Chemistry 121(01) Winter 2009
Introduction to Organic Chemistry and Biochemistry
Instructor Dr. Upali Siriwardane (Ph.D. Ohio State)
E-mail: upali@chem.latech.edu
Office: 311 Carson Taylor Hall ; Phone: 318-257-4941;
Office Hours: MTW 9:00 am - 11:00 am;
TR 9:00 - 10:00 am & 1:00-2:00 pm.
December 19, Test 1 (Chapters 12-14)
January 2 Test 1 (Chapters 15-16)
February 6 (Chapters 17-19)
February 27, (Chapters 20 & 22)
March 2, 2009, Make Up Exam:
Bring Scantron Sheet 882-E
Chemistry 121 Winter 2009 LA Tech
Chp. 21-1
Chapter 21. Enzymes and Vitamins
Sections
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Chp. 21-2
Chapter 21. Enzymes and Vitamins
21.1 General Characteristics of Enzymes
21.2 Nomenclature and Classification of Enzymes
21.3 Enzyme Structure
21.4 Models of Enzyme Action
21.5 Enzyme Specificity
21.6 Factors That Affect Enzyme Activity
21.7 Enzyme Inhibition
21.8 Regulation of Enzyme Activity: Allosteric Enzymes
21.9 Regulation of Enzyme Activity: Zymogens
21.10 Antibiotics That Inhibit Enzyme Activity
21.11 Medical Uses of Enzymes
21.12 Vitamins
21.13 Water-Soluble Vitamins
21.14 Fat-Soluble Vitamins
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Chp. 21-3
Chapter 21. Enzymes
Nomenclature and Classification
Activation Energy
Enzyme-Substrate Interaction
Cofactors and Coenzymes
Effect of pH and Temperature
Regulation of Enzyme Activity
Chemistry 121 Winter 2009 LA Tech
Chp. 21-4
Biological Catalysts
Typically very large proteins
Permit reactions to to “go” to conditions that the body
can tolerate
Can process millions of molecules per second
Are very specific-react with one or only a few types of
molecules (substrates).
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Chp. 21-5
Enzyme Nomenclature
Naming is easy compared to other organic compounds
Name is based on:
-What it reacts with
-how it reacts
-add -ase- ending
Examples
lactase
enzyme that reacts with lactose
pyruvate decarboxylase
remove carboxyl group from pyruvate
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Chp. 21-6
Classification of Enzymes
•
•
•
•
•
•
Oxidoreductases: catalyze oxidation-reduction.
Transferases: transfer of functional groups.
Hydrolases: catalyze hydrolysis reactions.
Lyases: catalyse the removal of chemical groups.
Isomerases: catalyze isomerization reactions.
Ligases: catalyze formation of chemical bonds, join two
molecules
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Chp. 21-7
Effect of Enzyme on Activation Energy
• Enzyme change how
a reaction will proceed.
• This reduces the
activation energy
• It makes it easier
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Chp. 21-8
Effect of Enzyme on Activation Energy
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Chp. 21-9
Effect of Substrate Concentration
• For non-catalyzed reactions
Reaction rate increase with concentration
• Enzyme catalyzed reactions
Also increase but only to a certain point
Vmax Maximum velocity
At Vmax, the enzyme is working as fast as it can
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Chp. 21-10
Effect of Substrate Concentration
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Chp. 21-11
Characteristics of Enzyme Active Sites
• Catalytic site
Where the reaction actually occurs.
• Binding site
Area that holds substrate in proper place.
Enzyme uses weak, non-covalent interactions to hold
the substrate in place based on alkyl (R) groups of
amino acids.
Shape is complementary to the substrate and determines
the specificity of the enzyme.
Sites are pockets or clefts on enzyme surface.
Chemistry 121 Winter 2009 LA Tech
Chp. 21-12
Steps in Enzymatic Reactions
• Enzyme and substrate combine to form a complex
• Complex goes through a transition state
-which is not quite substrate or product
• A complex of the enzyme and the product is produced
• Finally the enzyme and product separate
All these steps are equilibria
Lets review each step
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Chp. 21-13
The Players
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Chp. 21-14
Formation of Enzyme-substrate Complex
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Chp. 21-15
Formation of the Transition State
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Chp. 21-16
Formation of the Enzyme-Product Complex
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Chapter
Twenty One
Chemistry 121 Winter 2009 LA Tech
Enzymes
and Vitamins
Chp. 21-51
Enzymes and Vitamins cont’d
← CO 21.1
© Mark E. Gibson / CORBIS
Chemistry 121 Winter 2009 LA Tech
Chp. 21-52
Enzymes and Vitamins
← Fig. 21.1
Bread dough rises as
a result of the action
of yeast enzymes.
Steven Needham / Envision
Chemistry 121 Winter 2009 LA Tech
Chp. 21-53
Enzymes and Vitamins cont’d
Table 21.1
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Chp. 21-54
Enzymes and Vitamins cont’d
→ Fig. 21.2
The active site of an
enzyme is usually a
crevice-like region
formed as a result of
the protein’s
secondary and
tertiary structural
characteristics.
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Chp. 21-55
Enzymes and Vitamins cont’d
Fig. 21.3
The lock-and-key model for enzyme activity.
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Chp. 21-56
Enzymes and Vitamins cont’d
Fig. 21.4
The induced-fit model for enzyme
activity.
Chemistry 121 Winter 2009 LA Tech
Chp. 21-57
Enzymes and Vitamins
cont’d
← Fig. 21.5
A schematic
diagram
representing
amino acid R
group interactions
that bind a
substrate to an
enzyme active
site.
Chemistry 121 Winter 2009 LA Tech
Chp. 21-58
Enzymes and Vitamins cont’d
→ Fig. 21.6
A graph showing
the effect of
temperature on
the rate of
enzymatic
reaction.
Chemistry 121 Winter 2009 LA Tech
Chp. 21-59
Enzymes and Vitamins cont’d
→ CC 21.1
Meckles / Ottawa / Photo Researchers
Chemistry 121 Winter 2009 LA Tech
Chp. 21-60
Enzymes and Vitamins cont’d
← Fig. 21.7
A graph showing the
effect of pH on the
rate of enzymatic
reaction.
Chemistry 121 Winter 2009 LA Tech
Chp. 21-61
Enzymes and Vitamins cont’d
→ CC 21.2
© Leonard Lessin / Peter Arnold, Inc.
Chemistry 121 Winter 2009 LA Tech
© Leonard Lessin / Peter Arnold, Inc.
Chp. 21-62
Enzymes and Vitamins cont’d
→ Table 21.2
Chemistry 121 Winter 2009 LA Tech
Chp. 21-63
Enzymes and Vitamins cont’d
→ Fig. 21.8
A graph showing the
change in enzyme
activity with a change
in substrate
concentration.
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Chp. 21-64
Enzymes and Vitamins cont’d
← Fig. 21.9
A graph showing the
change in reaction
rate with a change in
enzyme
concentration for an
enzymatic reaction.
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Chp. 21-65
Enzymes and Vitamins cont’d
 CAG 21.1
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Chp. 21-66
Enzymes and Vitamins cont’d
→ Fig. 21.10
A comparison of an
enzyme with a
substance at its
active site (a) and an
enzyme with a
competitive inhibitor
at its active site (b).
Chemistry 121 Winter 2009 LA Tech
Chp. 21-67
Enzymes and Vitamins cont’d
← Fig. 21.11
The difference
between a
reversible
competitive
inhibitor and a
reversible
noncompetitive
inhibitor.
Chemistry 121 Winter 2009 LA Tech
Chp. 21-68
Enzymes and Vitamins cont’d
→ Fig. 21.12
Conversion of
zymogen to a
proteolytic enzyme.
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Chp. 21-69
Enzymes and Vitamins cont’d
CAG 21.2
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Chp. 21-70
Enzymes and Vitamins cont’d
← Fig. 21.13
Structures of selected
sulfa drugs in use
today as antibiotics.
Chemistry 121 Winter 2009 LA Tech
Chp. 21-71
Enzymes and Vitamins cont’d
→ Fig. 21.14
Structures of selected
penicillins in use
today as antibiotics
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Chp. 21-72
Enzymes and Vitamins cont’d
Fig. 21.15
Selective binding of penicillin to the active site
of transpeptidase.
Chemistry 121 Winter 2009 LA Tech
Chp. 21-73
Enzymes and Vitamins cont’d
→ Table 21.3
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Chp. 21-74
Enzymes and Vitamins cont’d
→ CC 21.3
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Chp. 21-75
Enzymes and Vitamins cont’d
→ Table 21.4
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Chp. 21-76
Enzymes and Vitamins cont’d
→ Fig. 21.16
Drawing of a blood
sample.
Saturn Stills / SPL / Photo Researchers
Chemistry 121 Winter 2009 LA Tech
Chp. 21-77
Enzymes and Vitamins cont’d
← Fig. 21.17
Rows of cabbage
plants.
© Jeff Greenberg / Peter Arnold, Inc.
Chemistry 121 Winter 2009 LA Tech
Chp. 21-78
Enzymes and Vitamins cont’d
→ Fig. 21.18
The quantity of
vitamin D synthesized
by exposure of the
skin to sunlight
varies with latitude,
exposure time, and
skin pigmentation.
Melissa Grimes-Guy / Photo
Researchers
Chemistry 121 Winter 2009 LA Tech
Chp. 21-79
Enzymes and Vitamins cont’d
→ Table 21.5
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Chp. 21-80
Enzymes and Vitamins cont’d
→ Table 21.6
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Chp. 21-81
Enzymes and Vitamins cont’d
→ Table 21.7
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Chp. 21-82