Chemical Reaction and Enzyme
H. Chemical Reactions and Enzymes
1. Chemical Reactions– process that changes
one set of chemicals into another set of chemicals.
CO2 + H2O
H2CO3
a. Chemical reactions always involve
changes in chemical bonds that join
atoms in compounds
b. Reactants– starting materials of
chemical reactions
c. Products– newly formed molecule or
end result of an chemical reactions.
2. Energy in Reactions– energy can be released
or absorbed whenever chemical bonds are made
or broken
a. Energy changes are
single most important
factor determining how
easily chemical reaction
will occur
1). Chemical reactions
that absorb energy (need
energy to occur) will not
proceed without a source
of energy
2). Activation energy– energy needed to get
reaction going; How tall is the energy hill?
3. Enzymes– specialized proteins that act as
biological catalysts
(catalysts– a substance that speeds up rate of
chemical reaction by lowering a reaction’s
activation energy)
a. Living cells use
enzymes to speed up
virtually every important
chemical reaction that
takes place in cells.
These reactions would
otherwise be too slow to
sustain life.
b. Enzymes are specific to
their substrate.
c. Name of enzyme derived
from reaction it catalyzes
(ends with –ase)
Ex: lactase breaks apart
lactose
d. Enzymes are not used up
in a chemical reaction.
e. Enzyme = Protein (chain
of amino acids)
4. Enzyme action– can
increase reaction speed 1010
times
1). reactants are known as
substrates
2). Substrates bind to enzyme
at Active site (shape of
active site fits substrate like
“lock and key”)
3). Once products made
enzyme is free to continue
catalyzing the process
Enzyme Lactase Activity:
• Enzymes are
specific: lactase can
only breakdown
lactose, not sucrose.
Factors affecting Enzymes
5. Enzymes affected by pH, temperature and
the concentration of enzyme/substrate
If an enzyme denatures because it is heated
to too high of a temperature, then it will lose
the 3D structure and its function. It may or
may not be able to re-fold or renature.
Important Enzyme in
your Body
Catalayse: breaks down hydrogen
peroxide (H2O2) to water and oxygen.
Amylase: breaks down starch into
glucose in the mouth.
Pepsin: works in the stomach to break
down protein into amino-acids
Trypsin: works in the small intestine to
break down protein into amino-acids.
• Identify optimal pH for
Pepsin and Trypsin
c. Cells can regulate activities of
enzymes. Proteins turn a gene
“on” or “off” so it is made into a
protein or not.