Which of the following statements best helps explain the reaction specificity of an enzyme?

• A. Enzymes are consumed during the reaction, ensuring only one type of reaction occurs.
• B. The concentration of substrate determines the specificity of the enzyme.
• C. Enzymes increase the temperature of the reaction environment to favor certain reactions.
• D. The active site of an enzyme has a unique three-dimensional structure that binds only specific substrates.

Answer: (D)

Verified step by step guidance

1. Understand the concept of enzyme specificity: Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy. Their specificity is determined by the unique three-dimensional structure of their active site.
2. Recognize the role of the active site: The active site is a specific region on the enzyme where the substrate binds. This binding is highly specific due to the complementary shape, charge, and chemical properties of the active site and the substrate.
3. Eliminate incorrect options: Analyze the provided statements. Enzymes are not consumed during the reaction; they remain unchanged and can catalyze multiple reactions. Substrate concentration affects reaction rate but does not determine enzyme specificity. Enzymes do not increase the temperature of the reaction environment; they work at physiological temperatures.
4. Identify the correct explanation: The correct statement is that the active site of an enzyme has a unique three-dimensional structure that binds only specific substrates. This structural complementarity ensures reaction specificity.
5. Relate to real-world examples: Consider examples like hexokinase, which specifically binds glucose and ATP to catalyze the phosphorylation of glucose, demonstrating the importance of the active site's structure in determining enzyme specificity.