When the solute concentration of the cell and its surrounding medium are the same, the solution is said to be

The correct answer is "isotonic." When the concentration of solutes in the cell and the surrounding medium is the same, the solution is said to be isotonic. In an isotonic solution, there is no net movement of water across the cell membrane, and the cell maintains its shape and size. On the other hand, in a hypertonic solution, the concentration of solutes is higher outside the cell, causing water to move out of the cell and leading to shrinkage or crenation of the cell. In a hypotonic solution, the concentration of solutes is lower outside the cell, causing water to move into the cell and leading to swelling or lysis of the cell. Maintaining the proper concentration of solutes inside and outside of cells is important for the proper functioning of living organisms. Cells use various mechanisms to regulate the movement of water and solutes across their membranes to maintain isotonic conditions when necessary.