THERMODYNAMICS OF THE PRIMARY REACTIONS OF PHOTOSYNTHESIS

Photochemistry and Photobiology - Tập 28 Số 3 - Trang 389-393 - 1978
William W. Parson1
1Department of Biochemistry, University of Washington, Seattle, WA 98195 U.S.A.

Tóm tắt

Abstract. It appears to be widely believed that fundamental thermodynamic limitations prevent the products of the primary electron transfer reactions of photosynthesis from exceeding the reactants in energy by more than about 0.7 hv0 where v0 is the frequency of the lowest energy absorption band of the reaction center. Specifically, in photosynthetic bacteria, where hv0? 1.34 eV, it is often said that the midpoint redox potentials of the primary electron donor and acceptor cannot differ by more than about 0.9 eV. This is incorrect. A simple expression is developed for δμ, the increase in the partial molecular free energy of an absorber under illumination. The magnitude of δμ gives one no information about the nature of the photochemical reactions that can result from excitation of the absorber. It puts no limits on the midpoint redox potentials of the reactants. However, knowing δμ does allow one to calculate the concentrations of the products if the system comes to equilibrium during illumination.

Từ khóa


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Photochemistry and Photobiology

Tập 28 Số 3

389-393

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