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The contractile vacuole allows free-living protists to expel extra water. <b>The contractile vacuole allows free-living protists to expel extra water <br /></b>.
1 Vacuole: A membrane-bound, fluid-filled sac inside plant and animal cells. 2  Contractile vacuoles of protists, such as the Paramecium, are specialized organelles for expelling excess water. 3  Food vacuoles of the Amoeba digest smaller cells captured by phagocytosis.