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An enzyme  is a biological catalyst. It accelerates the speed of biochemical reaction. Most biological metabolism reactions need enzymes. At the beginning of the catalyzed chemical reaction, the chemicals are called substrates, and the final elements in the reaction are called products. The activity of certain enzymes can be altered by the interaction with other molecules, such as enzyme inhibitors and activators. Enzyme inhibitors, inhibit the reaction, and enzyme activators, are the opposite of enzyme inhibitors.
 Enzyme. In Wikipedia. Retrieved October 2015, from http://en.wikipedia.org/wiki/Enzyme
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