Chapter 7, Problem 16STP

Summary Introduction

To describe:

When a cell is placed in a hypertonic solution and in a hypotonic solution.

Introduction:

The water potential of two solutions separated by a semi-permeable cell membrane is described as tonicity. Tonicity is influenced only by solutes that cannot cross the membrane. Tonicity is the relative concentration of solutes dissolved in the solution which determines the direction and extent of diffusion

Explanation of Solution

A hypertonic solution has a greater concentration of solutes than the cytosol inside the cell. When a cell is placed to a hypertonic solution, osmotic pressure tends to force water to flow out of the cell to maintain balance of concentration of solute on either side of the cell membrane. The water from inside the cell will move outwards. Since, the cell has a lower concentration of solutes than the extracellular fluid, the cell would shrink.

A solution outside of the cell is known as hypotonic if it has a lower concentration of solute relative to inside of the cell. When a cell is placed in a hypotonic extracellular fluid, the water moves from a region of high concentration to lower concentration. Thus, the fluid from surrounding will enter the cell causing the cell to swell up and cell appears turgid or bloated.

Conclusion

The relative concentration of solutes dissolved in solution determines the difference in the pressure when two solutions are separated by a membrane. It is of vital importance as the cell’s membrane is selective towards many of the solutes found in living organisms.