This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
Which of the following is true about glycine? 
Select and explain. 
A. Glycine is an essential amino acid, B. Sulphur containing at 4th position, C. Has a guanidine group, D. Optically inactive
D: Optically inactive
Answer: D: Optically inactive 
Explanation: 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.