L-Glutamine is an amino acid that is required for cell culture. L-Glutamine participates in the formation of purine and pyrimidine nucleotides, amino sugars, glutathione, L-glutamate, and other amino acids, as well as in protein synthesis and glucose production. Unlike most other amino acids, L-glutamine is not stable in solution. The rate at which degradation proceeds is a function of time, temperature, and pH. Gibco L-glutamine is a ready-to-use 200 mM stock solution that acts as a cell culture supplement. The optimal concentration is dependent upon the cell type and medium used to culture the cells, but generally falls in the range of 2–6 mM.