Original and improved approaches of PGA sink implementation based on the Laisk model. This analysis shows the comparison of original and modified implementation of the PGA sink based on the rate equation VPGAout from the Laisk model . Dotted line represents the original approach employed in the Laisk model. Dashed line indicates the response of the system due to 100-times increase of the stromal PGA. Solid line shows the extension of the equation system by adding the sink reaction (PGAstroma → PGAcytosol → Sink; first reaction is described by the rate equation VPGAout) which was necessary to stabilize the stromal PGA due to complexity and reversibility of the rate equation VPGAout . The initial concentrations and conditions were the same for all simulations.