The phenomenon of osmosis is familiar to most readers from their junior high school science class. A dialysis bag containing sugar is placed in beaker containing pure water. It is explained that the bag is semi-permeable: water molecules can pass through microscopic pores in the membrane, but sugar molecules are too large to pass. The student watches as water gradually flows into the bag, inflating it until it seems ready to burst. The mystery of osmosis is that water continues to flow in, even after the pressure within the bag exceeds that outside.This seemingly simple phenomenon is vitally important for plants and animals. Osmosis plays a role in the blood circulation, keeping just the right balance between the water content of the blood and the surrounding tissues. Osmosis drives fluid flow in the kidneys, preventing waste products from accumulating to dangerous levels. Osmosis is also the driving force behind plant cell expansion, playing a role in flower and fruit growth. [More]














Source: Osmosis Confusion: 60 Years and Counting