Biological_membranes - Biologicalmembranes Plasmamembrane ,

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Biological membranes Plasma membrane Introduced phosopholipids in the last section More on phospholipids and membranes Membrane is both a barrier, and selective door to the cell Keeps the distinction between inside and outside Very complex regulator of cell contents ‘semipermeable’ barrier Questions to think about Some questions to keep in mind What is the membrane permeable to? What chemical properties regulate this? What is the role of diffusion in determining cell contents? Can we move impermeable substances?\ What is the role of H2O? Membrane structure
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Physical nature of the membrane-chemical analysis-phospholipids How are phospholipids arranged? Monolayer (like a micelle) bilayer Gorter and Grendel experiment Isolate phospholipids from RBCs Obtain a sample of RBCs from an animal Determine the surface area of a RBC Estimate total surface area of these cells Isolate the phospholipids from all RBCs Determine the surface area of a monolayer of lipids Calculate the ratio Gorter and Grendel data (table) An im al #R BC s Surfa ce  area  of 1  RBC Surface  area of  all  RBCs Surface  area of all  lipids ra ti o Sh ee p 9,9 00 29.8 295,000 620,000 Ra bbi t 5,9 00 92.5 546,000 990,000 Go at 16, 50 0 17.8 294,000 617,400 Do g 6,8 00 90 612,000 12,240,00 0 Ma 4,7 99 465,000 883,500
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n 00 Membrane is bilayered allows measurement of area of monolayer compare to estimate of RBC surface area- find =2x RBC surface area membranes is bilayer Phospholipid structure Phospholipids are amphipathic Hydrophilic-phosphate-orient towards water Hydrophobic-fatty acid chains o Orient away from water o Orient towards each other-hydrophobic interactions
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Membrane properties are dominated by the hydrophobic tails Permeability of pure phospholipid bilayer Phospholipid bilayer should be permeable to: Nonpolar Small polar Phospolipid bilayer should be impermeable to: Large polar charged Membrane permeability (fig)
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What else is in a membrane? (fig 5.2)
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This note was uploaded on 04/11/2011 for the course BIO 111 taught by Professor Dr. bos during the Fall '10 term at Purdue University-West Lafayette.

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Biological_membranes - Biologicalmembranes Plasmamembrane ,

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