Used in biological systems as a key intermediate in one-carbon transfer reactions, essential for the synthesis of purines and thymidylate, which are building blocks of DNA and RNA. Plays a critical role in amino acid metabolism, particularly in the interconversion of serine and glycine. Also involved in folate-dependent pathways that support cell division and growth, making it important in rapidly dividing tissues. Its derivatives are studied for potential roles in cancer therapy and in understanding metabolic disorders related to folate deficiency.