The special molecules that speed up biochemical reactions are called:

1. A substance that helps a chemical reaction to occur is a catalyst. 2. Living cells use a protein catalyst for each step of a pathway. 3. The special molecules that catalyze biochemical reactions are called enzymes. 4. Each reaction step is facilitated, or catalyzed, by one of them. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 6 'Metabolism', sections 6.1-6.5_