La somme selon (8) des différentes différences de potentiel qui viennent d’être après regroupement des termes provenant des équilibres de Donnan et des. Request pdf on researchgate a donnan potential model for metal sorption onto bacillus subtilis in this study, we conducted electrophoretic mobility. En tant que solvant, celle-ci est chargée des substances résultant du un équilibre de partage con1 orme à la loi de Henry, ou à la règle de Donnan, ou encore.
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The Gibbs—Donnan effect also known as the Donnan’s effectDonnan lawDonnan equilibriumor Gibbs—Donnan equilibrium is a name for the behaviour of charged particles near a semi-permeable membrane that sometimes fail to distribute evenly across the two sides of the membrane. Because small cations are attracted, but are not bound to the proteins, small anions will cross capillary walls away from the anionic proteins more readily than small cations.
Some ionic species can pass through the barrier while others cannot. The solutions may be gels or colloids as well as solutions of electrolytesand as such the phase boundary between gels, or a gel and a liquid, can also act as a selective barrier. The electric potential arising between two such solutions equilibe called the Donnan potential.
The Donnan equilibrium is prominent in the triphasic model for articular cartilage donna by Mow and Lai, as well as in electrochemical fuel cells and dialysis.
The presence of a charged impermeant ion for example, a protein on one side of a membrane will result in an asymmetric distribution of permeant charged ions. Note that Sides 1 and 2 are no longer in osmotic equilibrium i.
I n vivoion balance does not equilibriate at the proportions that would be predicted by the Gibbs-Donnan model, because the cell cannot tolerate the attendant large influx of water.
Because there is a difference in concentration of ions on either side of the membrane, the pH donnsn also differ when protons are involved. In many instances, from ultrafiltration of proteins to ion exchange chromatography, the pH of the buffer adjacent to the charged groups of the membrane is different from the pH of the rest of the buffer solution. When the charged groups are positive acidicthen they will repel protons equilibree that the pH will be higher than the surrounding buffer.
Gibbs–Donnan effect – Wikipedia
When tissue cells are in a protein-containing fluid, the Donnan effect of the cytoplasmic proteins is equal and opposite to the Donnan effect of the extracellular proteins.
The opposing Donnan effects cause chloride ions to migrate inside the cell, increasing the intracellular chloride concentration. The Donnan effect may explain why some red blood cells do not have active sodium pumps; the effect relieves the osmotic pressure of plasma proteins, which is why sodium pumping is less important for maintaining the cell volume. Brain tissue swelling, known as cerebral oedema, results from brain injury and other traumatic head injuries that can increase intracranial pressure ICP.
Negatively charged molecules within cells create a fixed charge density, which increases intracranial pressure through the Donnan effect. ATP pumps maintain a negative membrane potential even though negative charges leak across the membrane; this action establishes a chemical and electrical gradient.
The negative charge in the cell and ions outside the cell creates a thermodynamic potential; if rquilibre occurs to the brain and cells lose their membrane integrity, ions will rush into the cell to balance chemical and electrical gradients that were previously established.
The membrane voltage will become zero, but the chemical gradient will still exist.
To neutralize the negative charges within the cell, cations flow in, which increases the osmotic pressure inside relative to the outside of the cell. The increased osmotic pressure forces water to flow into the cell and tissue swelling occurs.
From Wikipedia, the free encyclopedia. Archived from the xe on Ein Beitrag zur physikalisch-chemischen Physiologie” [The theory of membrane equilibrium and membrane potential in the presence of a non-dialyzable electrolyte. A contribution to physical-chemical physiology].
Annals of the New York Academy of Sciences. Donnan effect on chloride ion distribution as a determinant of body fluid composition that allows action potentials to spread via fast sodium channels.
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