Which molecules serve as identification tags on the cell surface?

Which molecules serve as identification tags on the cell surface?

• A. Glycolipids
• B. Glycoproteins
• C. Carbohydrates
• D. Cholesterol

Answer: (C)

Carbohydrate chains on the cell surface act as identification tags because they form unique patterns that other cells and the immune system recognize to distinguish self from non-self and to guide cell–cell interactions. These sugars are usually attached to proteins (glycoproteins) or lipids (glycolipids) that extend from the outer membrane, presenting the carbohydrate signature outward. The specific arrangement of sugar residues—such as those that define blood-group antigens like ABO—provides the recognizable identity markers for cells. Cholesterol, on the other hand, mainly helps maintain membrane structure and fluidity, not labeling. So the tagging function comes from the carbohydrate portions.

Carbohydrate chains on the cell surface act as identification tags because they form unique patterns that other cells and the immune system recognize to distinguish self from non-self and to guide cell–cell interactions. These sugars are usually attached to proteins (glycoproteins) or lipids (glycolipids) that extend from the outer membrane, presenting the carbohydrate signature outward. The specific arrangement of sugar residues—such as those that define blood-group antigens like ABO—provides the recognizable identity markers for cells. Cholesterol, on the other hand, mainly helps maintain membrane structure and fluidity, not labeling. So the tagging function comes from the carbohydrate portions.