So initially we have the enzyme by itself and then we add the substrate and the substrate is also by itself. But then what begins to happen is the substrate begins to bind onto that enzymes active site and we form an intermediate molecule known as the enzyme substrate complex. Now going this way the rate constant is k one, but once we form some of this complex it begins to dissociate back into these two reactants and the rate constant of that reverse reaction is K minus one, at the same time some of that complex. So we now have the substrate inside the active side and the enzyme will begin to transform that substrate into the product and once we form the product, it will dissociate from the active side to basically form these final molecules, the product and the enzyme in its individual form. Now going this way the rate constant is k two and going in reverse, the rate constant is k minus two. So this is the equation that basically describes what is taking place inside the beaker once we reach equilibrium, once we establish equilibrium.