Prokaryotes general

First Steps The Evolution of Prokaryotes General Considerations of the... 

Although tRNAs are quite stable in prokaryotes, they are somewhat less stable in eukaryotes. The opposite is tme for mRNAs, which are quite unstable in prokaryotes but generally stable in eukaryotic organisms. 

Fig. 5.1. The three domains of life in a radial time sequence based on genetic (RNA) analysis. The distinction between anaerobes and aerobes is not made here and the branching to eukaryotes is left unclear. All the domains advanced with time but in very different ways (see Woese, C. (1998) in Further Reading, and Sogin, M. (1993), Science, 260, 340). Note the general gene transfer in prokaryotes and to eukaryotes (see Chapter 7).

Some lines of prokaryote development are shown in Table 6.2 with a guide to oxidation/reduction potential ranges in Table 6.3. In all these and further changes the novel chemistry has to be built into the cooperative whole (see Section 3.9). Note again the necessity that the novel features must become part of a controlled autocatalytic restricted set of reaction paths, which become general to any further evolution. 

Before we conclude the functions of the elements and the proteome, there is a second general feature of eukaryote cells, much of which evolved from that of the prokaryotes - the types of metal-binding protein. The general supposition is that the number of folds are limited and certainly the number of metal-binding sites for any one metal ion is closely limited (see Section 4.15). We find that there are some general rules for protein-binding centres of metal ions and their geometry, mentioned only in brief in Chapters 5 and 6. 

Finally, note that eukaryote chemotypes have as a general feature the increase inside the cell vesicles of elements, here calcium, previously confined to the outside of prokaryotes, but these increases are different in different vesicles and organelles and in different organisms separating cells into different chemotypes. This is also seen in their minerals. There is as yet far too little quantitative analysis of calcium or indeed of elements generally to allow us to build a full picture of chemotypes together with genotypes (see Table 8.22). 

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