Download 2–4 Chemical Reactions and Enzymes

Chemical Reactions and
Enzymes
Why are enzymes important to
living things?
Standards
CLE 3210.1.3 – Describe how
enzymes regulate chemical reactions in
the body.
●Class Objectives:
Describe how the enzyme and
substrate interact to catalyze
chemical reactions.
Describe conditions that affect
enzyme function.
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Chemical Reactions
 process that changes one set
of chemicals into another set
of chemicals
Chemical Reactions
 always involve the breaking of
bonds in reactants and the
formation of new bonds in
products
 reactants - elements or
compounds that enter into a
chemical reaction
 products - elements or
compounds produced by a
chemical reaction
Energy in Reactions
 Energy is released or
absorbed whenever chemical
bonds form or are broken.
 Chemical reactions that
release energy often occur
spontaneously.
Energy may be released as
light, heat, and/or sound.
Energy in Reactions
 Chemical reactions that
absorb energy will not occur
without a source of energy.
 Every organism must have
a source of energy to carry
out chemical reactions
Activation Energy
 energy that is needed to get a
reaction started
Enzymes
 catalyst - substance that
speeds up the rate of a
chemical reaction
works by lowering a
reaction’s activation
energy
Enzymes
 enzymes - proteins that act
as biological catalysts
very specific, generally
catalyzing only one chemical
reaction
part of an enzyme’s name is
usually derived from the
reaction it catalyzes
Enzyme Naming
 The enzyme’s name is usually
from the chemicals in the reaction
it catalyzes.
 Usually ends in -ase
Enzyme examples
DNA polymerase – links
nucleotides together to
make DNA
Carbonic anhydrase –
speeds up the conversion
of CO2 to carbonic acid in
the blood
The Enzyme-Substrate
Complex
 Enzymes provide a site where
reactants can be brought
together to react.
 Such a site reduces the
energy needed for reaction.
 Substrates - reactants of
enzyme-catalyzed reactions
Enzyme-Substrate Complex(Lock
& Key Model)
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Substrate:
The reactant(s) of
the chemical
reaction.
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Active Site:
Part of the
enzyme into
which the
substrate fits.
Induced Fit Model
Enzyme-substrate complex
 Enzyme
how enzymes work…
 hexokinase
 Substrates
 Glucose
 ATP
 Substrates bind to active
site on enzyme
 lock and key
 Once reaction is over,
products of reaction are
released and enzyme is
free to start process
again
Synthesis and Decomposition
Enzymes can participate in two
types of reactions:
Synthesis:
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A reaction in which two or more substrates are
combined to form one product.
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Decomposition:
A reaction in which one substrate is separated
to form two or more products.
Regulation of Enzyme
Activity
 Enzymes can be affected by any
variable that influences a
chemical reaction
 pH
 temperature
 certain proteins help turn
enzymes “on” or “off”