Many biology and botany textbooks, and online resources, say YES. That osmosis is the special case of diffusion involving water molecules, as as solvent. Osmosis is the movement of water molecules from an area of high water concentration (weak/dilute solution) to an area of low water concentration (strong/concentrated solution) through a partially permeable membrane [1]. Or, that osmosis is a type of passive transport by which water diffuses across a membrane, in order to equalize the concentration of water inside and outside the cell [2].
The standard physics view (first published by Gibbs in 1897, about 120 years ago) has been NO to osmosis being a form of diffusion (osmosis is not a form or special case of diffusion, they are different physical phenomena), and NO to the biology camp description in diffusion terms, given above. The physics answer says that osmosis is the flow of solvent across a semipermeable membrane from a region of lower to higher solute concentration [3]. The solvent can be a liquid, such as water, or gas. In osmosis, according to physics, the flow of solvent (and osmotic pressure) is caused by the concentration difference of the solute, not the solvent.
Considering the importance of osmosis in biology and botany, and how it is presented today in educational materials aimed at students, I am looking for scientific counter claims to the physics view from biology, botany, or other camp. This issue is also important in communication, as in writing an essay, where one may be using an idea of diffusion whereas the right metaphor would be osmosis. Should biology change its view on osmosis, or should physics? Could both views be right?
[1] Biology courses online: http://www.passmyexams.co.uk/GCSE/biology/osmosis-in-cells.html and http://www.bbc.co.uk/bitesize/standard/biology/investigating_cells/cells_and_diffusion/revision/4/
[2] Biology course at a top US university, BILD 10: Fundamental Concepts of Modern Biology: http://classes.biology.ucsd.edu/bild10.WI14/BILD10/Lectures_files/BILD%2010.LECTURE%203.2014.The%20Cell.ppt.pdf [PDF below]
[3] Physics: Eric M. Kramer and David R. Myers, Five popular misconceptions about osmosis, Am. J. Phys. 80, 694 (2012). [PDF below]
Yes. Osmosis is movement of water through a membrane. diffusion is just more general.
The first definition you gave seems a bit odd to me because in biology it is unusual for the solute concentration to be so high that the concentration of water is substantially altered by it. It seems more reasonable to speak in terms of the solute concentration being the driving force for osmosis, as in your second definition, because it is common for the solute concentration to be quite different on either side of the membrane.
As to whether osmosis is a form of diffusion, I would say that it is a process that relies on diffusion. The solute (or solvent) molecules must diffuse to, and through, the semipermeable membrane for osmosis to occur.
Hi, I am not a biologist, but it seems that osmosis is one kind of diffusion. One can use the term "diffusion" for other purposes too. 'diffusion of innovation" , for example.
Hello all,
Due to recent interest in RG on this question, I'd like to add that diffusion is not restricted to the presence of any barrier. Osmosis, however, does not exist if a barrier does not exist. In other words, one could say that no barrier, no osmosis.
Notwithstanding, a barrier can follow a gradient, not to be noticed; or any other "impedance matching" form, without sharp transitions, with a low way of reflection. This might make diffusion appear to be dominant, but diffusion and osmosis remain as different processes.
Cheers, Ed Gerck
Hello all,
With worldwide recent interest in potable water purification from saline water, the answer highlights why osmosis can't be considered as a form of diffusion, being a completely different process.
This may also be important to California, currently four levels below "Abnormally Dry" and risking loss of most potable water due to the Central Valley sinking inexorably, already 20 or 30 ft below sea level (c.f. recent NASA JPL SAR measurements) due to groundwater pumping for farm purposes. The ground is in subsidence flow, over thousands of square miles.
Cheers,
Ed Gerck
Hello all: This is an opening to all researchers, what is today considered scientific in physics, and how to introduce valid, tested elements of thinking and proof.
This is also of particular interest in the Sciences today, and in institutional decisions.
This ‘new’ method was used by the Greeks, who could do something similar, already understanding without any rockets that the Earth is round, and even numerically calculating its accurate diameter. Without leaving the Earth, showing that physics is not armchair theory -- physics (qua "next physics") can have decisive, effective, unrefuted, universal results, without sensorial experimentation at all. Poincaré’s Conjecture, proved in mathematics, recently, is another evidence that something might be amiss in physics.
Read more at
https://www.researchgate.net/publication/326398997_The_next_physics
I would like to recommend you a paper about this issue.
Article Teaching about Water Relations in Plant Cells: An Uneasy Struggle
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