Substrate Concentration

For a fixed, unchanging amount of enzyme, the rate of an enzyme-catalysed reaction increases as the concentration of substrate increases - with more substrate molecules available, enzyme active sites are more likely to be occupied at any given moment, so more reactions can occur per unit time. However, this increase does not continue indefinitely. Once the substrate concentration rises high enough that essentially every enzyme active site is continuously occupied (a state called saturation), adding still more substrate has no further effect, because there simply are no free active sites left to bind it. At this point the reaction is proceeding at th …