The 10-state model drives more efficient efflux than uptake under physiological conditions. Unlike other simulations, internal pH was held constant at a physiological value (pH_int = 7.4), while external pH was varied. For the 8-state model (orange trace, EmrE-like rates, Table 3), symmetric transport behavior is observed for external pH values above and below the internal pH of 7.4. In the 10-state model (blue trace, EmrE-like rates, Table 3), a much larger drug gradient is achieved when external pH is lower than internal pH.