BRAINCAKEZwitterions and Isoelectric Points
An amino acid contains an acidic group (-COOH) and a basic group (-NH2) in the same molecule. These can react with each other: a proton moves from the carboxylic acid group to the amine group. The result is a zwitterion, an ion with both a positive and a negative charge but no overall charge:
Amino acids exist as zwitterions in the solid state. This explains their properties: the zwitterions are held in a lattice by strong ionic attractions, so amino acids are crystalline solids with high melting temperatures (many decompose before melting), and they are soluble in water.
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More in Amines, Amides, Amino Acids and Proteins
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All 12 lessons in Amines, Amides, Amino Acids and Proteins · All Edexcel A-level Chemistry topics