FIG. 5.

The response of the uncoupled system. The stimulus is [H] = 0.1 μM for t ∈ (0, 5). The numerical results can be compared with the analytical results obtained from the analysis in Section 4 and with Figure 6 to verify the steady-state additivity of the uncoupled system. (a) The dimensionless concentrations of HR_s (solid line) and HR_i (dashed line). (b) The dimensionless concentrations of ${\text{G}}_{\text{s}}^{\prime }$ (solid line) and ${\text{G}}_{\text{i}}^{\prime }$ (dashed line). Note that the half-time for the buildup of ${\text{G}}_{\text{i}}^{\prime }$ agrees well with the theoretical estimate but that the rise time for ${\text{G}}_{\text{s}}^{\prime }$ is longer than the theoretical estimate. This discrepancy indicates that the pseudo-steady-state hypothesis applied to [HR_sG_s] is probably not valid on this time scale.