02 Organelles&Epithelium

02 Organelles&Epithelium - The original...

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The original Singer-Nicholson fluid mosaic model Hydrophobic R-groups
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The Locations of Water, Lipid PHGs, and Fatty Acids in a Lipid Bilayer P 121 Karp 4 Thermal energy keeps fatty acid tails from being straight They bend, flex, vibrate, spin at high rates Water penetrates to the bottom of the PHGs
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Cholesterol Affects Bilayer Viscosity by Getting in the Way of Lipid Diffusion 4.7 K 2/4 It penetrates only about this far into the bilayer IML fatty acids interdigitate with the OML FAs. Cholesterol is smaller than other lipids in the bilayer and it occupies space between them With less free space there is less room for big lipids to diffuse Therefore, the bilayer becomes more viscous (less fluid) Cholesterol has higher affinity for some lipids than for others. It can form domains (rafts) with e.g., sphingomyelin. Longer FAs Higher viscosity Saturated FAs Higher viscosity Cholesterol at body temp Higher vis
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Some characteristics of IMPs 4.12 K4 4.17 K4
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“Corrals and Fences” Creating Domains From Within ~randomly diffusing IMP IMP in a corral “Fences” Motor-driven IMP IMP immobilized by interaction with ECM “Fencepost” IMP immobilized by interaction with cytoskeleton IMPs immobilized (rafted) by association 4.27 K4
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Rough Endoplasmic Reticulum (RER) The Signal Hypothesis … and how a cell threads a long, polar protein through a bilayer membrane SRP Free 40S + 60S ribo subunits combine with tRNAs and mRNA. Protein synthesis continues until the N- terminus extrudes from the hole in the 60S subunit. Then … Making IMPs with an N-terminal Signal Sequence Internal Start and Stop transfer sequences are also used to make multi- pass IMPs 8.9 K4
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The Exocytic Axis Material is transported along the axis by vesicles that are loaded at one organelle and unloaded by fusion with another. Newer version: Cisternal maturation moves outbound, Golgi function proteins move retrograde in vesicles. SORTING occurs both outbound and inbound but not in the ‘constitutive’, bulk flow pathway. TARGETING occurs with formation of each vesicle Formation of COP-II-coated vesicles 8.26 K4
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The Golgi Apparatus Golgi-Level Modifications to N-linked Carbohydrate Vesicles from RER PM and lysosomes
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Golgi apparatus, transmission EM Single Golgi bowl SEM
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Vesicles Form at the RER Cargo Entering Vesicles is Sorted
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Sorting at the TGN and PM Uses Clathrin Lysosomes and endosomes IMP cargo receptor cytosolic domain binds to adaptin, changing its 3 0 structure so it can bind to cadherin. Clathrin molecules bound to
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This note was uploaded on 02/16/2010 for the course BIO 542 taught by Professor Dr.philipbonner during the Spring '10 term at Kentucky.

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02 Organelles&Epithelium - The original...

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