Glycosylphosphatidylinositol (GPI) is a type of glycolipid that anchors proteins to the cell membrane. It consists of a carbohydrate moiety linked to a phosphatidylinositol molecule, which is embedded in the lipid bilayer. GPI anchors are important for the stability and function of various proteins, particularly in immune response and cell signaling. GPI-anchored proteins are found in many organisms, including humans and yeast. They play crucial roles in processes such as cell adhesion, signal transduction, and immune system regulation. Abnormalities in GPI anchoring can lead to various diseases, highlighting its significance in cellular functions.