|The Wicked Witch of the West melts after Dorothy dumps a bucket of water on her. Illustration by William Wallace Denslow from the original The Wonderful Wizard of Oz, by L. Frank Baum, 1900. Image available at Wikimedia Commons.|
When solutes are in water, they like to be evenly spread out. This is pretty easy if you just have a glass of water with salt in it. But let’s say you put a membrane in this glass that allows water, but not salts, to pass through it. Now if you put saltier water on one side of the membrane and less salty water on the other side, what do you think would happen? If the salt can’t cross to the less salty side, then the water will cross to the more salty side.
|If a membrane holds more salt (pink dots) on one side than the other, the water will |
move to the side with more salt so that the salt and water can be evenly spaced out.
|If a cell is hyperosmotic to its environment, the water will move into it and salts will |
leak out so that the salt and water can be evenly spaced out. Eventually, the cell
won’t function properly unless it can reabsorb some of these salts.
|A freshwater ramshorn snail has nightmares about kids with salt-shakers. |
Image by Alan R Walker at Wikimedia.