Which of the following correctly completes the equation for enzyme-catalyzed reactions: active enzyme + (1)______ \rightarrow (2)______ + (3)______?

• A. (1) substrate; (2) enzyme-substrate complex; (3) product
• B. (1) inhibitor; (2) enzyme-inhibitor complex; (3) product
• C. (1) product; (2) enzyme-product complex; (3) substrate
• D. (1) cofactor; (2) enzyme-cofactor complex; (3) substrate

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the context of enzyme-catalyzed reactions. Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy. They interact with specific molecules called substrates to form an enzyme-substrate complex.
2. Step 2: Analyze the equation provided in the problem. The equation describes the sequence of events in an enzyme-catalyzed reaction: active enzyme + (1)______ → (2)______ + (3)______.
3. Step 3: Recall the typical progression of enzyme-catalyzed reactions. First, the enzyme binds to the substrate to form the enzyme-substrate complex. Then, the substrate is converted into the product, and the enzyme is released unchanged.
4. Step 4: Match the options provided with the correct sequence of events. The correct sequence involves (1) substrate, (2) enzyme-substrate complex, and (3) product, as this reflects the standard mechanism of enzyme action.
5. Step 5: Eliminate incorrect options. For example, inhibitors do not form enzyme-substrate complexes, and cofactors are not substrates. Products are formed at the end of the reaction, not at the beginning.