Catalysts of Life
Review of Chemical Reactions
 A chemical reaction is a process that changes, or
transforms, one set of chemicals into another
 Reactants are elements or compounds that enter into a
chemical reaction
 Products are the elements or compounds produced by a
chemical reaction
 Chemical reactions usually require energy to get
started
 Activation energy is the energy that is needed to get a
reaction started
What are enzymes?
 Enzymes are proteins
that hasten, or speed up,
chemical reactions
 A catalyst is a substance
that speeds up the rate
of a chemical reaction
 Enzymes are biological
catalysts
 Enzymes speed up the
reactions that take place
in cells
How do enzymes work?
 The molecule that an enzyme
binds with or acts upon is
called the substrate
 The spot on an enzyme
where the enzyme and
substrate bind together is
called the active site.
 The active site is made of
deep folds created by the
folding of amino acid chains
 Enzymes can be used over
and over again after a reaction
is complete
How do enzymes work?
 Enzymes have a specific
shape
 Substrates also have a
specific shape
 In order for an enzyme
and substrate to bind
together and react, their
shapes MUST fit
together
 This is called the lockand-key model
How do enzymes work?
 If an enzyme shape does not match with a substrate, there
is no reaction
 An enzyme’s shape can be changed if conditions are not
right
 If an enzyme’s shape is changed due to changing
conditions, then the enzyme has been denatured
 No reaction can occur if an enzyme’s shape is denatured
 Factors that affect enzyme shape
 pH – too acidic or too basic
 Temperature – too hot or too cold
 Enzyme concentration – how many enzymes are there?
How do enzymes work?
 Web Link:
 http://www.lew-
port.com/10712041113402793/lib/10712041113402793/Ani
mations/Enzyme_activity.html
Other factors affecting enzymes
 Competitive inhibitors are molecules that are
similar to the substrate’s shape
 Competitive inhibitors get stuck in the active site and
prevent the enzyme from binding with the substrate
 Noncompetitive inhibitors are molecules that bind
near, but not at, the active site
 Noncompetitive inhibitors change the shape of the
active site and prevent the enzyme from binding with
the substrate