Cellular dynamics in noisy environment

Cells are continuously subjected to noisy internal and external environments. Though cellular functions are carried on quite reliably under such noise, they can also result in fluctuations of parameters of the various biochemical processes and cause the dynamics of the reaction pathway to change. To show the varied effects of noisy environment on cellular dynamics, we consider a model cell containing a minimal biochemical pathway that exhibits a wide array of dynamical behaviors - from equilibrium, simple limit cycles and higher periodics, birhythmicity, complex oscillations and chaos - that are observed in many cellular functions. We show that, even under constant parameters, small fluctuations in the variables (i.e., substrate concentrations) can facilitate switching of the dynamics between oscillatory states with very different amplitudes and frequencies. The final temporal behavior of the pathway is unpredictable for the range of parameters where birhythmicity is observed. Parametric noise can mask the original dynamics of the pathway in the birhythmic state, though considerable robustness in dynamics is seen in the presence of noise for other values of parameters. Thus we show that the cellular dynamics can exhibit both robust and non-robust behavior in noisy environment for different parameters in the same pathway