Dissipation in bioenergetic electron transfer chains |
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Authors: | Jérôme Lavergne Pierre Joliot |
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Affiliation: | (1) Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France;(2) CEA Cadarache, DEVM-LBC, 13108 Saint Paul-lez-Durance, France |
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Abstract: | This paper examines the processes by which wasteful dissipation of free energy may occur in bioenergetic electron transfer chains. Frictionless transfer requires high rate constants in order to achieve a quasi-equilibrium steady-state. Previous results concerning the maximum power available from a photochemical source are recalled. The energetic performance of the bacterial reaction center is discussed, characterizing the processes that decrease either the quantum yield (recombination and obstruction) or the chemical potential (friction and non-equilibrated mechanisms). Considering the whole chain, diffusive carriers are potentially weaker links, due to kinetic limitation and short-circuiting reactions. It is suggested that the evolutionary trend has been to limit their number by lumping them into tightly bound protein complexes or, in a more flexible way, into labile supercomplexes.Abbreviations Cyt cytochrome - F Faraday - H primary acceptor in the bacterial reaction center (bacteriopheophytin) - kB Boltzmann's constant - P primary photochemical donor (special bacteriochlorophyll pair) - RC reaction center - QA, QB primary, secondary quinone acceptor |
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Keywords: | energy conservation midpoint potential quantum yield rate constants reaction center supercomplexes |
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