<prompt> All are true about selenocystiene EXCEPT:Considered as 21stAmino acidCoded by UGAOccurs in glutathione peroxidaseMade of cysteine and methionine  <response>: Selenocysteine is found in approximately 25 human proteins. Enzymes which use selenocysteine at their active sites are known as Selenoproteins e.g. 1. Glutathione peroxidase 2. Thioredoxinreductase 3. Iodothyroninedeiodinase Precursor amino acid for selenocysteine is serine. not cysteine or methionine Coded by UGA codon 