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The Contributors and History of the Fluid Mosaic Model

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Transcript of The Contributors and History of the Fluid Mosaic Model

1774- 2011 The Contributors and history of the
Fluid Mosaic Model Benjamin Franklin Irving Langmuir lord Rayleigh (John William Strutt) 1862-1935 Agnes Pockels 1865-1933 Charles Overton 1881-1957 - is an author, philosopher, self-trained scientist, inventor an statesman
- performed an experiment to determine the characteristics of oil when it encounters water (Eichman, P .n.d.)
- realized that a small amount of oil, not even a teaspoon, had dampened out the waves (Eichman, P .n.d.)
- the dampening of the waves is caused by the thin layer of oil that spread across the water and its energy that spread from it (Eichman, P .n.d.)
- the small amount of oil had spread across a large area, and the water looked as smooth as a looking glass (Eichman, P .n.d.)
- the spread of energy is due to the movement of water as it compresses and stretches the layer of oil (Eichman, P .n.d.)
-research was not noticed but was later published in Philosophical Transactions of Royal Society (Eichman, P .n.d.) In 1774: 1706- 1790 “Benjamin Franklin.” Web. 10 April 2012. <http://www.nndb.com/people/578/000026500/franklin2color80.jpg> Figure 1: Benjamin Franklin 1842- 1919 In 1890: - Raleigh attended Cambridge University (Eichman, P. n.d.)
- was a major in mathematics and physics (Eichman, P. n.d.)
- repeated Franklin's experiments and was originally known as John William Strutt (Eichman, P. n.d.)
- in 1890, conducted experiments with oil and water (Eichman, P. n.d)
- was able to determine the area of water that the a known volume of oil would cover and also the thickness of the layer of oil (Eichman, P. n.d.)
-measured the thickness of the olive oil to be 0.000000163 cm ("What is the thickness of the cell membrane. n.d.) Figure 2: Lord Rayleigh
“Lord Rayleigh.” Web. 10 April 2013. <http://www.nndb.com/people/497/000099200/lord-rayleigh-1-sized.jpg> In 1891: - had sent a letter to Lord Raleigh, who was working on surface tension, describing her experiments that she conducted in her very own kitchen (Edidin, M 2003)
- had built an apparatus that measures the area covered by an oil film which was later named langmuir apparatus (Eichman, P.n.d)
- lord Raleigh helped to publish her results (Eichman, P.n.d) Figure 3: Agnes Pockel
“Agnes Pockel.” Web.10 April 2013 <http://home.frognet.net/~ejcov/pockels4.jpg> - came with the hypothesis that the membrane was composed of lipids and that substances that are soluble in lipids enter the cell more rapidly than ones that are insoluble (Edidin,M 2003)
-at this time, Overton was studyin botany, plants, at the University of Zurich (Eichman, P. n.d)
- Overton had discovered certain properties of the membrane by accident while working with these plants (Eichman, P. n.d)
- research was related to heredity of plants and during his study, had to find substances that are able to diffuse through the plant cells (Eichman, P. n.d)
- found that non-polar substances passed quickly through the membrane and came up with the hypothesis ( Campbell, N 1946)
- this was contrasting previous knowledge, since scientists thought water passed more quickly than the other substances (Eichman, P. n.d) Figure 4: Charles Overton
“Charles Overton.”Web. 10 April 2013. <http://www.unipublic.uzh.ch/archiv/magazin/gesundheit/2001/0366/overton.jpg> In 1895: In 1917: -more research done on oil films (Eichman, P. n.d.)
- had improved Agnes Pockel's apparatus which is now refered to as the Langmuir's apparatus (Eichman, P. n.d.)
-during the time he had studied physical chemistry and was researching on molecular monolayers (Eichman, P. n.d.)
- his research then altered to lipids and oil films on water -had published a paper on his findings where he displayed that lipids form a thin monomolecular layer on water (Eichman, P. n.d.)
- using the apparatus, he found the area covered per molecule of the lipid (Robertson, J.D. n.d.)
-also displayed that the hydrocarbon chains on the lipids were flexible meaning that they were kinked (Robertson, J.D. n.d.)
-made artificial membranes by dissolving phospholipids with benzene and even after the benzene evaporated, the phopholipid layer remained as a film on the water with the polar heads immersed in the water (Campbell, N 1946)
- came up with the model that the lipid layer forms a monolayer with the polar heads in contact with the water and their hydrocarbon tails away from the water (Eichman, P. n.d.) Figure 5: Irving Langmuir
“Irving Langmuir.”Web. 10 April 2013. <http://www.nndb.com/people/776/000079539/langmuir-3-sized.jpg> Ernest Gortner and F.Grendel In 1925: - were the first to study the lipids from the cell itself and they had used red blood cells, chromocytes (Eichman, P .n.d.)
- Gorter was Grendel's research assistant who had studied pediatrics and was a professor at the University of Leiden (Eichman, P .n.d.)
- had extracted the phopholipid part of the membrane from these cells using chemical solvents (Eichman, P .n.d.)
-had discovered that the phospholipid could cover the cell twice around since its surface area was double the surface area of the cell (Campbell, N 1946)
- this is when they proposed the idea of the phopholipid bilayer demonstrated by using a trough (Eichman, P .n.d.)
- their studies were repeated on various animals and concluded that red blood cell have a double phospholipid layer by using their observation (Eichman, P .n.d.)
- was not a model used for all cells but was a structure that was proposed (Eichman, P .n.d.)
- made sense since there was an aqueous environment on either side of the membrane where the polar heads immerse and the hydrophobic tails are facing the inside of the two layers (Campbell, N 1946)
- had made errors: underestimation of the surface area of the red blood cell and did not extract all of the lipids (Campbell, N 1946)
- the two errors cancelled out to give a correct result (Campbell, N 1946)
George. E. Palade 1912-2008 In 1930: -perfected Dr.Claude's, Palade's instructor, technique of cell fractionation-technique separates the cell parts and examine them under a powerful electron microscope ("George E. Palade" n.d.)
- with this technique, Palade described the endoplasmic reticulum as folds and discovered ribosomes ("George E. Palade" n.d.)
- knew that the ribosomes were attached to the endoplasmic reticulum and its function of sythesizing proteins ("George E. Palade" n.d.)
- was also able to examine secretory cells and how they remove proteins from the cell ("George E. Palade" n.d.)
- with this technique, Palade was able to study many other organelles and their functions ("George E. Palade" n.d.) Figure 6: George. E. Palade
"George. E. Palade" Web. 10 April 2013. <http://www.nndb.com/people/225/000130832/george-e-palade.jpg> James Danielli (1911-1984), E. Newton Harvey and Hugh Davson In 1935: - had proposed the model of the phospholipid layer in between two globular protein layers (Eichman, P. n.d)-Danielli found that protein obtained from mackerel eggs can be absorbed by oil droplets (Eichman, P. n.d)- meaning that the globular proteins on either side of the phospholipid layer is in place and is stable since they are absorbed by the phospholipid layer (Campbell, N 1946)-proposed this model since biological membranes are more water absorbent than artificial membranes and proteins absorb water (Campbell, N 1946)- the difference in the amount of water absorbed could be taken care of by the proteins (Campbell, N 1946) Figure 7: James Danielli
“James Danielli.” Web. 10 April 2013. <http://www.kcl.ac.uk/ImportedImages/Schools/BMS/People/History/JamesDanielli140x180.jpg> J. David Robertson
1806- 1896 In 1959: - proposed the unit membrane model (Eichman, P. n.d.)
- had aid from an electron microscope and realized that the cell membrane wass only 7-8 nm thick (Campbell, N 1946)
- this was too thin to fit the Davson-Denielli model (Campbell, N 1946)
- the model was modified from being layers of globular proteins to continuous layers of proteins (Campbell, N 1946)
- the electron microscope image also revealed a trilaminar appearance meaning it consists of two dark lines and the inner portion is light (Eichman, P. n.d.)
-the dark lines are the monolayer of proteins and are more dense than the inner portion which is the phospholipid layer (Eichman, P. n.d.) Jonathan Singer & Garth Nicolson In 1972: - proposed the fluid mosaic model which is currently used (Campbell, N 1946)
-issues were met for the unit membrane model (Campbell, N 1946)
-one of the issues being that not all membranes follow the unit membrane model (Campbell, N 1946)
- when looking at a mitochondrion organelle under the electron microscope, it has a different structure such as more proteins and is thinner than 7-8 nm (Campbell, N 1946)
-cell's have different structures and composition according to their functions (Campbell, N 1946)
- the second issue was how the protein was placed in the model (Campbell, N 1946)
- membrane proteins are not very soluble in water since they have both hydrophobic and hydrophilic parts (Campbell, N 1946)
- if they were placed a a monolayer, the hydrophobic parts would be in contact with the water and at the same time the hydrophilic heads of the lipids will not be in contact with the water (Campbell, N 1946)
-came up with the fluid mosaic model where proteins are inserted into the phospholipid bilayer (Campbell, N 1946)
- protein's hydrophobic parts will not be in contact with the water but its hydrophilic parts will reach out of the phopholipid layer and come into contact with the aqueous environment (Campbell, N 1946)
- maximizes the contact between the water and hydrophilic regions and reduces the contact between water and hydrophobic regions (Campbell, N 1946)
- called fluid mosaic since there is a collection of proteins that are floating in a fluid phopholipid bilayer (Campbell, N 1946) M. Mihailescu, et al. In 2011: -certain drugs target the proteins found in the cell membrane since they act as a channel ("Closer look at cell membrane show cholesterol 'keeping order' " 2011)
-when cholesterol is present, the hydrophobic tails line up tightly , forming a narrow strip ("Closer look at cell membrane show cholesterol 'keeping order' " 2011)
-the tails are in order but when cholesterol is not present, they whip around and push the hydrophilic heads ("Closer look at cell membrane show cholesterol 'keeping order' " 2011)
- cholesterol does manage disorders and may have to do with the channel proteins("Closer look at cell membrane show cholesterol 'keeping order' " 2011)
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