Glycoproteins are the type of proteins that identify the cell.
Glycoproteins are formed when a carbohydrate molecule attaches to a protein molecule. They are typically found on the extracellular surface of the cell membrane.
Every species has different glycoproteins and so do individuals of the same species. Even the different cells of an individual have unique glycoproteins that are different from those found in other cells. Because of their unique nature and their position on the extracellular surface of the membrane, glycoproteins on each cell act as cellular markers that help to identify the cell.