Lecture _7 - Membrane Structure and Transport

Lecture _7 - Membrane Structure and Transport - Membrane...

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embrane Structure and Transport Membrane Structure and Transport Lecture #7 Campbell –Reece, 8 th Edition Fibers of extracellular matrix (ECM) Glyco- protein Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Carbohydrate eading Assignment: Microfilaments of cytoskeleton Cholesterol Peripheral proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE Reading Assignment: Chapters 7 BIOL 203 – Spring 2010 Ralph Feuer
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Overview: Life at the Edge The plasma membrane Boundary that separates the living cell from its surroundings Exhibits selective permeability llowing me substances to cross it more easily than allowing some substances to cross it more easily than others Yeast Cells GFP-Ftr1p - plasma membrane iron permease FM4-64 - vacuolar membrane is stained with a red fluorescent dye DRAQ-5 blue dye – nuclear chromatin http://www.smbs.buffalo.edu/bch/Labs/Kosman/research.htm
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Cellular Membranes Are Fluid Mosaics f ipids And Proteins Of Lipids And Proteins embranes have been chemically analyzed Membranes have been chemically analyzed Found to be made of proteins and lipids Scientists studying the plasma membrane Reasoned that it must be a hospholipid ilayer phospholipid bilayer Phospholipids he ost abundant lipid in the plasma The most abundant lipid in the plasma membrane Amphipathic molecules containing hydrophobic and hydrophilic regions Hydrophilic head WATER Fluid mosaic model A membrane is a fluid structure Hydrophobic tail WATER With a “mosaic” of various proteins embedded in it
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Cellular Membranes Are Fluid Mosaics f ipids And Proteins Hugh Davson and James Danielli Of Lipids And Proteins Proposed a sandwich model (1935) the phospholipid bilayer lies between two layers of globular proteins Later studies found problems with this model The placement of membrane proteins, which have hydrophilic and hydrophobic regions J. Singer and G. Nicolson (1972) Phospholipid bilayer Proposed that the membrane is a mosaic of proteins Dispersed within the bilayer Only the hydrophilic regions exposed ater Hydrophobic regions of protein Hydrophilic regions of protein to water
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Freeze-Fracture Freeze-fracture Specialized preparation technique Splits a membrane along the middle of the phospholipid bilayer Freeze-fracture studies of the plasma membrane f fp Supported the fluid mosaic model TECHNIQUE RESULTS Extracellular layer Knife Proteins Inside of extracellular layer Inside of cytoplasmic layer Cytoplasmic layer Plasma membrane
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Freeze-Fracture Freeze-fracture Specialized preparation technique Splits a membrane along the middle of the phospholipid bilayer Freeze-fracture studies of the plasma membrane f fp Supported the fluid mosaic model TECHNIQUE RESULTS Extracellular layer Knife Proteins Inside of extracellular layer Inside of cytoplasmic layer Cytoplasmic layer Plasma membrane
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The Fluidity of Membranes Phospholipids in the plasma membrane
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Lecture _7 - Membrane Structure and Transport - Membrane...

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