The mathematical modelling of biochemical reaction networks is one of the mayor goals in the field of system biology. A great part of the theoretical work published so far makes use of the law of mass action and describes the temporal change of chemical concentrations by coupled, deterministic, first-order differential equations. This also reflects the traditional understanding of cellular signalling networks as deterministic circuits which always respond in the same way on external stimuli and internal conditions.
It is wellknown, however, that the deterministic picture must break down in the limit of small molecule numbers.
- Recent insight: Fluctuations can be useful (chemotaxis)