Question

In a chemical reaction, enzymes catalyse the reaction by
(A) lowering the activation energy.
(B) increasing the activation energy.
(C) decreasing the free energy change between reactants and products.
(D) increasing the free energy change between reactants and products.

Answer 1

Enzymes are called the biocatalyst. They act on the substrate and give us the final product. The enzymes speed up the rate of forward reaction. They do not get consumed during a chemical reaction.

Complete answer:
To answer this question, we must know about the mechanism of enzymatic action. The enzymes are the biological agents which speed up the forward reaction without getting itself consumed. It facilitates the formation of the product from the reactant or the substrate. The enzymes work efficiently by changing the activation energy of the reactants which leads to the product.

Activation energy is the energy required to start a chemical reaction. When the energy required to start the reaction will be less, the product formation will be faster. The rate of the reaction increases if the activation energy is lower. So we can say that enzymes lower the activation energy of the reactant so that the product is formed at the faster rate.

Now let us discuss the free energy in an enzymatic reaction.
Free energy- It is the amount of energy released in the conversion of the reactant to product under standard conditions. In case of enzymatic reactions, free energy does not have any effect on the formation of the product or by how much the reactant has been used up.

Additional Information: The enzymes have an active site which is specific for a particular substrate to bind so as to form a product. Sometimes instead of substrate, inhibitors which are similar in configuration to that of substrate bind at the active site and bring about inhibition of the enzyme action. This is known as competitive inhibition.

Therefore the correct answer is option ‘A’.

Note: The activation energy is dependent on the following factors.
Reactant concentration. Greater the concentration, faster the reaction.
- Surface area.
- Pressure.
- Temperature
- Presence or absence of catalyst.
-Nature of reactants.