Final answer:
The lock-and-key model is a hypothesis that explains how enzyme-substrate interactions work. Enzymes have a specific structure with an active site that is complementary to the substrate. This model suggests that enzymes only interact with specific substrates that match their active site.
Step-by-step explanation:
The lock-and-key model is a hypothesis that explains how enzyme-substrate interactions work. According to this model, enzymes have a specific structure with an active site that is complementary in shape to the substrate. Just like a key fits into a lock, the substrate fits into the active site of the enzyme, forming an enzyme-substrate complex. This model suggests that enzymes only interact with specific substrates that match their active site.