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Path to the Fluid Mosaic Model

BIOLOGY 12
by

Nikki Nandlal

on 10 April 2013

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Transcript of Path to the Fluid Mosaic Model

Path to the Fluid Mosaic Model By: Nikki Nandlal
Due Date: April 10, 2013
Teacher: Mrs Reid
Course Course: SBI4U1-04
1774 Benjamin Franklin (1706 - 1790)
- was an American chemist, politician, inventor and an author. 1890: Lord Rayleigh (1842 - 1919)
- was a English physicist 1891: Agnes Pockels (1862 - 1935)
- was a German chemist Charles Ernest Overton (1865 - 1933)
- was an English scientist Irving Langmuir(1881 - 1957)
was an American chemist/physicist Evert Gorter(1881–1954) and F. Grendel
- scientists 1925 James David Robertson( 1923 - 1995)
- was a biologist George E. Palade(1912 - 2008)
- was a Romanian cell biologist 1960

-Used electron microscopy and discovered important organelles: mitochondria, endoplasmic reticulum, ribosomes.

-Used cell fractionation, controlled by microscopy, to determine functions of many subcellular components (cells that are function basic unit of life) like cell membranes, ribosomes, etc.

-Improved procedures in electron microscopy and cell fractionation.

-Using electron microscopy and cell fractionation, he analyze the process of secretory protein in grandular cells (cell found in the cervix and the lining of the uterus).
- Experimented to observe effects of oil on a surface of water. Result: The oil began to spread immediately until a large part of the surface area of water in the pond was covered.

-Concluded the concept of repulsion, indirectly related to hydrophobic effect.

-Observations lead to discovering measure the dimensions of oil monolayers . Overtime, because of this discovery, the formulation of the lipid bilayer model of the cell membrane was created.
Conducted a series of experiments involving oil and water.

Successfully measured:
- the area to which volume of oil would spread
- calculated the thickness of the oil film James Danielli (1911 – 1984)
- was an English chemist 1935
Danielli and Davson, Harvey (studied cell surfaces)

-Created first model of the cell membrane to be accepted by superiority of scientists.
-Danielli worked with Harvey from 1933 – 1935.
-Danielli discovered proteins could absorb oil droplets, which is major component in membrane model, created by Davson and Danielli, seen in Figure 1.2.

E.Newton Harvey(1887–1959)
- cell biologist
Hugh Davson(1909 – 1996)
-English physiologisT Jonathan Singer and Garth Nicolson 1972 Nicolson on the left, Singer on the right 1957
- Proposed an altered portrayal of membrane model, based on electron microscope studies he referred to as the “unit membrane”

- Hypothesized that all cell membranes(that form plasma membranes and intracellular organelles) are made up on biomolecular leaflets(layers) of phospholipid with monolayers of proteins absorbed to their surfaces.



-Observed when salts were put into solutions & when streams of currents occurred. She placed a small float in the water to balance which helped to measure growth of surface tension.

-Studied properties of surfactants (a substance that typically decreases the surface tension of a liquid in which it is dissolved) and surface tension of liquid solutions.

-After recording her results of her qualitative observations, she wrote to Lord Rayleigh about them.

-was assisted by Lord Raleigh in publishing her first fourteen articles about her results. 1895
- After investigating osmotic properties of cells, he discovered that transportation of molecules through membranes is related to their division coefficient between water and oil.

-Hypothesized that thin membranes that surrounded cells have the properties of oil. 1917,
-discovered lipids form a monolayer on the surface of water.

Polar heads are hydrophilic and point towards water.
Non-polar tails are hydrophobic and point away from water.

- called the layers surrounding cells “lipoids” made from lipids and cholesterol.
John Aitken(1839 - 1919)
- was a Scottish meteorologist David Gidalevitz
-Professor of physics -Further elaborated on Franklin’s experiment
-Concluded: it is ‘‘not the bite, grip or friction of the air on the surface’’ that was reduced when oil was poured on water, which was believed by others, but it is the surface tension on the water surface, or the lack of it upon the spreading of oil, that resulted in oil spreading on surface of water.

1895 1917 -Developed apparatus (equipment with a purpose), where molecular layers of lipids were spread the air-water compound.

-Proposed that in molecular film, polar head groups were directed towards water phase, and hydrophobic hydrocarbons are pointed towards air phase.

-Created Langmuir-Blodgett trough, which is used to compressed monolayers of molecules on the surface of water.

-Created when he showed single water-surface monolayers could be transferred to solid substrates. In 1935, Dr. Blodgett discovered many of these single monolayers films could be stacked on top of one another to make multilayer films(creates thickness of films).

- investigated the surface area of lipids through experiments.

- withdrew lipids from red blood cells of a man and various animals. Lipids were spread
on a water surface and the area was measured using a Langmuir film balance.

- concluded that: red blood cells are covered by a layer of fatty substances that is two molecules thick, cell membranes are made of two opposing thin molecular layers.

- Double layer is made up of two lipid layers to form bilayer with polar head groups(hydrophilic) pointing towards aqueous environment.

- created first unofficial lipid bilayer structure, seen in Fig 1.1 References http://www.nndb.com/people/578/000026500/franklin2color80.jpg - Benjamin Franklin
2012 -Stated a more important understanding of cell membrane. The port entry for HIV and other pathogens (microorganisms that can cause diseases) may break this impasse.
-Concluded from research that the nature of biological membranes provides awareness into dynamic structures of cell membranes.
http://www.geop.itu.edu.tr/images/sr/006447.jpg - Lord Rayleigh (John William Strutt)
http://www.iara.org/newsfolder/pioneers/pictures/00AerosolPioneerEditedAugAitken.bmp - John Aitken Image:http://fe867b.medialib.glogster.com/media/0d/0d4bbdbe05a5b5845c42f9eafafcb7b10f60afbb59441f4f606679dc41f9762b/agnes-pockels.jpg - Agnes Pockels

http://www.unipublic.uzh.ch/archiv/magazin/gesundheit/2001/0366/overton.jpg - Charles Ernest Overton http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1932/langmuir.jpg - Irving Langmuir
http://www.kcl.ac.uk/biohealth/about/history/heroes.aspx#JDanielli - James Danielli
http://www.universityofcalifornia.edu/news/img/25/25458072448ef82e27cb78.jpg - George E. Palade
http://elprofedebiolo.blogspot.ca/2010/01/estructura-y-composicion-de-la-membrana.html - Jonathan Singer and Garth Nicolson http://cdn.medgadget.com/wp-content/uploads/2009/09/david-gidalevitz-290x290.jpg -David Gidalevitz Researcher at University of Illinois Mary Kraft
http://www.countrychristianchurch.com/images/elders/photo_unavailable.jpg - Photo unavaliable 2013 - Understandable recognition of such membrane dynamics led Singer to propose the “fluid mosaic” model of the cell membrane. - Both noted that the fluid mosaic membrane is most likely asymmetric & displays distinctly different features on the inside and the outside of cells. Asymmetry of membrane lipids has in fact been found in experiments.
- Observed cells that had low cholesterol. Assumed to play a key role in lipid aggregation. However, the lipids still formed domains and disruption to the cell's structural scaffold seemed to dissolve the lipid clusters. Stated: ``Cholesterol abundance is important. You change that, you tremendously change cell function.`` - concluded that some proteins seem to interact with the surrounding lipids and that protein function may depend on the presence of specific lipids

- proposed that the proteins are surrounded by a layer of strongly interacting lipids while most of the remaining lipids are hardly influenced by the presence of proteins. Presence of domains was somewhat affected by cholesterol but was more affected by the cytoskeleton
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