Vacuole

Source: Wikipedia, the free encyclopedia.
Not to be confused with vesicle (biology and chemistry).
Animal cell diagram
Components of a typical animal cell:
  1. Nucleolus
  2. Nucleus
  3. Ribosome (dots as part of 5)
  4. Vesicle
  5. Rough endoplasmic reticulum
  6. Golgi apparatus (or, Golgi body)
  7. Cytoskeleton
  8. Smooth endoplasmic reticulum
  9. Mitochondrion
  10. Vacuole
  11. Cytosol (fluid that contains organelles; with which, comprises cytoplasm)
  12. Lysosome
  13. Centrosome
  14. Cell membrane
Plant cell structure
Animal cell structure

A vacuole (

vesicles and are effectively just larger forms of these.[3]
The organelle has no basic shape or size; its structure varies according to the requirements of the cell.

Discovery

Spallanzani (1776) in protozoa, although mistaken for respiratory organs. Dujardin (1841) named these "stars" as vacuoles. In 1842, Schleiden applied the term for plant cells, to distinguish the structure with cell sap from the rest of the protoplasm.[4][5][6][7]

In 1885, de Vries named the vacuole membrane as tonoplast.[8]

Function

The function and significance of vacuoles varies greatly according to the type of cell in which they are present, having much greater prominence in the cells of plants, fungi and certain protists than those of animals and bacteria. In general, the functions of the vacuole include:

  • Isolating materials that might be harmful or a threat to the cell
  • Containing waste products
  • Containing water in plant cells
  • Maintaining internal
    turgor
    within the cell
  • Maintaining an acidic internal pH
  • Containing small molecules
  • Exporting unwanted substances from the cell
  • Allows plants to support structures such as leaves and flowers due to the pressure of the central vacuole
  • By increasing in size, allows the germinating plant or its organs (such as leaves) to grow very quickly and using up mostly just water.[9]
  • In seeds, stored proteins needed for germination are kept in 'protein bodies', which are modified vacuoles.[10]

Vacuoles also play a major role in

biogenesis (production) and degradation (or turnover), of many substances and cell structures in certain organisms. They also aid in the lysis and recycling of misfolded proteins that have begun to build up within the cell. Thomas Boller[11] and others proposed that the vacuole participates in the destruction of invading bacteria and Robert B. Mellor proposed organ-specific forms have a role in 'housing' symbiotic bacteria. In protists,[12] vacuoles have the additional function of storing food which has been absorbed by the organism and assisting in the digestive and waste management process for the cell.[13]

In animal cells, vacuoles perform mostly subordinate roles, assisting in larger processes of exocytosis and endocytosis.

Animal vacuoles are smaller than their plant counterparts but also usually greater in number.[14] There are also animal cells that do not have any vacuoles.[15]

Exocytosis is the extrusion process of proteins and lipids from the cell. These materials are absorbed into secretory granules within the Golgi apparatus before being transported to the cell membrane and secreted into the extracellular environment. In this capacity, vacuoles are simply storage vesicles which allow for the containment, transport and disposal of selected proteins and lipids to the extracellular environment of the cell.

Endocytosis is the reverse of exocytosis and can occur in a variety of forms.

lysosomes which complete the breakdown of the material which has been engulfed.[17]

Salmonella is able to survive and reproduce in the vacuoles of several mammal species after being engulfed.[18]

The vacuole probably evolved several times independently, even within the Viridiplantae.[14]

Types

Central

spiderwort
, in cells that have plasmolyzed

Most mature plant cells have one large vacuole that typically occupies more than 30% of the cell's volume, and that can occupy as much as 80% of the volume for certain cell types and conditions.[19] Strands of cytoplasm often run through the vacuole.

A vacuole is surrounded by a membrane called the tonoplast (word origin: Gk tón(os) + -o-, meaning “stretching”, “tension”, “tone” + comb. form repr. Gk plastós formed, molded) and filled with cell sap. Also called the vacuolar membrane, the tonoplast is the cytoplasmic membrane surrounding a vacuole, separating the vacuolar contents from the cell's cytoplasm. As a membrane, it is mainly involved in regulating the movements of ions around the cell, and isolating materials that might be harmful or a threat to the cell.[20]

Transport of

meristems contain small provacuoles and cells of the vascular cambium
have many small vacuoles in the winter and one large one in the summer.

Aside from storage, the main role of the central vacuole is to maintain

syn-propanethial-S-oxide when onions are cut.[citation needed
]

Vacuoles in fungal cells perform similar functions to those in plants and there can be more than one vacuole per cell. In

amino acids and polyphosphate and degradative processes. Toxic ions, such as strontium (Sr2+
), cobalt(II) (Co2+
), and lead(II) (Pb2+
) are transported into the vacuole to isolate them from the rest of the cell.[22]

Contractile

A contractile vacuole is a specialized osmoregulatory organelle that is present in many free-living protists.[23] The contractile vacuole is part of the contractile vacuole complex which includes radial arms and a spongiome. The contractile vacuole complex works periodically contracts to remove excess water and ions from the cell to balance water flow into the cell.[24] When the contractile vacuole is slowly taking water in, the contractile vacuole enlarges, this is called diastole and when it reaches its threshold, the central vacuole contracts then contracts (systole) periodically to release water.[25]

Digestive

Food vacuoles (also called digestive vacuole[26]) are organelles found in Ciliates, and Plasmodium falciparum, a protozoan parasite that causes Malaria.

Histopathology

In histopathology, vacuolization is the formation of vacuoles or vacuole-like structures, within or adjacent to cells. It is an unspecific sign of disease.[citation needed]

References

  1. ISBN 0-9762548-3-2
    .
  2. ISBN 978-3-540-26205-3
    .
  3. ISBN 978-0-07-326807-1
    .
  4. ^ Spallanzani L (1776). "Observations et expériences faites sur les Animalicules des Infusions". L'École Polytechnique. Paris: 1920.
  5. ^ Dujardin F (1841). "Histoire naturelle des zoophytes: Infusoires". Librairie Encyclopédique de Roret. Paris.
  6. ^ Schleiden MJ (1842). "Grundzüge der wissenschaftlichen Botanik". Leipzig: W. Engelmann. {{cite journal}}: Cite journal requires |journal= (help)
  7. ISBN 9780080921273
    .
  8. ^ de Vries H (1885). "Plasmolytische Studien über die Wand der Vakuolen". Jahrb. Wiss. Bot. 16: 465–598.
  9. PMID 19042915
    .
  10. ^ Matile P (1993). "Chapter 18: Vacuoles, discovery of lysosomal origin". Discoveries in Plant Biology. Vol. 1. World Scientific Publishing Co Pte Ltd.
  11. ^ Thomas Boller Archived 2013-12-06 at the Wayback Machine. Plantbiology.unibas.ch. Retrieved on 2011-09-02.
  12. ^ For example the food vacuole in Plasmodium.
  13. PMID 16329920
    .
  14. ^
    PMID 17964920
    .
  15. ^ Plant cells vs. Animal cells Archived 2019-02-01 at the Wayback Machine. Biology-Online.org
  16. ^ William F. Ganong, MD (2003). Review of medical physiology (21st ed.).
  17. PMID 16860663
    .
  18. S2CID 25646573
    .
  19. ISBN 978-0-8153-4111-6
    .
  20. PMID 17080938
    .
  21. ISBN 0-87893-856-7
    .
  22. PMID 2215422
    .
  23. PMID 22323285
    .
  24. S2CID 11384111
    .
  25. PMID 13563556
    .
  26. ^ "Food vacuole | biology". Encyclopedia Britannica. Retrieved 2021-02-21.

External links

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