Limitations of using mass action kinetics method in modeling biochemical systems: illustration for a second order reaction

Mathematical models for solving the nonlinear interactions in biological systems are a major component of computational systems biology. Deterministic method that is generally employed in these models assumes that the number of molecules in the well mixed reaction medium is large. When these assumptions are not valid, the system is stochastic. In deterministic methods, mass action kinetics terms are usually included. Herein, we illustrate that the results of deterministic mass action kinetics methods do not necessarily represent the average behavior of stochastic systems with a simple example of second order reaction.