Which statement correctly classifies spectrin and glycophorins?

• A. Spectrin- Integral; Glycophorins- Peripheral
• B. Spectrin- Peripheral; Glycophorins- Integral
• C. Spectrin- Peripheral; Glycophorins- Peripheral
• D. Spectrin- Integral; Glycophorins- Integral

Answer: (B)

In the red blood cell membrane, you distinguish proteins by how they associate with the lipid bilayer. Spectrin sits on the cytoplasmic face of the membrane as part of the cytoskeletal network. It is attached to the inner membrane through linker proteins like ankyrin and connections to transmembrane proteins, but it does not span the lipid bilayer itself. That makes spectrin a peripheral membrane protein.

Glycophorins, on the other hand, are transmembrane glycoproteins that span the lipid bilayer. Their extracellular domain protrudes outside the cell, and they have intracellular tails, anchoring them firmly in the membrane. That makes glycophorins integral membrane proteins.

So the statement that spectrin is peripheral and glycophorins are integral correctly reflects their different associations with the membrane.