What happens to red blood cells in water?
Red blood cells will swell when placed into a solution of pure water. This is due to the osmolarity. Normal blood osmolarity is around 310 milliosmoles. The osmolarity difference when putting the red blood cell from blood into water will cause swelling of the cell. Osmotic pressure will be driving water from the environment into the cell in an effort to create equal osmotic pressures in the two environments, the cytoplasm of the red blood cell and the water solution. Ultimately, the too much water will flow into the red blood cells and they will inevitably lyse.
