Prokaryotic cytoplasm

Fig. 3-7 A thin section through a prokaryotic cell. Note that the nuclear material (N) is not bound by a membrane, but is free in the cytoplasm. Mitochondria and other intracytoplasmic structures are absent. (Reprinted with permission from J. J. Cardamone, Jr., Univ. of Pittsburgh/Biological Photo Service.)...

Cell envelopes of prokaryotic organisms (archaea and bacteria) are characterized by the presence of two distinct components the cytoplasmic membrane, which constitutes the inner layer, and an outer supramolecular layered cell wall (for reviews see Ref. 4), which pre-... 

The above description provides a possible starting background for the description of the beginning of cellular chemotypes, prokaryotes, but even this is less complicated than the only cells for which we have evidence since they have at least two additional groups of more sophisticated chemicals - coenzymes (see Tables 5.3 and 5.4) and certain metal cofactors, which we presume were additions to the most primitive cells. After we have described them, we shall return to the problem of cellular (cytoplasmic) organisation. Note that coenzyme novelty is not in basic pathways but in control of rates and in energy management. 

We shall examine first the chemistry developed for the protection of the prokaryote cytoplasm from 02, 02 and H202 and then the first uses of oxidised elements, S, Fe, N and finally the rise of true aerobes. 

From this account of the protoaerobic and aerobic prokaryotes it is clear that the change of the environment from a moderately reducing to an oxidising environment with the need to maintain the reductive metabolism of the cell cytoplasm placed a burden on what was possible for these small cells. We describe another way round these problems other than protected cytoplasmic reactions before we discuss the extra problems of controlling the new activities. 

Turning to the additional metabolism that needs extra controls there was little change in basic prokaryote reductive metabolism in the cytoplasm from anaerobes to aerobes but as stated above there were added several oxidative reactions and... 

Before we describe the chemistry of the compartments involved, note that like prokaryotes, a number of oxidative enzymes are found in the cytoplasm but they do not release damaging chemicals (see Section 6.10). We also observed that such kinds of kinetic compartments are not enclosed by physical limitations such as membranes. We have also mentioned that increased size itself makes for kinetic compartments if diffusion is restricted. In this section, we see many additional advantages of eukaryotes from those given in Section 7.4. How deceptive it can be to use just the DNA, the all-embracing proteome, metabolome or metallome in discussing evolution without the recognition of the thermodynamic importance of compartments and their concentrations These data could be useful both here and in simpler studies of single-compartment bacteria even in the analysis of species but not much information is available. 

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