The essential substance that increases the rate of a biochemical reaction is an enzyme.

Here's why:

* Enzymes are biological catalysts: They speed up reactions without being consumed in the process.

* They lower activation energy: Enzymes provide an alternative pathway for the reaction to occur, requiring less energy to start.

* Specificity: Enzymes are highly specific, meaning they typically catalyze only one or a small number of reactions.

Let me know if you'd like to know more about enzymes!