A catalyst is something that can participate in chemical reactions, while it remains unchanged. It can speed the reaction along. Catalysts can cause a higher reaction rate than an uncatalyzed reaction, at the same temperature. In terms of living things, enzymes are called organic catalysts. They facilitate reactions in metabolism and catabolism. Enzymes are very important proteins necessary in the body for biochemical pathways. Enzymes work best in optimal conditions of ph, temperature, concentration of enzyme or substrate. Enzymes allow chemical reactions to proceed at body temperature which might normallly occur at much higher temperatures, in the absence of the enzyme.