<prompt> The amino acid that lacks chiralityLysineLeucineHistidineGlycine  <response>: Ans. is d i.e. Glycine The Alpha carbon of each amino acid is attached to four different chemical groups and is therefore a chiral or optically active carbon atom. Glycine is the exception because its alpha carbon has two hydrogens substituents 2 H atoms attached to alpha carbon and is therefore optically inactive lacks chirality. All amino acids except glycine exists as two stereoisomers or optical isomers or enantiomers, designated asD dextro L levo forms.All the amino acids found in proteins are of the L-configurationAlso rememberSmallest and simplest amino acid - GlycineAmino acid responsible for flexibility of proteins is - Glycine 