What is the effect of hypotonic fluids on cells?

The effect of hypotonic fluids on cells is that they cause cells to swell. This occurs because hypotonic solutions contain a lower concentration of solutes compared to the inside of the cells. When cells are placed in a hypotonic environment, water moves into the cells to equalize the solute concentration both inside and outside the cell.

As water enters the cell, the increased volume can lead to swelling and, if enough water enters, may even result in the cell rupturing. However, the primary and immediate effect, especially in healthy cells, is the swelling due to osmosis. This phenomenon is particularly significant in red blood cells, which can visibly change shape and size when exposed to hypotonic fluids.

In contrast, isotonic solutions do not affect cell size because they have the same solute concentration as the cell, and hypertonic solutions cause cells to shrink because water moves out of the cells to balance the solute concentration. Therefore, the correct and most direct effect of hypotonic fluids on cells is their tendency to swell.