The Scientific Contributions and Process Towards the Creation of the Fluid Mosaic Model of the Cell Membrane

Benjamin Franklin (1706-1790)

Apr 10, 1774

In 1774, Franklin dropped a small amount of olive oil onto the surface of a pond. He observed that the oil quickly spread out on the surface of the water. Soon, most of the water had a thin film of oil over it, "as smooth as a looking glass." Benjamin found that the oil did not mix with the water and formed a layer above the water (Richmond,2004). This experiment displays the hydrophobic nature of lipids and is later done by Lord Rayleigh which helps him determine the thickness of a monolayer.

Lord Rayleigh (John William Strutt) (1842 - 1919)

Apr 10, 1890

Following Franklin's observations in 1980, Rayleigh repeated Franklin's experiments. He found that a given amount of olive oil would cover a set amount of the water's surface. Knowing the molecular structure of lipids, he assumed that the oil spread out until the layer was one molecule thick. Through a series of calculations, Rayleigh determined the thickness was 2.5 nm (Nuffield Foundation). Later on, Rayleigh's calculation would prove to be an accurate thickness of a lipid monolayer.

Agnes Pockels (1862-1935)

Jan 10, 1891

Aided by Rayleigh, Pockels published various articles on experiments she had done in her home. Her first article discussed surface tension of water. Through an apparatus of her own making, involving a tin box, Pockels experimented with surface tension of both pure water and 'contaminated' water ( water with an oil film on top). Her experiments also measured the exact area of an oil film (Pockels, 1981). Pockels' apparatus would soon be re-made by Langmuir for his experiments.

Charles Ernest Overton (1865-1933)

Apr 10, 1895

In 1895, Overton postulated the osmotic property of the cell membrane. He hypothesized that the lipid layer gave the cell membrane osmotic properties that allowed the membrane to diffuse and undergo active transport. He also suggested that some molecules passed through the membrane by 'dissolving' into the lipid layer (Deamer, 1999).

Irving Langmuir (1881 - 1957)

Apr 10, 1917

Langmuir improved Pockels' tin box apparatus and is now called Langmuir's trough. He used the trough to further learn about the relationship of water and oil as well as accurately determine the surface area covered by quantities of oil. After experimentation, Langmuir proposed that the fatty acids formed a monolayer where the molecules were vertical with the carboxyl group touching the water and the hydrocarbon chains away from the water (Eichman).

Ernest Gorter(1881 - 1954) & F. Grendel

Apr 10, 1925

In 1925,Gorter and Grendel extracted the lipid from a red blood cell (RBC). Knowing that RBCs have no nuclei or membrane-bound organelles, they assumed the lipids were from the cell membrane. Using a modified trough, they determined the lipids covered twice the surface area of the cell. Through this, Grendel concluded that the membrane is two layers thick, or a bilayer.Using this, they determined that the polar heads faced aqueous environments for both molecular layers (or leaflets)(Karp, 2004).

George E. Palade (1912-2008)

Apr 10, 1930

George Palade perfected the process of what is now called cell fractionation. Palade grinded cells together to break the membrane and have its organelles spill out. By using a centrifuge to separate organelles by mass, organelles can be examined individually. Through this process, Palade further discovered functions and structures of different organelles ("George E. Palade").Thus, adding crucial info to what will be known as the endomembrane system.

James Danielli (1911-1984), E. Newton Harvey (1886-1957), and Hugh Davson (1906-1996)

Apr 10, 1935

In 1935, Davson and Danielli proposed that the bi-lipid membrane was sandwiched by two layers of globular proteins. Although biologists agreed that proteins were a part of the membrane, the model would be incorrect since solutes would need to diffuse through the membrane which would not be possible with two layers of protein blocking the way. In the 1950s, Davson and Danielli revised their model with protein pores after researching about the membrane being selectively permeable (Karp,2004).

J. David Robertson (1923-1995)

Apr 10, 1957

With the electron microscope, biologists determined that the membrane was too thin for Danielli's sandwich model. Robertson proposed a variation of the model where the bi-layers were surrounded by a thin layer of proteins and carbohydrates. Robertson called it the 'unit membrane' and hypothesized that all membranes in the cell are of this model (Robertson, 1981).

Jonathan Singer and Garth Nicolson

Apr 10, 1972

Singe and Nicolson introduced the fluid mosaic model in 1972.The model still has the lipid bilayer structure as proposed by Grendel and Gorter. However, in this model, proteins penetrate the bi-layer and are shown to be studded around the membrane. Proteins are suggested to contain channels and that the entire model is fluid, meaning that all molecules are freely moving (Karp, 2004).

Mary Kraft, Peter Weber, Joshua Zimmerberg

Jan 8, 2013

Jan 28,2013 - The team of Mary, Joshua, and Peter published new findings discussing their research on the organization within the cell membrane. It is suggested that lipids congregate in groups, known as domains, which differ in composition. The team plans on researching how this organization affects cell function and how lipids perform multiple functions. The image is a congregation of lipids which form a domain (Stark, 2013).