Answer: The active site changes shape to better fit the substrate.
- A The enzyme shape is rigid and does not change
- B The active site changes shape to better fit the substrate
- C The substrate changes shape to fit the active site
- D Enzyme and substrate have identical shapes
Correct answer: B. The active site changes shape to better fit the substrate
Explanation: In the induced fit model (Koshland, 1958), the enzyme active site flexibly adjusts its shape when the substrate binds. This is more accurate than the rigid lock-and-key model.
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.