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nmdcat.online June 29, 2026

The amino acid glycine is unique among the 20 standard amino acids because its R-group is a hydrogen atom. This structural simplicity results in glycine being

A. Optically active and levorotatory
B. The only achiral standard amino acid
✓
C. An essential amino acid with an aromatic side chain
D. The primary sulfur-containing amino acid

📝 Explanation

A carbon atom must be bonded to four different groups to be chiral. The α-carbon of glycine is bonded to an amino group, a carboxyl group, and two hydrogen atoms. Since two substituents are identical, it is not a chiral center, and glycine is optically inactive.

📖 Additional Information

  • Optically active and levorotatory
  • The only achiral standard amino acid
  • An essential amino acid with an aromatic side chain
  • The primary sulfur-containing amino acid

A carbon atom must be bonded to four different groups to be chiral. The α-carbon of glycine is bonded to an amino group, a carboxyl group, and two hydrogen atoms. Since two substituents are identical, it is not a chiral center, and glycine is optically inactive.

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