Answer: Decreasing Vmax without changing Km.
- A Increasing Km and decreasing Vmax
- B Decreasing Vmax without changing Km
- C Increasing Vmax without changing Km
- D Decreasing Km only
Correct answer: B. Decreasing Vmax without changing Km
Explanation: Non-competitive inhibitors bind to the allosteric site (not active site) and reduce Vmax by decreasing enzyme efficiency. Km is unchanged because substrate can still bind with same affinity.
As substrate concentration rises, reaction rate increases steeply at first, then plateaus at Vmax once every enzyme molecule is working at full capacity; Km is the substrate concentration giving half-maximal rate, and a LOWER Km means the enzyme reaches that rate with less substrate (higher affinity).
Concept context
Carbohydrates, proteins, lipids, nucleic acids, and enzyme kinetics. Essential foundation for understanding metabolism.