Model number
0381

  

Two solutes, A and B, reversibly react to form C. A + B <---> C reaches equilibrium at the ratio A*B/C = Kd.

Description

   Pseudo-equilibria are often assumed in reaction processes,
and if efficient to compute, can save much computation time
and avoid using the on- and off- rate constants of the reaction. 
This is interesting since the "ratio" A*B/C progresses with time
becoming Kd if t.max is long enough, while the implicit solution 
gives ratio = Kd immediately.

The implicit solution solves

 Mass conservation from initial concentrations
 Definition of chemical equilibrium
 Change from initial concentrations same for ssA and ssB
 
and fails to be compiled if any one of the three equations is omitted.

fig1

 

Comparison of Ordinary Differential Equation model with implicit and analytic solutions.

Equations

The equations for this model may be viewed by running the JSim model applet and clicking on the Source tab at the bottom left of JSim's Run Time graphical user interface. The equations are written in JSim's Mathematical Modeling Language (MML). See the Introduction to MML and the MML Reference Manual. Additional documentation for MML can be found by using the search option at the Physiome home page.

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References
  none
Key terms
reaction
rxn
biochemistry
dissociation
Kd
equilibrium
reversible
ODEs
implicit
steady state
analytic
A+B
A+B<->C
Acknowledgements

Please cite https://www.imagwiki.nibib.nih.gov/physiome in any publication for which this software is used and send one reprint to the address given below:
The National Simulation Resource, Director J. B. Bassingthwaighte, Department of Bioengineering, University of Washington, Seattle WA 98195-5061.

Model development and archiving support at https://www.imagwiki.nibib.nih.gov/physiome provided by the following grants: NIH U01HL122199 Analyzing the Cardiac Power Grid, 09/15/2015 - 05/31/2020, NIH/NIBIB BE08407 Software Integration, JSim and SBW 6/1/09-5/31/13; NIH/NHLBI T15 HL88516-01 Modeling for Heart, Lung and Blood: From Cell to Organ, 4/1/07-3/31/11; NSF BES-0506477 Adaptive Multi-Scale Model Simulation, 8/15/05-7/31/08; NIH/NHLBI R01 HL073598 Core 3: 3D Imaging and Computer Modeling of the Respiratory Tract, 9/1/04-8/31/09; as well as prior support from NIH/NCRR P41 RR01243 Simulation Resource in Circulatory Mass Transport and Exchange, 12/1/1980-11/30/01 and NIH/NIBIB R01 EB001973 JSim: A Simulation Analysis Platform, 3/1/02-2/28/07.