Enzymes
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Most chemical reactions require energy to
begin
The amount of energy needed to start the
reaction is called activation energy


Certain chemical
substances
(catalysts)
reduce the
amount of
activation energy
required
Biological
catalysts are
called enzymes

Enzymes are an important class of
catalysts in living organisms
 Mostly protein
 Thousands of different kinds
 Each specific for a different chemical
reaction
Enzyme Structure
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Enzymes work on substances
called substrates
Substrates must fit into a
place on an enzyme called
the active site
Enzymes are reusable!