Question

what is the next step in the process after a substrate enters the active site of an enzyme?
○ the chemical reaction occurs.
○ new substances called products are formed.
○ the enzyme and the substrate bind to form the enzyme - substrate complex.
○ the enzyme and the products bind to form the enzyme - products complex.

Explanation:

To determine the next step after a substrate enters the active site of an enzyme, we recall the enzyme - substrate interaction process. The steps in enzyme - catalyzed reactions are as follows: first, the substrate enters the active site of the enzyme. Then, the enzyme and the substrate bind to form the enzyme - substrate complex. After that, the chemical reaction occurs, and finally, products are formed and released from the enzyme.

• Option 1 ("The chemical reaction occurs") is not the immediate next step after the substrate enters the active site. The binding to form the complex happens first.
• Option 2 ("New substances called products are formed") is a later step in the process, after the chemical reaction has taken place.
• Option 3 ("The enzyme and the substrate bind to form the enzyme - substrate complex") is the correct next step. Once the substrate is in the active site, the enzyme and substrate bind to form this complex.
• Option 4 ("The enzyme and the products bind to form the enzyme - products complex") is incorrect because products are formed after the reaction, and this binding does not occur right after the substrate enters the active site.

Answer:

The enzyme and the substrate bind to form the enzyme - substrate complex.