<?xml version="1.0" encoding="UTF-8"?>
<sbml xmlns="http://www.sbml.org/sbml/level2/version4" level="2" version="4">
    <model id="facilitated_ca_diffusion">
        <listOfUnitDefinitions>
            <unitDefinition id="substance">
                <listOfUnits>
                    <unit kind="mole" scale="-6"/>
                </listOfUnits>
            </unitDefinition>
            <unitDefinition id="area">
                <listOfUnits>
                    <unit kind="metre" scale="-6" exponent="2"/>
                </listOfUnits>
            </unitDefinition>
            <unitDefinition id="per_second">
                <listOfUnits>
                    <unit kind="second" exponent="-1"/>
                </listOfUnits>
            </unitDefinition>
            <unitDefinition id="litre_per_mole_per_second">
                <listOfUnits>
                    <unit kind="mole" exponent="-1" scale="-6"/>
                    <unit kind="litre" exponent="1"/>
                    <unit kind="second" exponent="-1"/>
                </listOfUnits>
            </unitDefinition>
            <unitDefinition id="subs_per_vol">
                <listOfUnits>
                    <unit kind="mole" exponent="1" scale="-6"/>
                    <unit kind="litre" exponent="-1"/>
                </listOfUnits>
            </unitDefinition>
        </listOfUnitDefinitions>
        <listOfCompartments>
            <compartment id="Extracellular" 
                         spatialDimensions="3" size="1"/>
            <compartment id="PlasmaMembrane" 
                         outside="Extracellular" spatialDimensions="2" size="1"/>
            <compartment id="Cytosol" 
                         outside="PlasmaMembrane" spatialDimensions="3" size="1"/>
        </listOfCompartments>
        <listOfSpecies>
            <species id="CaBPB_C" 
                     compartment="Cytosol" initialConcentration="47.17"/>
            <species id="B_C" 
                     compartment="Cytosol" initialConcentration="396.04"/>
            <species id="CaB_C" 
                     compartment="Cytosol" initialConcentration="3.96"/>
            <species id="Ca_C" 
                     name="Ca" compartment="Cytosol" initialConcentration="0.1"/>
            <species id="Ca_EC"
                      name="Ca" compartment="Extracellular" initialConcentration="1000"/>
            <species id="CaCh_PM" 
                     compartment="PlasmaMembrane" initialConcentration="1"/>
            <species id="CaPump_PM" 
                     compartment="PlasmaMembrane" initialConcentration="1"/>
            <species id="CaBP_C" 
                     compartment="Cytosol" initialConcentration="202.83"/>
        </listOfSpecies>
        <listOfReactions>
            <reaction id="CalciumCalbindin_gt_BoundCytosol" fast="true">
                <listOfReactants>
                    <speciesReference species="CaBP_C"/>
                    <speciesReference species="Ca_C"/>
                </listOfReactants>
                <listOfProducts>
                    <speciesReference species="CaBPB_C"/>
                </listOfProducts>
                <kineticLaw>
                    <notes>
                        <p xmlns="http://www.w3.org/1999/xhtml">
                           (((Kf_CalciumCalbindin_BoundCytosol * CaBP_C) * Ca_C) -
                              (Kr_CalciumCalbindin_BoundCytosol * CaBPB_C))
                        </p>
                    </notes>
                    <math xmlns="http://www.w3.org/1998/Math/MathML">
                        <apply>
                            <times/>
                            <ci> Cytosol </ci>
                            <apply>
                                <minus/>
                                <apply>
                                    <times/>
                                    <ci> Kf_CalciumCalbindin_BoundCytosol </ci>
                                    <ci> CaBP_C </ci>
                                    <ci> Ca_C </ci>
                                </apply>
                                <apply>
                                    <times/>
                                    <ci> Kr_CalciumCalbindin_BoundCytosol </ci>
                                    <ci> CaBPB_C </ci>
                                </apply>
                            </apply>
                        </apply>
                    </math>
                    <listOfParameters>
                        <parameter id="Kf_CalciumCalbindin_BoundCytosol" value="20.0" 
                                   units="litre_per_mole_per_second"/>
                        <parameter id="Kr_CalciumCalbindin_BoundCytosol" value="8.6" 
                                   units="per_second"/>
                    </listOfParameters>
                </kineticLaw>
            </reaction>
            <reaction id="CalciumBuffer_gt_BoundCytosol" fast="true">
                <listOfReactants>
                    <speciesReference species="Ca_C"/>
                    <speciesReference species="B_C"/>
                </listOfReactants>
                <listOfProducts>
                    <speciesReference species="CaB_C"/>
                </listOfProducts>
                <kineticLaw>
                    <notes>
                        <p xmlns="http://www.w3.org/1999/xhtml">
                        (((Kf_CalciumBuffer_BoundCytosol * Ca_C) * B_C) -
                            (Kr_CalciumBuffer_BoundCytosol * CaB_C))
                        </p>
                    </notes>
                    <math xmlns="http://www.w3.org/1998/Math/MathML">
                    <apply>
                        <times/>
                        <ci> Cytosol</ci>
                        <apply>
                            <minus/>
                            <apply>
                                <times/>
                                <ci> Kf_CalciumBuffer_BoundCytosol </ci>
                                <ci> Ca_C </ci>
                                <ci> B_C </ci>
                            </apply>
                            <apply>
                                <times/>
                                <ci> Kr_CalciumBuffer_BoundCytosol </ci>
                                <ci> CaB_C </ci>
                            </apply>
                        </apply>
                    </apply>
                    </math>
                    <listOfParameters>
                        <parameter id="Kf_CalciumBuffer_BoundCytosol" value="0.1" 
                                   units="litre_per_mole_per_second"/>
                        <parameter id="Kr_CalciumBuffer_BoundCytosol" value="1.0" 
                                   units="per_second"/>
                    </listOfParameters>
                </kineticLaw>
            </reaction>
            <reaction id="Ca_Pump">
                <listOfReactants>
                    <speciesReference species="Ca_C"/>
                </listOfReactants>
                <listOfProducts>
                    <speciesReference species="Ca_EC"/>
                </listOfProducts>
                <listOfModifiers>
                    <modifierSpeciesReference species="CaPump_PM"/>
                </listOfModifiers>
                <kineticLaw>
                    <notes>
                        <p xmlns="http://www.w3.org/1999/xhtml">
                        ((Vmax * kP * ((Ca_C - Ca_Rest) / (Ca_C + kP)) / 
                            (Ca_Rest + kP)) * CaPump_PM)
                        </p>
                    </notes>
                    <math xmlns="http://www.w3.org/1998/Math/MathML">
                    <apply>
                        <times/>
                        <ci> PlasmaMembrane</ci>
                        <apply>
                            <divide/>
                            <apply>
                                <times/>
                                <ci> Vmax </ci>
                                <ci> kP </ci>
                                <ci> CaPump_PM </ci>
                                <apply>
                                    <minus/>
                                    <ci> Ca_C </ci>
                                    <ci> Ca_Rest </ci>
                                </apply>
                            </apply>
                            <apply>
                                <times/>
                                <apply>
                                    <plus/>
                                    <ci> Ca_C </ci>
                                    <ci> kP </ci>
                                </apply>
                                <apply>
                                    <plus/>
                                    <ci> Ca_Rest </ci>
                                    <ci> kP </ci>
                                </apply>
                            </apply>
                        </apply>
                    </apply>
                    </math>
                    <listOfParameters>
                        <parameter id="Vmax" value="4000" units="per_second"/>
                        <parameter id="kP" value="0.25" units="subs_per_vol"/>
                        <parameter id="Ca_Rest" value="0.1" units="subs_per_vol"/>
                    </listOfParameters>
                </kineticLaw>
            </reaction>
            <reaction id="Ca_channel">
                <listOfReactants>
                    <speciesReference species="Ca_EC"/>
                </listOfReactants>
                <listOfProducts>
                    <speciesReference species="Ca_C"/>
                </listOfProducts>
                <listOfModifiers>
                    <modifierSpeciesReference species="CaCh_PM"/>
                </listOfModifiers>
                <kineticLaw>
                    <notes>
                        <p xmlns="http://www.w3.org/1999/xhtml">
                            (J0 * Kc * (Ca_EC - Ca_C) / (Kc + Ca_C) * CaCh_PM)
                        </p>
                    </notes>
                    <math xmlns="http://www.w3.org/1998/Math/MathML">
                    <apply>
                        <times/>
                        <ci> PlasmaMembrane </ci>
                        <apply>
                            <divide/>
                            <apply>
                                <times/>
                                <ci> CaCh_PM </ci>
                                <ci> J0 </ci>
                                <ci> Kc </ci>
                                <apply>
                                    <minus/>
                                    <ci> Ca_EC </ci>
                                    <ci> Ca_C </ci>
                                </apply>
                            </apply>
                            <apply>
                                <plus/>
                                <ci> Kc </ci>
                                <ci> Ca_C </ci>
                            </apply>
                        </apply>
                    </apply>
                    </math>
                    <listOfParameters>
                        <parameter id="J0" value="0.014" units="litre_per_mole_per_second"/>
                        <parameter id="Kc" value="0.5" units="subs_per_vol"/>
                    </listOfParameters>
                </kineticLaw>
            </reaction>
        </listOfReactions>
    </model>
</sbml>
