Hypotonic

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In Biology, a hypotonic cell environment is an environment with a lower concentration of solutes than the cytoplasm of the cell. In a hypotonic environment, osmosis causes a net flow of water into the cell, causing the swelling and expansion of the cell. This swelling may lead to the bursting of the cell.

In summary, a hypertonic solution contains a higher concentration compared to the cell. Hypotonic means it has a lower concentration compared to the cell. Isotonic is a situation in which the concentrations of the cell and of the solution are in an equal ratio.

[edit] Living in a Hypotonic Environment

Plants thrive in hypotonic environments. Their cells have rigid cell walls that prevent bursting. In fact, the pressure of the cytoplasm against the cell wall keeps the plant from wilting and losing its shape. This pressure is called turgor pressure or osmotic pressure. On the other hand, cells without cell walls will swell and, if the environment is sufficiently hypotonic, burst (lyse) and die (referred to as cytolysis).

Some protists (such as Paramecium) counteract this with the use of contractile vacuoles that pump water rapidly out of the cell. Other organisms actually pump solutes out of the cell in order to lower the concentration gradient of the solute in the cell and hopefully create an isotonic environment.

The opposite of hypotonic is hypertonic, where the net movement of water is directed out of the cell into the environment; the intermediate state is called isotonic, where there is no net movement of water in and out of the cell.

A salt water fish in a fresh water aquarium is an example of hypotonic osomosis.The fish has a higher salt concentration than the water, so water flows into the fish (which acts as a membrane)to reach equillibrium between the fish and the environement.