<prompt> Which of the following is true about glycine?Glycine is an essential amino acidSulphur containing at 4th positionHas a guanidine groupOptically inactive  <response>: Ans: d Optically inactive Ref: Vasudevan, 4th, ed, p. 5th ed, p. 173Glycine is the simplest amino acid.Optically inactive.It forms every third amino acid in collagen and most abundant amino acid in collagen.Glycine is a glucogenic amino acid formed from serine.Guanido group is present in arginine.ESSENTIAL AMINO ACIDNON ESSENTIAL AMINO ACIDLeucineValine,AlanineGlutamic acidLysineThreonine,GlycineAspartic acidIsoleucineTiyptophan,ProlineTyrosinePhenylalanineMethionineCysteineSerineAsparagineGlutamineSEMI ESSENTIAL AMINO ACIDS:Arginine, histidine. 