Difference between revisions of "Bal 2012 PLOS ONE"
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|abstract=The comparison of volumes of cells and subcellular structures with the pH values reported for them leads to a conflict with the definition of the pH scale. The pH scale is based on the ionic product of water, | |abstract=The comparison of volumes of cells and subcellular structures with the pH values reported for them leads to a conflict with the definition of the pH scale. The pH scale is based on the ionic product of water, ''K''<sub>w</sub> = [H<sup>+</sup>]×[OH<sup>−</sup>]. We used ''K''<sub>w</sub> [in a reversed way] to calculate the number of undissociated H<sub>2</sub>O molecules required by this equilibrium constant to yield at least one of its daughter ions, H<sup>+</sup> or OH<sup>−</sup> at a given pH. In this way we obtained a formula that relates pH to the minimal volume ''V''<sub>pH</sub> required to provide a physical meaning to ''K''<sub>w</sub>, (where ''N''<sub>A</sub> is Avogadro’s number). For example, at pH 7 (neutral at 25 °C) ''V''<sub>pH</sub> = 16.6 aL. Any deviation from neutral pH results in a larger ''V''<sub>pH</sub> value. Our results indicate that many subcellular structures, including coated vesicles and lysosomes, are too small to contain free H<sup>+</sup> ions at equilibrium, thus the definition of pH based on ''K''<sub>w</sub> is no longer valid. Larger subcellular structures, such as mitochondria, apparently contain only a few free H<sup>+</sup> ions. These results indicate that pH fails to describe intracellular conditions, and that water appears to be dissociated too weakly to provide free H<sup>+</sup> ions as a general source for biochemical reactions. Consequences of this finding are discussed. | ||
|editor=Gnaiger E | |editor=Gnaiger E | ||
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Revision as of 10:51, 25 November 2020
Bal W, Kurowska E, Maret W (2012) The final frontier of pH and the undiscovered country beyond. PLOS ONE 7(9):e45832. |
» https://doi.org/10.1371/journal.pone.0045832
Bal W, Kurowska E, Maret W (2012) PLOS ONE
Abstract: The comparison of volumes of cells and subcellular structures with the pH values reported for them leads to a conflict with the definition of the pH scale. The pH scale is based on the ionic product of water, Kw = [H+]×[OH−]. We used Kw [in a reversed way] to calculate the number of undissociated H2O molecules required by this equilibrium constant to yield at least one of its daughter ions, H+ or OH− at a given pH. In this way we obtained a formula that relates pH to the minimal volume VpH required to provide a physical meaning to Kw, (where NA is Avogadro’s number). For example, at pH 7 (neutral at 25 °C) VpH = 16.6 aL. Any deviation from neutral pH results in a larger VpH value. Our results indicate that many subcellular structures, including coated vesicles and lysosomes, are too small to contain free H+ ions at equilibrium, thus the definition of pH based on Kw is no longer valid. Larger subcellular structures, such as mitochondria, apparently contain only a few free H+ ions. These results indicate that pH fails to describe intracellular conditions, and that water appears to be dissociated too weakly to provide free H+ ions as a general source for biochemical reactions. Consequences of this finding are discussed.
• Bioblast editor: Gnaiger E
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Preparation: Isolated mitochondria
Regulation: pH