Vacuole

A vacuole is a membrane-bound sac within a cell that functions in storage and transport of substances. Vacuoles often contain water, nutrients, or waste products; for example, plant cells have a large central vacuole that stores water and helps maintain turgor pressure (keeping the cell rigid). In some cells, vacuoles also have digestive functions similar to lysosomes.

• Plants: The central vacuole in plant cells can occupy most of the cell-s volume; it stores water, ions, and nutrients, and its pressure against the cell wall keeps the plant cell firm (turgid).
• Protists: Certain single-celled eukaryotes have contractile vacuoles that pump out excess water to prevent bursting.
• Animals: Animal cells generally have many small vacuoles (often called vesicles). Animal vacuoles are used for transport and storage of materials, but digestion of macromolecules is typically handled by lysosomes.

• Plant vs. animal cell diagram - A large fluid-filled sac in a plant cell diagram is the central vacuole; in an animal cell such a large vacuole would not be present (animal cells have smaller vesicles).
• Function association - If a question mentions storage of substances or maintenance of cell rigidity in plants, it-s referring to the vacuole (for rigidity via water pressure in plants).
• Terminology check - Don-t confuse -vacuole- with -vesicle.- Generally, vacuoles are larger and more prominent in plant cells (for storage and support), while -vesicle- often refers to smaller membrane-bound transport sacs in animal cells.