What happens to enzyme activity if the substrate concentration increases?

• A. It decreases initially then increases
• B. It remains constant
• C. It increases until a saturation point is reached
• D. It will lead to enzyme denaturation

Answer: (C)

Enzyme activity typically increases with substrate concentration until it reaches a certain saturation point. At low substrate concentrations, more substrate is available for the enzyme to bind to, which increases the rate of the reaction. As substrate concentration continues to rise, the rate of reaction increases further because there are more substrate molecules available for the active sites of the enzyme.

However, this increase in activity does not continue indefinitely. Once the enzyme molecules become saturated with substrate—that is, when all active sites are occupied—the maximum rate of the reaction (Vmax) is reached. Beyond this saturation point, adding more substrate will not increase the reaction rate because there are no additional active sites available for the substrate to bind to.

This saturation behavior is characteristic of many enzyme-catalyzed reactions and reflects the kinetics described by the Michaelis-Menten model, which describes how reaction rates vary with substrate concentration.