The molecules that control all chemical reactions in the body are called enzymes.

Here's why:

* Catalysts: Enzymes act as catalysts, meaning they speed up chemical reactions without being consumed in the process.

* Specificity: Each enzyme is highly specific for a particular reaction or a small group of reactions. This means they only work on certain molecules (substrates).

* Regulation: Enzyme activity is tightly regulated within the body. This allows the body to control the rate of various metabolic processes and maintain homeostasis.

While other molecules play roles in chemical reactions, enzymes are the primary catalysts and control centers of most biological processes.