Uncatalyzed versus enzmatically-catalyzed cellular reactions

    In the absence of a catalyst (left), conversion of a substrate (S) to a product (P) requires the input of a large energy of activation (Ea). For example, many reactions will proceed when heated: the albumin protein in an egg coagulates when boiled. However, the amount of energy required is typically incompatible with most cellular processes: most biological systems will not survive boiling. 

    In the presence of an enzyme catalyst (E) (right), an enzyme / substrate complex (ES) forms, for which the required Ea is much less, and the reaction can proceed under physiological conditions. When the reaction is complete, the enzyme is released unchanged, and can be recycled for use in subsequent reactions.

All text material ©2009  by Steven M. Carr