3.3.13.1 amino acids

• amino acid 


  compound with an amine group and a carboxylic acid group within the molecule
• amine group 


  always on the 2nd carbon in the chain - always named '2-amino acids'
• amino acid structure

  
• second carbon is often chiral as it has 4 different groups bonded to it - amino acids exist as optical isomers
• nearly all amino acids exist as a single negative enantiomer so they 'fit' into the correct cells within living organisms
• zwitterions


  the 2 functional groups within a single molecule means that amino acids can react as both acids and bases depending on the conditions of the reaction
• zwitterions in acidic conditions

  the lone electron pair is more likely to accept a hydrogen atom, producing a positive end to the molecule

  
• zwitterions in basic conditions

  the hydrogen atom on the -OH group is more likely to be lost, producing a negative end to the molecule

  
• when does a zwitterion form?

  when the overall pH of the molecule is zero, known as the isoelectric point

  
• thin-layer chromatography


  can be used to identify unknown amino acids using UV light to view the traces on the silica plate