Enzymes are protein molecules that function as catalysts which speed up a chemical reaction. They take part in the reaction, by providing an alternative pathway with lower activation energy; they are involved in the reaction, but are not consumed or permanently changed by the reaction. Without enzymes, the cellular reactions required for life would take greater time to happen, therefore not keeping the organism functioning. Enzymes are substrate-specific meaning that there is a different enzyme involved in different chemical reactions taking place inside a cell. For two molecules to begin working, they must collide strongly with one another, so that the there is enough activation energy. The enzyme has an active site, which is where an enzyme