Biochemistry—Core Properties of Enzymes Which of the following statements correctly describes enzymes and their catalytic function?

Introduction / Context:
Enzymes are nature’s catalysts, enabling rapid, specific chemical transformations in living systems. Understanding what enzymes change (rate, pathway) and what they do not change (overall thermodynamic favorability) is foundational to biochemistry and cell physiology.

Given Data / Assumptions:

• Reactions have an intrinsic free energy change (ΔG) governed by reactants and products.
• Activation energy (Ea) determines the kinetic barrier to reaction.
• Protein conformation dictates active-site geometry and specificity.

Concept / Approach:
Evaluate each statement against enzyme principles: enzymes lower Ea by stabilizing the transition state, orienting substrates, and providing catalytic groups. They do not change ΔG, equilibrium constant, or reaction stoichiometry; they simply allow equilibrium to be reached faster. Their function depends critically on native 3D structure (fold) that forms the active site.

Step-by-Step Solution:

Verification / Alternative check:
Thermodynamic cycles show ΔG depends only on initial and final states; catalysts change the pathway, not the endpoints. Kinetic data demonstrate exponential sensitivity of rate to Ea.

Why Other Options Are Wrong:

• E excludes statement B, which is a central truth about protein enzymes.

Common Pitfalls:
Thinking enzymes change equilibrium position; ignoring that some catalysts can be RNA (ribozymes), though the general protein statement remains valid for most enzymes.

Final Answer:
All of the above