The 20 Common Amino Acids
Proteins, like nucleic acids, are classified as macromolecules; which means they are long chains (polymers) of repeating units (monomers). A process called dehydration synthesis links the monomers together to form the large molecule, or polymer. The protein would represent the large molecule, or polymer, and the 20 common amino acids represent the basic subunits, or monomers, of proteins. When amino acids are adjacent, and lined up in a particular arrangement, dehydration synthesis will occur. Water will be removed and a peptide bond will form between the two amino acids. Generally small chains of amino acids are called polypeptide chains where as long chains of amino acids are called proteins.
Proteins are essential for the functions of the cell. They are used for structural support (collagen and elastin), transport (hemoglobin), signaling between cells (insulin and other hormones), defense (antibodies), movement (actin and myosin) and as enzymes. A human has tens of thousands of different kinds of protein, each with a specific structure of amino acids and function as determined by the sequence of nucleotides in DNA.
Each amino acid has four partners covalently bonded to a central carbon atom. Three of these partners will always be a hydrogen atom (H), a carboxyl group (COOH) and an amino group (NH2). The fourth partner is the side chain, usually shown as -R. The differences in the atoms of the side chain is what makes each amino acid unique.
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Amino Acid Name
|
Abbreviation
|
chemical property
|
|
glycine
|
|
Gly
|
|
|
non-polar
|
|
alanine
|
|
Ala
|
|
|
non-polar
|
|
valine
|
|
Val
|
|
|
non-polar
|
|
leucine
|
|
Leu
|
|
|
non-polar
|
|
isoleucine
|
|
Ile
|
|
|
non-polar
|
|
methionine
|
|
Met
|
|
|
non-polar
|
|
phenylalanine
|
Phe
|
|
|
non-polar
|
|
tryptophan
|
|
Trp
|
|
|
non-polar
|
|
proline
|
|
Pro
|
|
|
non-polar
|
|
serine
|
|
Ser
|
|
|
polar
|
|
threonine
|
|
Thr
|
|
|
polar
|
|
cysteine
|
|
Cys
|
|
|
polar
|
|
tyrosine
|
|
Tyr
|
|
|
polar
|
|
asparagine
|
|
Asp
|
|
|
polar
|
|
glutamine
|
|
Gln
|
|
|
polar
|
|
aspartic acid
|
Asp
|
|
|
acidic
|
|
glutamic acid
|
Glu
|
|
|
acidic
|
|
lysine
|
|
Lys
|
|
|
basic
|
|
arginine
|
|
Arg
|
|
|
basic
|
|
histadine
|
|
His
|
|
|
basic
|
