Model is underconstrained.
The following variables couldn't be defined:
 * G_alpha_GTP in component G_alpha_GTP
 * kp in component G_alpha_GTP
 * PLC in component PLC
 * kd in component DAG
 * IP3 in component Ca_i
 * hp in component PLC_active
 * d/dt G_alpha_GTP in component G_alpha_GTP
 * d/dt DAG in component DAG
 * d/dt Ca_i in component Ca_i
 * d/dt PLC_active in component PLC_active
 * d/dt G_alpha_GDP in component G_alpha_GDP