A Review of Amino Acids

Equation

This brief tutorial covers the chemical and structural properties of the 20 Amino Acids commonly found in proteins.

The tutorial contains a number of graphic images, it may take a while to download, so please be patient. After reviewing the amino acids, try out the Interactive Quiz.

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Amino Acid Properties

Amino acids are the basic structural units of proteins. An alpha-amino acid consists of an amino group, a carboxyl group, a hydrogen atom, and a distinctive R group bonded to a carbon atom, which is called the alpha-carbon because it is adjacent to the carboxyl (acidic) group. An R group is referred to as a side chain.(Stryer,1988)

Amino Acids are commonly classified into the following groups based on the chemical and/or structural properties of their side chains :

Amino Acid Structures

Rasmol ImageAmino Acid3-letter
code
1-letter
code
PropertiesStructure
(un-ionised form)
Amino Acid Alanine AlaAaliphatic
hydrophobic
neutral
Amino Acid
Amino Acid Arginine ArgR polar
hydrophilic
charged (+)
Amino Acid
Amino Acid Asparagine AsnN polar
hydrophilic
neutral
Amino Acid
Amino Acid Aspartate Asp D polar
hydrophilic
charged (-)
Amino Acid
Amino Acid Cysteine Cys C polar
hydrophobic
neutral
Amino Acid
Amino Acid Glutamine Gln Q polar
hydrophilic
neutral
Amino Acid
Amino Acid Glutamate Glu E polar
hydrophilic
charged (-)
Amino Acid
Amino Acid Glycine Gly G aliphatic
neutral
Amino Acid
Amino Acid Histidine His H aromatic
polar
hydrophilic
charged (+)
Amino Acid
Amino Acid Isoleucine Ile I aliphatic
hydrophobic
neutral
Amino Acid
Amino Acid Leucine Leu L aliphatic
hydrophobic
neutral
Amino Acid
Amino Acid Lysine Lys K polar
hydrophilic
charged (+)
Amino Acid
Amino Acid Methionine Met M hydrophobic
neutral
Amino Acid
Amino Acid Phenylalanine Phe F aromatic
hydrophobic
neutral
Amino Acid
Amino Acid Proline Pro P hydrophobic
neutral
Amino Acid
Amino Acid Serine Ser S polar
hydrophilic
neutral
Amino Acid
Amino Acid Threonine Thr T polar
hydrophilic
neutral
Amino Acid
Amino Acid Tryptophan Trp W aromatic
hydrophobic
neutral
Amino Acid
Amino Acid Tyrosine Tyr Y aromatic
polar
hydrophobic
Amino Acid
Amino Acid Valine Val V aliphatic
hydrophobic
neutral
Amino Acid


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