The Role of Membrane Carbohydratesin Cell-Cell Recognition• Cells recognize each other by binding to surfacemolecules, often containing carbohydrates, on theextracellular surface of the plasma membrane.• Membrane carbohydrates may be covalently bondedto lipids (forming glycolipids) or more commonly toproteins (forming glycoproteins).• Carbohydrates on the external side of the plasmamembrane vary among species, individuals, and evencell types in an individual.