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An asymmetric carbon center also known as a chiral center refers to a carbon atom that is attached to four different types of atoms or groups of atoms.

Most of the chiral (having non-superimposable mirror images) molecules in organic chemistry have at least one carbon atom that is bonded to four different groups.

Essential amino acids refer to those amino acids which cannot be synthesized or made by the human body but are required for the proper health and functioning of the body. So organism needs to ingest essential amino acids through food because it is necessary for nutrition and cannot be synthesized by the body. The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Out of these nine essential amino acids, threonine and Isoleucine have more than one asymmetric center.

Isoleucine an essential amino acid is the only other amino acid that has more than one asymmetric center. Like threonine, it also has two asymmetric centers as shown in the figure given below: