In the lock and key model, the active site is like a keyhole; what must the drug possess?

In the lock and key model, the active site is like a keyhole; what must the drug possess?

• A. A covalent bond to the receptor
• B. High lipophilicity only
• C. Complementary size, shape, and charge
• D. A flexible structure that adapts after binding

Answer: (C)

In the lock and key idea, the active site is a highly specific pocket with particular size, shape, and charge. For binding to occur, the drug must have complementary size and shape so it fits precisely, and a matching charge distribution to form stabilizing non-covalent interactions (like hydrogen bonds and ionic or van der Waals contacts). This precise fit allows strong, selective binding without needing covalent bonds. Lipophilicity alone isn’t enough to ensure proper binding, and a flexible structure that adapts after binding reflects a different model (induced fit) rather than the rigid lock-and-key picture.

In the lock and key idea, the active site is a highly specific pocket with particular size, shape, and charge. For binding to occur, the drug must have complementary size and shape so it fits precisely, and a matching charge distribution to form stabilizing non-covalent interactions (like hydrogen bonds and ionic or van der Waals contacts). This precise fit allows strong, selective binding without needing covalent bonds. Lipophilicity alone isn’t enough to ensure proper binding, and a flexible structure that adapts after binding reflects a different model (induced fit) rather than the rigid lock-and-key picture.