Tonicity refers to how a solution affects water movement across a cell membrane based on the concentration of solutes. Here’s how different solutions compare in terms of their osmolarity and their effect on cells:
- Isotonic solutions have an osmolarity of 275-295 mOsm/L, which is similar to that of blood plasma. There is no net movement of water into or out of the cells, so the cells maintain their normal shape and size.
- Hypotonic solutions have an osmolarity lower than that of blood plasma, typically <275 mOsm/L. Water moves into the cells, causing them to swell and potentially burst.
- Hypertonic solutions have an osmolarity higher than that of blood plasma, usually >295 mOsm/L. Water moves out of the cells, leading to cell shrinkage and dehydration.
Tonicity is essential for maintaining cell shape and function, and it plays a critical role in fluid balance in the body.