What occurs when substrate concentration is too high and exceeds the number of active sites?

When substrate concentration is too high and exceeds the number of active sites available on the enzymes, the reaction reaches a point where all active sites are occupied. At this saturation level, adding more substrate does not increase the rate of reaction because there are no free active sites available for the additional substrate to bind to. This results in a scenario where the excess substrate molecules cannot participate in the reaction effectively, which is why they are described as becoming ineffective. The reaction rate plateaus because enzyme activity is limited by the number of available active sites, illustrating the concept of enzyme saturation.