Which membrane protein carries carbohydrates attached to it to enable self/non-self recognition?

• A. Enzymatic Proteins
• B. Channel Protein
• C. Receptor Protein
• D. Cell-Recognition Proteins

Answer: (D)

Carbohydrate groups attached to membrane proteins form glycoproteins, which are key players in cell–cell recognition. The carbohydrate portions extend into the extracellular space, creating the glycocalyx pattern that other cells (and immune cells) read to distinguish self from non-self. This recognition helps the immune system decide whether to attack or tolerate a cell, and it underlies tissue compatibility and communication between cells.

Among membrane proteins, those described as cell-recognition proteins are the ones whose primary role involves presenting these carbohydrate-rich markers on the surface. While enzymatic proteins, channel proteins, and receptor proteins perform other essential functions (catalysis, transport, and signaling, respectively), they are not defined by carrying carbohydrate markers for self/non-self identification in the same way.