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Refer to chapter 18, Stryer, 5e

Energy generation in mitochondria I. The overall scheme is known as the chemiosmotic mechanism: Two questions need to be answered: How does electron transport result in the expulsion of protons? How is the inward flow of protons used to drive ATP synthesis?. Refer to chapter 18, Stryer, 5e.

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Refer to chapter 18, Stryer, 5e

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  1. Energy generation in mitochondria I • The overall scheme is known as the chemiosmotic mechanism: Two questions need to be answered: • How does electron transport result in the expulsion of protons? • How is the inward flow of protons used to drive ATP synthesis? Refer to chapter 18, Stryer, 5e Lecture 22, Michael Schweizer

  2. Overview of carbon metabolism in a eukaryotic cell Karp 3e, Figure 5.5

  3. The structure of a mitochondrion Figure 5.2c

  4. Electron Flow produces heat All chemical energy from electron transfer converted to heat energy Bio-wire is the respiratory assembly; electron flow produces ATP Bio-battery

  5. Principle of the electron transport chain

  6. Respiratory Chain Electron transfer from NADH to O2 involves multisubunit inner membranecomplexes I, III & IV, plusCoQ&cyt c. Within each complex, electrons pass sequentially through a series of carriers. Complex II exists attached to flavoprotein enzymes. CoQ is located in the lipid core of the membrane, and there are CoQ binding sites in protein complexes. Cytochrome c resides in the intermembrane space. It alternately binds to complex III or IV during e- transfer.

  7. Vectorial positioned proteins Proteins in cytoplasm or lumen or organelles are in solution and free-moving Random orientation of reaction Proteins in membranes are insoluble and fixed in orientation Reactions can be directed Substrates received and products formed vectorially

  8. Structure of NADH dehydrogenase, determined by EM

  9. Respiratory assembly • Located in plasmamembrane of bacteria inner mitochondrial membrane • Consists of 4 complexes (I to IV) immobilised multiproteins/cofactors 2 mobile electron shuttles Ubiquinone (co-enzyme Q) between I/II and III Cytochrome c between III and IV • Accepts electrons (and H+) from NADH and FADH2 generated at numerous oxydation steps • Donates • electrons to terminal acceptor O2 • electrons to S, NO3- (inorganic respiration), etc Bio-wire

  10. Respiratory chain • Propel electrons through multi-enzyme complexes • Convert released energy (DG) to form a H+-gradient across membrane • Establish a H+ cycle back across membrane • Use of H+ cycle to drive ADP + Pi ATP • Power transmission by proton gradients: • Rotate flagella to propel bacterium • Active transport of nutrients into cell • Heat production • =>Proton gradients are a central interconvertible currency of free energy in biological systems

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