consumes four substrate H(+)'s from the matrix side of the complex
- it uses the energy of this redox reaction to pump one proton outward into the intermembrane space for ea/ electron that goes through, adding to the electrochemical potential created by complexes I and III
- overall rxn is 4 Cyt c(reduced) + 8 H(+) + O2 --> 4 Cyt c (oxidized) + 4 H(+) + 2 H2O
- (show figure 19-14)
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Term
| The Energy of Electron Transfer is efficiently conserved in a proton gradient and summary of reaction |
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Definition
- Transfer of 2 electrons from NADH in the resp. chain: NADH + H(+) + 1/2 O2-->NAD(+) + H2O
- very exergonic, - 220kj/mol
- high energy is used to pump protons out of the matrix
- for each pair of electrons transferred to O2, 4 protons are pumped out by complex I, four by complex III and 2 by complex IV
- NADH + 11H(+) + 1/2 O2--> NAD(+) + 10H(+) + H2O
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Term
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Definition
- electrochemical energy inherent in difference in proton concentration and separation of charge represents a stored energy - called proton motive force
- 2 components: 1) chemical potential energy due to the differential concentration of a chemical species(H(+) separated by a membrane 2)electrical potential energy that results from the separation of charge when a proton moves across a membrane w/o counter ion
- when protons spontaneously flow down their electrochemical gradient, energy is made available to do work. this drives the synthesis of ATP
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Term
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Definition
- Chemiosmotic model:
- electrochemical gradient due to proton concentration and separation of charge accross the inner mitochondrial membrane.
- This drives the synthesis of ATP as protons flow down the [] gradient through a pore associated with ATP synthase
- show figure 19-19
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