Lecture 8 Pumps and Channels

Lecture 8 Pumps and Channels - Biochemistry415/515...

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1 Biochemistry, Seventh Edition Chapter 12 and 13 Biochemistry 415/515 Mark A Saper  Lecture 21 Membranes Channels and Pumps Figures in this presentation, unless otherwise noted, are ©2011, 2007, 2002 by W. H. Freeman & Co.
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2 Section 2 Monday’s class (10/31/2011) is in North Lecture Hall Exam next Wednesday on lectures through today Section 1 Exam Locations: Section 2 Exam Locations: 1210 & 1640 CHEM, 6311 MS I
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3 From membrane lipids to lipid membranes: Eukaryotic cells contain multiple compartments bounded by membranes • Phospholipids, glycolipids, and cholesterol form the basic structure of membranes. • Proteins carry out most membrane functions.
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4 Membrane lipids are amphipathic molecules: contain both a hydrophobic and hydrophilic moiety A common structural theme Cholesterol Hydrocarbon tails interact with one another in preference to water Polar head group favors contact with water
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5 Section of a fatty acid micelle Polar heads face the water Hydrophobic tails associate. Hydrophobic interactions drive the self-assembly of micelles and bilayers
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6 Lipid bilayers form spontaneously by a self assembly process Hydrophobic interactions are the driving force for lipid bilayer formation Phospholipids and glycolipids form bilayers
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7 Membranes are three-dimensional solutions of oriented lipids and globular proteins Functions of the bilayer: 1) as a solvent for integral membrane proteins 2) as a permeability barrier Fluid mosaic model
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8 Fluid mosaic model membrane asymmetry Proteins and lipids diffuse laterally
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9 Biological membranes are structurally and functionally asymmetric Outer and inner surfaces of membranes have different components and enzymatic activities Lipids are asymmetrically distributed: Outer leaflet: sphingomyelin, PC Inner leaflet: PE, PS Proteins are asymmetrically oriented with functional consequences (receptors for growth factors, Na + -K + pump)
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10 Length affects Tm: Long hydrocarbon chains interact more strongly than short (Tm increases with increasing chain length) Double bonds affect Tm: A cis double bond introduces a bend which interferes with packing of the hydrocarbon chains, lowering Tm Membrane fluidity is controlled by fatty acid composition and cholesterol content
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11 In animals , cholesterol is a key regulator of membrane fluidity How do bacteria regulate membrane fluidity? At
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This note was uploaded on 01/16/2012 for the course BIOLCHEM 415 taught by Professor Michaeluhler during the Fall '06 term at University of Michigan.

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Lecture 8 Pumps and Channels - Biochemistry415/515...

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