Expert: Walter Hintz - 10/11/2008

Question
Hello, I am glad that i found a great site.
i want to know about why water moved into or out of the potato for each of the solutions. And also i dont exactly know why salt water can help reduce the swelling of the gums.
Thanks for your time :)

Answer
 Hi Travis
The movement of water through membranes is called osmosis and the movement always goes from an are oh high concentration to an area of lower concentration. Potato cells have a certain salt concentration.  If we out the potato in water with a greater salt amount (hypotonic) then water leaves the potato. If we put it water with less concentration (hypertonic) there is less water concentration in the potato so water goes in.  If the concentration is the same inside the potato and outside (isotonic) then water leaving is equal the amount going in.
The cells in the gums swell with extra water.  If we bathe them with salt water water leaves just like it would in a potato