what compound has the highest concentration in a cell?
It depends on the conditions. In a hypertonic solution, a higher concentration of water is inside of the cell. The outside of the cell has more salt concentration than inside the cell. The cell tries to compensate for the higher concentration of salt outside of the cell, so water from inside flows back outside in order to dilute the salt. In a hypotonic solution, a higher concentration of water is outside the cell, and a higher concentration of salt is inside of the cell.