Here's why:

* Active sites are three-dimensional pockets or clefts on the surface of an enzyme.

* They are formed by the specific arrangement of amino acids within the protein's folded structure.

* This unique shape allows the enzyme to bind to a specific substrate molecule (the molecule the enzyme acts upon).

* The active site facilitates the chemical reaction by providing a specific environment for the substrate to undergo a transformation.

Let me know if you'd like more information about how active sites work!