The model contains one compartment called C. There are four species called A1, A2, A3 and A4 and four parameters called Kf1, Kr1, Kf and Kr. The model contains two reactions defined as:

Reaction Rate
A4 ↔ A2 (Kf1 · A4 − Kr1 · A2) · C
A1 + A2 ↔ A3 (Kf · A1 · A2 − Kr · A3) · C

where the first reaction is marked as 'fast' and therefore should be assumed to be operating on a time scale significantly faster than the second reaction. Fast reactions are considered to be instantaneous relative to slow reactions.

The initial conditions are as follows:

Value Units
Initial amount of A1 2 mole
Initial amount of A2 3 mole
Initial amount of A3 4 mole
Initial amount of A4 1 mole
Value of parameter Kf1 1 second-1
Value of parameter Kr1 2 second-1
Value of parameter Kf 1 litre mole-1 second-1
Value of parameter Kr 2 second-1
Volume of compartment C 1 litre

The species values are given as amounts of substance to make it easier to use the model in a discrete stochastic simulator, but (as per usual SBML principles) their symbols represent their values in concentration units where they appear in expressions.