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The Path Towards Understanding the Fluid Mosaic Model

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Jalal Barat

on 30 September 2016

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Transcript of The Path Towards Understanding the Fluid Mosaic Model

The Path Towards Understanding the Fluid Mosaic Model
Presented by: Jalal Barat
Teacher: Mrs. Reid
Class: SBI4U1-03
Date: April 23rd, 2014

Benjamin Franklin - 1774
Mainly known for his participation in the writing of The Declaration of Independence and his work on electricity
Tested the effects of oil on water and saw that the oil spread across the surface area of the water until a large portion of surface looked like it was coated with glass
From this experiment he devised the concept of particle repulsion which indirectly related to the hydrophobic effect ("Benjamin Franklin" 22 Apr. 2014)
His discovery lead other scientist to observe the dimensions of oil monolayers. This discovery eventually lead to the formation of the lipid bilayer model of the cell membrane.

Lord Rayleigh ( John William Strutt) – 1890
Rayleigh repeated Franklin’s experiments using olive oil.
Through a series of experiments and calculations he was able to determine the thickness of a lipid monolayers
Determined the thickness to be 2.5 nm ("Lord Rayleigh" 22 Apr. 2014).
While working on his experiments he went under the assumption that the oil spread across the surface of water until it was one molecule thick

Angnes Pockels - 1891
Published various articles she had done in her on home involving water and oil
Studied the properties of substances of substances that decrease the surface tension of a liquid in which it is dissolved in, also known as a surfactants ("Lipids and Membranes" 22 Apr. 2014)
Through a creation of hers, known as the Langmuir apparatus, she was able to measure the surface area of an oil film
She sent many of her findings from her experiments Lord Raleigh and soon Lord Raleigh assisted in publishing her results

John Aitken - 1895
Expanded on Franklin’s experiments
It was thought that when oil as poured onto a liquid it was capable of spreading across the surface due to the friction of the air on the surface ("Richard" 22 Apr. 2014)
Aitken concluded that it as the lack of surface tension upon spreading of the oil that resulted in the oil being evenly distributed across the surface

Charles Overton - 1895
Was working on plants when he discovered certain properties of the cell membrane
Hypothesized that the cell membrane was made out of lipids and substances soluble in lipids enter the cell more rapidly than ones that are insoluble ("Charles Overton" 22 Apr. 2014)
Found that non-polar substances passed quickly through the cell membrane, which contrasted previous knowledge which said that water passed more quickly than other substances

Irving Langmuir - 1917
Improved on Pockel’s apparatus and officially gave it the name “Langmuir apparatus”
Conducted an experiment in which he dissolved phospholipids with benzene and after dissolving the benzene he noticed that the phospholipid layer remained as a film on the water ("History of the Study of the Membrane" 22 Apr. 2014)
Concluded that when the lipid layer forms a monolayer on water, the polar heads (hydrophilic ends) come in contact with the water’s surface while the hydrocarbon tails (hydrophobic ends) do not come in contact with the water and are essentially facing away from the water’s surface

Ernest Gorter and F. Grendel - 1925
Extracted the lipid cell membrane (specifically the phospholipid part) from a red blood cell knowing that red blood cells have no nuclei or membrane-bound organelles (Richard 22 Apr. 2014)
Noticed that the phospholipid layer could cover twice the cells surface area
Determined that a cell’s membrane is two layers thick
This lead them to believe that the polar heads of a lipid faced towards the polar environments and the hydrophobic tails are facing the inside of the two layers
Essentially created the first lipid bilayer structure

George E. Palade - 1930
Perfected the technique of cell fractionation
Cell fractionation is the process in which the cells are grinded out resulting in the membranes to brick and have its organelles spill out. A centrifuge was then used separate the organelles according to their masses and enabled scientist to examine the organelles individually. ("George E. Palade" 22 Apr. 2014)
Described the endoplasmic reticulum as folds and discovered the presence of ribosomes
Stated that the ribosomes were attached to the endoplasmic reticulum and had the function of protein synthesis
Examined secretory cells and the method involved in removing proteins from the cell
Essentially he found many functions to what we now know as the endomembrane system

Figure 1: An image of Benjamin Franklin
Source: http://upload.wikimedia.org/wikipedia/commons/2/25/Franklin-Benjamin-LOC.jpg
Figure 2: An image of Lord Rayleigh
Source: http://upload.wikimedia.org/wikipedia/commons/thumb/2/28/John_William_Strutt.jpg/446px-John_William_Strutt.jpg
Figure 3: An image of Agnes Pockels
Source: http://www.agnespockelslabor.de/en/xb-ap-gross.jpg
Figure 4: An image of John Aitken
Source: http://callcapsule.weebly.com/uploads/4/3/5/4/4354730/226661.jpg
Figure 5: An image of Charles Overton
Source: http://www.mackinac.org/media/images/2005/v2005-10a.jpg
Figure 6: An image of Irving Langmuir
Source: http://upload.wikimedia.org/wikipedia/commons/f/f0/Irving_Langmuir.jpg
Figure 7: An image of Ernest Gorter
Source: http://photos.aip.org/history/Thumbnails/barr_ernest_a1.jpg
Figure 8: An image of George E. Palade
Source: http://www.nobelprize.org/nobel_prizes/medicine/laureates/1974/palade_postcard.jpg
James Danielli, E. Newton Harvey, and Hugh Davson - 1935
Studied cell surfaces
Proposed that the lipid membrane was squeezed in between a layer of globular proteins on both sides
Many agreed that proteins were present in the cell membrane but a few disagreed with the idea because many solutes would not be able to diffuse through the membrane if it was coated with a protein coating ("James Danielli" 22 Apr. 2014)
The model was revised to the conclusion that the membrane contains “protein pores”

Figure 9: An image of Jame Danielli
Source: http://4.bp.blogspot.com/_bXiAT6MOo8E/S2T8ijYzqHI/AAAAAAAACJM/6LLpce0Ft4E/s640/cole.jpg
J. David Robertson - 1957
Came to the conclusion, with the aid of an electron microscope, that the cell membrane is too thin for Davson-Danielli’s sandwich model to hold true (Richard 22 Apr. 2014)
Proposed a newer model in which the bilayers were surrounded by a thin layer of proteins and carbohydrates
Called this model the “Unit membrane model”

Jonathan Singer and Garth Nicolson - 1972
Proposed the fluid mosaic model
Still contains the lipid bilayer structure proposed by Grendel and Gorter
States that protein penetrate the bilayer and are studded around the membrane or on the membrane’s surface (integral proteins or peripheral proteins)
Referred to as the fluid mosaic model since there is a collection of proteins that are floating in a fluid phospholipid bilayer ("History of the Study of the Membrane" 22 Apr. 2014)

Figure 10: An image of Jonathan Singer
Source: http://scarc.library.oregonstate.edu/coll/nonspcoll/catalogue/portrait-singer-600w.jpg
M. Mihailescu, et al. - 2011
Proposed the idea that cholesterol in the cell membrane manages disorder and may have something to do with channel proteins
The presence of cholesterol causes the hydrophobic tails to become more organized and more structured (Anne M. 22 Apr. 2014)
This means that at room temperature and higher, the presence of cholesterol increases the intermolecular forces in the membrane and holds it more tightly together, thus reducing fluidity
At lower temperatures this would mean that cholesterol molecules break up the packing that occurs as phospholipids solidify into a gel

Mary Kraft, Joshua Zimmerberg, and Peter Weber – 2013
The team is currently researching the organization within a cell membrane
It was found that lipids assemble in groups, known as domains.
Different domains have different functions
This is key to the model as the assembly of these domains may play a role in how the cell functions and how the cell membrane may perform other unknown tasks (Anne M. 22 Apr. 2014)

Figure 11: An image of Mary Kraft
Source: https://chbe.illinois.edu/sites/chbe.illinois.edu/files/kraft_mary_b.jpg
Works Cited
“Benjamin Franklin.” Web. 10 April 2012. <http://www.nndb.com/ >
“Charles Overton.”Web. 10 April 2013. <http://www.unipublic.uzh.ch/ >
"George. E. Palade" Web. 10 April 2013. <http://www.nndb.com/people/225/000130832/george-e-palade.jpg>
Harth, Richard. “New Membrane Research Takes Shape.” Illinois Institute of technology. 2012. Web.
22 April 2014. < http://www.iit.edu >
“History of the Study of Membranes.” Web. 22 April 2014. < http://www.willamette.edu/ >
“James Danielli.” Web. 10 April 2013. <http://www.kcl.ac.uk >
“Lipids and Membranes.” 2012. Web. 22 April 2014. < http://saf.bio.caltech.edu >
“Lord Rayleigh.” Web. 10 April 2013. <http://www.nndb.com/people/497/000099200/lord-rayleigh-1-sized.jpg>
Stark, Anne M. “ New look at cell membrane reveals surprising organization.” Lawrence Livermore
National Laboratory. Web. 22 April 2014. < www.llnl.gov >
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