Which of the following is a modified amino acid?: (A) Arginine, (B) Cysteine, (C) Asparagine, (D) Threonine
Answer is B. Two molecules of cysteine make cysteine (cys-cys) or dithio b, b-a amino propionic acid. The SS linkage is called as disulfide bridge. Ref: Textbook of medical biochemistry, MN Chatterji, 8th edition, page no: 78