Molecular Structure of the Photosynthetic Apparatus
Yanina S. DeRuyter and Petra Fromme
from: The Cyanobacteria: Molecular Biology, Genomics and Evolution (Edited by: Antonia Herrero and Enrique Flores). Caister Academic Press, U.K. (2008)
The process of conversion of light energy from the sun into chemical energy is catalyzed by oxygenic photosynthesis. It is the process that provides all higher life on earth with energy. All oxygen in the atmosphere is evolved by this process, which was invented 2.8 billion years ago by the ancestors of cyanobacteria. Cyanobacteria are even nowadays very important members of the global ecosystem, and contribute up to 30% of the yearly oxygen production on earth. This chapter describes the structure and function of the protein complexes that catalyze the first steps of the energy conversion. Light is captured by antenna complexes and transferred to two large bio-solar systems, photosystem I and II, which catalyze the transmembrane charge separation. This drives the photosynthetic process and provides the energy for production of the high-energy substrate ATP and reduced hydrogen in the form of NADPH. The photosystems are functionally coupled by the cytochrome b6f complex, the membrane intrinsic plastoquinone pool and lumenal electron carriers. The reactions of the electron transport chain lead to an electrochemical proton gradient, which drives synthesis of ATP by the molecular motor, the ATP synthase. The structures of the complexes are described and discussed in respect to the function and evolution of the photosynthetic apparatus read more ...