Macromolecules in the cell such as DNA, RNA, and proteins are interdependent for mutual synthesis. Within the cell, proteins used for enzyme catalysis, structural components, energy generation, and digestion of food, are produced through an amazing manufacturing process, involving DNA as a template for the three types of RNA (mRNA, tRNA, and rRNA), which in turn act as different components in the synthesis and coding of each protein molecule. But, each step in this complicated synthesis is catalyzed by an enzyme, which, since it is a protein, would have had to be synthesized by the same process! In other words, the end products of this reaction aid in the synthesis of the starting components and catalyzes each reaction along the way, making up a complicated series of interrelationships. In order to explain life, then, the appearance of this entire machinery must be explained.