Multipurpose members of the endomembrane system that in many species serve as containers for relatively small molecules and ions found in aqueous solution.
The constituents of vacuoles can be waste materials, stored materials including water, or simply something that is less expensive to produce and maintain, per unit volume, than cytosol. Vacuoles can also exert hydrostatic pressure on the rest of the cell, maintaining turgidity, i.e., a stiffness of cytoplasm against the cell wall. Basically, the term vacuole has been used to describe a rather large number of diverse endomembrane structures.
Perhaps most prominent of vacuoles is the central vacuole associated with plant cells which makes up a substantial portion of cell volume. The lipid bilayer surrounding and defining the vacuole as a membrane-bound organelle is called a tonoplast. See also food vacuole.
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