A membrane-bound vesicle within the cytoplasm of a living cell that is filled with air, water or other liquid, cell sap, or food particles. Vacuoles are derived from the endoplasmic reticulum and Golgi apparatus, and form part of the endomembrane system of the cell. Plant vacuoles perform various functions, including storage of food reserves or waste products; in some cases these are toxic or unpalatable substances that deter browsing animals. Vacuoles in cells of petals or other flower parts may contain the colourful anthocyanin pigments that attract pollinators, whereas in seeds vacuoles store proteins for use by the germinating embryo. As plant cells mature smaller vacuoles coalesce to form usually one large central vacuole bounded by a single-layered membrane (tonoplast or vacuole membrane). This central vacuole occupies most of the cell’s interior. It is filled with cell sap, including most of the cell’s inorganic ions, and it swells by absorbing water from the cytoplasm. The pressure exerted by the vacuole is transmitted through the cytoplasm to the cell wall; in a growing cell this turgor pressure helps the cell wall to expand, whereas in a mature cell it stiffens the wall, thus lending support to the plant. Animal cells usually have several small vacuoles. See also contractile vacuole.