According to the induced fit model of enzyme action, the active site
Correct answer: B. changes shape slightly as the substrate binds
- A. is already an exact complement of the substrate before binding
- B. changes shape slightly as the substrate binds
- C. plays no part in catalysis
- D. binds any substrate regardless of shape
Explanation
Koshland's induced fit model replaced the rigid lock and key picture: the active site is flexible and moulds itself around the substrate as binding occurs, straining the bonds that are about to break. The lock and key model is the one that treats the site as pre-formed and rigid. Specificity is retained in both models, so an enzyme still does not bind just any substrate.
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About Mode of Enzyme Action
Enzyme action depends on the active site forming a temporary enzyme substrate complex, then converting substrate into products with lower activation energy. The lock and key and induced fit models explain specificity and binding, while cofactors and changes in enzyme shape can affect catalysis.
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