Cell biology regulatory processes

Uptake of Ca2+ into cells, or release of this ion from intracellular stores, is a major regulatory mechanism in many if not all cells (see Section E). Mn2+ activates phosphoenolpyruvate carboxykinase (Eq. 13-46) and maybe a regulator of gluconeogenesis.142 Iron controls the synthesis of ferritin and of transferrin receptors137 (Chapter 16). The specific metal ions present in many biological macromolecules are likely to participate in additional regulatory processes. 

Figure 14.6 A schematic for the integration of predictive QSAR and systems biology methods to enable the prediction of the interactions of xenobiotics with transporters, enzymes, and the cell signaling and regulatory processes.

We may conclude that many important biological rhythms originate from positive feedback mechanisms whose nonlinearity is further strengthened by the cooperative nature of the regulatory process. Although the detailed molecular implementation of the feedback process differs in each case, it is the self-amplification with which it is associated that gives rise to instabilities followed by sustained oscillations in biochemical systems as well as in cardiac or neural cells (Goldbeter, 1992). 

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