AMINO ACIDS
AMINO ACIDS
COOH
H2N
H
R
the R group varies
Naturally-occurring amino acids have L-configuration
….. with only a very few having D-configuration
Amino Acids
COOH
H
R
COOH
NH2
H2N
D-
L-
H
R
naturally-occurring
amino acids are
generally L-series
SOME EXAMPLE AMINO ACIDS
COOH
H2N
H
glycine - the only achiral
amino acid
R=H
H
COOH
H2N
H
alanine
R = CH3
CH3
COOH
H2N
CH3
H
CH
CH3
valine
R = CH(CH3)2
20 different ones occur in proteins
SOME EXAMPLE AMINO ACIDS
COOH
H2N
glycine - the only achiral
amino acid
H
R=H
H
COOH
H2N
H
alanine
R = CH3
valine
R = CH(CH3)2
CH3
COOH
H2N
CH3
H
CH
CH3
20 different amino acids occur in proteins
They differ by the R group
THE 20 COMMON AMINO ACIDS
Amino acids are classified by their R group
NON-POLAR
POLAR AMINO ACIDS
•NEUTRAL
•ACIDIC
•BASIC
THE 9 NON-POLAR AMINO ACIDS
COOH
H2N
H
H2 N
H
H2N
H
H
CH3
Glycine
Gly
Alanine
Ala
H2 N
COOH
H
CH CH3
HN
H
H2N
H2N
H
CH CH3
CH2
CH3
CH CH3
Valine*
Val
CH3
H
CH2
H2N
H
CH2
COOH
H2N
H
CH2
CH2
NH
CH3
Proline
Isoleucine*
Pro
Ile
* Essential amino acids
Leucine*
Leu
COOH
COOH
COOH
COOH
COOH
COOH
Phenylalanine*
Phe
Tryptophan*
Trp
CH2 S CH3
Methionine*
Met
THE 6 NEUTRAL POLAR AMINO ACIDS
COOH
H2N
H
H2N
CH2 OH
H2 N
H
COOH
H
CH2
O C
NH2
Asparagine
Asn
* Essential amino acid
CH3
Threonine*
Thr
COOH
H2 N
OH
Tyrosine
Tyr
H
CH2
CH2
O C
NH2
Glutamine
Gln
H
CH2
CH OH
serine
H2 N
COOH
COOH
COOH
H2 N
H
CH2 SH
Cysteine
Cys
THE ACIDIC AMINO ACIDS
COOH
COOH
H2 N
H
CH2
COOH
aspartic acid
Asp
H2N
H
CH2
CH2
COOH
glutamic acid
Glu
The Two Acidics
THE BASIC AMINO ACIDS
COOH
H2 N
H
CH2
CH2
CH2
CH2
NH2
Lysine*
Lys
* Essential amino acids
COOH
H2N
H
CH2
CH2
COOH
H2 N
CH2
CH2
NH
C NH
NH2
Arginine*
Arg
H
N
NH
Histidine*
His
The Three Basics
Which of the following compounds is an -amino acid?
1.
2.
3.
4.
Only (a)
(a) and (b)
(a) and (c)
(a) and (d)
Which of the following compounds is an -amino acid?
1.
2.
3.
4.
Only (a)
(a) and (b)
(a) and (c)
(a) and (d)
Which of the following amino acids is achiral?
1.
2.
3.
4.
Alanine
Aspargine
Glycine
Threonine
HO
| ||
+
H3N–C–C–O–
|
CH3
Alanine, Ala
H O
| ||
+
H3N–C–C–O–
|
H
Glycine, Gly
HO
H O
| ||
| ||
+
H3N–C–C–O– +H3N–C–C–O–
|
|
CH2CNH2
CHCH 3
||
|
O
OH
Asparagine, Asn Threonine, Thr
Which of the following amino acids is achiral?
1.
2.
3.
4.
Alanine
Aspargine
Glycine
Threonine
HO
| ||
+
H3N–C–C–O–
|
CH3
Alanine, Ala
H O
| ||
+
H3N–C–C–O–
|
H
Glycine, Gly
HO
H O
| ||
| ||
+
H3N–C–C–O– +H3N–C–C–O–
|
|
CH2CNH2
CHCH 3
||
|
O
OH
Asparagine, Asn Threonine, Thr
The amino acid shown below has a side chain
that is
1.
2.
3.
4.
acidic
basic
nonpolar
polar, neutral
The amino acid shown below has a side chain
that is
1.
2.
3.
4.
acidic
basic
nonpolar
polar, neutral
Which of the following amino acids can form hydrogen
bonds between their side-chain groups?
HO
| ||
+
H3N–C–C–O–
|
CH3
Alanine, Ala
H O
| ||
+
H3N–C–C–O–
|
H
Glycine, Gly
HO
H O
| ||
| ||
+
H3N–C–C–O– +H3N–C–C–O–
|
|
CH2CNH2
CHCH 3
||
|
O
OH
Asparagine, Asn Threonine, Thr
1. Alanine and glycine
2. Alanine and aspargine
3. Aspargine and
threonine
4. Glycine and threonine
Which of the following amino acids can form hydrogen
bonds between their side-chain groups?
HO
| ||
+
H3N–C–C–O–
|
CH3
Alanine, Ala
H O
| ||
+
H3N–C–C–O–
|
H
Glycine, Gly
HO
H O
| ||
| ||
+
H3N–C–C–O– +H3N–C–C–O–
|
|
CH2CNH2
CHCH 3
||
|
O
OH
Asparagine, Asn Threonine, Thr
1. Alanine and glycine
2. Alanine and aspargine
3. Aspargine and
threonine
4. Glycine and threonine
Unusual L-Amino Acids Found
in Proteins
Fig. 3-8a