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concentration is the same as that of another solution. In biology, the solutions on either side of a cell membrane are isotonic if the concentration of solutes outside the cell is equal to the concentration of solutes inside the cell. In this case the cell neither swells nor shrinks because there is
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Unlike osmotic pressure, tonicity is influenced only by solutes that cannot cross the membrane, as only these exert an effective osmotic pressure. Solutes able to freely cross the membrane do not affect tonicity because they will always equilibrate with equal concentrations on both sides of the
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inside the cell. When a cell is immersed in a hypertonic solution, osmotic pressure tends to force water to flow out of the cell in order to balance the concentrations of the solutes on either side of the cell membrane. The cytosol is conversely categorized as hypotonic, opposite of the outer
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no concentration gradient to induce the diffusion of large amounts of water across the cell membrane. Water molecules freely diffuse through the plasma membrane in both directions, and as the rate of water diffusion is the same in each direction, the cell will neither gain nor lose water.
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Argyropoulos, Christos; Rondon-Berrios, Helbert; Raj, Dominic S; Malhotra, Deepak; Agaba, Emmanuel I; Rohrscheib, Mark; Khitan, Zeid; Murata, Glen H; Shapiro, Joseph I.; Tzamaloukas, Antonios H (2 May 2016).
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A hypotonic solution has a lower concentration of solutes than another solution. In biology, a solution outside of a cell is called hypotonic if it has a lower concentration of solutes relative to the
277:. In plant cells the terms isotonic, hypotonic and hypertonic cannot strictly be used accurately because the pressure exerted by the cell wall significantly affects the osmotic equilibrium point.
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takes on extra water and pushes the cell membrane against the cell wall. Due to the rigidity of the cell wall, it pushes back, preventing the cell from bursting. This is called
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Lodish, Harvey; Berk, Arnold; Zipursky, S. Lawrence; Matsudaira, Paul; Baltimore, David; Darnell, James (2000). "Osmosis, Water
Channels, and the Regulation of Cell Volume".
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than another solution. In biology, the tonicity of a solution usually refers to its solute concentration relative to that of another solution on the opposite side of a
400:). Thus, normal saline is almost isotonic to blood plasma. Neither sodium nor chloride ions can freely pass through the plasma membrane, unlike
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An iso-osmolar solution can be hypotonic if the solute is able to penetrate the cell membrane. For example, an iso-osmolar
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dissolved in water to a total volume of one liter, is a close approximation to the osmolarity of NaCl in blood (about 290
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such as animal cells, if the gradient is large enough, the uptake of excess water can produce enough pressure to induce
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When plant cells are in a hypertonic solution, the flexible cell membrane pulls away from the rigid
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There are three classifications of tonicity that one solution can have relative to another:
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Some organisms have evolved intricate methods of circumventing hypertonicity. For example,
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Buckley, Gabe (20 January 2017). "Hypertonic
Solution". In Biologydictionary.net (ed.).
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Soult, Allison (2020). "8.4 - Osmosis and
Diffusion". In University of Kentucky (ed.).
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A red blood cell in a hypertonic solution, causing water to move out of the cell.
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A red blood cell in a hypotonic solution, causing water to move into the cell.
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across a cell membrane which determine the direction and extent of osmotic
30:"Hypotonic" and "Hypertonic" redirect here. For the physical diseases, see
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of the cell. When plant cells are in a hypotonic solution, the central
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that live in it. Because the fish need a large surface area in their
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membrane without net solvent movement. It is also a factor affecting
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A hypertonic solution has a greater concentration of non-permeating
521:"Hypertonicity: Pathophysiologic Concept and Experimental Studies"
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LibreTexts
Project: Medicine (18 July 2018). "3.3C - Tonicity".
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Measure of water potential across a semi-permeable cell membrane
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Cell
Physiology Source Book: Essentials of Membrane Biophysics
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solution is hypotonic to red blood cells, causing their
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Depiction of a red blood cell in an isotonic solution.
576:(4th ed.). New York: W. H. Freeman and Company
229:. A hypotonic solution example is distilled water.
71:. Unsourced material may be challenged and removed.
601:. Open Education Resource (OER) LibreTexts Project
158:Micrographs of osmotic pressure on red blood cells
269:. The cells often take on the appearance of a
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368:A solution is isotonic when its effective
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474:(Online ed.). Biologydictionary.net
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499:(Online ed.). med.libretexts.org/
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69:adding citations to reliable sources
626:The Journal of Experimental Biology
190:. Tonicity depends on the relative
622:"Osmoregulation in marine mammals"
496:Anatomy and Physiology (Boundless)
332:, or bloated. For cells without a
206:immersed in an external solution.
194:of selective membrane-impermeable
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147:Effect of different solutions on
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447:. Academic Press. p. 288.
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170:is a measure of the effective
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662:"Definition — hypotonic"
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18:Hyperosmotic
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356:Isotonicity
275:plasmolysis
430:References
388:, 9 grams
271:pincushion
258:solution.
219:hypertonic
212:imbibition
91:newspapers
80:"Tonicity"
36:Hypertonia
668:23 August
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342:rupturing
338:cytolysis
334:cell wall
324:. Due to
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282:saltwater
263:cell wall
223:hypotonic
180:solutions
32:Hypotonia
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424:Salinity
408:See also
227:isotonic
188:membrane
168:tonicity
548:4895078
419:Osmosis
346:vacuole
322:cytosol
255:cytosol
247:solutes
196:solutes
178:of two
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370:osmole
330:turgid
225:, and
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382:lysis
340:, or
290:gills
204:cells
186:cell
112:JSTOR
98:books
670:2012
644:PMID
607:2021
582:2021
553:PMID
505:2021
480:2021
449:ISBN
402:urea
394:mOsm
390:NaCl
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286:fish
200:flux
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162:In
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