Enzymes act as reusable catalysts

Steps:

• Recall that enzymes are biological catalysts that speed up reactions without being consumed.
• Understand the enzyme-substrate complex forms temporarily, then breaks apart, releasing products.
• Note that the enzyme returns to its original shape and state after the reaction.
• Eliminate options that suggest permanent change or consumption, leaving the reusability choice.

Why D is correct:

• Enzymes are catalysts defined as substances that lower activation energy and remain unchanged, allowing reuse for the same reaction.

Why the others are wrong:

• A: Enzymes retain their active site structure and can bind substrates repeatedly.
• B: Enzymes are highly specific to one type of reaction due to their unique shape.
• C: Enzymes are not incorporated into products; they only facilitate the reaction.

Final answer: D