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== α-amino acids ==

== α-amino acids ==

'''α-amino acids''' (α is the greek letter ''[[alpha]]'') have the general formula '''NH₂CHRCOOH'''.  There are around 20 naturally occurring α-amino acids which [[polymer|polymerise]] by [[condensation polymerisation]] to form all known [[polypeptides]] (which form the primary structure of [[proteins]]) in biological organisms during [[gene translation]].

'''α-amino acids''' (α is the greek letter ''[[alpha]]'') have the general formula '''RCH(NH₂)COOH'''.  There are around 20 naturally occurring α-amino acids which [[polymer|polymerise]] by [[condensation polymerisation]] to form all known [[polypeptides]] (which form the primary structure of [[proteins]]) in biological organisms during [[gene translation]].

== Zwitterions ==

== Zwitterions ==

=== Formation of zwitterions ===

=== Formation of zwitterions ===

Zwitterions from from amino acids when the hydrogen from the carboxylic acid group (-COO'''H''') dissociates from the molecule and forms a [[dative covalent bond]] with the nitrogen in the amine group (-'''N'''H₂).  This forms an ion with two charges: H⁺NH₂CHRCOO^-.

Zwitterions from from amino acids when the hydrogen from the carboxylic acid group (-COO'''H''') dissociates from the molecule and forms a [[dative covalent bond]] with the nitrogen in the amine group (-'''N'''H₂).  This forms an ion with two charges: RCH(NH₃⁺)COO^-.

=== Physical properties of α-amino acids due to zwitterions ===

=== Physical properties of α-amino acids due to zwitterions ===

== Optical isomerism of amino acids ==

== Optical isomerism of amino acids ==

All α-amino acids except glycine (NH₂CH₂COOH) have four different groups around the alpha carbon, forming a [[chiral centre]] and allowing [[optical isomerism]] to occur.

All α-amino acids except glycine CH₂(NH₂)COOH have four different groups around the alpha carbon, forming a [[chiral centre]] and allowing [[optical isomerism]] to occur.

== References ==

== References ==