These are the membrane-boundspace found in the cytoplasm. It contains water, sap, excretory product and other materials not useful for the cell.
Vacuole is bound by a single membrane called tonoplast.
In plant cells, the vacuoles can occupy up to 90% of the volume of the cell.
In plants, the tonoplastfacilitates the transport of a number of ionsand other materials against concentration gradients into the vacuole; hence their concentration is significantly higher in the vacuole than in the cytoplasm.
In Amoeba, the contractile vacuole is important for excretion. In many cells, as in protists, food vacuoles are formed by engulfing the food particles.
