The R groups and names for each amino acid are listed in the table.
The Proteinogenic Amino Acids
All 20 of the proteinogenic amino acids
have the common structure below
The R groups and names for each amino acid are listed in the table.
| Neutral Amino Acids |
Name & Abbreviations |
R |
pKa1 α-CO2H |
pKa2 α-NH3+ |
pKa sidechain |
Isoelectric Point |
Alanine Ala (A) |
 |
2.34 |
9.69 |
x |
6.01 |
Asparagine Asn (N) |
 |
2.02 |
8.80 |
x |
5.41 |
Cysteine Cys (C) |
 |
1.96 |
10.28 |
8.08 |
5.07 |
Glutamine Gln (Q) |
 |
2.17 |
9.13 |
x |
5.65 |
Glycine Gly (G) |
 |
2.34 |
9.60 |
x |
5.97 |
Isoleucine Ile (I) |
 |
2.36 |
9.60 |
x |
6.02 |
Leucine Leu (L) |
 |
2.36 |
9.60 |
x |
5.98 |
Methionine Met (M) |
 |
2.28 |
9.21 |
x |
5.74 |
Phenylalanine Phe (F) |
 |
1.83 |
9.13 |
x |
5.48 |
Proline Pro (P) |
 |
1.99 |
10.60 |
x |
6.30 |
Serine Ser (S) |
 |
2.21 |
9.15 |
x |
5.68 |
Threonine Thr (T) |
 |
2.09 |
9.10 |
x |
5.60 |
Tryptophan Trp (W) |
 |
2.83 |
9.39 |
x |
5.89 |
Tyrosine Tyr (Y) |
 |
2.20 |
9.11 |
10.07 |
5.66 |
Valine Val (V) |
 |
2.32 |
9.62 |
x |
5.96 |
| Acidic Amino Acids |
Name & |
R
|
pKa1
α-CO2H |
pKa2
α-NH3+ |
pKa
sidechain |
Isoelectric
Point |
Aspartic Acid
Asp (D) |
 |
1.88
|
9.60
|
3.65
|
2.77
|
Glutamic Acid
Glu (E) |
 |
2.19
|
9.67
|
4.25
|
3.22
|
| Basic Amino Acids |
Name &
Abbreviations |
R
|
pKa1
α-CO2H |
pKa2
α-NH3+ |
pKa
sidechain |
Isoelectric
Point |
Arginine
Arg (R) |
 |
2.17
|
9.04
|
12.48
|
10.76
|
Histidine |
 |
1.82
|
9.17
|
6.00
|
7.59
|
Lysine |
 |
2.18
|
8.95
|
10.53
|
9.74
|