Enzymes
Chemical Reactions
 In order for chemical reactions to take place, enzymes must be
present to help speed up the reaction.
 Chemical bonds connect atoms
to make molecules.
 Chemical reactions can do two things:


They can join atoms to make molecules.
They can break bonds in molecules.
 The sum of all the chemical reactions that take place within a
cell is referred to as the cell’s metabolism.
Chemical Reactions
 The molecules or atoms at the beginning of a
chemical reaction are called the reactants.
 The materials produced by the chemical
reaction are called products.
2H2 + O2
Reactants

2H2O
Product
Law of Conservation of Matter/Energy
 Matter and Energy cannot be created or destroyed in
chemical reactions
Energy-Absorbing vs. Energy-Releasing Reactions
Energy-Absorbing Reaction
Endothermic Reaction
Energy-Releasing
Reaction
The molecules or atoms at the beginning of a
chemical reactions are called ______.
A. Enzymes
25%
25%
25%
25%
B. Reactants
C. Products
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Pr
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D. Active sites
Chemical reactions in which the products have more energy
than the reactants are called _________ reactions.
A. Energy-Releasing
50%
50%
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Ex
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En
do
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ic
B. Energy-Absorbing
Which graph illustrates an energy-releasing
reaction?
A. Graph A
B. Graph B
Introduction to Enzymes
 Enzymes are proteins that act as biological
catalysts.
Catalysts - speed up chemical reactions.
 Enzymes- speed up chemical reactions in living things.

Structure and Function of Enzymes
 A substrate is the molecule that the
enzyme changes.

It is the reactant a chemical reaction controlled by an
enzyme!
 Each enzyme has an active site which
is the place where the enzyme and
substrate attach.
Structure and Function of Enzymes
 During a chemical reaction, the enzyme helps the
reactant turn into product, however, the enzyme is not
changed.
 Enzymes can be used over and over again.
Reactant/Substrate
Enzyme
Product
No change in the
shape of
enzyme/ready to
catalyze next
reaction.
Enzymes are specific types of which biological
macromolecule?
A. Carbohydrates
70%
B. Proteins
C. Lipids
D. Nucleic acids
25%
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5%
The molecule on which an enzyme acts:
A. Catalyst
86%
B. Substrate
C. Metabolism
D. Homeostasis
14%
eo
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0%
Ho
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Which shape is the enzyme?
A
2. B
3. C
4. D
1.
25%
25%
B
A
D
A
25%
C
A
C
B
D
A
D
25%
Which shape is the product of the
chemical reaction shown below?
A
2. B
3. C
4. D
1.
25%
25%
B
A
D
A
25%
C
A
C
B
D
A
D
25%
Enzyme Specificity
 Enzymes are very specific. This means that
each enzyme can only work on one substrate.
 For
example:
 1.
Maltase only breaks down maltose (a carbohydrate).
 2.
Lipase only works on certain lipids.
 3.
Protease only works on certain proteins.
 Does a specific enzyme work on more than one
substrate?
• NO!!!
Enzyme Specificity
 Therefore you need thousands of different
enzymes for the thousands of different
chemical reactions in your body.
 The names of many enzymes (Amylase, Lipase,
Pepsin, Trypsin) usually end in ase or in.
Enzyme Specificity
 The diagram below shows the lock and key model of how
enzymes work on a specific substrate.
 Just like every lock has one type of key that opens it, every
substrate has one type of enzyme that works on it.
How Enzymes Work
 Lower activation energy
 Energy that is needed to start a chemical reaction
 Puts substrates in a good position to make/break bonds with
each other
Reaction with enzyme vs. Reaction without enzyme
The energy that is required to start a chemical
reaction is called
A. Endothermic
25% 25% 25% 25%
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energy
B. Exothermic energy
C. Enzyme energy
D. Activation energy
How do catalysts speed up or facilitate
chemical reactions?
A. Lower the activation
48%
energy
B. Add energy to the
reaction
C. Break hydrogen bonds in
the chemicals
D. Decrease the number of
reactants
33%
14%
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Enzymes lower activation energy
Enzymes and Their Environment
 Most cells function best within a narrow range
of temperature and pH.
 At very low temperatures, enzymes work too
slow.
Enzymes and Their Environment
 At high temperatures or extremes of pH
the enzymes lose their shape.
 What would happen if a key lost its shape?
It wouldn’t turn or fit in the hole.
 What will happen if an enzyme lost its
shape?
It wouldn’t recognize or bind with it’s
substrate.
Enzymes and Their Environment
 When an enzyme loses its shape and can no
longer work correctly, it has been denatured.
Enzymes stop functioning if:
A. They act on a
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Th
substrate
B. They become
denatured due to
improper pH or
temperature
C. They catalyze too
many reactions
D. They bind with the
wrong substrate
95%
When proteins, such as enzymes, lose their
specific shape they have become __________.
A. Passive
25%
25%
25%
25%
B. Endothermic
C. Exothermic
at
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D. Denatured
What is the optimum pH for the enzyme pepsin?
A. 1
B. 2.5
C. 5
D. 6.5
pepsin
trypsin
Introduction to Macromolecules
Building Macromolecules
 Polymer – large biomolecules made by linking together a
large number of the same type of subunit
 Monomer- small molecule that is a subunit of a polymer
(building blocks)
 Chemical reactions link monomers together to build
polymers or break down polymers into monomers

Enzymes help speed up these reactions!!
Organic Macromolecules (Polymers)
MONOMER
POLYMER
Amino Acid
Protein
Sugar
(monosaccharide)
Carbohydrate
(polysaccharide)
Nucleotide
Nucleic Acid
Polymers are large biomolecules made of
repeated subunits called
A. Enzymes
25%
25%
25%
25%
B. Sugars
C. Monomers
ns
Pr
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M
on
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Su
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es
D. Proteins
Proteins are polymers made of monomers called
A. Monosaccharides
25% 25% 25% 25%
B. Fatty acids
C. Amino acids
M
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D. nucleotides