It can be difficult to picture chemistry in real life. However, tonicity is a perfect example of chemistry functioning in the real world to save lives. Medical professionals who administer hypertonic solutions and hypotonic solutions rely on fundamental chemistry concepts like osmosis and diffusion to treat conditions that cause cells to shrink or swell.
Tonicity is the osmotic pressure of a solution compared with a reference solution. When separated by a semi-permeable membrane, the solvent (usually water) of the solution with a lower relative concentration will diffuse across the membrane into the solution with the higher concentration. Hypertonic solutions have higher osmotic pressure and force water to diffuse out of cells while hypotonic solutions have lower osmotic pressure and force water to diffuse into cells.
The terms hypotonic and hypertonic both refer to a solution’s tonicity, or the osmotic pressure of a solution when compared with a reference solution. When you separate two solutions with a semi-permeable membrane, the relative concentration of the solutes (usually salt or other electrolytes) in each solution determine the direction of diffusion across the membrane. Due to osmosis, the solvent (usually water) will diffuse from the less concentrated solution to the more concentrated solution.
Hypertonic solutions have higher osmotic pressure. This means that a cell surrounded by a hypertonic solution will have a lower concentration of solute than the solution does, forcing water to diffuse out of the cell. This causes the cell to shrink.
Hypotonic solutions have lower osmotic pressure. A cell in a hypotonic solution will have a higher concentration of solute than the surrounding solution does, forcing water to diffuse into the cell. This causes the cell to swell.
Isotonic solutions have equal concentrations on either side of the membrane, so diffusion will not occur on its own.
In a clinical setting, medical professionals use hypertonic solutions and hypotonic solutions to make changes in the cells of the human body. For instance, in cases of dehydration, administering a hypotonic solution will force water to diffuse into the cells, causing the cells to swell and reversing the dehydration.
On the other hand, sometimes cells may become overloaded with fluid like during edema or after a traumatic injury. In these cases, administering a hypertonic solution will force water to diffuse out of the cells, causing the cells to shrink. This is especially critical when treating swelling that may become perilous such as swelling of the brain after a trauma.
Hypertonic solutions and hypotonic solutions are valuable components of medical care and perfect examples of how chemistry functions in the world around you.
