Penetration of Red Cell Membranes by Some Membrane-Associated Particles

Replicas of freeze-cleaved and replicated red cells produced with an improved Bullivant-Ames apparatus show the plasma membrane to be thin and sheet-like with its inner and outer surface partially covered with a small particulate component. In cross section, some of these particles appear to extend through the full thickness of the membrane. Discontinuities in the thin sheet-like membrane accommodate these penetrating particles. These findings give morphologic evidence of structural specialization of the plasma membrane.