Give the name and function of the membrane-bound structure that occupies most of the space in a plant cell.

(A) $\Rightarrow$ The structure is called the $Vacuole$.
$\Rightarrow$ The vacuole is a 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.
$\Rightarrow$ 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.