What happens to the reaction rate if substrate concentration remains unchanged while enzyme concentration is increased?

Increasing the enzyme concentration while keeping the substrate concentration unchanged typically leads to an increase in the reaction rate. This is because more enzyme molecules are available to catalyze the conversion of substrate to product, enhancing the overall efficiency of the reaction.

When there are more enzymes present, assuming substrate is still available in sufficient quantity to bind with all active sites of the enzyme, the rate at which the enzyme-substrate complexes can form increases. As a result, the rate of reaction will rise until a point is reached where the substrate becomes the limiting factor, at which stage adding more enzymes would no longer have an effect.

In this scenario, since the question specifies that the substrate concentration remains unchanged, the initial increase in enzyme concentration directly correlates with an increase in reaction rate, thus supporting the rationale for the correct answer.