Membrane cell energy conservation

In many organisms, a cyclic process takes place, in which the reduced electron acceptor transfers its electron through a series of carriers back to the oxidized donor. Energy conservation is achieved by coupling proton translocation across a membrane to the electron flow. This type of cyclic electron flow occurs in eukaryotes under some conditions and in many anoxygenic photosynthetic bacteria. No NADPFl is produced, only ATP. This process occurs when cells may require additional ATP, or when there is no NADP+ to reduce to NADPFl. In other organisms, noncyclic electron flow takes... 

Once inside the cell, arsenate ions can be reduced to arsenite via membrane-bound or cytoplasmic enzymes. The former are linked to cellular energy conservation and are described in detail later in this chapter and in Chapter 12 the latter are characteristic of As-resistant microbes, do not conserve energy, and have been described in Chapter 10. Before detailing the bioinorganic chemistry of arsenic by micro-organisms, however, we will briefly discuss the incorporation of arsenic into organic compounds. For more details on this subject, we refer the reader to comprehensive reviews by Phillips (6) and Reimer (7). 

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