Neu5Ac, or N-acetylneuraminic acid, is a type of sialic acid commonly found on the surface of cells in animals. It plays a crucial role in various biological processes, including cell recognition, signaling, and immune response. Neu5Ac is involved in the formation of glycoproteins and glycolipids, which are essential for cell communication. This compound is significant in the study of glycobiology and has implications in medicine, particularly in understanding viral infections and autoimmune diseases. Neu5Ac can influence how pathogens interact with host cells, making it a key focus in research related to vaccines and therapeutics.