Cytolysis
From Wikipedia, the free encyclopedia
Osmosis is when water travels from an area of high concentration to an area of low concentration. When a cell has a lower concentration than its surroundings, it takes in water until either the cell contains the same percentage of water as that of its surroundings, or the cell bursts (cytolosis).
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[edit] Cause and effects
Osmotic lysis occurs in a hypotonic environment, where water diffuses into the cell. As the water continues to diffuse into the cell, the cell grows larger, and will eventually burst if too much water enters. The cell membrane is not strong enough to prevent and stop the swelling of the cell, and eventually will rupture, releasing the cell contents.
Cytolysis does not occur in plant cells because plant cells have a strong cell wall that contains the osmotic pressure, or turgor pressure, which would otherwise cause cytolysis to occur. Contrary to organisms without a cell wall, plant cells must be in a hypotonic environment in order to have this turgor pressure, which provides the cells more structural support, preventing the plant from wilting. In a hypertonic environment, plasmolysis occurs, which is nearly the complete opposite of cytolysis: Instead of expanding, the cytoplasm of the plant cell retracts from the cell wall, causing the plant to wilt.
Osmotic lysis is often the result of a stroke, since a stroke leads to a malfunctioning of the cell's metabolism, which results in an inflow of extracellular fluid into the cell.
[edit] Preventing osmotic lysis
Different cells and organisms have adapted different ways of preventing cytolysis from occurring. For example, the paramecium uses a contractile vacuole, which rapidly pumps out excessive water to prevent the build-up of water and the otherwise subsequent lysis.
Other organisms pump solutes out of their cytosol, which brings the solute concentration closer to that of their environment and slows down the process of water's diffusion into the cell, preventing cytolysis. If the cell can pump out enough solutes so that an isotonic environment can be achieved, there will be no net movement of water.
