Fig 7. Comparison of internal nutrient-dependent regulation of transporter synthesis and activity-dependent transporter downregulation.

For different normalized concentrations of S_ext, the values of n and $k_{{\gamma }_T}^a/k_{{\gamma }_T}^c$ required to achieve either 0.8 or 0.95 robustness (blue curve and black curve respectively) are plotted. Four different specific normalized S_ext values are represented by the four colored dots. We assumed nutrient uptake per transporter was Michaelian $u(S_{ext})=\frac{S_{ext}}{S_{ext}+K_{ext}}$.