Simulations of ppERK dynamics in cell populations. A. Simulated RasGTP dynamics for different EGF doses. Simulations were done as described in the “Materials and Methods” section. B-D. Simulated dose and dynamic ppERK responses for the PF (B), US (C) and NF (D) models. To facilitate comparison of these simulations with the experimental data, normally distributed noise with mean and standard deviation of 10 nM was added to the raw simulation data. (E-G) Dynamics and dose response of the ERK-on population mean for the PF (E), US (F), and NF (G) models. Simulated population responses were parsed into ERK-on and ERK-off populations based on a cutoff of 100 nM.