Contractile vacuole

A membrane-bound cell compartment that collects and expels excess water, helping organisms in dilute environments maintain osmotic balance.

Osmoregulation: The control of water and dissolved-solute balance in an organism or cell. Contractile vacuoles are specialized organelles for cellular osmoregulation.
Paramecium: A genus of single-celled ciliates commonly found in freshwater. Its paired contractile vacuoles make the organelle’s water-expulsion cycle readily observable.
Endomembrane system: A network of eukaryotic membranes and organelles involved in processing and transporting cellular materials. Contractile-vacuole membranes are linked to trafficking pathways within this cellular system.
Central vacuole: A large plant-cell compartment that stores water and solutes and helps maintain turgor pressure. Unlike contractile vacuoles, central vacuoles mainly store materials rather than cyclically expelling excess water.
Osmosis: The net movement of water across a selectively permeable membrane toward higher solute concentration. Water enters many protists by osmosis, creating the excess the vacuole removes.
Amoeba proteus: A large freshwater amoeba that moves and feeds by extending pseudopodia. Its contractile vacuole periodically discharges water gained from its dilute surroundings.
Vesicle: A small membrane-bound sac that transports or stores substances within a cell. Vesicles can deliver membrane and fluid to the contractile vacuole.
Food vacuole: A membrane-bound compartment in which a cell digests ingested food. Food vacuoles process nutrients, whereas contractile vacuoles remove excess water.
Contractile vacuole complex: A contractile vacuole together with the membrane tubules and vesicles that supply it with fluid. The vacuole often works as part of a larger system that gathers water.
Trypanosoma cruzi: A parasitic protozoan that causes Chagas disease in humans. Its contractile-vacuole system supports osmoregulation in aquatic stages of its life cycle.

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