Question

The diagram illustrates energy changes in an enzyme controlled reaction.


Which of the following represents the lowering of the activation energy?

• A. X
• B. Y
• C. Z
• D. Z - Y

Answer 1

The correct option is D Z - Y

In enzymatically catalysed reactions, enzymes lower the amount of activation energy required to start the reaction. Activation energy is defined as the minimum amount of extra energy required by reacting molecules to get converted into the product(s).
The peaks of the curves refer to the transition state of the substrate being converted into the product(s). The difference in the energy level of the substrate and transition state is the activation energy required to start the reaction.

In the given graph, the addition of an enzyme has lowered the transition state that is represented by the peak of the curve Y. The difference in the transition state of curve Z and curve Y represents how much activation energy has been lowered due to the addition of enzymes. The lowering of the activation energy can be calculated by computing the difference between Z and Y transition states (Z-Y). Hence, the correct option is (d).