Answer: Substrate concentration at half Vmax.
- A The maximum reaction rate achieved when the enzyme is fully saturated
- B Substrate concentration at half Vmax
- C The total enzyme concentration present within the reaction mixture
- D The pH value at which the enzyme shows peak catalytic activity
Correct answer: B. Substrate concentration at half Vmax
Explanation: Km is the substrate concentration at which the reaction velocity is half of Vmax. A lower Km means higher affinity of enzyme for substrate.
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.