Contractile vacuole

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Parent
Organelle
Subordinate
Vacuole membrane
porus
lumen
protein complexes
Gene Ontology
QuickGO
The paramecium aurelia with contractile vacuoles and supplying radar channels

Contractile vacuoles (formerly also: pulsating vacuoles ) are contracting vesicles, e.g. B. in paramecia or Euglena . They serve to excrete water by rhythmically enlarging and absorbing fluid from the cytoplasm and releasing it to the outside. This is necessary because osmosis causes water to constantly flow into your cell . This influx of water comes about due to the higher internal osmotic pressure. The salt concentration within the cells is therefore higher than in the fresh water surrounding them. Without the contractile vacuoles, the cells would burst.

If the salt content of the surrounding water is increased in an experiment, the water influx decreases more and more and the activity of the contractile vacuoles decreases. For this reason, many marine species do not have contractile vacuoles; the salinity of their internal environment often largely corresponds to that of the surrounding medium.

functionality

The cell uses proton pumps to pump protons into the contractile vacuole. The resulting proton gradient then serves as an energy source for the transport of ions (presumably carbonate ) into the vacuole. The high salt concentration causes water to diffuse from the cytoplasm into the vacuole. Once the vacuole has absorbed enough water, it fuses with the cell membrane or - if present - opens the porus so that the water is discharged from the cell.

See also

literature

  • Michael T. Madigan, John M. Martinko, Jack Parker: Brock Microbiology. German translation edited by Werner Goebel, 1st edition. Spektrum Akademischer Verlag GmbH, Heidelberg / Berlin 2000, ISBN 978-3-8274-0566-1 .

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