32
Chapter 2
Charge on side chain
Side chain
Amino acid
Ionized
Polar
Nonpolar
R
O
OH
C
H
C
CH
3
CH
3
H
C
COOH
CH
2
CH
2
CH
2
NH
3
CH
2
CH
2
NH
2
NH
2
NH
2
NH
2
Carboxyl (acid) group
Amino group
Leucine
Serine
Lysine
CH
H
C
COOH
+
O
H
C
COOH
H
(
δ
+
)
(
δ
)
Figure 2–13
Representative structures of each class of amino acids found in proteins.
CO
H
NH
2
CH
CH
O
NH
2
CO
H
O
CO
H
O
R
1
R
1
R
2
R
2
NH
O
C
CH
CH
COOH
NH
2
NH
2
R
1
R
3
R
5
R
2
R
4
R
6
Peptide bond
Peptide bonds
Side group 1
Side group 2
Amino
group
Carboxyl
(acid) group
Amino
group
Carboxyl
(acid) group
Additional amino acids
Dehydration
+
+
H
2
O
Amino acid 1
Amino acid 2
Polypeptide
+
Figure 2–14
Linkage of amino acids by peptide bonds to form a polypeptide.
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