Difference between revisions of "Vacuole" - New World Encyclopedia

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{{Copyedited}}{{Images OK}}{{Approved}}
 
[[image:biological cell.svg|thumb|300px|Schematic of typical animal cell, showing subcellular components: <br/>  
 
[[image:biological cell.svg|thumb|300px|Schematic of typical animal cell, showing subcellular components: <br/>  
(1) [[nucleolus]]<br/>
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(1) [[nucleolus]]<br/>  
(2) [[cell nucleus|nucleus]]<br/>
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(2) [[cell nucleus|nucleus]]<br/>  
(3) ribosomes (little dots)<br/>
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(3) ribosomes (little dots)<br/>  
(4) [[vesicle (biology)|vesicle]]<br/>
+
(4) [[vesicle (biology)|vesicle]]<br/>  
(5) rough [[endoplasmic reticulum]] (ER)<br/>
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(5) rough [[endoplasmic reticulum]] (ER)<br/>  
(6) [[Golgi apparatus]]<br/>
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(6) [[Golgi apparatus]]<br/>  
(7) [[Cytoskeleton]]<br/>
+
(7) [[Cytoskeleton]]<br/>  
(8) smooth ER<br/>
+
(8) smooth ER<br/>  
(9) [[mitochondrion|mitochondria]]<br/>
+
(9) [[mitochondrion|mitochondria]]<br/>  
(10) [[vacuole]]<br/>
+
(10) [[vacuole]]<br/>  
 
(11) [[cytoplasm]]<br/>  
 
(11) [[cytoplasm]]<br/>  
(12) [[lysosome]]<br/>
+
(12) [[lysosome]]<br/>  
 
(13) [[centriole]]s within [[centrosome]]]]
 
(13) [[centriole]]s within [[centrosome]]]]
  
'''Vacuoles''' Vacuoles are [[cell membrane|membrane]]-bound compartments within some [[eukaryote|eukaryotic]] [[cell (biology)|cells]] that can serve a variety of secretory, excretory, and storage functions.  
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'''Vacuoles''' are membrane-bound compartments within some [[eukaryote|eukaryotic]] [[cell (biology)|cells]] that serve a variety of secretory, excretory, and storage functions. These [[organelle]]s are found in the cytoplasm of most [[plant]] cells and some [[animal]] cells. In [[protist]]s, vacuoles function in [[food]] and [[water]] storage and contractile vacuoles play a role in osmoregulation.  
 
 
are found in the cytoplasm of most plant cells and some animal cells.
 
 
 
 
 
Vacuoles and their contents are considered to be distinct from the [[cytoplasm]], and are classified as [[Ergastic substances|ergastic]] according to some authors.<ref>
 
Esau, K. (1965). ''Plant Anatomy'', 2nd Edition. John Wiley & Sons. 767 pp.</ref> Vacuoles are especially  conspicuous in most [[plant cell]]s.
 
 
 
 
 
: is a specialized structure within a cell that performs a specific function and that generally is considered to be separately enclosed within its own lipid membrane.
 
membrane bound cellular structure (organelle)
 
subcellular structural unit.
 
 
 
non-protoplasm materials found in cells. The living protoplasm of a cell is sometimes called the bioplasm and distinct from the ergastic substances of the cell. The latter are usually organic or inorganic substances that are products of metabolism, and include crystals, oil drops, gums, tannins, resins and other compounds that can aid the organism in defense, maintenance of cellular structure, or just substance storage.
 
 
 
itmay occupy up to ninety percent of the cell volume and function not only in space filin buttalo intracellular digestion (Alberts et al.)
 
  
 +
Vacuoles and their contents are considered to be distinct from the [[cytoplasm]], and are classified as [[Ergastic substances|ergastic]] (non-protoplasm material) according to some authors (Esau 1965). Vacuoles are especially conspicuous in most [[plant cell]]s, where they can occupy up to ninety percent of the cell volume and function in filling space (Alberts et al. 1989).
 +
{{toc}}
 +
Organelles, such as the vacuole, are part of the harmony seen in the natural world, whereby entities provide a function for the larger entity of which they are part. Just as the vacuole provides a function for the cell, the cell provides a function for an organism (via tissues, organs, and organ systems), and organisms contribute to the [[ecosystem]] of which they are part.
  
 
==Functions==
 
==Functions==
 
+
In general, vacuole functions include:
In general, vacuole functions include also
+
* Removing unwanted structural debris
* Removing unwanted structual debris
 
 
* Isolating materials that might be harmful or a threat to the cell
 
* Isolating materials that might be harmful or a threat to the cell
 
* Containing waste products
 
* Containing waste products
 
* Maintaining internal [[hydrostatic pressure]] or [[turgor]] within the cell
 
* Maintaining internal [[hydrostatic pressure]] or [[turgor]] within the cell
* Maintaining an [[acidic]] internal pH
+
* Maintaining an [[acidic]] internal [[pH]]
 
* Containing small molecules
 
* Containing small molecules
 
* Exporting unwanted substances from the cell
 
* Exporting unwanted substances from the cell
 +
* Filling space
 +
* Intracellular digestion
  
Vacuoles also play a major role in [[autophagy]], maintaining a balance between [[biogenesis]] (production) and degradation (or turnover), of many substances and cell structures. Vacuoles store food and other materials needed by a cell. They also aid in destruction of invading [[bacteria]] or of misfolded proteins that have begun to build up within the cell. The vacuole is a major part in the plant and animal cell. flash:11
+
Vacuoles also play a major role in [[autophagy]] (degradation of a cell's own components), maintaining a balance between [[biogenesis]] (production) and degradation (or turnover), of many substances and cell structures. Vacuoles store food and other materials needed by a cell. They also aid in destruction of invading [[bacteria]] or of misfolded proteins that have begun to build up within the cell. The vacuole is a major part in the plant and animal cell.  
  
[[Image:Paramecium_with_contractile_vacuole.jpg|thumb|right|'''Figure 1:''' A paramecium. The contractile vacuole can be seen as the multiple 'armed' structure on the right-hand side of the ciliate. ]]
+
In macroautophagy, there is [[sequestration]] of [[organelle]]s and long-lived [[protein]]s in a double-membrane [[vesicle]] called an autophagic vacuole (AV). The outer membrane of the autophagic vacuole (or autophagosome) fuses in the [[cytoplasm]] with a [[lysosome]] to form an autolysosome or autophagolysosome, where their contents are degraded via [[Acid hydrolase|acidic lysosomal hydrolases]] (Rubinsztein et al. 2005).
  
A '''contractile vacuole''' is a sub-cellular structure involved in [[osmoregulation]]. It pumps excess water out of a [[Cell (biology)|cell]] and is found prominently in freshwater [[protists]].
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A contractile vacuole is a sub-cellular structure involved in [[osmoregulation]]. It pumps excess water out of a [[Cell (biology)|cell]] and is found prominently in freshwater [[protists]]. Basically, the contractile vacuole stores extra water. If the cell has a need for water, the contractile vacuole can release more water into the cell. But if water is in excess, the contractile vacuole will remove it.
  
In [[Paramecium]], a common freshwater protist, the vacuole is surrounded by several canals, which absorb [[water]] by [[osmosis]] from the [[cytoplasm]].  After the canals fill with water, the water is pumped into the vacuole.  When the vacuole is full, it expels the water through a [[pore]] in the cytoplasm which can be opened and closed.
+
==Protists==
Other protists, such as [[Amoeba]], have contractile vacuoles that move to the surface of the cell when full and undergo [[exocytosis]].
+
Some [[protist]]s and [[macrophage]]s use ''food vacuoles'' as a stage in [[phagocytosis]]&mdash;the intake of large [[molecule]]s, particles, or even other cells, by the cell for [[digestion]]. They are also called "storage sacs."
  
Basically, the contractile vacuole stores extra water. If the cell has a need for water, the contractile vacuole can release more water into the cell. But if water is in excess, the contractile vacuole will remove it.
+
A [[contractile vacuole]] is used to pump excess water out of the cell to reduce [[turgor|osmotic pressure]] and keep the cell from bursting, which is referred to as [[cytolysis]] or [[osmotic lysis]]. In [[Paramecium]], a common freshwater protist, the vacuole is surrounded by several canals, which absorb [[water]] by [[osmosis]] from the [[cytoplasm]]. After the canals fill with water, the water is pumped into the vacuole. When the vacuole is full, it expels the water through a [[pore]] in the cytoplasm, which can be opened and closed. Other protists, such as [[Amoeba]], have contractile vacuoles that move to the surface of the cell when full and undergo [[exocytosis]].
  
 
Contractile vacuoles are often used as a cell's method of propulsion.
 
Contractile vacuoles are often used as a cell's method of propulsion.
  
==Protists==
+
==Budding yeast==
Some [[protist]]s and [[macrophage]]s use '''''food vacuoles''''' as a stage in [[phagocytosis]]&mdash;the intake of large molecules, particles, or even other cells, by the cell for [[digestion]]. They are also called "storage sacs."
+
In budding [[yeast]] cells, vacuoles act as storage compartments of [[amino acid]]s and [[detoxification]] compartments. Under conditions of starvation, proteins are degraded in vacuoles in a process known as autophagy. First, [[cytoplasm]]s, [[mitochondrion]], and small [[organelle]]s are covered with multiplex plasma membranes called autophagosomes. Next, the autophagosomes fuse the vacuoles. Finally, the cytoplasms and the organelles are degraded.  
 
 
A '''[[contractile vacuole]]''' is used to pump excess water out of the cell to reduce [[turgor|osmotic pressure]] and keep the cell from bursting, which is referred to as [[cytolysis]] or [[osmotic lysis]].
 
 
 
==Budding yeast==  
 
In budding [[yeast]] cells, vacuoles act as storage compartments of [[amino acids]] and [[detoxification]] compartments. Under conditions of starvation, proteins are degraded in vacuoles; this is called autophagy. First, [[cytoplasm]]s, [[mitochondrion]], and small [[organelle]]s are covered with multiplex plasma membranes called autophagosomes. Next, the autophagosomes fuse the vacuoles. Finally, the cytoplasms and the organelles are degraded.  
 
 
 
 
 
In a vacuole of budding yeast, black particles sometimes appear, called a dancing body. The dancing body moves actively in the vacuole and appears and disappears within 10 minutes to several hours. In previous research, it was suggested but not proven that the main component of the dancing body is [[polyphosphate]] acid. But the main component has been determined to be crystallized sodium polyphosphate and its function has been studied.{{Fact|date=June 2008}} It is thought that its function is to supply and store phosphates in budding yeast cells.
+
In a vacuole of budding yeast, black particles sometimes appear, called a dancing body. The dancing body moves actively in the vacuole and appears and disappears within ten minutes to several hours. In previous research, it was suggested but not proven that the main component of the dancing body is [[polyphosphate]] acid. It is believed that the main component is crystallized sodium polyphosphate and its function is thought to be to supply and store phosphates in budding yeast cells.
  
 
==Plants==
 
==Plants==
Most mature [[plant cell]]s have one or several '''vacuoles''' that typically occupy more than 30% of the cell's volume, and that can occupy as much as 90% of the volume for certain cell types and conditions.<ref>
+
Most mature [[plant cell]]s have one or several vacuoles that typically occupy more than 30 percent of the cell's volume, and that can occupy as much as 90 percent of the volume for certain cell types and conditions (Alberts et al. 2002). A vacuole is surrounded by a membrane called the ''tonoplast''.  
Alberts, Bruce, Johnson, Alexander, Lewis, Julian, Raff, Martin, Roberts, Keith, and Walter, Peter (2002). ''Molecular Biology of the Cell (Fourth Edition),'' (Garland Science, New York), p. 740.</ref> A vacuole is surrounded by a membrane called the '''tonoplast'''.  
 
  
This vacuole houses large amounts of a liquid called [[cell sap]], composed of water, [[enzymes]], inorganic ions (like K<sup>+</sup> and Cl<sup>-</sup>), salts (such as [[calcium]]), and other substances, including toxic byproducts removed from the cytosol to avoid interference with [[metabolism]]. Toxins present in the vacuole may also help to protect some plants from predators. Transport of [[proton]]s from cytosol to vacuole aids in keeping cytoplasmic [[pH]] stable, while making the vacuolar interior more acidic, allowing degradative enzymes to act. Although having a large central vacuole is the most common case, the size and number of vacuoles may vary in different tissues and stages of development. Cells of the [[vascular cambium]], for example, have many small vacuoles in winter, and one large one in summer.  
+
This vacuole houses large amounts of a liquid called [[cell sap]], composed of water, [[enzyme]]s, inorganic ions (like K<sup>+</sup> and Cl<sup>-</sup>), salts (such as [[calcium]]), and other substances, including toxic byproducts removed from the [[cytosol]] to avoid interference with [[metabolism]]. Toxins present in the vacuole may also help to protect some plants from predators. Transport of [[proton]]s from cytosol to vacuole aids in keeping cytoplasmic [[pH]] stable, while making the vacuolar interior more acidic, allowing degradative enzymes to act. Although having a large central vacuole is the most common case, the size and number of vacuoles may vary in different tissues and stages of development. Cells of the [[vascular cambium]], for example, have many small vacuoles in winter, and one large one in summer.  
  
Aside from storage, the main role of the central vacuole is to maintain [[turgor]] pressure against the [[cell wall]]. Proteins found in the tonoplast control the flow of water into and out of the vacuole through [[active transport]], pumping [[potassium]] (K<sup>+</sup>) [[ion]]s into and out of the vacuolar interior. Due to [[osmosis]], water will diffuse into the vacuole, placing pressure on the cell wall. If water loss leads to a significant decline in turgor pressure, the [[cell]] will [[plasmolysis|plasmolyse]]. Turgor pressure exerted by vacuoles is also helpful for cellular elongation: as the cell wall is partially degraded by the action of [[auxins]], the less rigid wall is expanded by the pressure coming from within the vacuole. Vacuoles can help some plant cells to reach considerable size. Another function of a central vacuole is that it pushes all contents of the cell's cytoplasm against the cellular membrane, and thus keeps the [[chloroplasts]] closer to light.  
+
Aside from storage, the main role of the central vacuole is to maintain [[turgor]] pressure against the [[cell wall]]. Proteins found in the tonoplast control the flow of water into and out of the vacuole through [[active transport]], pumping [[potassium]] (K<sup>+</sup>) [[ion]]s into and out of the vacuolar interior. Due to [[osmosis]], water will diffuse into the vacuole, placing pressure on the cell wall. If water loss leads to a significant decline in turgor pressure, the [[cell]] will [[plasmolysis|plasmolyse]]. Turgor pressure exerted by vacuoles is also helpful for cellular elongation: as the cell wall is partially degraded by the action of [[auxin]]s, the less rigid wall is expanded by the pressure coming from within the vacuole. Vacuoles can help some plant cells to reach considerable size. Another function of a central vacuole is that it pushes all contents of the cell's cytoplasm against the cellular membrane, and thus keeps the [[chloroplast]]s closer to light.  
  
 
The vacuole also stores the [[pigment]]s in [[flower]]s and [[fruit]]s.
 
The vacuole also stores the [[pigment]]s in [[flower]]s and [[fruit]]s.
  
 
==Animals==
 
==Animals==
 +
Vacuoles in [[animal]]s are a part of the processes of [[exocytosis]] and [[endocytosis]].
  
Vacuoles in animals are a part of the processes of [[exocytosis]] and [[endocytosis]].
+
Exocytosis is the extrusion process by which a cell directs secretory vesicles out of the cell. Proteins from the [[Golgi apparatus]] initially enter secretory granules, where processing of prohormones to the mature hormones occurs before exocytosis. Exocytosis also allows the animal cell to rid waste products from the cell.
Exocytosis is the extrusion process of proteins from the [[Golgi apparatus]] initially enter secretory granules, where processing of prohormones to the mature hormones occurs before exocytosis, and also allows the animal cell to rid waste products.
 
Endocytosis is the reverse of exocytosis. There are various types. [[Phagocytosis]] ("cell eating") is the process by which bacteria, dead tissue, or other bits of material visible under the microscope are engulfed by cells. The material makes contact with the cell membrane, which then invaginates. The invagination is pinched off, leaving the engulfed material in the membrane-enclosed vacuole and the cell membrane intact. [[Pinocytosis]] ("cell drinking") is essentially the same process, the difference being that the substances ingested are in solution and not visible under the microscope <ref name=Ganong2003>{{cite journal | author = William F. Ganong, MD | title = REVIEW OF MEDICAL PHYSIOLOGY - 21st Ed. | year = 2003}}</ref>
 
  
Hydropic (vacuolar) changes are of importance of identifying various pathologies, such as the reversible cell swelling in renal tubules caused by hypoperfusion of the kidneys during open heart surgery.
+
Endocytosis is the reverse of exocytosis. There are various types. [[Phagocytosis]] ("cell eating") is the process by which [[bacteria]], dead tissue, or other bits of material visible under the microscope are engulfed by cells. The material makes contact with the cell membrane, which then invaginates. The invagination is pinched off, leaving the engulfed material in the membrane-enclosed vacuole and the cell membrane intact. [[Pinocytosis]] ("cell drinking") is essentially the same process, the difference being that the substances ingested are in solution and not visible under the microscope (Ganong 2003).
 +
 
 +
Hydropic (vacuolar) changes are of importance of identifying various pathologies, such as the reversible cell swelling in renal tubules caused by hypoperfusion of the [[kidney]]s during open heart surgery.
  
 
==References==
 
==References==
<div class="small>
 
<references/>
 
</div>
 
* (2003) Lange Medical Books/McGraw-Hill, Medical Publishing Division, New York
 
 
 
 
* Alberts, B., D. Bray, J. Lewis, M. Raff, K. Roberts, and J. D. Watson. ''Molecular Biology of the Cell'', 2nd edition. New York: Garland Publishing, 1989. ISBN 0824036956.
 
* Alberts, B., D. Bray, J. Lewis, M. Raff, K. Roberts, and J. D. Watson. ''Molecular Biology of the Cell'', 2nd edition. New York: Garland Publishing, 1989. ISBN 0824036956.
 +
* Alberts, B., A. Johnson, J. Lewis, M. Raff, K. Roberts, and P. Walter. 2002. ''Molecular Biology of the Cell'', 4th edition. New York: Garland Science. ISBN 0815332181.
 +
* Esau, K. 1965. ''Plant Anatomy'', 2nd edition. John Wiley & Sons.
 +
* Ganong, W. F. 2003. ''Review of Medical Physiology'', 21st edition. New York: McGraw-Hill. ISBN 0071402365.
 +
* McPhee, S. J., V. R. Lingappa, and W. F. Ganong. 2003. ''Pathophysiology of Disease: An Introduction to Clinical Medicine''. New York: Lange Medical Books/McGraw-Hill. ISBN 0071387641.
 +
* Rubinsztein, D. C., M. DiFiglia, N. Heintz, R. A. Nixon, Z. H. Qin, B. Ravikumar, L. Stefanis, and A. Tolkovsky. 2005. [http://www.ncbi.nlm.nih.gov/pubmed/16874045 Autophagy and its possible roles in nervous system diseases, damage and repair] ''Autophagy'' 1(1): 11-22. PMID 16874055. Retrieved July 5, 2008.
  
 
{{organelles}}
 
{{organelles}}

Latest revision as of 23:00, 13 November 2022

Schematic of typical animal cell, showing subcellular components:
(1) nucleolus
(2) nucleus
(3) ribosomes (little dots)
(4) vesicle
(5) rough endoplasmic reticulum (ER)
(6) Golgi apparatus
(7) Cytoskeleton
(8) smooth ER
(9) mitochondria
(10) vacuole
(11) cytoplasm
(12) lysosome
(13) centrioles within centrosome

Vacuoles are membrane-bound compartments within some eukaryotic cells that serve a variety of secretory, excretory, and storage functions. These organelles are found in the cytoplasm of most plant cells and some animal cells. In protists, vacuoles function in food and water storage and contractile vacuoles play a role in osmoregulation.

Vacuoles and their contents are considered to be distinct from the cytoplasm, and are classified as ergastic (non-protoplasm material) according to some authors (Esau 1965). Vacuoles are especially conspicuous in most plant cells, where they can occupy up to ninety percent of the cell volume and function in filling space (Alberts et al. 1989).

Organelles, such as the vacuole, are part of the harmony seen in the natural world, whereby entities provide a function for the larger entity of which they are part. Just as the vacuole provides a function for the cell, the cell provides a function for an organism (via tissues, organs, and organ systems), and organisms contribute to the ecosystem of which they are part.

Functions

In general, vacuole functions include:

  • Removing unwanted structural debris
  • Isolating materials that might be harmful or a threat to the cell
  • Containing waste products
  • Maintaining internal hydrostatic pressure or turgor within the cell
  • Maintaining an acidic internal pH
  • Containing small molecules
  • Exporting unwanted substances from the cell
  • Filling space
  • Intracellular digestion

Vacuoles also play a major role in autophagy (degradation of a cell's own components), maintaining a balance between biogenesis (production) and degradation (or turnover), of many substances and cell structures. Vacuoles store food and other materials needed by a cell. They also aid in destruction of invading bacteria or of misfolded proteins that have begun to build up within the cell. The vacuole is a major part in the plant and animal cell.

In macroautophagy, there is sequestration of organelles and long-lived proteins in a double-membrane vesicle called an autophagic vacuole (AV). The outer membrane of the autophagic vacuole (or autophagosome) fuses in the cytoplasm with a lysosome to form an autolysosome or autophagolysosome, where their contents are degraded via acidic lysosomal hydrolases (Rubinsztein et al. 2005).

A contractile vacuole is a sub-cellular structure involved in osmoregulation. It pumps excess water out of a cell and is found prominently in freshwater protists. Basically, the contractile vacuole stores extra water. If the cell has a need for water, the contractile vacuole can release more water into the cell. But if water is in excess, the contractile vacuole will remove it.

Protists

Some protists and macrophages use food vacuoles as a stage in phagocytosis—the intake of large molecules, particles, or even other cells, by the cell for digestion. They are also called "storage sacs."

A contractile vacuole is used to pump excess water out of the cell to reduce osmotic pressure and keep the cell from bursting, which is referred to as cytolysis or osmotic lysis. In Paramecium, a common freshwater protist, the vacuole is surrounded by several canals, which absorb water by osmosis from the cytoplasm. After the canals fill with water, the water is pumped into the vacuole. When the vacuole is full, it expels the water through a pore in the cytoplasm, which can be opened and closed. Other protists, such as Amoeba, have contractile vacuoles that move to the surface of the cell when full and undergo exocytosis.

Contractile vacuoles are often used as a cell's method of propulsion.

Budding yeast

In budding yeast cells, vacuoles act as storage compartments of amino acids and detoxification compartments. Under conditions of starvation, proteins are degraded in vacuoles in a process known as autophagy. First, cytoplasms, mitochondrion, and small organelles are covered with multiplex plasma membranes called autophagosomes. Next, the autophagosomes fuse the vacuoles. Finally, the cytoplasms and the organelles are degraded.

In a vacuole of budding yeast, black particles sometimes appear, called a dancing body. The dancing body moves actively in the vacuole and appears and disappears within ten minutes to several hours. In previous research, it was suggested but not proven that the main component of the dancing body is polyphosphate acid. It is believed that the main component is crystallized sodium polyphosphate and its function is thought to be to supply and store phosphates in budding yeast cells.

Plants

Most mature plant cells have one or several vacuoles that typically occupy more than 30 percent of the cell's volume, and that can occupy as much as 90 percent of the volume for certain cell types and conditions (Alberts et al. 2002). A vacuole is surrounded by a membrane called the tonoplast.

This vacuole houses large amounts of a liquid called cell sap, composed of water, enzymes, inorganic ions (like K+ and Cl-), salts (such as calcium), and other substances, including toxic byproducts removed from the cytosol to avoid interference with metabolism. Toxins present in the vacuole may also help to protect some plants from predators. Transport of protons from cytosol to vacuole aids in keeping cytoplasmic pH stable, while making the vacuolar interior more acidic, allowing degradative enzymes to act. Although having a large central vacuole is the most common case, the size and number of vacuoles may vary in different tissues and stages of development. Cells of the vascular cambium, for example, have many small vacuoles in winter, and one large one in summer.

Aside from storage, the main role of the central vacuole is to maintain turgor pressure against the cell wall. Proteins found in the tonoplast control the flow of water into and out of the vacuole through active transport, pumping potassium (K+) ions into and out of the vacuolar interior. Due to osmosis, water will diffuse into the vacuole, placing pressure on the cell wall. If water loss leads to a significant decline in turgor pressure, the cell will plasmolyse. Turgor pressure exerted by vacuoles is also helpful for cellular elongation: as the cell wall is partially degraded by the action of auxins, the less rigid wall is expanded by the pressure coming from within the vacuole. Vacuoles can help some plant cells to reach considerable size. Another function of a central vacuole is that it pushes all contents of the cell's cytoplasm against the cellular membrane, and thus keeps the chloroplasts closer to light.

The vacuole also stores the pigments in flowers and fruits.

Animals

Vacuoles in animals are a part of the processes of exocytosis and endocytosis.

Exocytosis is the extrusion process by which a cell directs secretory vesicles out of the cell. Proteins from the Golgi apparatus initially enter secretory granules, where processing of prohormones to the mature hormones occurs before exocytosis. Exocytosis also allows the animal cell to rid waste products from the cell.

Endocytosis is the reverse of exocytosis. There are various types. Phagocytosis ("cell eating") is the process by which bacteria, dead tissue, or other bits of material visible under the microscope are engulfed by cells. The material makes contact with the cell membrane, which then invaginates. The invagination is pinched off, leaving the engulfed material in the membrane-enclosed vacuole and the cell membrane intact. Pinocytosis ("cell drinking") is essentially the same process, the difference being that the substances ingested are in solution and not visible under the microscope (Ganong 2003).

Hydropic (vacuolar) changes are of importance of identifying various pathologies, such as the reversible cell swelling in renal tubules caused by hypoperfusion of the kidneys during open heart surgery.

References
ISBN links support NWE through referral fees

  • Alberts, B., D. Bray, J. Lewis, M. Raff, K. Roberts, and J. D. Watson. Molecular Biology of the Cell, 2nd edition. New York: Garland Publishing, 1989. ISBN 0824036956.
  • Alberts, B., A. Johnson, J. Lewis, M. Raff, K. Roberts, and P. Walter. 2002. Molecular Biology of the Cell, 4th edition. New York: Garland Science. ISBN 0815332181.
  • Esau, K. 1965. Plant Anatomy, 2nd edition. John Wiley & Sons.
  • Ganong, W. F. 2003. Review of Medical Physiology, 21st edition. New York: McGraw-Hill. ISBN 0071402365.
  • McPhee, S. J., V. R. Lingappa, and W. F. Ganong. 2003. Pathophysiology of Disease: An Introduction to Clinical Medicine. New York: Lange Medical Books/McGraw-Hill. ISBN 0071387641.
  • Rubinsztein, D. C., M. DiFiglia, N. Heintz, R. A. Nixon, Z. H. Qin, B. Ravikumar, L. Stefanis, and A. Tolkovsky. 2005. Autophagy and its possible roles in nervous system diseases, damage and repair Autophagy 1(1): 11-22. PMID 16874055. Retrieved July 5, 2008.
Organelles of the cell
Acrosome | Chloroplast | Cilium/Flagellum | Centriole | Endoplasmic reticulum | Golgi apparatus | Lysosome | Melanosome | Mitochondrion | Myofibril | Nucleus | Parenthesome | Peroxisome | Plastid | Ribosome | Vacuole | Vesicle

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