Figure 3.

Solution of eqs 2a to 2e (in the presence of mass-transfer limitations across the cell membrane) for the set of parameter values in Figure 1 and k_tr = 0.0025s^–1. Note that due to mass-transfer limitations the observed δ¹³C = 2.2‰ at steady-state notably reduced from 5.4% in Figure 1. It is worth mentioning that inside cells (i.e., at the bioavailable domain) the δ¹³C is equal to the expected value of 5.4‰ (data not shown).