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Membrane models
Before the emergence of electron microscopy in the 1950s, scientists and researchers did not know what the structure of a cell membrane looked like or what components made up a cell membrane. To assist in comprehending the concept of ''cells'', researchers and biologists used indirect evidence to create an understanding of membranes before the membranes could actually be visualized. It is with these specific models of ''Overton'', ''Langmuir'', ''Gorter and Grendel'', and ''Davson and Danielli'' we can clarify that membranes have lipids, proteins, and a bilayer. After the creation of the electron microscopes the findings of J. David Robertson, the proposal of Singer and Nicolson, and the additions of Unwin and Henderson contributed to the making of the modern membrane model. However, a further understanding of the past membrane models elucidates our perception of the present membrane visual. With intense experimental research, the membrane models of the precedent century made way for the ''Fluid Mosaic Model'', (with refined additions), used today.
==Overton and Langmuir's contributions (1890s)==
A convenient starting point about the models of membrane structure is the pioneering work of the scientist Charles Ernest Overton in the 1890s. In the late 19th century, he investigated the osmotic properties of cells and noticed that the permeation of molecules through membranes is related to their partition coefficient between water and oil. From his studies, Overton led to the hypothesis that the thin membranes surrounding cells have the properties of oil, and are lipids which regulate the permeability of the cell. Therefore, working with cells of plant root hairs, he observed that lipid-soluble substances penetrate readily into cells, whereas water-soluble substances do not. A decade later, a second significant advance came through the work of Irving Langmuir. He studied the behavior of purified phospholipids by dissolving them in benzene and layering samples of the benzene-lipid solution onto a water surface. As the benzene evaporated, the molecules were left as a lipid monolayer. Since phospholipids are amphipathic molecules, Langmuir concluded that the phospholipids orient themselves on water such that their hydrophilic heads face the water and their hydrophobic tails protrude away from the water. Therefore, Langmuir’s lipid monolayer became the underlying support or foundation in the studies of the membrane structure.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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