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A vacuole () is a
membrane-bound organelle In cell biology, an organelle is a specialized subunit, usually within a cell (biology), cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as Organ (anatomy), organs are to the ...
which is present in
plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...

plant
and
fungal A fungus (plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of a noun typically denotes a quantity great ...

fungal
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious recluse lives * Prison cell, a room used to hold peopl ...
and some
protist A protist () is any (that is, an organism whose contain a ) that is not an , , or . While it is likely that protists share a (the ), the exclusion of other eukaryotes means that protists do not form a natural group, or . Therefore, some pro ...
,
animal Animals (also called Metazoa) are organisms that form the Animalia. With few exceptions, animals , , are , can , and grow from a hollow sphere of , the , during . Over 1.5 million animal have been —of which around 1 million are —b ...

animal
, and
bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of all known organisms. Cells are the sm ...

bacteria
l cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including
enzymes Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates int ...
in
solution Solution may refer to: * Solution (chemistry) Image:SaltInWaterSolutionLiquid.jpg, upMaking a saline water solution by dissolving Salt, table salt (sodium chloride, NaCl) in water. The salt is the solute and the water the solvent. In chemistry ...
, though in certain cases they may contain solids which have been engulfed. Vacuoles are formed by the fusion of multiple membrane
vesicles Vesicle may refer to: ; In cellular biology or chemistry * Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane * Synaptic vesicle ; In human embryology * Vesicle (embryology), bulge-like features of ...
and are effectively just larger forms of these. The organelle has no basic shape or size; its structure varies according to the requirements of the cell.


Discovery

Contractile vacuoles ("stars") were first observed by
Spallanzani Lazzaro Spallanzani (; 12 January 1729 – 11 February 1799) was an Italian Catholic The Catholic Church, often referred to as the Roman Catholic Church, is the List of Christian denominations by number of members, largest Christian chur ...

Spallanzani
(1776) in
protozoa Protozoa (singular protozoon or protozoan, plural protozoa or protozoans) is an informal term for a group of Unicellular organism, single-celled eukaryotes, either free-living or Parasitism, parasitic, that feed on organic matter such as other mi ...

protozoa
, although mistaken for respiratory organs.
Dujardin Dujardin is a French surname, meaning "from the garden", and may refer to: * Charlotte Dujardin, British dressage rider * Édouard Dujardin, French writer * Félix Dujardin (1801–1860), French biologist * Jean Dujardin, French actor and comedian ...
(1841) named these "stars" as ''vacuoles''. In 1842,
Schleiden Schleiden is a town in North Rhine-Westphalia, Germany. It lies in the Eifel hills, in the district of Euskirchen (district), Euskirchen, and has 12,998 inhabitants as of 30 June 2017. Schleiden is connected by a tourist railway to Kall, Germany, K ...

Schleiden
applied the term for plant cells, to distinguish the structure with cell sap from the rest of the
protoplasmProtoplasm (/prəʊtə(ʊ)ˌplaz(ə)m/, plural protoplasms) is the living part of a cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or ...

protoplasm
. In 1885,
de Vries De Vries is one of the most common Netherlands, Dutch surnames.Brouwer, Leendert''De top 100 van de familienamen in Nederland'' Royal Netherlands Academy of Arts and Sciences, KNAW/Meertens Instituut, 2010. It indicates a geographical origin: "Vrie ...

de Vries
named the vacuole membrane as tonoplast.


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
hydrostatic pressure Fluid statics or hydrostatics is the branch of fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mechanics (Ancient Greek, Greek: ) is the area of physics concerned with the motions of physical object ...

hydrostatic pressure
or
turgor Turgor pressure is the force within the cell that pushes the plasma membrane cell membrane vs. Prokaryotes A prokaryote () is a single-celled organism A unicellular organism, also known as a single-celled organism, is an organism In bi ...
within the cell * Maintaining an
acid An acid is a or capable of donating a (hydrogen ion H+) (a ), or, alternatively, capable of forming a with an (a ). The first category of acids are the proton donors, or s. In the special case of , proton donors form the H3O+ and are ...
ic internal
pH
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. * In seeds, stored proteins needed for germination are kept in 'protein bodies', which are modified vacuoles. Vacuoles also play a major role in
autophagy Autophagy (or ''autophagocytosis'') (from the Ancient Greek Ancient Greek includes the forms of the used in and the from around 1500 BC to 300 BC. It is often roughly divided into the following periods: (), Dark Ages (), the perio ...

autophagy
, maintaining a balance between
biogenesis Biogenesis is the production of new living organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by tax ...
(production) and degradation (or turnover), of many substances and cell structures in certain organisms. They also aid in the
lysis Lysis ( ; Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10 ...
and recycling of misfolded proteins that have begun to build up within the cell. Thomas Boller and others proposed that the vacuole participates in the destruction of invading
bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of all known organisms. Cells are the sm ...

bacteria
and Robert B. Mellor proposed organ-specific forms have a role in 'housing' symbiotic bacteria. In protists, 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. In animal cells, vacuoles perform mostly subordinate roles, assisting in larger processes of
exocytosis Image:Synapse diag1.svg, 300px, Exocytosis of neurotransmitters into a synapse from neuron A to neuron B. Exocytosis () is a form of active transport and solvent drag, bulk transport in which a cell transports molecules (e.g., neurotransmitters an ...
and
endocytosis Endocytosis is a in which are brought into the cell. The material to be internalized is surrounded by an area of , which then buds off inside the cell to form a containing the ingested material. Endocytosis includes (cell drinking) and (cell ...

endocytosis
. Animal vacuoles are smaller than their plant counterparts but also usually greater in number. There are also animal cells that do not have any vacuoles. Exocytosis is the extrusion process of proteins and lipids from the cell. These materials are absorbed into secretory granules within the
Golgi apparatus The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that stud ...

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.
Phagocytosis Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis Endocytosis is a cellular process i ...

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 In developmental biology, invagination is a mechanism that takes place during gastrulation. This mechanism or cell movement happens mostly in the vegetal pole. Invagination consists of the folding of an area of the exterior sheet of cells towards ...

invagination
is pinched off, leaving the engulfed material in the membrane-enclosed vacuole and the cell membrane intact.
PinocytosisImage:Pinocytosis.svg, 250px, Pinocytosis In cellular biology, pinocytosis, otherwise known as fluid endocytosis and bulk-phase pinocytosis, is a mode of endocytosis in which small particles suspended in extracellular fluid are brought into the cell ...

Pinocytosis
("cell drinking") is essentially the same process, the difference being that the substances ingested are in solution and not visible under the microscope. Phagocytosis and pinocytosis are both undertaken in association with
lysosomes A lysosome () is a found in many animal s. They are spherical that contain s that can break down many kinds of s. A lysosome has a specific composition, of both its s, and its proteins. The lumen's pH (~4.5–5.0) is optimal for the enzymes ...

lysosomes
which complete the breakdown of the material which has been engulfed. ''
Salmonella ''Salmonella'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruse ...
'' is able to survive and reproduce in the vacuoles of several
mammal Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republ ...
species after being engulfed. The vacuole probably evolved several times independently, even within the
Viridiplantae Viridiplantae (literally "green plants") are a clade A clade (), also known as a monophyletic group or natural group, is a group of organism In biology, an organism () is any organic, life, living system that functions as an indi ...
.


Vacuole types


Gas vacuoles

Gas vesicle Gas vesicles, also known as gas vacuoles, are nanocompartments in certain prokaryotic organisms, which help in buoyancy. Gas vesicles are composed entirely of protein Proteins are large biomolecules or macromolecules that are comprised of one ...
s, also known as gas vacuoles, are nanocompartments which are freely permeable to gas, and occur mainly in Cyanobacteria, but are also found in other bacteria species and some archaea. Gas vesicles allow the bacteria to control their buoyancy. They are formed when small biconical structures grow to form spindles. The vesicle walls are composed of a hydrophobic gas vesicle protein A (GvpA) which form a cylindrical hollow, proteinaceous structure that fills with gas. Small variances in the amino acid sequence produce changes in morphology of the gas vesicle, for example, GvpC, is a larger protein.


Central vacuoles

Most mature
plant cell Plant cells are eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are class ...

plant cell
s 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. Strands of
cytoplasm In , the cytoplasm is all of the material within a , enclosed by the , except for the . The material inside the nucleus and contained within the is termed the . The main components of the cytoplasm are (a gel-like substance), the s (the cell' ...
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. Transport of
proton A proton is a subatomic particle, symbol or , with a positive electric charge of +1''e'' elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collecti ...

proton
s from the cytosol to the vacuole stabilizes cytoplasmic , while making the vacuolar interior more acidic creating a
proton motive forceChemiosmosis is the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient An electrochemical gradient is a gradient In vector calculus, the gradient of a scalar-valued function, scalar-valued dif ...
which the cell can use to transport nutrients into or out of the vacuole. The low pH of the vacuole also allows
degradative enzymeA degradative enzyme is an enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the e ...
s to act. Although single large vacuoles are most common, the size and number of vacuoles may vary in different tissues and stages of development. For example, developing cells in the
meristems The meristem is a type of tissue found in plants. It consists of undifferentiated cells (meristematic cells) capable of cell division Cell division is the process by which a parent Cell (biology), cell divides into two or more daughter cells. C ...
contain small provacuoles and cells of the
vascular cambium The vascular cambium is the main growth tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ...
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
turgor Turgor pressure is the force within the cell that pushes the plasma membrane cell membrane vs. Prokaryotes A prokaryote () is a single-celled organism A unicellular organism, also known as a single-celled organism, is an organism In bi ...
pressure against the
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane cell membrane vs. Prokaryotes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to a ...
. Proteins found in the tonoplast (
aquaporins Aquaporins, also called water channels, are channel proteins from a larger protein family, family of major intrinsic proteins that form Ion channel pore, pores in the cell membrane, membrane of cell (biology), biological cells, mainly facilitatin ...
) control the flow of water into and out of the vacuole through
active transport In cellular biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processe ...

active transport
, pumping
potassium Potassium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

potassium
(K+)
ion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ...
s into and out of the vacuolar interior. Due to
osmosis Osmosis (, ) is the spontaneous net movement or diffusion File:DiffusionMicroMacro.gif, 250px, Diffusion from a microscopic and macroscopic point of view. Initially, there are solute molecules on the left side of a barrier (purple line) an ...

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 . Turgor pressure exerted by vacuoles is also required for cellular elongation: as the cell wall is partially degraded by the action of
expansinExpansin refers to a family of closely related nonenzymatic proteins found in the plant cell wall, with important roles in plant cell growth, fruit softening, abscission, emergence of root hairs, pollen tube invasion of the stigma and style, meristem ...
s, the less rigid wall is expanded by the pressure coming from within the vacuole. Turgor pressure exerted by the vacuole is also essential in supporting plants in an upright position. 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 Chloroplasts are organelles that conduct photosynthesis, where the photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in the energy-storage molecules Adenosine triphosphate, ATP and NADPH while fr ...

chloroplasts
closer to light. Most plants store chemicals in the vacuole that react with chemicals in the cytosol. If the cell is broken, for example by a
herbivore A herbivore is an animal Animals (also called Metazoa) are organisms that form the Animalia. With few exceptions, animals , , are , can , and grow from a hollow sphere of , the , during . Over 1.5 million animal have been —of ...
, then the two chemicals can react forming toxic chemicals. In garlic,
alliin Alliin is a sulfoxide A sulfoxide is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element ...

alliin
and the enzyme
alliinase In enzymology, an alliin lyase () is an enzyme that catalysis, catalyzes the chemical reaction :an ''S''-alkyl-L-cysteine ''S''-oxide \rightleftharpoons an alkyl sulfenate + 2-aminoacrylate Hence, this enzyme has one substrate (biochemistry), s ...
are normally separated but form
allicin Allicin is an obtained from , a species in the family . It was first isolated and studied in the laboratory by and John Hays Bailey in 1944. When fresh garlic is chopped or crushed, the enzyme converts into allicin, which is responsible for t ...

allicin
if the vacuole is broken. A similar reaction is responsible for the production of syn-propanethial-S-oxide when
onion The onion (''Allium cepa'' L., from Latin ''cepa'' "onion"), also known as the bulb onion or common onion, is a vegetable Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still com ...

onion
s are cut. Vacuoles in fungal cells perform similar functions to those in plants and there can be more than one vacuole per cell. In
yeast Yeasts are eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classifie ...

yeast
cells the vacuole is a
dynamic Dynamics (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million ...
structure that can rapidly modify its
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...
. They are involved in many processes including the
homeostasis In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...
of cell pH and the concentration of ions,
osmoregulation Osmoregulation is the active regulation of the osmotic pressure of an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, ...
, storing
amino acids Amino acids are organic compounds that contain amino (–NH2) and Carboxylic acid, carboxyl (–COOH) functional groups, along with a Substituent, side chain (R group) specific to each amino acid. The key Chemical element, elements of an amino ...

amino acids
and
polyphosphatePolyphosphates are salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline mineral is known as ...
and degradative processes. Toxic ions, such as
strontium Strontium is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

strontium
(),
cobalt Cobalt is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical element ...

cobalt
(II) (), and
lead Lead is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elements ...

lead
(II) () are transported into the vacuole to isolate them from the rest of the cell.


Contractile vacuoles

Contractile Vacuoles is a specialized osmoregulatory organelle that is present in many free-living protists. 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. 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.


Food vacuoles

Food vacuole The food vacuole, or digestive vacuole, is an organelle In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anato ...
s (also called digestive vacuole) are organelles found in
Ciliate The ciliates are a group of protozoan Protozoa (singular protozoon or protozoan, plural protozoa or protozoans) is an informal term for a group of single-celled eukaryote Eukaryotes () are organisms whose Cell (biology), cells have a c ...

Ciliate
s, and
Plasmodium falciparum ''Plasmodium falciparum'' is a unicellular A unicellular organism, also known as a single-celled organism, is an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contig ...

Plasmodium falciparum
, a protozoan parasite that causes
Malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign fo ...

Malaria
.


Histopathology

In
histopathology Histopathology (compound of three Greek language, Greek words: ''histos'' "tissue", πάθος ''pathos'' "suffering", and -λογία ''-logy, -logia'' "study of") refers to the light microscope, microscopic examination of Tissue (biology), tiss ...
, vacuolization is the formation of vacuoles or vacuole-like structures, within or adjacent to cells. It is an unspecific sign of disease.


References


External links

{{Authority control Vesicles Plant anatomy Cell anatomy