Q.18 Identify the statement that is NOT applicable to an enzyme catalyzed reaction.
(A) Enzyme catalysis involves propinquity effects
(B) The binding of substrate to the active site causes a strain in the substrate
(C) Enzymes do not accelerate the rate of reverse reaction
(D) Enzyme catalysis involves acid-base chemistry

Enzyme catalysis lowers activation energy for both forward and reverse reactions equally, achieving rate accelerations of 10^6-10^12 fold through multiple mechanisms. Propinquity effects, induced strain, and acid-base chemistry all contribute to transition state stabilization. The incorrect statement claims enzymes fail to accelerate reverse reactions, contradicting fundamental catalysis principles.

Correct Answer

Option (C) “Enzymes do not accelerate the rate of reverse reaction” proves false. Enzymes reduce Eₐ for both directions equally per thermodynamic principles: if forward rate increases by factor X, reverse rate increases by identical factor. Equilibrium constant (K_eq =

/[reactants]) remains unchanged; only approach velocity accelerates. For A ⇌ B catalyzed by enzyme E, k_forward and k_reverse both multiply by same enhancement factor.

Option Explanations

• Propinquity effects (A): Correct—enzymes position substrates in optimal orientation, increasing effective molarity by 10^5-10^8 M through proximity and desolvation in active site.

• Substrate strain (B): Correct—induced fit distorts substrate bonds toward transition state geometry, reducing ΔG‡ via rack mechanism or differential binding.

• Reverse reaction myth (C): FALSE—enzymes catalyze reversibly; chymotrypsin hydrolyzes AND synthesizes peptide bonds depending on [H2O] vs [amine] concentrations.

• Acid-base chemistry (D): Correct—general acid/base catalysis via His/Asp dyads (serine proteases) or Ser/Lys pairs protonates/deprotonates during catalysis.

Biotech Applications

Understanding bidirectional catalysis proves essential for enzyme kinetics in Jaipur fermentation labs, where reverse reactions determine product yields in reversible transaminases. SEO-optimized publications leverage this principle for directed evolution, screening both k_cat/K_M forward and reverse to engineer industrial biocatalysts with balanced thermodynamics.