[Kinetics of cellular response. Signal transduction in the second messenger system]

The author proposes a functional model of the cell as a set of the simplest functional blocks each of which consists of a cellular signal receptor, a system of signal transmission in the chain of secondary intermediaries and an element whose numerical value characterizes the cellular response. The steady-state approximation of the dependence of the cellular response on the concentration of an activator and inhibitors was analyzed quantitatively and qualitatively. Mathematic criteria for the existence were defined. Analysis was made of the properties of the maximal signal enhancement mode, of the signal enhancement lack mode, and of the intermediate and bifurcation modes. Equations were derived, connecting the experimentally observed parameters of the concentration dependencies with the parameters of the simplest functional blocks.