10-1-07_lecture_plasamem2A

10-1-07_lecture_plasamem2A - A process which led from the...

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A process which led from the amoeba to man appeared to the philosophers to be obviously a progress though whether the amoeba would agree with this opinion is not known. Bertrand Russell Blue Falcon : Dyno-mutt has been dealt a devastating blow. Dexter : Sheesh, no kidding. Blue Falcon : I'm extremely wealthy. Dexter : Quickly, to the laboratory!
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Announcements Written assignments due this Friday, October 3, at noon. The writing should be in your own words as much as possible Identify and describe the key methods that contribute to the results of the article. Other methods reported in the methods section can be de-emphasized. It is expected that you will consult additional sources for help in understanding the methods, background and significance for the article.
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Cleland plots are diagrams that are used to represent the transition states Left, ordered sequential reaction Right, random sequential reaction, showing all possibilities Arrows towards line show binding to enzyme Arrows away from line show release of product from enzyme complex If order is important (left), then there must be some reason for its being fussy about the binding sequence, such as the first substrate causes a conformational change in the enzyme for instance. Peter Birch, University of Paisley (UK) Ordered sequential Random sequential
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Multisubstrate ping-pong mechanism After EA complex forms, FP complex forms F is an altered enzyme conformation that is covalently bound to a portion of what was A The remainder of A is now the product P F releases P and then B can bind to F The covalently bound portion of the first substrate A (FB) s transferred to B to create the second product Q (EQ) Q is released and E is reset Used in some enzymes, such as trypsin and chymotrypsin Peter Birch, University of Paisley (UK)
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None shall pass: The plasma membrane is a multifunctional, selective barrier in cells
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Current model of the plasma membrane Slightly revised fluid mosaic model. Membrane spanning portion of proteins are typically alpha helices with hydrophobic side chains pointed out into fatty acids Extracellular portions of most membrane proteins and some phospholipids coated with sugar chains (oligosaccharide), glycoproteins and glycolipids Two bilayer leaflets contain different lipid compositions On outer leaflet, specialized membrane microdomains called lipid rafts
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Lipid chemical structure Plasma membranes are amphipathic (hydrophilic and hydrophobic portions) Diversity can be in polar head or hydrocarbon chain Choline and ethanolamine are neutral, while serine and inositol are neg. charged at phys. pH.
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Cholesterol: your doctor’s favorite lipid Typically hydroxyl towards membrane surface Ring structure is rigid and stiffens membrane when present Cholesterol regulation is important not only for heart disease, but also for cell function and signaling
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10-1-07_lecture_plasamem2A - A process which led from the...

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