Substrate

Real World Example

Imagine trying to find the right key to unlock a door in a large keychain. Just like the right key fits perfectly into the lock to open a door, a substrate is the specific reactant that fits into an enzyme's active site to initiate a reaction. In this analogy, the key represents the substrate, the door lock symbolizes the enzyme's active site, and just as only the correct key will unlock the door, only the correct substrate will bind to the enzyme to trigger a chemical reaction.