Contractile vacuoles in protists collect accumulated waste products and excess water from inside the cell. They expel these waste products into the environment by attaching to the cell wall, then contracting to release these products outside the cell.
Contractile vacuoles in protista are important to the life of the organism. As one-celled organisms, protists are susceptible to changes in osmotic pressure, wide variations in temperature and pH, and exposure to different chemicals in their surroundings. Contractile vacuoles regulate the contents of the cell, the osmotic pressure and the internal environment by expelling material unnecessary or even deleterious to the survival of the organism.