General properties of nonlinear processes in biology

Author(s): Hess, B.

Journal/Book: Proc GIRI. 1991; 5: 9.

Abstract: New physical techniques in combination with suitable computer and mathematical methodology allow to explore highly complex, nonlinear, dissipative processes and to unravel the dynamic nature of time and space structures in many areas of science. Bio- logical systems are built on the intricate and dynamic interplay of millions of elementary biochemical reaction steps and transport processes organized in reactin cycles within a hierachical network in cells. within homogeneous cell populations and complex cellular networks of tissues, organs and organisms. Their nonlinear kinetics arise mainly from the following sources: 1. Multiple types of positive and negative feedback interactions, 2. Control by allosteric and interconvertible enzymes and receptor proteins, 3. Vectorial processes in terms of macroscopic diffusion and membran transport. Depending on the parameter values. a rich variety of dynamic states, separated by bifurcation points, is observed thoretically and experimentally, with three phase variables. such as: entrain- ment by periodic substrate input flux with period doubling cascades, quasiperiodicity, chaos (acting as random generator), coexistence of attractors in phase space allowing swiching by control pulses of metabolites. hysteresis controlled by parameter settings, strong amplification of noise, hyperstability. critical decay (crisis), amplitude and fre- quency modulation. complex interaction between chaos and ordered states. Some of these feature relevant to high sensitivity responses will be discussed.

Keyword(s): hom. rel. theor

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