Plant cells additionally possess large, fluid-filled vesicles called vacuoles within their cytoplasm. Vacuoles typically compose about 30 percent of a cell's volume, but they can fill as much as ...

Cell wall: a tough outer layer of the cell, which contains cellulose to provide strength and support to the plant. Vacuole: a space inside the cytoplasm that contains a watery liquid called cell sap.

The two main types are the protein storage vacuoles of neutral pH, and the lytic vacuoles of acidic pH, which are equivalent in function to lysosomes in mammalian cells (Figure 1).