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Tonicity In healthcare settings and biology labs, it’s often helpful to think about how solutions will affect water movement into and out of cells. The ability of an extracellular solution to make water move into or out of a cell by osmosis is known as its tonicity. Tonicity is a bit different from osmolarity because it takes into account both relative solute concentrations and the cell membrane’s permeability to those solutes. Three terms—hypertonic, hypotonic, and isotonic—are used to describe whether a solution will cause water to move into or out of a cell: If a cell is placed in a hypertonic solution, there will be a net flow of water out of the cell, and the cell will lose volume. A solution will be hypertonic to a cell if its solute concentration is higher than that inside the cell, and the solutes cannot cross the membrane. If a cell is placed in a hypotonic solution, there will be a net flow of water into the cell, and the cell will gain volume. If the solute concentration outside the cell is lower than inside the cell, and the solutes cannot cross the membrane, then that solution is hypotonic to the cell. If a cell is placed in an isotonic solution, there will be no net flow of water into or out of the cell, and the cell’s volume will remain stable. If the solute concentration outside the cell is the same as inside the cell, and the solutes cannot cross the membrane, then that solution is isotonic to the cell. Keywords: A scientist takes a group of erythrocytes (red blood cells) and places them in a beaker containing a solution. The cells begin to shrink and eventually lyse. What can be concluded about the solution? A) The solution was hypotonic to the erythrocytes B) The solution contained albumin C) The solution was isotonic to the erythrocytes D) The solution contained bicarbonate E) The solution was hypertonic to the erythrocytes #tonicity #hypertonic #hypotonic #Isotonic #RBC #redBloodCells #solution #osmoticPressure
