In studying cell responses to salt solutions, which concentration would cause no change in the size of cells?

The concentration that would cause no change in the size of cells is typically an isotonic solution, where the concentration of solutes outside the cell equals the concentration of solutes inside the cell. In this case, a 1% salt solution is often used as an example of an isotonic environment for many cells, particularly animal cells.

When cells are placed in an isotonic solution, there is no net movement of water into or out of the cells. This stability in water movement maintains the cells' shape and size. In contrast, higher concentrations of salt solutions would create a hypertonic environment, leading to water leaving the cells and causing them to shrink. On the other hand, lower concentrations might lead to a hypotonic environment, resulting in water entering the cells and potentially causing them to swell or burst.

Thus, a 1% salt solution provides the right balance, allowing cells to remain unchanged in size.