The lock-and-key analogy for enzymes applies to the specificity of enzymes a) as they form their tertiary and quaternary structure
b) binding to their substrate
c) interacting with water
d) interacting with ions

The correct answer is: B) binding to their substrate

The catalytic mechanism of an enzyme starts when the substrate binds to its active site (specific region of an enzyme). There is a theory (lock and key) that explains the mechanism of this binding: the lock is the enzyme and the key is the substrate and only if they fit the enzyme will work. The binding of the substrate to the enzyme causes conformational changes of the enzyme, and as a result, products are formed. The products are then released from the surface of tat enzyme. The enzyme is regenerated for another reaction cycle.