Eduprobe
Question:
Which of the following describes the given graph correctly?
Exothermic reaction with energy a is absence of enzyme and B in presence of enzyme.
Endothermic reaction with energy A in absence of enzyme and B in presence of enzyme.
Exothermic reaction with energy A in presence of enzyme and B in absence of enzyme.
Endothermic reaction with energy A is presence of enzyme and B in absence of enzyme.
Solution:
Any chemical reaction includes formation of a transition state between reactant and product. Formation of a transition state requires high energy content of reactant molecules for alignment of reacting groups, formation of transient unstable charges, rearrangements of chemical bonds, etc. The energy required for formation of a transition state is termed as activation energy. Enzymes enhance the rate of reaction by lowering down the activation energy of the transition state. In the given graph, the energy of the substrate is higher than that of the product, reflecting the endothermic nature of the reaction. B is the activation energy in the absence of an enzyme, which is lowered down to A in the presence of an enzyme. Therefore, the correct answer is option B.