BIOCHEMISTRY A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site cysteine Ball-and-stick representation of the cysteine molecule. Gray=C, red=O, blue=N, yellow=S, white=H A sulfur-containing amino acid (HSCH2CH2COOH) that occurs in animal proteins, especially those in hair, hooves, and the keratin of skin; the HS– group in it makes it the catalytic element in some enzymes. The disulfide (S-S) links between adjacent cysteine molecules in polypeptide chains contribute to the three-dimensional molecular structure of proteins. Related entries    • acetylcysteine    • homocysteine Related category    • BIOCHEMISTRY Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP