Electron transport chain diagram

Figure 3. Diagram of a section through the cell wall of Acidithiobacillus ferrooxidans modified from Blake et al. (1992) showing the relationship between iron oxidation and pyrite dissolution. OM =outer membrane, P = periplasm, IM = inner or (cytoplasmic) membrane, cty = cytochrome, pmf = proton motive force. Passage of a proton (driven by proton motive force) into the cell catalyzes the conversion of ADP to ATP. Ferrous iron binds to a component of the electron transport chain, probably a cytochrome c, and is oxidized. The electrons are passed to a terminal reductase where they are combined with O2 and to form water, preventing acidification of the cytoplasm. Ferric iron can either oxidize pyrite (e.g. within the ore body) or form nanocrystalline iron oxyhydroxide minerals (often in surrounding groundwater or streams).

Figure 16-1. Schematic diagram of electron transport chain ATP synthase and ATP/ADP translocase.

Fig. 8. Simplified free energy diagram of the photosynthetic electron transport chain (for details see Ref.27, 69X For the sake of simplicity only the reduced forms of the corresponding redox carriers are given. The electronic excitations are symbolized by thick open arrows, thermal redox reactions in the dark are indicated by thin arrows. Abbreviations Cyt fre(j = reduced cytochrome f, NADPH = reduced nicotinamide adenine dinucleotidphosphate, PCjgj = reduced plastocyanine, PQH2 = plastohydroquinone, Xf and X 320- are the reduced forms of the primary electron acceptor of C[ and Qj, respectively [see Eq. (14a, b)l, Y = watersplitting enzyme system...

On the basis of the corresponding midpoint potentials there is given in Fig. 8 a free energy diagram of the main steps of the photosynthetic electron transport chain. According to the relation AG = — n AE (n = number of electrons transferred, 5 = Faraday... 

Figure 11.2 Electron transport in the respiratory chain. The diagram details the flow of electrons from the Krebs cycle intermediates malate and succinate via the electron transport chain (complexes 1, II, III and IV) to oxygen. 

Fig. 3. These diagrams (A, B) are intended to illustrate the regulation and operation of these mitochondrial fatty acid synthetic systems using a hydrodynamic analogy. Electron pressure and flow are depicted as fluid pressure and flow under gravitational influence. Electron flow down the electron transport chain is ultimately controlled by (ADP Pi) ATP ratio. When the latter ratio is high (A, left) electron flow rate is maximal and the steady-state NADHiNAD" ratio is low (State 3 Chance and Williams, 1956), On the other hand, (B, right) when either the (ADP + P,) ATP ratio is low or oxygen is lacking, substrate reduces NAD+ faster than it can be oxidized. The elevated NADHiNAD ratio reverses the usual flow of electrons from fatty acid oxidation. Acetate now becomes incorporated into fatty acids with the consequent oxidation of NADH and, therefore, perhaps permits some ATP to be synthesized via other substrate-level energy conserving steps.

Figure 6. Pathways of protons and electrons during mitochondrial oxidations. The diagrams show the pathways of electrons which enter the electron chain at the level ofcomplexi (a)orcomplex II (b). Complexes I, III, and IV usethefreeenergy of electron transport to pump protons out of the matrix. This diagram also distinguishes formally between protons released by dehydrogenation and those which are pumped out of the matrix, although they all enter or leave the same pool.

Figure 9.14 Simple diagram illustrating the transport of the major fuels for the Krebs q/cle, and hydrogen atoms for the electron transfer chain, across the inner mitochondrial membrane.

Diagram of the functional complexes of the electron transport system within the respiratory chain. Fnad = NADH dehydrogenase flavoprotein Fs = succinate dehydrogenase flavoprotein Fefn.h.) = nonheme iron. 

From the previous section it is evident that our knowledge about the respiratory chain is still quite incomplete. We know which prosthetic groups participate (cf. diagram in Section 4). It remains to be clarified, however, to what proteins they are bound and what role the metals and any new cofactors might play. The reason for this unsatisfactory state of knowledge is that the enzymes under consideration are bound very firmly to the mitochondrial structure (cf. Chapt. XIX-3). Only very recently have techniques been developed to subdivide the mitochondria in such a manner that most of their activity is retained. The subunits thus obtained have been called electron-transport particles (Green and co-workers). Some of the catalytic capabilities have been sacrificed (e.g. the enzymes of the citric acid cycle). But they are still able to oxidize NADHs or succinate with consumption of Oj and formation of ATP (see below). With the further destruction of these subunits, the capacity for oxidative phosphorylation disappears. 

The sequence of four enzyme reactions shown in the diagram below results in the removal of two pairs of hydrogen atoms from the fatty acyl CoA molecule which are passed to the cofactors NAD+ and FAD which become reduced to NADH and FADH2. As these reactions occur in the mitochondria, it is easy for the cofactors to be rapidly reoxidized by the electron transport process (the cytochrome chain) and this results in ATP synthesis. A molecule of acetyl CoA is produced per turn of the p-oxidation spiral. This acetyl CoA can be further metabolized to CO2, but cannot be used as a source of intermediates for glucose synthesis by gluconeogenesis. 

A simplified version of the complex chain of electron transport from the Krebs cycle reactions to oxygen is shown below (Fig. 4.12). This also indicates the sites of oxidative phosphorylation. CoQ in this diagram represents a quinone termed co-enzyme Q which is now thought to be interposed in the chain between the metallo-flavoproteins (FP) and the cytochrome complex. 

Figure 13.1 Oxidative phosphorylation. A cartoon representation of electron and proton transport via the respiratory chain which produces ATP by oxidative phosphorylation. A concise version of this diagram, which is more appropriate for examination purposes, is shown in Chapter 11, Fig. 11.2.

From ferredoxin the electron pair returns to chlorophyll over a chain of redox catalysts (see left half of the diagram. Fig. 41). One of these redox catalysts— perhaps the first one—is the system plastoquinone/plastohydroquinone with a redox potential of 0.00 volt furthermore, cytochrome f is interposed here. The transport of electrons from plastoquinone to chlorophyll a E = H-0.45 volt) is coupled to a phosphorylation step just as in the respiratory chain, one inorganic phosphate is taken up and stored as ATP. 

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