Question

(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
Choose the correct answer from the options given below:

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

Hint:

Enzymes lower the activation energy of a reaction using weak, non-covalent interactions (hydrogen, ionic, hydrophobic) to bind the substrate, accelerating rates by immense factors (\(10^5\text{ to }10^{17}\)).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Enzymes are highly efficient biological catalysts that accelerate chemical reactions in living cells without being consumed in the process.
The mechanism of enzyme action relies on binding substrates at the active site, forming an enzyme-substrate (ES) complex.
This binding stabilizes the transition state of the reaction, reducing the energy barrier required for the reactants to convert into products.
Understanding the thermodynamic and kinetic principles of enzymes is fundamental to biochemistry.

Step 2: Detailed Explanation:
Let us evaluate each of the given statements:
Statement (A) is incorrect:
Enzymes are extraordinarily efficient catalysts, enhancing reaction rates by massive factors ranging from \(10^5\) to \(10^{17}\) times compared to uncatalyzed reactions.
Stating that they enhance reaction rates by a factor of only 2 to 10 is completely incorrect, as such low values are characteristic of minor temperature increases rather than enzyme catalysis.
Statement (B) is correct:
The primary mechanism by which enzymes accelerate reactions is by lowering the activation energy (\( \Delta G^\ddagger \)) required to reach the transition state.
They do not alter the overall free energy change (\( \Delta G \)) of the reaction or the equilibrium constant, but they make the path to the transition state much easier.
Statement (C) is correct:
The interactions between an enzyme's active site and its substrate are primarily weak, non-covalent interactions.
These include hydrogen bonds, electrostatic (ionic) interactions, hydrophobic interactions, and van der Waals forces.
These weak interactions are highly specific and provide the binding energy needed to stabilize the transition state.
Statement (D) is incorrect:
Substrate concentration (\([S]\)) has a direct, profound effect on the rate of enzyme-catalyzed reactions.
As described by Michaelis-Menten kinetics, the reaction rate increases linearly with substrate concentration at low levels, and then approaches a maximum velocity (\( V_{\max} \)) asymptotically as the enzyme becomes saturated with substrate.
Therefore, statements (B) and (C) are correct, which corresponds to option (B).

Step 3: Final Answer:
Thus, the correct statements are represented by (B) and (C) only.