This supported their hypothesis, which led to the conclusion that cell membranes are composed of two opposing molecular layers. In comparing the two, they calculated an estimated ratio of 2:1 Mono-layer of lipids: Plasma membrane. They measured the total surface area of the plasma membrane of red blood cells, and using Langmuir's method, they measured the area of the monolayer of lipids. and then spreading the lipids as a mono-layer in a Langmuir-Blodgett trough. To examine their hypothesis, they performed an experiment in which they extracted lipids from a known number of red blood cells ( erythrocytes) of different mammalian sources, such as humans, goats, sheep, etc. They simply hypothesized that if the plasma membrane is a bi-layer, then the surface area of the mono-layer of lipids measured would be double the surface area of the plasma membrane.
The yellow polar head groups separate the grey hydrophobic tails from the aqueous cytosolic and extracellular environments.Įvert Gorter and François Grendel (Dutch physiologists) approached the discovery of our present model of the plasma membrane structure as a lipid bi-layer. Gorter and Grendel's membrane theory (1920) ĭiagram of the arrangement of amphipathic lipid molecules to form a lipid bi-layer. Following intense experimental research, the membrane models of the preceding century gave way to the fluid mosaic model that is accepted today. However, understanding of past membrane models elucidates present-day perception of membrane characteristics. David Robertson, the proposal of Singer and Nicolson, and additional work of Unwin and Henderson all contributed to the development of the modern membrane model. The advent of the electron microscope, the findings of J. Specifically, it was through the models of Overton, Langmuir, Gorter and Grendel, and Davson and Danielli, that it was deduced that membranes have lipids, proteins, and a bilayer.
For artificial membranes, see Model membrane.īefore the emergence of electron microscopy in the 1950s, scientists did not know the structure of a cell membrane or what its components were biologists and other researchers used indirect evidence to identify membranes before they could actually be visualized.
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