Question

You have a liposome containing an interior aqueous solution containing 200 mM of NaCl. If you want to shrink the liposome, what should be the concentration of solution of NaCl in which you would you drop it? Give a specific concentration (mM).

Answer 1

To achieve this the solution in which the liposome is dropped must be hypertonic. In a hypertonic solution, there are more salts than in the cell or, in this case, a liposome. When we put cell or liposome in the hypertonic solution, there is more water inside than outside. The aim is to balance water concentration on the inside and outside of cell or liposome. So, the water will exit the cell and consequently it will shrink in size.
If we want the extracellular solution to be hypertonic, it must have more salts than the liposome. The concentration of NaCl must be higher than 200mM. If in liposome there are 200 mM of NaCl, in order to shrink, on the outside there must be twice that concentration (400 mM). So, all the water bound to the internal NaCl will exit the liposome and bind to the external NaCl.