Question

Which of the following observations favors the induced-fit model for enzyme-substrate interactions?

1) The active site of enzymes often includes charge or polar amino acids.
2) The active site of enzymes is composed of amino acids that are not necessarily next to each other in the polypeptide before it folds.
3) X-ray diffraction allows identification of the amino acids that have side chains protruding into an active site.
4) X-ray diffraction shows that enzymes bound to substrate have different shapes from those same enzymes in the absence of substrate binding

Answer 1

Observation 4 supports the induced-fit model because it demonstrates that enzymes change shape when binding to substrates, as evidenced by X-ray diffraction studies.

Step-by-step explanation:

The question asks which observation favors the induced-fit model for enzyme-substrate interactions. The induced-fit model suggests that enzymes are flexible and can undergo a conformational change upon binding with a substrate, adapting to its shape for optimal interaction. From the provided options, observation 4, which states that "X-ray diffraction shows that enzymes bound to substrate have different shapes from those same enzymes in the absence of substrate binding," directly supports the induced-fit model. This observation indicates that the enzyme's active site changes shape during the catalysis process to accommodate the substrate, which aligns with the concept that the enzyme and substrate adjust to each other, rather than being a perfect fit from the start as suggested by the lock-and-key model.