Nutrition Science and Everyday Application - beta v 0.1

PROTEIN FUNCTIONS 323
ENZYMES
Enzymes are proteins that conduct specific chemical reactions. An enzyme’s job is to provide
a site for a chemical reaction and to lower the amount of energy and time it takes for
that chemical reaction to happen (this is known as “catalysis”). On average, more than 100
chemical reactions occur in cells every single second, and most of them require enzymes.
The liver alone contains over 1,000 enzyme systems. Enzymes are specific and will use only
particular substrates that fit into their active site, similar to the way a lock can be opened
only with a specific key. Fortunately, an enzyme can fulfill its role as a catalyst over and
over again, although eventually it is destroyed and rebuilt. All bodily functions, including the
breakdown of nutrients in the stomach and small intestine, the transformation of nutrients
into molecules a cell can use, and building all macromolecules, including protein itself,
involve enzymes.
Figure 6.11. Enzymes are proteins. An enzyme’s job is to provide a site for substances to
chemically react and form a product, and decrease the amount of energy and time it takes for this
to happen.