Module 6.3: Substrate

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The Substrate model shows the removal of a substrate's concentration in an enzymatic reaction. This model is based on the differential equation where

d[S]/dt = k2[ES] - k1[E][S].
S = substrate
E = enzyme
In this equation, the rate of change of removal of [E] is the same as the rate of change of removal of [S]. E can be formed from ES by forward and backward reactions, with a rate of change proportional to ES.

In this model, ES, S, and E concentration are all represented by stocks. S formation and S removal are flows going in and out of the S concentration stock.

The S formation flow contains the term k2, the reverse reaction rate of ES back to substrate S and enzyme E, multiplied by the ES concentration.

The S removal flow contains the equation: k1 * E concentration * S concentration. k1 is the reaction rate of substrate S in the presence of enzyme E to intermediate enzyme-substrate complex ES.

E concentration, S concentration, ES concentration, k1, the removal constant and k2, the formation constant, are all controlled by sliders in this model. The graph shows S concentrations over time