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MARIETTA BIOL 309 - Membrane Structure

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PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Membrane Structure 1Membrane StructureChapter 11Questions in this chapter you should be able to answer:Chapter 11- #s1 - 19Membrane Structure 2Membranes are described as a “2-dimensional liquid”. Why?Laser TweezersMembrane FluidityJmol membrane modelMembrane Structure 3How can we measure membrane fluidity?FRAP: ‘Fluorescence Recovery After Photobleaching’GFP: Green fluorescent proteinCell fusion alsoshows fluiditySee Figure 11-30P 378FRAPMembrane Structure 4What factors determine how fluid a membrane is?Properties of P-lipids: Chain length SaturationProperties of membranes: Cholesterol content Cytoskeleton associationMembrane Structure 5What are the principal membrane lipids?PhospholipidsGlycolipidsOther membrane lipids(not phospholipids)CholesterolCerebrosidesSphingolipidsCeramideMembrane Structure 6How are P-lipids distributed in lipid bilayers?P-lipids are synthesized on the ER membrane….How do they get to other side of membrane?How is asymmetry achieved?Scramblase vs FlippaseMembrane Structure 7What are the principal functions of membrane proteins?How are membrane proteins connected to the membrane?Membrane associated (peripheral)Covalent vs NoncovalentTransmembrane (integral)Single-pass Multi-passMembrane Structure 8Why do transmembrane proteins occur as alpha helices and beta-pleated sheets??Jmol Transmembrane proteinsMembrane Structure 9How can membrane proteins be purified and studied?-- detergents ‘mimic’ P-lipid structure around proteins Question 11-5Why is red part hydrophilic and blue part hydrophobic?Membrane Structure 10What do we know about the structure of bacteriorhodopsin?Function?Structure?Mechanism?BacteriorhodopsinMembrane Structure 11How is the cell membrane structurally reinforced?-- Cell cytoskeleton-- also influences fluidityMembrane Structure 12Why are carbohydrates particularly abundant on the cell surface?Functions:Surface protectant Cell recognitionCell adhesion-- extracellular matrixMembrane Structure 13How can protein movement in cell membrane be restricted?Consider challenge of intestinal epithelium…Fig 12-16 p 395Membrane Structure 14You have isolated two mutants of a normally pear-shaped microorganism that have lost their distinctive shape and are now round. One of the mutants has a defect in a protein you call A and the other has a defect in a protein you call B. You grind up mutant and normal cells separately and separate the plasma membranes from the cytoplasm by centrifugation. You then wash the membrane fraction with a low concentration of urea ( which disrupts their ability to interact with other proteins) and centrifuge the mixture. The membranes and their constituent proteins form a pellet while the proteins liberated by the urea wash remain in the supernatant. When you check each of the fractions for the presence of A or B, you obtain the results given below.First cell extractAfter urea wash and centrifugationMembrane Cytosol Membrane SupernatantNormal cells A and B no A or B B AMutant A B A B no A or BMutant B B A B no A or BAnswer the following statements about your results?(a) Which is an integral and which is a peripheral membrane-associated protein. The results for which cell-type shows this?(b) How does the mutation to protein-A alter its properties?(c) How does the mutation to protein-B alter its properties?(d) Which result(s) most indicate an interaction between A and B?


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