Figure 15: Phase–plane dynamics of the auxiliary reaction mechanism (47)— (48) when t_c1 ≪ t_c2 ≪ t_s2 ≪ t_s1.

The thick black curve is the numerically-integrated solution to the mass action equations (49a)–(49d), the dashed/dotted red curve is the c₂-nullcline and the dashed/dotted blue curve is the stationary s₂-nullcline. Notice that the trajectory does not follow a path that lies close to either nullcline in the approach to x*. The constants (without units) used in the numerical simulation are: $e_1^0=1$, $s_1^0=1000$, $e_2^0=10$, k₁ = 1, k₂ = 1, k₃ = 10, k₋₃ = 1, k₄ = 100 and k₋₁ = 1.