Question

Choose the correct answer from the options given below :
(A) Enzymes enhance reaction rate by a factor of 2 to 10.
(B) Activation energy of a reaction is lowered by enzymes.
(C) Interactions between enzymes and substrates are hydrogen, ionic and hydrophobic bonds.
(D) Substrate concentration does not affect the rate of enzyme-catalyzed reactions.

• (A) and (B) only.
• (B) and (C) only.
• (A) and (C) only.
• (A) and (D) only.

Hint:

Remember that enzymes lower the activation energy ($E_a$) but leave the starting reactants and ending products ($\Delta G$) completely unchanged.
They speed up how fast a reaction reaches equilibrium, but they do not change the position of that equilibrium.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Enzymes are biological catalysts (mostly proteins) that accelerate the rates of biochemical reactions.
They function by stabilizing transition states and lowering the energy barriers of reactions.

Step 3: Detailed Explanation:
Let us analyze each statement:
Statement (A): "Enzymes enhance reaction rate by a factor of 2 to 10."
This statement is incorrect.
Enzymes are incredibly powerful catalysts, typically enhancing reaction rates by factors of $10^5$ to $10^{17}$ compared to uncatalyzed reactions.
A factor of 2 to 10 is far too low.
Statement (B): "Activation energy of a reaction is lowered by enzymes."
This statement is correct.
Enzymes do not change the overall free energy change ($\Delta G$) of a reaction, but they lower the activation energy barrier ($E_a$) required to reach the transition state, allowing more molecules to react at a given temperature.
Statement (C): "Interactions between enzymes and substrates are hydrogen, ionic and hydrophobic bonds."
This statement is correct.
The initial binding of a substrate to an enzyme's active site relies on weak, reversible non-covalent interactions, including hydrogen bonds, ionic bonds (electrostatic interactions), and hydrophobic interactions.
Statement (D): "Substrate concentration does not affect the rate of enzyme-catalyzed reactions."
This statement is incorrect.
According to Michaelis-Menten kinetics, the rate of an enzyme-catalyzed reaction increases with substrate concentration until the enzyme becomes saturated ($V_{\max}$).

Step 4: Final Answer:
Only Statements (B) and (C) are correct.
This corresponds to Option (B).