Question

NaCl is a nonpenetrating solute, urea is a penetrating solute that distribute equally across the membrane, and glucose is a penetrating solute that gets transported into the cell and stays there, i.e. can't get out once it is in the cell. Red blood cells are placed in each of the following solutions below. The intracellular concentration of nonpenetrating solute is 300 mOsM. What will happen to the cell volume in each solution? Increase, decrease or not change? Explain. Assume 1M NaCl = 2 OsM, 1M urea = 1 OsM, 1M glucose = 1 OsM 100 mM NaCl, 10 mM urea, 10 mM glucose: 300 mM NaCI, 100 mM urea, 0 mM glucose:

Answer 1

a) The total concentration of solution is 100mM + 10 mM + 10 mM which is lesser than 300 mOSM of internal cell concentration. In 100 mM NaCl solution, As cell concentration is 300 mOSM, the water(solvent) molecules transfer from out side to inside the cell and increases the volume..

b) With solution of 300 mM+10 mM glucose, only glucose molecules are transfering in to cell and there is no change in cell volume as glucose molecules can takes place in the cell.