Which statement about enzymes is true?

• A. They are not consumed in the reaction
• B. They are consumed during the reaction
• C. They are permanently altered into products
• D. They change the equilibrium constant of the reaction

Answer: (A)

Enzymes function as biological catalysts by lowering the activation energy of a reaction, allowing it to proceed more rapidly. They are not consumed in the process; after the substrates are converted to products, the enzyme is free to catalyze additional rounds. The enzyme itself is not permanently altered into a product. Additionally, enzymes do not change the equilibrium constant of a reaction—they speed up reaching equilibrium by increasing both forward and reverse reaction rates, but the final balance of products and reactants remains the same. Thus the statement that enzymes are not consumed in the reaction is the correct one.