Amino Acids.pdf

For students

1. Dr. Mausumi Adhya
Associate Professor
Supreme Knowledge Foundation, Hooghly
Amino acid: Amino acid-definition, classification, function, properties

2. Amino acids
Amine group –NH2 Acid group -COOH H
N
H
C
H
R
C
OH
O
H
N
+
H
C
H
R
C
O
--
O
H
amino acid
(free)
amino acid
(zwitter ion)
Although over 200 different amino acids occur in nature, only 20 of these form backbone
of proteins.
L–α–amino acids
α-amino group, a α-carboxylic acid group

3. Building block of peptides and proteins.
Source of sulfur: sulfur containing amino acids cysteine, methionine.
Source of energy: Amino acids converts to glucose by gluconeogenesis.
Precursor of biological molecules: tyrosine is the precursor of hormone thyroxine and
skin pigment melanin, tryptophan is the precursor of vitamin ??????
� (niacin).
Functions amino acids in human body

4. Structure of L–α–amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids

5. CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids CH
COOH
NH
2
H
CH
COOH
NH
2
CH
3
CH
COOH
NH
2
CH
CH
3
CH
3
CH
COOH
NH
2
CH
2
CH
CH
3
CH
3
Glycine
Alanine
Valine
Leucine
CH
COOH
NH
2
CHCH
2
CH
3
CH
3
Isoleucine
CH
COOH
NH
2
CH
2
CH
2
SCH
3
Methionine
C
COOH
H
NH
CH
2
CH
2
CH
2
Proline
CH
COOH
NH
2
CH
2
OH
Serine
CH
COOH
NH
2
CH
2
SH
Cysteine
CH
COOH
NH
2
CHCH
3
OH
Threonine
CH
COOH
NH
2
CH
2
COOH
Aspartic acid
HOOC
CH
COOH
NH
2
CH
2
CH
2
CH
3
Glutamic acid
HOOC
CH
COOH
NH
2
CH
2
CONH
2
Asparagine
CH
COOH
NH
2
CH
2
CH
2
CONH
2
Glutamine
Phenylalanine
CH
COOH
NH
2
CH
2
Tyrosine
CH
COOH
NH
2
CH
2OH
Tryptophan
CH
COOH
NH
2
CH
2
CH
N
H
CH
COOH
NH
2
CH
2
CH
2
CH
2
CH
2
NH
2
Lysine
CH
COOH
NH
2
CH
2
CH
2
CH
2
NHCHNH
2
NH
Arginine
CH
COOH
NH
2
CH
2
CHC
N NH
CH
Histidine
Structure of amino acids Structure of L–α–amino acids

6. Classification of amino acids
based on the structure of the side chain ??????
based on their acid and base nature
based on the polarity of the side chain ??????
based on their nutritional value
based on their metabolic fate H
N
H
C
H
R
C
OH
O
H
N
+
H
C
H
R
C
O
--
O
H
amino acid
(free)
amino acid
(zwitter ion)

7. Phenylalanine
Based on the structure of the side chain ??????
Aliphatic amino acids: having aliphatic groups in their side chains
Glycine
Alanine
Valine
Leucine
Methionine
 Aspartic acid
 Asparagine
 Glutamic acid
Isoleucine
 Serine
 Threonine
 Cysteine
Glutamine
 Arginine
 Proline
 Lysine
Aromatic amino acids: having aromatic groups in their side chains.
Histidine Tryptophan Tyrosine

8. Based on their acid and base nature
Acidic amino acids: Side chain ?????? contains a carboxylic acid functional group.
Glutamic acid Aspartic acid
Basic amino acids: Side chain ?????? contains an amine functional group.

 Arginine Histidine.
Lysine
Neutral amino acids: Dont have any amino group or carboxylic acid group in side chain R.
Glycine
Alanine
Valine
Leucine
Methionine
Asparagine
 Phenylalanine
Tyrosine
Isoleucine
 Serine
 Threonine
 Cysteine
Glutamine
Proline
 Tryptophan

9. Based on the polarity of the side chain ??????
Polar amino acids: Various functional groups like acid, amide, alcohol, amine in side chain R
Serine
 Threonine
 Tyrosine
Asparagines
 Cysteine
 Glutamine
Aspartic acid
 Glutamic acid
 Histidine
Lysine
Arginine
Non-polar amino acids: Pure hydrocarbon groups (aliphatic and aromatic) in side chain R
Glycine
Alanine
 Valine
Leucine
 Isoleucine
 Phenylalanine
Tryptophan
 Methionine
Proline

10. Based On Their Nutritional Value
Essential amino acids: Can not be synthesized in human body and must be taken in diet.
Valine
 Leucine
*Arginine and histidine are essential in children, but not in adults.
Isoleucine
 Phenylalanine
Methionine
 Tryptophan
Threonine
 Histidine
Lysine
Arginine
 Non-essential amino acids: Can be synthesized in human body and hence they are non-
essential in the diet.
Alanine
asparagine
Aspartic Acid
 Glutamic Acid
Glutamine
Glycine
Proline
Serine
Cysteine
Tyrosine

11. Based On Their Metabolic Fate
Glucogenic amino acids: Used for glucose synthesis only.
Glycine
Alanine
Methionine
 Aspartic acid
Cysteine
Histidine
Glutamine
Arginine
 Proline
Valine
Serine
Asparagine
 Glutamic acid
Ketogenic amino acids: Used for ketone body synthesis only.
Lysine Leucine
Ketogenic and glucogenic amino acids: Used for both
ketone body synthesis and glucose synthesis.
Tryptophan Tyrosine Threonine  Isoleucine Phenylalanine

12. General properties of α-amino acids
1.Optical activity
2.Acid-Base properties of amino acids
3.Amphoteric properties of amino acids
4.Zwitterions form
5.Isoelectric point pI
6.Buffering capacity of amino acids
7.Physical properties of amino acids
:

13. Buffering capacity of amino acids
Physical properties of amino acids
Amino acids are mainly water soluble.
They are soluble in polar solvents and not soluble in non-polar solvents.
They have high melting point.
A buffer is a solution which resists changes in ???????????? when limited amount of acid or base is
added to it.
 A buffer is a mixture of a weak acid and its conjugate base or a weak base and its
conjugate acid.

14. Buffering capacity of amino acids
An amino acid has both an acidic group (carboxyl ) and a basic group (amine). Carboxyl
group acts as conjugate acid (proton donor) and amino group acts as proton
acceptor. Therefore together carboxyl group and amino group resists change in pH when
small amount of acid or base is added.
For example glycine, glutamic acid and histidine use for preparation of buffer.

15. Optical activity of amino acids
The ability of a substance to rotate plane-polarized monochromatic light is called
optical activity.
The compound having carbon atom with four different groups is generally optically
active.
All amino acids except glycine contain a tetrahedral carbon attached to four different
groups (-COOH, -NH
2, -R and –H).
In glycine, the tetrahedral carbon is attached to three different groups (-COOH, -NH
2,
and –H).
Therefore all amino acids except glycine is optically active.

16. Acid-Base properties of amino acids
All amino acids contain at least two ionizable groups; an amine group (-NH
2) and a
carboxylic acid group (-CO
2H).
Some amino acids contain an additional acidic (-CO
2H) or basic group (-NH
2) in their side
chain, which are responsible for acid-base behaviour of amino acids.
Aspartic acid, glutamic acid are acidic amino acids.
Arginine, histidine, lysine are basic amino acids.
Other 15 amino acids are neutral.

17. Zwitterions form of amino acids
A zwitterion is a neutral molecule with a positive and a negative electrical charge. All
neutral amino acids are present in zwitterions form at physiological ??????� (around 7.4). H
N
H
C
H
R
C
OH
O
H
N
+
H
C
H
R
C
O
--
O
H
amino acid
(free)
amino acid
(zwitter ion)
But acidic and basic amino acids form zwitter ions at different pH. RCCOOH
NH
3
H
RCCOO
--
NH
3
H
RCCOO
--
NH
2
H
pK
a1 pK
a2
H
+
HO
--
+ +
at acidic pH (cation) at neutral pH (zwitterion) at basic pH (anion)

18. Isoelectric point (??????�) of amino acids
All amino acids have specific pH in which they form zwitter ion.
It is that ??????� at which net electrical charge of an amino acid is equal to zero ,and
thus at this ??????� the amino acid can not move in an electric field.
??????� value varies from one amino acid to other. It is the average of two ????????????
?????? values.
??????�=
�
�
(????????????
??????� + ????????????
??????�)

19. RCCOOH
NH
3
H
RCCOO
--
NH
3
H
RCCOO
--
NH
2
H
pK
a1 pK
a2
H
+
HO
--
+ +
at acidic pH (cation) at neutral pH (zwitterion) at basic pH (anion) Amphoteric properties
An amphoteric species is a molecule or ion that can
react as an acid as well as a base. Due to presence of
ionizable amine and carboxylic acid groups, amino
acids can act sometimes as acids and sometimes as
bases depending on the ??????� of their media and
isoelectric point.
H+ donate: Acid
H+ accept: Base
OH- donate: base
OH- accept: acid
Electrons donate: Base
Electrons accept: acid