Electron transport strategies

To resolve this issue, it is crucial to establish whether there are some PS I complexes in the appressed grana partitions or none at all. The suggestion of extreme lateral heterogeneity with exclusion of all PS I complexes from appressed mem- 

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The TCA cycle can now be completed by converting succinate to oxaloacetate. This latter process represents a net oxidation. The TCA cycle breaks it down into (consecutively) an oxidation step, a hydration reaction, and a second oxidation step. The oxidation steps are accompanied by the reduction of an [FAD] and an NAD. The reduced coenzymes, [FADHg] and NADH, subsequently provide reducing power in the electron transport chain. (We see in Chapter 24 that virtually the same chemical strategy is used in /3-oxidation of fatty acids.)... 

The microbes use two general strategies to synthesize ATP respiration and fermentation. A respiring microbe captures the energy released when electrons are transferred from a reduced species in the environment to an oxidized species (Fig. 18.1). The reduced species, the electron donor, sorbs to a complex of redox enzymes, or a series of such complexes, located in the cell membrane. The complex strips from the donor one or more electrons, which cascade through a series of enzymes and coenzymes that make up the electron transport chain to a terminal enzyme complex, also within the cell membrane. 

Metabolic Strategies 227 Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway 242 The Tricarboxylic Acid Cycle 282 Electron Transport and Oxidative Phosphorylation 305 Photosynthesis 330 Structures and Metabolism of Oligosaccharides and Polysaccharides 356... 

We now come to the subject of simplified reaction-center complexes, which have been found to be particularly valuable for the study of various components along the electron-transport chain in photosystem I. The basic strategy used for obtaining simplified PS-I reaction-center complexes was to selectively remove the components one-by-one cumulatively along the electron-carrier sequence, starting from the terminal end of the chain. 

In Chapter 10 the basic principles of oxidative phosphorylation, the complex mechanism by which modem aerobic cells manufacture ATP, are described. The discussion begins with a review of the electron transport system in which electrons are donated by reduced coenzymes to the electron transport chain (ETC). The ETC is a series of electron carriers in the inner membrane of the mitochondria of eukaryotes and the plasma membrane of aerobic prokaryotes. This is followed by a description of chemiosmosis, the means by which the energy extracted from electron flow is captured and used to synthesize ATP. Chapter 10 ends with a discussion of the formation of toxic oxygen products and the strategies that cells use to protect themselves. 

This strategy has led to commercial development of herbicide resistance for glu-fosinate, glyphosate and bromoxynil. Glufosinate and glyphosate resistance will be discussed in detail in later sections of this chapter (see also Chapter 6.2). Bro-moxynil s herbicide activity is due to inhibition of electron transport in photosystem II. Crops engineered with bromoxynil nitrilase metabolize the herbicide to a non-phytotoxic compound [5]. 

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