We know that cells maintain their water content through osmosis. Now we can see what happens when someone deliberately screws around with osmosis. Some cells explode. Others turn into “ghosts.”

Osmosis is a very useful phenomenon. You start with a semi-permeable membrane, like a cell wall. When solutes — we use table salt in high school labs but there are all kinds of little particles that will work — are present in a higher concentration on one side of the barrier than the other, the liquid flows to the area of higher solute concentration until the concentration evens out. Cells use osmosis to take on water when they get dehydrated, and osmosis helps the digestive system filter harmful chemicals out of the body.

In this video, we see what happens when scientists screw with a cell’s ability to maintain a steady water level. The liquid around the blood cells goes from hypertonic (very salty, relative to the cells) to isotonic (at the same salinity) over and over. The cells have to keep adjusting. At the end, the liquid around becomes hypotonic — much less salty. In the distilled water, liquid pours across the cell membrane and into the “saltier” cells. They swell up. The leukocytes, white blood cells, swell up and burst. (That starts happening at the forty-seven second mark of the video.) But notice what happens at the thirty-nine second mark. The erythrocytes suddenly disappear, turning into “ghosts.” Erythrocytes are red blood cells and carry hemoglobin. They expel their hemoglobin, and, with the “red” gone out of their cell, we can’t see them under the microscope anymore. They vanish.


Image: Scanning Electron Image Blood Cell.