Though these scientists accept (without question) the "lipid bilayer membrane" notion (refuted directly long ago by Gilbert Ling and others), they have provided support for the alternative hypothesis:
QUOTE: The means by which proteins provide a 'border control' service, allowing cells to take up chemicals and substances from their surroundings, whilst keeping others out, is revealed in unprecedented molecular detail for the first time, 16 October in Science Express... UNQUOTE.
Source: http://www.sciencedaily.com/releases/2008/10/081016140800.htm
Gilbert Ling has written a succinct and excellent review of how this impossible notion (that is, a structurally crucial "lipid bilayer membrane") came into existence:
QUOTE: ...In the early investigation of the living cell, mature plant cells were the preferred material for study. Plant materials were more readily available and they last well. Mature plant cells are large with well-delineated boundaries marked by walls. These characteristics were prized by the early observers because they assured the observers that they were looking at characteristic individual units rather than random artifacts. While these tangible advantages made the mature plant cells the preferred objects of study, the naturalists at the time could not and did not know that mature plant cells are highly unusual cells. They exhibit anatomical traits not shared by most living cells---but that perception came from a later chapter of investigations.
Of all the unusual features mature plant cells have, its possession of a gigantic central cavity or vacuole is the most striking--- occupying often close to the entire volume of the cell. This central vacuole is filled with a liquid hard to distinguish from ordinary water. Surrounding this central vacuole is a thin layer of gelatinous material later known as protoplasm. Still further outward, one finds the enclosing rigid cell wall.
Modern biology textbooks show that on the inner surface of the thin protoplasmic layer of a mature plant cell is a very thin membrane called the tonoplast (or vesicular membrane) and on the outside of the protoplasmic layer is another very thin membrane called the plasma membrane or the cell membrane. Both of these membranes are so thin, that one cannot see them with even the best light microscope available today. To visualize them, one must use an electron microscope ---a much later invention---and then only after the specimen has undergone special treatment and stained with electron-dense stains such as uranium or lead.
Since one cannot see the cell membrane even with the best light microscope today, it is an indisputable fact that naturalists in the 19th century with their much more primitive light microscopes could not have seen the cell membrane or the tonoplast. Common sense also dictates that those early naturalists had no reason to describe a structure which they could not and did not see. They must have seen something consistently; and that something must be thin but not invisible to them.
From these facts and reasoning , one is left with one and only one interpretation: What the 19th century naturalists called the cell membrane is in fact the thin layer of protoplasm, including the "invisible" plasma membrane and the equally "invisible" tonoplast surrounding the central vacuole, and what they thought was the cell substance is in fact the content of the big central vacuole---and there is no question that this central vacuole is filled with a watery liquid.
It is only in the light of this interpretation can one comprehend how Theodor Schwann (1810-1882), the founder of the "Cell Theory", could argue that "the containing membrane (of a cell) --was prior in importance to its contents. The content of the cellular cavity,....is typically a homogeneous, transparent liquid." (See Thomas S. Hall, "Ideas on Life and Matter, vol. 2, p. 194, 1969, Univ. Of Chicago Press, Chicago)
With the discovery of protoplasm by Felix Dujardin (1801-1860 ) and the extensive studies of many types of young and old plants as well as animal cells, the error of the earlier idea that the cells are membrane-enclosed bag of fluid became widely recognized. Thus in 1858-1860, Max Schultze defined the cell as a "naked little lump of protoplasm with a nucleus". In 1928, the eminent American cytologist, E. B.Wilson, in his monumental treatise, "The Cell in Development and Heredity" (Macmillan, New York, 3rd ed.,1928), further emphasized that cells "do not, in general, have the form of hollow chambers as the name suggests but are typically solid bodies."(p.4).
One would have expected that the erroneous notion that the cells are hollow chambers filled with watery liquid would be replaced soon after. It was the irony of history, that that was not to be the case.
For by this time another group of scientists interested in the living cell had taken over the perpetration of what I call the "Vesicular Doctrine", i.e., cells are empty chambers filled with a clear watery liquid.
That group of scientists were the early cell physiologists, beginning with the eminent French naturalist, Rene Dutrochet. Dutrochet's extensive study of "osmotic" movements of water into and out of mature plant cells set the direction of cell physiological research for the future. The long erroneous usage and the work of early cell physiologists drove deep into the psyche of biologists the belief that cells are hollow chambers filled with a watery liquid---- which lasted in the text books version of cell physiology to this very day... UNQUOTE.
Source: http://gilbertling.org/lp6.htm |
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