Amino Acids
- building blocks of protein • Proteins serve many functions, including
the following. Given are examples of each.
Protein
- Derived from the Greek word "proteios", • 1.Structure: collagen and keratin are the
meaning "first". It is made up of chemical chief constituents of skin, bone, hair, and
'building blocks' called amino acids. A nails.
essential nutrients for the human body and
the building block of tissues and organs. • 2. Catalysts: virtually all reactions in living
systems are catalyzed by proteins called
Dates, lima beans, cornmeal, and enzymes.
peanuts represent plant foods that are
deficient in one or more essential amino • 3. Movement: muscles are made up of
acids and that furnish low-quality protein. proteins called myosin and actin.
The high-quality protein of eggs tumlishes • 4. Transport: hemoglobin transports
us with essential amino acids in nearly the oxygen from the lungs to cells; other
ame ratios found in human protein. proteins transport molecules across cell
membranes.
Animal products such as milk, fish, beef,
and chicken typically provide more • 5. Hormones: many hormones are
high-quality protein than do plant products. proteins, among them insulin, oxytocin, and
human growth hormone.
ESSENTIAL AMINO ACIDS
• 6. Protection: blood clotting involves the
Obtain from the protein in the diet protein fibrinogen; the body used proteins
called antibodies to fight disease.
Example:
• 7. Storage: casein in milk and ovalbumin
● Arginine in eggs store nutrients for newborn infants
● Histidine and birds; ferritin, a protein in the liver,
● Isoleucine stores iron.
● Leucine
● Lysine • 8. Regulation: certain proteins not only
● Methionine control the expression of genes, but also
● Phenylalanine control when gene expression takes place.
● Threonine
● Tryptophan Proteins are divided into two types:
● Valine • fibrous proteins
● • globular proteins
Lacks of this can result to the loss of hair
coloring and a swollen abdomen are typical Amino acid: a compound that contains both
symptoms of the protein deficiency known an amino group and a carboxyl group.
as kwashiorkor.
, • a-Amino acid: an amino acid in which the If we dissolve an amino acid in water, it is
amino group is on the carbon adjacent to present in the aqueous solution as its
the carboxyl group. zwitterion.
Although a-amino acids are commonly If we now add a strong acid such as HCl to
written in the un-ionized form, they are more bring the pH of the solution to 2.0 or lower,
properly written in the zwitterion (internal the strong acid donates a proton to the -
salt) form. COO of the amino acid turning the
zwitterion into a positive ion.
Chirality of Amino Acids
If we add a strong base such as NaOH to
• With the exception of glycine, all the solution and bring its pH to 10.0 or
protein-derived amino acids have at least higher, a proton is transferred from the NH
one stereocenter (the a-carbon) and are group to the base turning the zwitterion into
chiral. The vast majority of protein-derived a negative ion.
a-amino acids have the L- configuration at
the a-carbon. Isoelectric point, pl: The pH at which the
majority of molecules of a compound in
Chirality of Amino Acids solution have no net charge
• A comparison of the stereochemistry of
L-alanine and D- glyceraldehyde (as Fischer Hydroxylation (oxidation) of proline,
projections): lysine, and tyrosine, and iodination for
tyrosine, give these nonstandard amino
A comparison of the stereochemistry of acids.
L-alanine and D- glyceraldehyde (as Fischer
projections): • In 1902, Emil Fischer proposed that
proteins are long chains of amino acids
1. All 20 are a-amino acids. joined by amide bonds.
2. For 19 of the 20, the a-amino group is • peptide bond: The special name given to
primary; for proline, it is secondary. the amide bond between the a-carboxyl
group of one amino acid and the a- amino
3. With the exception of glycine, the group of another.
a-carbon of each is a stereocenter.
• Peptide: A short polymer of amino acids
4. Isoleucine and threonine each contain a joined by peptide bonds; they are classified
second stereocenter. by the number of amino acids in the chain.
lonization vs pH • Dipeptide: A molecule containing two
amino acids joined by a peptide bond.
• The net charge on an amino acid depends
on the pH of the solution in which it is • Tripeptide: A molecule containing three
dissolved. amino acids joined by peptide bonds.
- building blocks of protein • Proteins serve many functions, including
the following. Given are examples of each.
Protein
- Derived from the Greek word "proteios", • 1.Structure: collagen and keratin are the
meaning "first". It is made up of chemical chief constituents of skin, bone, hair, and
'building blocks' called amino acids. A nails.
essential nutrients for the human body and
the building block of tissues and organs. • 2. Catalysts: virtually all reactions in living
systems are catalyzed by proteins called
Dates, lima beans, cornmeal, and enzymes.
peanuts represent plant foods that are
deficient in one or more essential amino • 3. Movement: muscles are made up of
acids and that furnish low-quality protein. proteins called myosin and actin.
The high-quality protein of eggs tumlishes • 4. Transport: hemoglobin transports
us with essential amino acids in nearly the oxygen from the lungs to cells; other
ame ratios found in human protein. proteins transport molecules across cell
membranes.
Animal products such as milk, fish, beef,
and chicken typically provide more • 5. Hormones: many hormones are
high-quality protein than do plant products. proteins, among them insulin, oxytocin, and
human growth hormone.
ESSENTIAL AMINO ACIDS
• 6. Protection: blood clotting involves the
Obtain from the protein in the diet protein fibrinogen; the body used proteins
called antibodies to fight disease.
Example:
• 7. Storage: casein in milk and ovalbumin
● Arginine in eggs store nutrients for newborn infants
● Histidine and birds; ferritin, a protein in the liver,
● Isoleucine stores iron.
● Leucine
● Lysine • 8. Regulation: certain proteins not only
● Methionine control the expression of genes, but also
● Phenylalanine control when gene expression takes place.
● Threonine
● Tryptophan Proteins are divided into two types:
● Valine • fibrous proteins
● • globular proteins
Lacks of this can result to the loss of hair
coloring and a swollen abdomen are typical Amino acid: a compound that contains both
symptoms of the protein deficiency known an amino group and a carboxyl group.
as kwashiorkor.
, • a-Amino acid: an amino acid in which the If we dissolve an amino acid in water, it is
amino group is on the carbon adjacent to present in the aqueous solution as its
the carboxyl group. zwitterion.
Although a-amino acids are commonly If we now add a strong acid such as HCl to
written in the un-ionized form, they are more bring the pH of the solution to 2.0 or lower,
properly written in the zwitterion (internal the strong acid donates a proton to the -
salt) form. COO of the amino acid turning the
zwitterion into a positive ion.
Chirality of Amino Acids
If we add a strong base such as NaOH to
• With the exception of glycine, all the solution and bring its pH to 10.0 or
protein-derived amino acids have at least higher, a proton is transferred from the NH
one stereocenter (the a-carbon) and are group to the base turning the zwitterion into
chiral. The vast majority of protein-derived a negative ion.
a-amino acids have the L- configuration at
the a-carbon. Isoelectric point, pl: The pH at which the
majority of molecules of a compound in
Chirality of Amino Acids solution have no net charge
• A comparison of the stereochemistry of
L-alanine and D- glyceraldehyde (as Fischer Hydroxylation (oxidation) of proline,
projections): lysine, and tyrosine, and iodination for
tyrosine, give these nonstandard amino
A comparison of the stereochemistry of acids.
L-alanine and D- glyceraldehyde (as Fischer
projections): • In 1902, Emil Fischer proposed that
proteins are long chains of amino acids
1. All 20 are a-amino acids. joined by amide bonds.
2. For 19 of the 20, the a-amino group is • peptide bond: The special name given to
primary; for proline, it is secondary. the amide bond between the a-carboxyl
group of one amino acid and the a- amino
3. With the exception of glycine, the group of another.
a-carbon of each is a stereocenter.
• Peptide: A short polymer of amino acids
4. Isoleucine and threonine each contain a joined by peptide bonds; they are classified
second stereocenter. by the number of amino acids in the chain.
lonization vs pH • Dipeptide: A molecule containing two
amino acids joined by a peptide bond.
• The net charge on an amino acid depends
on the pH of the solution in which it is • Tripeptide: A molecule containing three
dissolved. amino acids joined by peptide bonds.
