Glutamine, a non-essential but conditionally essential amino acid, plays a crucial role in various biological processes. It is the most abundant free amino acid in human plasma and serves as an important source of nitrogen for protein synthesis. Glutamine derivatives include both naturally occurring forms, such as γ-glutamyl cyclic peptides (γ-GCPs) found in certain microorganisms, and synthetic analogues developed for therapeutic purposes. In cellular metabolism, glutamine acts as a major metabolic fuel, supporting the growth and survival of rapidly dividing cells, including cancer cells. Its role extends to its involvement in the production of nucleotides, which are essential components of DNA and RNA. Additionally, glutamine derivatives can modulate immune function by acting on immune cells such as T-cells and macrophages. In research applications, glutamine is widely used as a component in cell culture media, providing critical support for maintaining cell health and proliferation. Synthetically derived glutamine analogues have shown promise in various therapeutic settings, including the treatment of metabolic disorders, immune dysfunction, and certain types of cancer. Overall, glutamine and its derivatives are essential molecules with diverse applications across biotechnology, pharmaceuticals, and biomedical research.