<prompt> Selenocysteine is derivative of which aminoacid -SerineAlanineArginineGlycine  <response>: Ans. is a i.e., Serine o Selenocysteine is considered as 21 standard amino acid. o It is present at the active site of some enzymes that catalyze redox reactions, e.g. thioredoxin reductase, glutathione peroxidase, and the deiodinase converts thyroxin to triiothyronine. o Biosynthesis of selenocysteine requires cysteine, serine, ATP and a specific t-RNA o Serine provides the carbon skeleton of selenocysteine. o Selenocysteine has a structure similar to cysteine, but containing the trace element selenium in place of sulfur atom of cysteine. 