# Rate limited active transport of calcium.

    KINETIC pmp {
            ~ cabulk <-> cam                (1/tau, 1/tau)
            ~ cam + pump <-> capump         (k1, k2)
            ~ capump <-> cao + pump         (k3, k4)
            ica_pmp = 2*FARADAY*(f_flux - b_flux)

            ~ cam << -(ica) : there is a problem here

            COMPARTMENT width {cam} : volume in (um)
            COMPARTMENT 1 {pump capump} : area is dimensionless
            COMPARTMENT 1(m) {cao cabulk}
    }