Glycine (C₂H₅NO₂) — Properties, Uses & Safety

Overview

Glycine (C2H5NO2), also known as aminoacetic acid, is the simplest of the 20 standard amino acids that make up proteins. With a molar mass of 75.03 g/mol, glycine is a white crystalline solid with a slightly sweet taste (its name derives from the Greek word glykys, meaning sweet). Its molecular structure consists of an amino group (-NH2) and a carboxyl group (-COOH) attached to a single hydrogen-bearing carbon atom, making it the only amino acid without a chiral center — it is achiral and therefore does not rotate plane-polarized light. In aqueous solution at physiological pH, glycine exists as a zwitterion (H3N⁺CH2COO⁻), with the amino group protonated and the carboxyl group deprotonated. This zwitterionic nature is a key concept in amino acid chemistry and explains why amino acids have high melting points and are soluble in water despite being organic molecules. Glycine plays numerous biological roles. As a building block of proteins, it is particularly abundant in collagen (the most abundant protein in the human body), where every third amino acid is glycine — its small size allows it to fit into the tight triple-helix structure of collagen. Glycine is also a major inhibitory neurotransmitter in the spinal cord and brainstem, where it binds to glycine receptors to reduce neuronal excitability. Additionally, glycine is a precursor to many important biomolecules including glutathione (the body's primary antioxidant), heme (the oxygen-carrying component of hemoglobin), purines (building blocks of DNA and RNA), and creatine (important for muscle energy). Glycine is classified as a non-essential amino acid because the body can synthesize it from serine. It is found in protein-rich foods such as meat, fish, dairy, and legumes. Glycine supplements are used for sleep improvement and as a sweetener in some pharmaceutical formulations. Glycine has no significant GHS hazards and is generally recognized as safe. For chemistry students, glycine is the perfect starting point for learning about amino acid structure and nomenclature, zwitterions and isoelectric points, peptide bond formation (condensation reactions), acid-base behavior of amphoteric molecules, and protein chemistry. Its simplicity makes it the ideal model compound for understanding the fundamental chemistry shared by all amino acids.

IUPAC Name

2-aminoacetic acid

CAS Number

56-40-6

PubChem CID

750

Molecular Formula

C₂H₅NO₂

Molar Mass

75.032 g/mol

State at STP

solid

Appearance

White crystalline solid, sweet taste