Which statement best describes the difference between kcat and Km?

• A. Both kcat and Km are measures of the rate-limiting step of a reaction.
• B. kcat and Km both measure the same aspect of enzyme kinetics.
• C. kcat measures catalytic efficiency, while Km measures substrate binding affinity.
• D. Km measures catalytic efficiency, while kcat measures substrate binding affinity.

Answer: (C)