Contractile vacuole

Contractile vacuoles ( formerly: pulsating vacuoles ) are contracting bubbles eg paramecium or euglena. They serve the excretion of water by enlarging rhythmically, thereby absorb fluid from the cytoplasm and release to the outside. This is necessary because constantly flows through osmosis water in her cell. This inflow of water comes about by the higher osmotic pressure. The salt concentration within the cells is therefore greater than in the surrounding freshwater. Without the contractile vacuoles of the cells would burst.

Increasing, in an experiment the salt content of the surrounding water, so the inflow of water decreases, more and more, and decreases the activity of the contractile vacuoles. For this reason, many marine species have no contractile vacuoles; The salt content of its internal environment often corresponds largely to that of the surrounding medium.

Operation

With proton pump cell pumps protons into the contractile vacuole. The resulting proton gradient is then used as a source of energy for the transport of ions (presumably carbonate ) in the vacuole. The high salt concentration causes water to diffuse out of the cytoplasm into the vacuole. Does the vacuole added enough water, they fused with the cell membrane, or open - if available - the pore so that the water from the cell is discharged.