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Cell Membrane John Lenyo Corrina Perez Hazel Owens Cell Membrane http://micro.magnet.fsu.edu/cells/plasmamembrane/plasmamembrane.html • Cell membranes are composed of proteins and lipids. • Since they are made up of mostly lipids, only certain substances can move through. spmbiology403.blogspot.com •Phospholipids are the most abundant type of lipid found in the membrane. Phospholipids are made up of two layers, the outer and inner layers. The inside layer is made of hydrophobic fatty acid tails, while the outer layer is made up of hydrophilic polar heads that are pointed toward the water. academic.brooklyn.cuny.edu •Membrane structure relies on the tendency of fatty acid molecules to spread on the surface of water. • Membrane proteins (which take up half of the membrane) determine what gets into and leaves the cell. •Glycolipids are found on the outer part of the cell membrane. Single Chain vs. Phospholipid • Single chain lipids were assumed to be the first of those to form cell membranes with the more complex phospholipids evolving later • Phospholipids can be synthesized in an abiotic environment without enzymes now • Phosphoplipid bilayers now make up the plasma cell membranes that regulate movement into and out of prokaryotic and eukaryotic cells. Single chain lipid http://web.nestucca.k12.or.us/nvhs/staff/whitehead/homewor http://clincancerres.aacrjournals.org/content/11/5/2018/F1. k.htm expansion Types of Lipids • Today Plasma Membranes are made primarily of phospholipids • It is thought that early membranes may have been made of simpler fatty acids. http://exploringorigins.org/fattyacids.html Properties of Fatty Acids • They are Ampipathic, meaning that they have a hydrophobic (“water hating”) end and a hydrophilic (water loving”) end. •Hydrophobic molecules are nonpolar. They prefer other neutral or non‐polar molecules and avoid polar molecules, such as water. i.e. oil and vinegar http://www.cool‐science‐fair‐experiments.com/oil‐and‐vinegar‐separation‐ experimen/ •When fatty acids or phospholipids are put into an aqueous solution, they will self‐assemble into a ball. Their hydrophobic ends will face inward and hydrophilic Micelles • Micelles are basically spheres of fatty acids. • They will self‐assemble in an aqueous solution in low concentrations • Their hydrophilic ends point outward making contact with the water and the hydrophobic http://en.wikipedia.org/wiki/File:Micelle_scheme‐en.svg ends cluster together. Vesicles • Research from the Stoztak Lab at Massachusetts General Hospital has shown that micelles can form vesicles under the right conditions (pH, concentration, etc.) (http://genetics.mgh.harvard.edu/szostakweb/researchVesicles.html ) http://en.wikipedia.org/wiki/File:Lip osome_scheme‐en.svg •Vesicles are membrane‐enclosed sacks that form in aqueous solutions (http://en.wikipedia.org/wiki/Vesicle_(biology) ) •Once formed, phospholipid vesicles are highly stable •Fatty acid lipids are much more dynamic (http://exploringorigins.org/fattyacids.html ) Early Vesicles • Vesicles made of fatty acids are stable, but very dynamic. Fatty acids are constantly flipping in and out of the membrane. • This may have provided the opportunity for other monomers or macromolecules to enter the vesicle. http://genetics.mgh.harvard.edu/szostakweb/exploringOriginsDownloads/p rotocell.jpg Vesicle Research • In a cooperative effort from Harvard and other genetic research institutions efforts are being made to replicate working vesicles from plasma membranes. http://genetics.mgh.harvard.edu/szostakweb/researchVesicles.html http://www.hms.harvard.edu/dms/prospective/AboutDMS.html Early Earth • Some scientists propose that early earth had the capacity to form fatty acids, most likely near hydrothermal vents • Clays are thought to have played a role in catalyzing the formation of fatty acid tails from H and CO2 gases. • In large enough quantities, these fatty acids have been shown to self‐assemble into micelles, or vesicles (http://exploringorigins.org/fattyacids.html ) Early Earth • Research has shown that the clay montmorillonite can catalyze the formation of vesicle formation (http://exploringorigins.org/fattyacids.html ) • The vesicle is crucial to the formation of the protocell and is thought to be the precursor to the cell membrane • Today, however, plasma membranes are synthesized and regulated by the cell. Cell Membranes and Technology • European Researcher Pascal Jonkheijm is working to create artificial cell membranes on microchips to better understand how cells communicate with each other • Jonkheijm believes that the knowledge he gains can be a stepping stone into regenerative research. http://www.nanowerk.com/news/newsid=18101.php http://www.utnieuws.utwente.nl/new/?artikel_id=76814.
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