Which proteins enable cells to distinguish their own cells from those of other organisms?

Which proteins enable cells to distinguish their own cells from those of other organisms?

• A. Cell recognition protein
• B. Channel proteins
• C. Transport proteins
• D. Enzymes

Answer: (A)

Cells carry identity markers on their outer surface that help the immune system tell self from non-self. The proteins that do this are cell recognition proteins, often glycoproteins with specific carbohydrate patterns that mark a cell as belonging to the body. This labeling allows immune cells to survey and decide whether to tolerate or attack a cell, and it also underlies tissue compatibility and recognition of foreign invaders. Channel proteins form pores to let ions pass through the membrane; they’re about movement, not identity. Transport proteins shuttle substances across the membrane, enabling nutrient uptake and waste removal. Enzymes on the membrane or inside the cell catalyze chemical reactions. None of these primarily provide the identity signals needed to distinguish one organism’s cells from another’s, which is why cell recognition proteins are the best answer.

Cells carry identity markers on their outer surface that help the immune system tell self from non-self. The proteins that do this are cell recognition proteins, often glycoproteins with specific carbohydrate patterns that mark a cell as belonging to the body. This labeling allows immune cells to survey and decide whether to tolerate or attack a cell, and it also underlies tissue compatibility and recognition of foreign invaders.

Channel proteins form pores to let ions pass through the membrane; they’re about movement, not identity. Transport proteins shuttle substances across the membrane, enabling nutrient uptake and waste removal. Enzymes on the membrane or inside the cell catalyze chemical reactions. None of these primarily provide the identity signals needed to distinguish one organism’s cells from another’s, which is why cell recognition proteins are the best answer.