What is the effect of an isotonic solution on cell water balance?

An isotonic solution is one where the concentration of solutes outside the cell is equal to the concentration of solutes inside the cell. When cells are placed in an isotonic solution, there is no net movement of water across the cell membrane because the osmotic pressure inside and outside the cell is balanced. This equilibrium means that while water molecules continue to move in and out of the cell through osmosis, the rates of movement are equal, resulting in no overall gain or loss of water by the cell. Consequently, the cells maintain their normal shape and function without swelling or shrinking.

In contrast, if a cell were placed in a hypotonic solution, it would gain water and possibly swell or even burst, while in a hypertonic solution, cells would lose water, leading to shrinkage. Neither of these scenarios occurs in an isotonic environment. The cell's ability to maintain osmotic balance in isotonic conditions is crucial for homeostasis within the body.