Osmotic Theory: An Example of Lag between Research and Teaching

Stein, Howard J.

doi:10.2307/1293626

Cited by 2 publications

(1 citation statement)

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“…There have been several attempts primarily directed at biologists to set the record straight on the physical basis of osmosis (Stein, 1966; Kiil, 1982; Kramer and Myers, 2012), as well as accounts of the Debye model in journals (Manning, 1968; Oster and Peskin, 1992; Borg, 2003; Marbach and Bocquet, 2019; Song et al, 2021) and textbooks (Benedek and Villars, 1974; Weiss, 1996; Baumgarten and Feher, 2011; Nelson, 2014), but despite these efforts, misconceptions have persisted. The apparent simplicity of osmosis may have masked what is at bottom a rather subtle phenomenon with enormous implications for biology (Dick, 1966; House, 1974; Andersen, 2015).…”

Section: Introductionmentioning

confidence: 99%

The Physical Basis of Osmosis

Manning

Kay

2023

Preprint

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Osmosis is an important force in all living organisms, yet the molecular basis of osmosis is widely misunderstood as arising from differences in water concentration in solutions of differing osmolarities. In 1923 Debye proposed a physical model for a semipermeable membrane that was hardly noticed at the time and slipped out of view. We show that Debye's analysis of van't Hoff's law for osmotic equilibrium provides a consistent and plausible explanation for osmotic flow. A difference in osmolyte concentrations in solutions separated by a semipermeable membrane generates different pressures at the two water-membrane interfaces. Water is therefore driven through the membrane for exactly the same reason that pure water flows in response to an imposed hydrostatic pressure difference. In this paper we present the Debye model in both equilibrium and flow conditions. We point out its applicability regardless of the nature of the membrane with examples ranging from predominantly convective flow of water through synthetic membranes to purely diffusive flow of independent water molecules through a lipid bilayer and the flow of strongly interacting water molecules in single file across narrow protein channels.

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