1) cysteine. The American HeritageŽ Dictionary of the English Language: Fourth Edition. 2000.

...An amino acid, C3H7O2NS, derived from cystine and found in most proteins. Alteration of cystine....

2) homocysteine. The American HeritageŽ Dictionary of the English Language: Fourth Edition.
2000.
...of blood vessels and enhancing blood clotting. homo-, homologous with (from homologous) +
cysteine