HEAT CONDUCTANCE, DIFFUSION-THEORY AND INTRACELLULAR METABOLIC-REGULATION

Diffusion theory played a major role in the development of biology as an exact science. The question is raised, however, as to its relevance and applicability in the molecular interactions which occur in metabo lism in the living cell. This review looks at diffusion theory from it s inception and subsequent introduction into biology, its shortcomings with regard not only to whole-body physiology, but more pertinently a t the intracellular level, with its failure to offer a rational basis for metabolic regulation in the internum of the cell. The conclusion i s reached that although diffusion inevitably occurs within cells, its role is of little importance with regard to most metabolic activity. I n comparison, perfusion of the internal surfaces of the cell by stream ing of the fluid compartment of the cytoplasm seems to be the modus op erandi which allows molecular interactions to occur at rates far beyon d those that diffusion would permit, and at the same time offers a mec hanism which permits sensitive control of metabolic activity.