Lock and Key Hypothesis for Enzyme Action

Steps:

• The lock and key hypothesis states that enzymes catalyze reactions by binding specific substrates at their active site.
• The active site is a region on the enzyme with a shape complementary to the substrate.
• In the analogy, the enzyme's active site acts as the lock, and the substrate acts as the key that fits perfectly.
• Match choices to this: active site on enzyme (true), on substrate (false), substrate as lock (false), as key (true).

Why A is correct:

• It accurately reflects the hypothesis definition, where the enzyme's active site is the lock and the substrate is the key.

Why the others are wrong:

• B: Falsely locates active site on substrate and calls substrate the lock, reversing the analogy.
• C: Incorrectly places active site on substrate while partially matching the key role.
• D: Same as C, wrongly attributes active site to substrate.

Final answer: A