RLO: Lock and Key Hypothesis

 

Lock and Key analogy

You may have the idea from the diagram of the cell, that the specificity in the reaction between a drug its target, relies on shape-specificity, and indeed this is the case. The relationship is often described using the analogy of a lock and its key.

If we take a step back for a moment, and use the analogy of the lock on the drugs cupboard itself we can explain how this works. To be secure this lock must only be opened by a specific key, otherwise it would be useless. This specificity relies on the shape of the key. There is a close physical interaction between the lock and its key- which must fit into the lock exactly in order to open it. Other keys, even closely related in shape, are unable to open the lock.