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Name: Lisa
Status: Student
Grade:  9-12
Location: NY
Country: United States
Date: January 2005

How is the reversibility of an enzyme controlled? What determines whether it will make a product or dismantle it?

The enzyme does not affect the equilibrium of the reaction, that is, the ratio of substrate to product. If an enzyme is added to a solution of S it will produce P until the equilibrium ratio of S/P is attained. If enzyme is added to a solution of P, it will produce S until the same equilibrium ratio is attained . At equilibrium, the rate of formation of P from S is the same as the rate of formation of S from P in terms of moles/unit time. In short, the direction that the enzyme catalyzes depends on how far away from equilibrium the reaction is.

Ron Baker, Ph.D.

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