Vacuole

A vacuole is a membrane-bound organelle.^[1] They are a kind of vesicle. Vacuoles are closed sacs, made of membranes with inorganic or organic molecules inside, such as enzymes. They have no set shape or size, and the cell can change them as needed. They are in most eukaryotic cells and do many things. They can store waste. Vacuoles and their contents are distinct from the cytoplasm, and are classified as ergastic according to some people.^[2] The solution that fills the vacuole is called cell sap.

What a vacuole does and how important it is depends on what kind of cell they are in. They are much more important in plant and fungus cells than in animal cells. Some common jobs of a vacuole are to:

• Hold waste products, and keep things separate from the rest of the cell
• Hold water in plant cells
• Keep the internal hydrostatic pressure or turgor steady in a cell. In land plants, this holds the stem upright.
• Keep an acidic pH on the inside of a cell
• Hold small molecules
• In seeds, proteins that seeds use to sprout are put in 'protein bodies'. Protein bodies are just vacuoles that are a little bit different from normal.^[3]

Vacuoles are also important in autophagy, keeping a balance between making and getting rid of many things in cells and organisms. They also help with destroying and recycling broken proteins that build up in cells. Vacuoles may help attack bacteria and some kinds of vacuoles may act as a house for symbiotic bacteria. In protists, vacuoles also store and help digest food that the protist ate.^[4]

1. ↑ Venes D (2001). Taber's Cyclopedic Medical Dictionary (20th ed.). Philadelphia: F.A. Davis. p. 2287. ISBN 0-9762548-3-2.
2. ↑ Esau K. 1965. Plant Anatomy, 2nd ed. John Wiley.
3. ↑ Matile, Phillipe 1993. Chapter 18: Vacuoles, discovery of lysosomal origin. In Discoveries in Plant Biology: v. 1. World Scientific Publishing.
4. ↑ Jezbera Jan, Karel Hornak, Karel Simek (2005). "Food selection by bacterivorous protists: insight from the analysis of the food vacuole by means of fluorescence in situ hybridization". FEMS Microbiology Ecology. 52 (3): 351–363. doi:10.1016/j.femsec.2004.12.001. PMID 16329920.{{cite journal}}: CS1 maint: multiple names: authors list (link)