Substrate

In biochemistry, a substrate is a molecule undergoing a reaction, for which the presence of an enzyme lowers the activation energy. The substrate binds with the enzymes active site, and the enzyme provides an alternative reaction pathway with a lower activation enthalpy.

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In biology, a substrate is an environment in which an organism lives, and which it feeds on. For example, in many households, a bruised apple is a substrate for the growth of a fungus