Upon completion of this module, you should be able to distinguish between various types of solutions. Solutions can be saturated, unsaturated, or supersaturated. A saturated solution is a solution in which no more solute can be dissolved in the solvent. Any additional solute added to a saturated solution will not dissolve. Solution concentrations are important in biology where it is useful to think of biological cells in solutions. There is a solution inside the cell and outside the cell separated by a semipermeable membrane. The solutions outside the cell can be isotonic, hypertonic, or hypotonic.