Question

Which statement describes the currently accepted theory of how an enzyme and its substrate fit together?

Option 1: As the product is released, the enzyme breaks down.
Option 2: The reactants are like a key that fits into the enzyme, which is like a lock.
Option 3: The active site is permanently changed by its interaction with the substrate.
Option 4: As any substrate binds to an enzyme, the shape of the active site changes to accommodate the reaction.

Answer 1

The induced fit hypothesis is the accepted model, where the enzyme's active site changes shape to accommodate the substrate, forming an enzyme-substrate complex and catalyzing the reaction.

Step-by-step explanation:

The currently accepted theory of how an enzyme and its substrate fit together is best described by the induced fit hypothesis. According to this model, when a substrate approaches an enzyme, it induces a conformational change in the active site of the enzyme. This change allows the active site to more effectively accommodate the substrate, resulting in an enzyme-substrate complex that facilitates the chemical reaction.

Option 4, 'As any substrate binds to an enzyme, the shape of the active site changes to accommodate the reaction,' correctly reflects this induced fit model. The other options either describe outdated models or inaccurately portray the behavior of enzymes, like the enzyme breaking down after releasing the product, the active site being permanently changed, or the substrate being a perfect fit without any change in enzyme structure.