Download Chemical Reactions and Enzymes

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Energy
◦ The ability to do work or cause change
◦ Occurs in various forms
◦ Can be converted to another form
◦ Forms important to biological systems
are chemical, thermal, electrical and
mechanical energy
◦ Free energy is the energy in a system
that is available for work
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Atoms are in constant motion
The rate at which atoms or molecules in a
substance move determines its state
◦ Solid
 Molecules are tightly linked.
 Little energy
◦ Liquid
 Molecules are not as tightly
linked
 Medium amount of energy
◦Gas
Molecules have little or no
attraction to each other
Fill the volume of the occupied
container
Move most rapidly
To cause a substance to
change state, thermal energy
(heat) must be added to or
removed from a substance
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Living things undergo
thousands of
chemical reactions as
part of the life
process
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Many are very complex
involving multistep sequences
called biochemical pathways
Chemical equations represent
chemical reactions
◦ Reactants are shown on the
left side of the equation
◦ Products are shown on the
right side
 A+B
C+D

Much of the energy
organisms need is
provided by sugar
(food)
◦ Undergoes a series of
chemical reactions in
which energy is released
(cell respiration)

The net release of
free energy is called
an exothermic
reaction
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Reactions that
involve a net
absorption of free
energy are called
endothermic
reactions
Photosynthesis is
an example
Mix Barium
hydroxide
and
aluminum
salt, and
the
products
dissolve in
water of
hydration.
This is
VERY COLD!
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Most chemical reactions require energy to
begin
The amount of energy needed to start the
reaction is called activation energy

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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
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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!