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21 Cards in this Set
- Front
- Back
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Chemoosmotic theory |
E to convert ADP to ATP is provided by a flow of e- down the electrochemical gradient The E released is used to transport protons against the gradient |
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E coupling requires membranes |
The proton gradient needed for ATP synthesis is across the membrane: Plasma membrane in bacteria, inner membrane of mitochondria, and thylakoid membrane in chloroplasts Membrane must contain proteins that couple the downhill flow of e- with the uphill flow of H+ |
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Structure of mitochondria: double membrane leads to 4 compartments |
1. Outer membrane: porous 2. Intermembrane space : higher H+ concentration (low pH) 3. Inner membrane: mostly impermeable w H+ gradient across it, location of ETC complexes, cristae increase surface area 4. Matrix: location of TCa cycle, part of lipid and AA metabolism, lower H+ concentration (high pH) |
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Electron transport chain uses a series of e- carriers |
Multiple redox centers at each complex: Flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), cytochromes a, b, c, iron-sulfur cluster Order of transfer depends on reduction potential Ends with O being reduced to water |
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FMN and FAD : e- funnels |
Can bind to proteins to funnel and distribute e- Accept 2 e- from carrier and donate 1 e- at a time |
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Cytochromes |
One-electron carriers Do so by iron coordinating porphoryn ring a, b, c differ by ring additions |
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Iron sulfur clusters |
One-electron carriers Coordinating by cysteines in proteins Contain equal number of iron and sulfur atoms |
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Coenzyme Q (ubiquinone) |
Lipid soluble, carries 1 or 2 e- If accepts 2 e-, called ubiquinol which can freely diffuse carrying e- from one side of membrane to other Mobile carrier and transports e- from complex I, II, and III. |
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Complex I: ubiquinone oxireductase |
Largest macro-molecule in mammals NADH binding site on matrix side FMN accepts 2 e- from NADH Several iron sulfur centers pass one e- at a time toward the Q binding site |
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It is a proton pump |
Transfer 2 e- from NADH to Q is accompanied by a transfer of H+ from the matrix (N) to the intermembrane space (P). 4 H+ per NADH transferred Proteins are transported by protein wires |
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Complex II: Succinate dehydrogenase |
FAD accepts 2 e- from succinate e- are passed one at a time via iron-sulfur centers to Q becoming reduced QH2 Does not transport H+ Succinate dehydrogenase is a single enzyme with dual roles: converting fumarate in CAC and capture and donate e- in ETC |
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Complex III: cytochrome c oxidoreductase |
Creates QH2 and in complex I and II so now use it to reduce 2 molecules of cytochrome c (bc they can only hold one each) Done through iron clusters cytochrome b and c Results in translocation of 4 additional H+ to intermembrane space |
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The Q cycle |
4 H+ are transported across membrane per 2 e- that reach cyt c (2 of 4 H+ come from QH2) Occurs in 2 stages 2 molecules of QH2 became oxidized releasing H+ in the intermembrane One molecule becomes re-reduced totaling 4 H+ per Q |
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Cytochrome c |
The 2nd mobile e- carrier Soluble heme (Fe) so able to move through membrane Carries single e- |
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Complex IV: cytochrome oxidase |
Membrane protein with 13 subunits Contains 2 heme groups Contains copper ions: CuA: 2 ions that accept e- from cyt c CuB: bonded to heme forming center that transfers 4 e- to O |
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e- flow through complex IV |
4 e- are used to reduce 1 O molecule into 2 water molecules 4 H+ are picked up from matrix in this process 4 additional H+ are passed from matrix to intermembrane space |
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Summary of e- flow |
See pic. Also in book on 672 |
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Summary of how many H+ we get |
See pic |
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Another helpful image of transport chain |
See pic and on page 675 |
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Damage to biological macromolecules: free radicals |
Q can be leaky and is unstable Single e- becomes free radical and can become H2O2 Glutathione helps to convert to water |
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Proton-motive force m: 3 ways that create the electrochemical proton gradient |
1. Actively transporting H+ across membrane (complex I and IV) 2. Chemically removing H+ from matrix (reduction of Q and O) 3. Releasing H+ into intermembrane space (oxidation of QH) |
