Which of the following is not true about the plasma membrane of human erythrocytes?

The plasma membrane of RBC is permeable to anions but not cations. Chemical studies on the cell membrane, especially in human RBCs, enabled the scientists to deduce the possible structure of plasma membrane. In human beings, the membrane of the erythrocyte has approximately 52 per cent protein and 40 per cent lipids. Antigens like antigen A, antigen B and Rh antigen present on the plasma membrane of the RBC form the basis of blood grouping.