Enzymes speed up chemical reactions without being used up in the reaction.

Question

BlackTom AI · Accepted Answer

Enzymes are biological catalysts that increase reaction rates by lowering the activation energy of a reaction without being permanently altered or consumed in the process.

1. Relevant knowledge points and concepts
- Catalyst: a substance that increases the rate of a chemical reaction while remaining chemically unchanged at the end of the reaction cycle.
- Active site and enzyme-substrate complex: enzyme binds substrate(s) to form a transient complex that facilitates bond-making/bond-breaking.
- Turnover: one enzyme molecule can convert many substrate molecules into product because it is released unchanged and available to bind another substrate.
- Cofactors/coenzymes: non-protein components may assist catalysis but the enzyme itself still functions catalytically.

2. Step-by-step reasoning
- Step 1: Substrate binds to the enzyme’s active site, forming an enzyme-substrate complex.
- Step 2: The enzyme stabilizes the transition state, lowering activation energy and accelerating conversion of substrate to product.
- Step 3: Product is released from the enzyme’s active site.
- Step 4: The enzyme returns to its original state and is free to catalyze another reaction cycle.

3. Intermediate steps and details
- Binding is typically reversible; formation and breakdown of the enzyme-substrate complex are part of a cyclic process (E + S ⇌ ES → E + P).
- Because the enzyme is regenerated after product release, the same enzyme molecule can catalyze many reaction cycles (high turnover number).

4. Why the correct answer is correct
- The defining property of enzymes as catalysts is that they are not consumed by the reactions they catalyze; they facilitate but do not become permanent reactants or products. Empirical evidence (enzyme kinetics) shows enzymes remain available after product formation.

5. Why the other option is incorrect
- The statement “False” would imply enzymes are used up in the reaction. That contradicts the catalyst definition and observations of enzyme turnover. Although enzymes can be temporarily modified or irreversibly inactivated (e.g., proteolytic cleavage of a zymogen or irreversible inhibitors), these are exceptions to the general catalytic property, not the rule.

6. Conclusion
- The correct answer is True, matching the provided answer.

Enzymes speed up chemical reactions without being used up in the reaction.判断题

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