Write a note on vacuole.

(N/A) $\Rightarrow$ The vacuole is the membrane-bound space found in the cytoplasm. It contains water,sap,excretory products,and other materials not useful for the cell.
$\Rightarrow$ The vacuole is bound by a single membrane called the tonoplast.
$\Rightarrow$ In plant cells,the vacuoles can occupy up to $90\%$ of the volume of the cell. In plants,the tonoplast facilitates the transport of a number of ions and other materials against concentration gradients into the vacuole; hence,their concentration is significantly higher in the vacuole than in the cytoplasm.
$\Rightarrow$ In $Amoeba$,the contractile vacuole is important for excretion. In many cells,such as in protists,food vacuoles are formed by engulfing food particles.