Final answer:
The "lock and key" model describes the highly specific interaction between an enzyme and a substrate, where the enzyme's active site has a particular shape that only allows a corresponding substrate to fit, comparing it to a key fitting into a lock.
Step-by-step explanation:
The Lock and Key Model
The "lock and key" model refers to the interaction between an enzyme and a substrate. In this model, the enzyme's active site is shaped in such a way that only a specific substrate can fit into it, much like a key fitting into a lock. This highlights the specificity between enzymes and substrates where the molecular shapes of the active site and substrate are complementary to one another, leading to the formation of an enzyme-substrate complex.
The lock-and-key model is a simplistic way to describe this interaction, portraying the enzyme as conformationally rigid, bonding only with substrates that exactly fit its active site. However, this model has been refined by the induced fit model, which suggests that the enzyme structure is somewhat flexible and can adjust to better accommodate the substrate.