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Chemistry 24.3
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24.3
Amino Acids and Their Polymers
Many people are lactose
intolerant. These people
cannot digest milk products
because their bodies do not
produce enough of the enzyme
lactase to digest lactose, the
sugar found in milk. You will
learn what enzymes are and
what function they serve in the
body.
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Amino Acids and Their Polymers
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Amino Acids
Amino Acids
What is the general structure of an
amino acid?
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Amino Acids
An amino acid is any compound that contains
an amino group (—NH2) and a carboxyl group
(—COOH) in the same molecule.
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Amino Acids
Amino acids have a skeleton that
consists of a carboxyl group and an
amino group, both of which are
covalently bonded to a central carbon
atom. The remaining two groups on the
central carbon atom are hydrogen and an
R group that constitutes the amino acid
side chain.
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Amino Acids
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Peptides
Peptides
Which functional groups are always
involved in amide bonds between
amino acids?
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Peptides
A peptide is any combination of amino acids in
which the amino group of one amino acid is
united with the carboxyl group of another amino
acid.
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Peptides
The amide bond between the carboxyl group of
one amino acid and the nitrogen in the amino
group of the next amino acid in the peptide chain
is called a peptide bond.
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Peptides
The amide bonds between amino acids
always involve the central amino and
central carboxyl groups. The side chains
are not involved in the bonding.
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Proteins
Proteins
What determines the differences in the
chemical and physiological properties of
peptides and proteins?
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Proteins
A peptide with more than about 100 amino acids
is called a protein.
• Your skin, hair, nails, and muscles are made
of protein.
• Proteins are needed for almost all chemical
reactions that take place in the body.
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Proteins
Amino Acids in a Peptide Chain
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Proteins
Sections of a peptide chain may coil into a
regular spiral, known as a helix.
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Proteins
Peptide chains may also be arranged side by
side to form a pleated sheet.
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Proteins
Differences in the chemical and
physiological properties of peptides and
proteins result from differences in the
amino acid sequence.
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Proteins
The Shape of Myoglobin
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Enzymes
Enzymes
How do enzymes affect the rates of
reactions in living things?
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Enzymes
Enzymes are proteins that act as biological
catalysts.
Enzymes increase the rates of chemical
reactions in living things.
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Enzymes
The enzyme urease hydrolyzes urea, a
constituent of urine, into ammonia and carbon
dioxide.
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Enzymes
How Enzymes Work
Enzymes catalyze most of the chemical changes
that occur in the cell.
• Substrates are the molecules on which an
enzyme acts.
• The place on an enzyme where a substrate
binds is called the active site.
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Enzymes
In a typical enzymatic reaction, the substrate
interacts with side chains of the amino acids on
the enzyme. These interactions cause the
making and breaking of bonds.
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Enzymes
An HIV particle (red) infects a human white
blood cell (orange). The diagram models the
enzyme HIV protease.
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Enzymes
The enzyme carbonic anhydrase catalyzes the
reversible breakdown of carbonic acid to carbon
dioxide and water.
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Enzymes
Coenzymes
Coenzymes are metal ions or small organic
molecules that must be present for an enzymecatalyzed reaction to occur.
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Enzymes
The enzyme catalase includes an iron(III) ion in
its structure. Catalase catalyzes the breakdown
of hydrogen peroxide to water and oxygen.
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24.3 Section Quiz.
Assess students’ understanding
of the concepts in Section 24.3.
Continue to:
-or-
Launch:
Section Quiz
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24.3 Section Quiz.
1. Choose the correct words for the spaces. An
amino acid is a compound having the
________ group and the _________ group
bonded to a central carbon atom.
a. carboxyl, amino
b. carbonyl, amide
c. amino, peptide
d. carbohydrate, amide
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24.3 Section Quiz.
2. Choose the correct words for the space. A
protein is a peptide with ___________ amino
acids linked in a chain.
a. more than about 100
b. less than about 100
c. two
d. zero
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24.3 Section Quiz.
3. Enzymes affect biochemical reactions by
a. changing the equilibrium position of the
system.
b. acting as catalysts to speed up the
reaction.
c. being consumed as the reaction
progresses.
d. decreasing the size of competing
substrates.
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24.3 Section Quiz.
4. Some vitamins participate in biological
processes as
a. peptides.
b. amino acids.
c. enzymes.
d. coenzymes.
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