Model is underconstrained.
The following variables couldn't be defined:
 * S1 in component S1
 * v1 in component v1
 * v2 in component v2
 * v6 in component v6
 * v3 in component v3
 * v4 in component v4
 * J in component S4_flux_rate_across_the_plasma_membrane
 * v7 in component v7
 * v5 in component v5
 * A2 in component A
 * N1 in component N
 * f_A3 in component v1
 * d/dt S1 in component S1
 * d/dt S2 in component S2
 * d/dt S3 in component S3
 * d/dt S4 in component S4
 * d/dt S4_ex in component S4_ex
 * d/dt A3 in component A3
 * d/dt N2 in component N2