Erythrocytes swell or shrink rapidly in response to changes in the osmolarity of the blood by moving water molecules through plasma membrane channels call aquaporins (aqp). aqp1 is a tetramer that consists of four identical monomers, each of which has a transmembrane pore. a human erythrocyte has approximately 2 × 105 aqp1 monomers and a total volume of 5 × 10–11 ml. water molecules flow through the plasma membrane at a rate of 5 × 108 molecules per aqp1 tetramer per second.

calculate the number of water molecules in an erythrocyte. assume that the erythrocyte consists entirely of water. calculate the amount of time that it takes for the erythrocyte to lose half of its volume of water when it encounters the high osmolarity (1 m) in the interstitial fluid of the renal medulla.