active site
The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds.

allosteric site    (AL-oh-STEER-ik)
A specific receptor site on an enzyme molecule remote from the active site. Molecules bind to the allosteric site and change the shape of the active site, making it either more or less receptive to the substrate.

anabolic reactions
The process by which living organisms form complex molecules from simpler ones while storing energy.

catabolic reactions
A metabolic reaction that releases energy by breaking down complex molecules into simpler compounds.

competitive inhibitor
A substance that reduces the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics.

feedback inhibition
A method of metabolic control in which the end-product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.

hydrolysis    (hy-DROL-eh-sis)
A chemical process that lyses or splits molecules by the addition of water; an essential process in digestion.

An enzyme that converts sucrose to glucose and fructose.

metabolism    (meh-TAB-oh-liz-um)
The totality of an organism’s chemical processes, consisting of catabolic and anabolic pathways.

noncompetitive inhibitor
A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing its conformation so that it no longer binds to the substrate.

The substance on which an enzyme works.