Question

The graph given shows the effect of substrate concentration on the rate of reaction of the enzyme.

What does the graph indicate?

• A. The rate of enzyme reaction is directly proportional to the substrate concentration.
• B. Presence of an enzyme inhibitor in the reaction mixture.
• C. Formation of an enzyme-substrate complex.
• D. At higher substrate concentration the pH increase.

Answer 1

The correct option is B Presence of an enzyme inhibitor in the reaction mixture.

• According to Michaelis- Menton equation, the rate of reaction is directly proportional to the substrate concentration. With an increase in the substrate concentration, the velocity or rate of the reaction also increases.
• It has been proved experimentally that if the enzyme concentration is kept constant and the substrate concentration is increased gradually, the rate of the reaction will increase until it reaches a maximum. After this point, the increase in substrate concentration will not increase the rate of the reaction and the graph will reach a saturation point.
• The given graph initially follows the above law, but after reaching the maximum substrate concentration the rate of the reaction declines with increase in the substrate concentration. This can only happen when there is presence of enzyme inhibitor in the reaction mixture. The enzyme inhibitor will prevent the enzyme from binding to the substrate, resulting in no formation of a product.
• Thus, the graph shows a declining rate even with an increase in the substrate concentration.