The Cybernetics of Biological Macromolecules

Abstract

It used to be said, in accordance with Newtonian philosophy, that everything in this world of ours is in some degree related to everything else. And I suppose that at a macroscopic level, the same may still be maintained, although to be sure there are macroscopic situations, as in the case of evolution, where chance, or apparently chance, events, come into play. Nowhere is this interdependence of macroscopic events more apparent than in living organisms, whose very name stems from, recognition of their high degree of organization; and nowhere in the organism is this more evident than in the polyfunctional macromolecules of which it is composed. Here the interrelated events to a large extent involve and depend upon the specific binding of smaller molecules which may be regarded as ligands. These may be such simple inorganic substances as proton, oxygen, CO₂, phosphate or other ions, which react with specific sites in the macromolecule, as in the respiratory proteins; or they may be more complex substances such as hormones and neurotransmitters or even another macromolecule. The interactions may involve the successive binding of molecules of a given ligand by a set of sites specific for that ligand, or the binding of different ligands by their several sites. In the one case we speak of the interactions as homotropic, in the other as heterotropic; both types are associated with phenomena of cooperativity and anticooperativity.