Amino acids are the building blocks of proteins and are also used by the cell as neurotransmitters, sources of energy and in a variety of other processes. The a-amino acids all have the same basic structure shown below, where the R-group is the portion that is unique for each amino acid. They are called a amino acids, because an amino group is attached to the carbon next to (alpha to) the carboxylic acid group. The table below contains a list of amino acids, abbreviations, side chain pKA values and complete structures.
| Name | Abbreviations | Structure | pKA1 | |
|---|---|---|---|---|
| 3 letter | 1 letter | |||
| Nonpolar | ||||
| Alanine | Ala | A |  |
|
| Leucine | Leu | L |  |
|
| Valine | Val | V |  |
|
| Isoleucine | Ile | I |  |
|
| Proline | Pro | P |  |
|
| Methionine | Met | M |  |
|
| Phenylalanine | Phe | F |  |
|
| Tryptophan | Trp | W |  |
|
| Polar, uncharged | ||||
| Glycine | Gly | G |  |
|
| Serine | Ser | S |  |
|
| Threonine | Thr | T |  |
|
| Asparagine | Asn | N |  |
|
| Glutamine | Gln | Q |  |
|
| Acidic | ||||
| Aspartic acid | Asp | D |  |
4.4 |
| Glutamic acid | Glu | E |  |
4.4 |
| Cysteine | Cys | C |  |
8.5 |
| Tyrosine | Tyr | Y |  |
10.0 |
| Basic | ||||
| Lysine | Lys | K |  |
10.0 |
| Arginine | Arg | R |  |
12.0 |
| Histidine | His | H |  |
6.5 |
1These are pKA values that are commonly found for these side chains when they are part of a protein. The pKA values for these side chains may be quite different for the free amino acid in solution.
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