Which of the following statements best describes the interaction between an enzyme's active site and its substrate?

• A. The substrate and active site must have identical shapes for binding to occur.
• B. The substrate can bind to any region of the enzyme, regardless of shape.
• C. The substrate and active site bind only if they have no structural similarity.
• D. The substrate and active site must have complementary shapes for binding to occur.

Answer: (D)

Verified step by step guidance

1. Understand the concept of enzyme-substrate interaction: Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy. The active site of an enzyme is a specific region where the substrate binds to form an enzyme-substrate complex.
2. Learn about the 'lock and key' model: This model suggests that the active site of the enzyme and the substrate have complementary shapes, much like a key fitting into a lock. This structural complementarity ensures specificity in the binding process.
3. Explore the 'induced fit' model: While the 'lock and key' model emphasizes static complementarity, the 'induced fit' model explains that the active site can undergo slight conformational changes to better fit the substrate upon binding, enhancing the interaction.
4. Clarify misconceptions: The substrate does not bind to any random region of the enzyme; it specifically binds to the active site. Additionally, the substrate and active site must have structural similarity or complementarity, not identical shapes, for effective binding.
5. Conclude with the correct statement: The substrate and active site must have complementary shapes for binding to occur. This complementarity ensures the enzyme's specificity and efficiency in catalyzing the reaction.