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cysteine vs. cystine

cysteine vs. cystine: What's the difference?

Cysteine and cystine are both crystalline amino acids. Cystine, C6H12O4N2S2, occurs in the keratin proteins in hair, wool, and horns, and yields cysteine, C3H7O2NS, when reduced. The names come from cyst- ‘bladder or sac’ because these elements are also found in the bladder.

cysteine

[ sis-tee-een, -in ]
noun
  1. a crystalline amino acid, C3H7O2NS, a component of nearly all proteins, obtained by the reduction of cystine. Abbreviation: Cys; Symbol: C

cystine

[ sis-teen, -tin ]
noun
  1. a crystalline amino acid, C6H12O4N2S2, occurring in most proteins, especially the keratins in hair, wool, and horn, and yielding cysteine on reduction.

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