Chapter 14

The Nature of Living Things

The purpose of this and the following chapter is to give an overview of living systems,

especially directed at the bioinformatician who has previously dealt purely with the

computational aspects of the subject.

Figure 14.1 (cf. a simplified version in Fig. 2.1) shows, in a highly compressed

and schematic form, the major processes taking place within living beings. The first

priority of any living being is simply to survive. In the language of Sect. 3.2, the

being must maintain its essential variables within the range corresponding to life. In

succinct form, “to be or not to be—that is the question”.

The biosynthetic processes of life maintenance, indicated at the bottom of

Fig. 14.1, lead beyond the living part of the organism to produce external structures,

like exoskeletons and shells, which are sometimes gigantic, such as coral reefs, giant

redwood tree trunks, guano hills, and, indeed, beaver dams and buildings of human

construction.

Bioinformatics is particularly concerned with the processes of information flow

(cf. the “central dogma”); that is, d comma e comma fd, e, f in Fig. 14.1, and with the regulation of the

material processes that maintain life (g comma h comma ig, h, i). This chapter sets out to give the wider

context.

The simplest organisms are single cells, slightly more elaborate organisms such as

sponges consist of aggregates of cells constrained to live together, and more complex

organisms are highly constrained assemblies of cells.

14.1

The Cell

The basic unit of life is the cell. Many organisms consist of only one cell. There-

fore, even a single cell carries all that is needed for life. The cell contains the DNA

coding for proteins and all the machinery necessary for maintaining life—enzymes,

multiprotein complexes, and so forth. The body of the cell, the cytoplasm, is a thick,

viscous aqueous medium full of macromolecules. If intact cells are centrifuged, one

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J. Ramsden, Bioinformatics, Computational Biology,

https://doi.org/10.1007/978-3-030-45607-8_14

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