<prompt> Which is not an essential amino acid?TryptophanThreonineHistidineCystein  <response>: Ans: d Cystein Ref: Vasydevan, 4th ed, p. 5th ed, p. 191; Harper, p. 28Essential amino acids:PhenylalanineLeucineLysineValineIsoleucineThreonineMethionineTryptophanSemi essential amino acids:ArginineHistidineAmino acids with basic side chain:or positively charged amino acidsArginine - most basic amino acidLysineHistidineAmino acids with acidic side chain:or negatively charged amino acidsAspartate AspargineGlutamate Glutamine Amino acids with side chain containing sulphur:CysteineMethionineAmino acids producing hypoglycaemia:Leucine by increasing insulin secretionArginineAmino acids with aromatic side chain:i Phenyl alanineii Tyrosineiii Tryptophaniv HistidineAmino acids with aliphatic side chain:GlycineAlanineValineLeucineIsoleucineIminoacid:ProlineSelenocysteineNOTE: 21st amino acid--selenocysteine 