The effect of substrate concentration on the rate of enzyme activity can be described using the Michaelis-Menten kinetics model. As the substrate concentration increases, the rate of enzyme activity also increases, but only up to a certain point. This is because enzymes have a limited number of active sites where the substrate can bind. When these active sites are saturated, the enzyme is working at its maximum rate, and further increases in substrate concentration will not increase the rate of enzyme activity.The relationship between substrate concentration and enzyme activity can be represented by the Michaelis-Menten equation:v = Vmax * [S] / Km + [S] where:v = rate of enzyme activityVmax = maximum rate of enzyme activity[S] = substrate concentrationKm = Michaelis constant, which represents the substrate concentration at which the enzyme works at half its maximum rateThe presence of an inhibitor can affect this relationship in two main ways, depending on the type of inhibition:1. Competitive inhibition: In this case, the inhibitor competes with the substrate for the active site of the enzyme. The inhibitor can bind to the active site, but no reaction occurs. This reduces the number of available active sites for the substrate, effectively increasing the Km value. As a result, a higher substrate concentration is needed to achieve the same rate of enzyme activity. However, the Vmax remains unchanged, as the enzyme can still reach its maximum rate if the substrate concentration is high enough to outcompete the inhibitor.2. Non-competitive inhibition: In this case, the inhibitor binds to a different site on the enzyme allosteric site , causing a conformational change in the enzyme that reduces its catalytic activity. This type of inhibition affects the enzyme's ability to reach its maximum rate, resulting in a decrease in Vmax. The Km value remains unchanged, as the substrate can still bind to the active site with the same affinity, but the overall rate of enzyme activity is reduced due to the presence of the inhibitor.In summary, substrate concentration affects the rate of enzyme activity, with the rate increasing until the enzyme's active sites are saturated. The presence of an inhibitor can alter this relationship, either by competing with the substrate for the active site competitive inhibition or by binding to a different site and reducing the enzyme's catalytic activity non-competitive inhibition .