#22 Enzymes - 'Lock and key' model

Enzymes are very specific, each kind of enzyme catalyse one kind of reaction only. To catalyse a reaction, enzyme molecule and substrate molecule need to meet and joint together by a temporary bond.

Each molecule has a special shape and an active site into which its substrate molecule fits exactly.

This enzyme is amylase, and its active site is just the right size and shape

for a substrate molecule (starch in this case).

The starch slots into the active site.

The starch is split into maltose molecules.

The enzyme is unaltered, and ready to accept another part of the starch molecule