Chapter 5 Chemical Reactions and Enzymes

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
Objectives:
◦ Take quiz on energy conversions
◦ Describe how an enzyme works
◦ Complete toothpick enzyme lab

Review Questions:
◦ 1. What does the Law of Conservation of Energy
say?
◦ 2. What type of energy conversion does a solar
panel on a house carry out?


Other Instructions: Turn in vocab., 11x17
Coloring sheet, and fill-in-the-blank from
yesterday
 What
happens to chemical
bonds during chemical
reactions?
 How do energy changes affect
whether a chemical reaction
will occur?
 Why are enzymes important to
living things?
 Living
things are made up of
chemical compounds
 Everything that happens to an
organism is based on chemical
reactions
A
process that changes or
transforms one set of
chemicals into another
 Elements
or compounds that
enter into a reaction
 Elements
or compounds
produced by a chemical
reaction
 In
the blood
CO2 + H20  H2CO3 (carbonic acid)
 In the lungs
H2CO3  CO2 + H2O
Released as you
breathe
Energy-Absorbing Reaction
Energy-Releasing Reaction
Activation
energy
Products
Activation energy
Reactants
Reactants
Products
 The
energy that is needed to
get a reaction started
 Some
chemical reactions are
too slow or have activation
energies that are too high to
make them practical for living
tissue
 These chemical reactions are
made possible by catalysts
 Substance
that speeds up the
rate of chemical reactions
 Work by lowering a reactions
activation energy
 Are
known as Biological
catalysts
 Speed up reactions in cells
 Very specific name for the
reaction is catylzes
 Enzyme names always end in ase
Reaction pathway
without enzyme
Activation energy
without enzyme
Reactants
Reaction pathway
with enzyme
Activation
energy
with enzyme
Products
 The
reactants of enzyme
catalyzed reactions
 The active site of the enzyme
and the substrate have
complementary shapes
 Fit like a lock and key
Enzyme – substrate complex
ADP
Enzyme
(hexokinase)
Glucose
Substrates
Products
ATP
Glucose-6phosphate
Products
are released
Active site
Enzyme-substrate
complex
Substrates
are converted
into products
Substrates
bind to
enzyme

1.
2.
3.
Enzymes are affected by any
variable that affects chemical
reactions
pH
Temperature
Concentration
of enzyme
1.
What happens to chemical bonds
during chemical reactions
Bonds are broken in reactants
and new bonds are formed in
products
2. Describe the role of energy in
chemical reactions
some chemical reactions release
energy, and other chemical
reactions absorb energy. Energy
changes determine how easily a
3. What are enzymes, and how
are they important to living
things?
Enzymes are biological
catylasts. Cells use enzymes to
speed up virtually every
important chemical reaction
that takes place in cells
4. Describe how enzymes work,
including the role of the
enzyme substrate complex
Substrates, the reactants of an
enzyme-catylzed reaction,
attach to the enzyme at an
active site and form an
enzyme – substrate complex.
Once the complex is formed,
the enzyme helps convert
5. A change in pH can change the
protein. How might a change in
pH affect the function of an
enzyme such as hexokinase (hint:
think about the analogy of the
lock and key)
A change in pH could change the
shape of hexokinase. This change
would diminish the ability of
glucose and ATP to bind to the
active site of the enzyme.
 1.
Temperature (high and low)
 2. pH (generally low)
 3. enzyme concentration
In colder temps., the enzyme and
substrate are moving slower, so
they do not collide as often,
causing the rate of the reaction to
decrease (less products formed)

Enzyme is denatured, which
means that it changes shape
such that it can no longer
bind to the substrate
 More
enzyme available (higher
enzyme concentration =
reaction happens faster) more
product made
 Low
pH tends to break hydrogen
bonds, changing the shape of the
enzyme (denatured) so that it can
no longer bind to the substrate
1.
What happens to chemical bonds
during chemical reactions
Bonds are broken in reactants
and new bonds are formed in
products
2. Describe the role of energy in
chemical reactions
some chemical reactions release
energy, and other chemical
reactions absorb energy. Energy
changes determine how easily a
chemical reaction will occur
3. What are enzymes, and how
are they important to living
things?
Enzymes are biological
catylasts. Cells use enzymes to
speed up virtually every
important chemical reaction
that takes place in cells
4. Describe how enzymes work,
including the role of the
enzyme substrate complex
Substrates, the reactants of an
enzyme-catylzed reaction,
attach to the enzyme at an
active site and form an
enzyme – substrate complex.
Once the complex is formed,
the enzyme helps convert
substrate into product
5. A change in pH can change the
protein. How might a change in
pH affect the function of an
enzyme such as hexokinase (hint:
think about the analogy of the
lock and key)
A change in pH could change the
shape of hexokinase. This change
would diminish the ability of
glucose and ATP to bind to the
active site of the enzyme.
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