Define the term 'water potential' and describe the difference between isotonic, hypotonic and hypertonic solutions. Suggest the different effects on cells placed in the different solutions.

Water potential refers to the measure of the ability of water to move from one location to another. It is expressed in units of pressure, such as megapascals (MPa) or kilopascals (kPa). The water potential of pure water at standard conditions is defined as zero. Any solute that is dissolved in water will reduce the water potential below zero.

The terms isotonic, hypotonic, and hypertonic are used to describe the relative concentration of solutes in two different solutions separated by a semipermeable membrane, such as a cell membrane.

An isotonic solution has the same concentration of solutes as the cell. In this case, there is no net movement of water across the cell membrane, and the cell will maintain its normal shape and size.

A hypotonic solution has a lower concentration of solutes than the cell. When a cell is placed in a hypotonic solution, water will move into the cell, causing it to swell and possibly burst. This process is known as cytolysis and can be observed in red blood cells placed in distilled water.

A hypertonic solution has a higher concentration of solutes than the cell. When a cell is placed in a hypertonic solution, water will move out of the cell, causing it to shrink or shrivel up. This process is known as plasmolysis and can be observed in plant cells placed in a solution with a high salt concentration.

In summary, an isotonic solution has no effect on cell shape, a hypotonic solution causes cells to swell, and a hypertonic solution causes cells to shrink.