Coenzymes play a role in the functions of cells. Reactions within the cells work to either break down nutrients or combine molecules for cellular activities that keep the cells alive. Enzymes speed up these reactions. Without enzymes, these reactions may not occur. Coenzymes, in turn, support the functions of enzymes. They loosely bind to enzymes to help them complete their activities. Coenzymes are nonprotein, organic molecules that facilitate the catalysis, or reaction, of its enzyme.