The cytoplasm of many plant and some animal cells contains numerous small or large sized, hollow, liquid filled structures, the vacuoles. The vacuoles of plant cells are bounded by a single semipermeable membrane known as tonoplast. These vacuoles contain water, phenol, flavonols, anthocyanins, alkaloids and storage products such as sugars and proteins. The vacuoles of animal cells are bounded by a lipoproteinaceous membrane and their function is storage, transmission of materials and maintenance of internal pressure of cell.