Question

The figure given above shows the conversion of a substrate into produced by an enzyme. In which one of the four option (1-4), the components of reaction labelled as A, B, C and D are identified correctly.

	A	B	C	D
1	Activation energy with enzyme	Transition state	Activation energy without enzyme	Potential energy
2	Potential energy	Transition state	Activation energy with enzyme	Activation energy without enzyme
3	Transition state	Potential energy	Activation energy without enzyme	Activation energy with enzyme
4	Potential energy	Transition state	Activation energy with enzyme	Activation energy without enzyme

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

The correct option is C 3

Enzymes are usually proteins that act like catalysts. The enzyme's ability to make the reaction faster depends on the fact that it stabilizes the transition state. The transition state's energy or, in terms of a reaction, the activation energy is the minimum energy that is needed to break certain bonds of the reactants so as to turn them into products. Enzymes decreases activation energy by shaping its active site such that it fits the transition state even better than the substrate.

When the substrate binds, the enzyme may stretch or distort a key bond and weaken it so that less activation energy is needed to break the bond at the start of the reaction. By optimizing binding of a tetrahedral atom, the substrate is helped on its way to the transition state and, therefore, lowers the activation energy, allowing more molecules to be able to turn into products in a given period of time.

In the transition state theory, the mechanism of interaction of reactants is not considered; the important criterion is that colliding molecules must have sufficient energy to overcome a potential energy barrier (the activation energy) to react. It takes a lot of energy to achieve the transition state, so the state is a high-energy substance. The potential energy of the system increases at this point because the approaching reactant molecules must overcome the mutual repulsive forces between the outer shell electrons of their constituent atoms and atoms must be separated from each other as bonds are broken. This increase in potential energy corresponds to an energy barrier over which the reactant molecules must pass if the reaction is to proceed.

The transition state occurs at the maximum of this energy barrier. The transition state is an unstable transitory combination of reactant molecules that occurs at a potential energy maximum. The energy difference between the reactants and the potential energy maximum is referred to as the activation energy.