Vacuoles

1. By Jeffrey Ho, Jesse Bogdan, and Maggie Klureza Vacuoles

2. Basics of Vacuoles • Vacuoles are: • relatively large, membrane-bound organelles • not a distinct shape but rather appear as expandable sacs that are often filled with water, organic and inorganic material • primarily found in plant and fungi cells, occasionally in protist and bacterial cells, but never in animal cells • generally used for structural support, waste removal and storage, but can have distinctive functions for certain cells • both structure and function can vary between different vacuoles, even between two in the same cell

3. General Structure – Plants and Fungi • Plant and fungi cells have one large, central vacuole, which can take up as much as 80% of the space in the cell. This vacuole is made up of: • Tonoplast, the membrane which encloses the vacuole • Cell sap, the liquid that fills the vacuole instead of protoplasm • Because it is enclosed by a membrane, the vacuole is part of the endomembrane system. Essentially, this means that it is part of a group of organelles made from membranes, connected by the cytoplasmic network.

4. General Structure – Plants and Fungi

5. Vacuoles in Animals? • Vacuoles are only found in plant cells, fungi cells and some protist and bacteria cells, NOT in animal cells. • Animal cells DO have similar organelles, known as vesicles. • Vesicles are generally much smaller than vacuoles but much more abundant. Whereas plant and fungi cells often only have one, animal cells can have many. • Vesicles can have slightly different functions than vacuoles and are also used for transporting material from one part of the cell to another. • In lower-level sources, the two terms, vesicle and vacuole, are sometimes combined under the term “vacuole”. This is technically incorrect but more a matter of terminology than concept.

6. General Functions in Cells • Though specific function varies between different vacuoles, the majority of vacuoles share the following functions: • Containment – storing, decomposing or removing unwanted substances from the cell’s interior • Protection – storing and isolating dangerous substances, toxic to the cell’s health • Defense – storing chemicals to be used against invading bacteria • Autophagy – breaking down and decomposing old cell parts at a rate that balances out the production of cell organelles • Homeostasis – maintaining an acidic internal pH, turgor pressure and fluid balance

7. Specific Functions – Plants and Fungi • In addition to the general functions, in plant and fungi cells, where vacuoles play major roles, vacuoles may also have the following functions: • Growth and Development – storing salts, minerals, nutrients, and proteins that assist in plant growth • Attraction – storing pigment that provides the plant and its flowers their color, allowing them to attract insects for pollination • Defense – releasing poisonous or irritating molecules and chemicals that discourage predators from consuming the plant • Structure – exerting pressure against the plant’s cell walls, enabling the cell to maintain its form

8. Glossary • Cell Sap – the liquid enclosed in the vacuole (as opposed to cytoplasm); is composed primarily of water, but exact composition can vary from cell to cell. • Tonoplast – literally meaning stretching, it is the cytoplasmic membranes of vacuoles • Turgor Pressure - the pressure the vacuole exerts on a plant or fungi cell’s wall, which is determined by the volume of water in the vacuole • Vesicles – similar to vacuoles but are smaller and have some different functions; they are found in animal cells

9. Bibliography Pictures • http://www.tutorvista.com/biology/function-of-vacuole • www.library.thinkquest.org • www.micro.magnet.fsu.edu/cells/plants/vacuole.html Information • www.newton.dep.anl.gov/askasci/zoo00/zoo00296.htm • www.dictionary.reference.com/browse/vacuoles • www.iscid.org/encyclopedia/Vacuole • http://www.buzzle.com/articles/vacuole-function.html