Chapter 1 - Claudio Grosman Associate Professor Department...

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Unformatted text preview: Claudio Grosman Associate Professor Department of Molecular and Integrative Physiology Center for Biophysics and Computational Biology Program in Neuroscience University of Illinois at Urbana-Champaign Undergraduate degree in Biochemistry, University of Buenos Aires, Argentina Ph.D. in Biophysics, University of Buenos Aires, Argentina Postdoctoral training in Ion-Channel Biophysics, SUNY at Buffalo, NY Why multiple-choice exams? More practice questions, quizzes … we need a way to study!! These exams require thought!! WHAT YOU SHOULD AND SHOULDN'T EXPECT Why not + and – grades? More time for tests! Take attendance so that I can earn more points! Have office hours! Give homework assignments! Can you write a recommendation letter for me? PHYSIOLOGY Whole body Organ System of organs Tissue Cells Subcellular compartments Molecules “… when you can measure what you are speaking about, and express it in numbers, you know something about it; [otherwise] , your knowledge is of a meager and unsatisfactory kind .” William Thompson (Lord Kelvin) (1824-1907) “ Almost all aspects of life are engineered at the molecular level and without understanding molecules we can only have a sketchy understanding of life itself ” Francis Crick, in 1988 BIOLOGICAL MEMBRANES The extracellular and intracellular compartments have different compositions and, thus, need to be separated by a selectively permeable barrier: the plasma membrane. The same is the case between the cytosol and the organellar compartments. TWO APPOSED PLASMA MEMBRANES AS SEEN WITH AN ELECTRON MICROSCOPE A CARTOON REPRESENTATION OF A PLASMA MEMBRANE CELL AND ORGANELLAR MEMBRANES ARE ASSEMBLED ON PHOSPHOLIPID BILAYERS AS THE FRAMEWORK POLAR (HYDROPHILIC) HEAD NON POLAR (HYDROPHOBIC) TAILS SYMBOL The polar head is “zwitterionic” E LIPID VESICLE • Phospholipids (“PLs”) are amphipatic molecules. • Cellular membranes are more than mere molecular sieves. • Pure PL-bilayers are impermeable to most water-soluble solutes (ions, proteins, sugars, nucleic acids). • The physico-chemical properties of a lipid bilayer depend on its chemical composition. • Cell PL-bilayers are not homogeneous. “Lipid rafts”, which are microdomains rich in cholesterol, glycosphingolipids and certain proteins can form. These have important roles in protein trafficking and signal transduction. • Cell-membrane PLs are not chemically inert. Rather, they are fundamental players of the signal-transduction machinery. The PC polar head is zwitterionic as well PS has 1 extra negative charge PI has 1 net negative charge, but exists in very low abundance phosphatidylinositol phosphatidylserine cholesterol phosphatidylcholine Is the structure of membrane lipids conserved across the three kingdoms of life?...
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This note was uploaded on 10/31/2011 for the course MCB 401 taught by Professor Grossman during the Fall '09 term at University of Illinois at Urbana–Champaign.

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Chapter 1 - Claudio Grosman Associate Professor Department...

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