MMG Chapter 11 - MMG CHAPTER 11 Plasma membranes serve as...

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MMG CHAPTER 11 Plasma membranes serve as both barriers and conduits. Integral membrane proteins, transport proteins, are embedded in plasma membrane - permit controlled and selective transport of molecules and ions across the membrane Moving from higher to lower concentrations-it’s a thermodynamically spontaneous process, doesn’t require input of energy * Examples: movement of water or glucose from blood into cell body Others move from lower to higher concentrations * Examples: concentrating protons within lysosomes to generate a low pH in the lumen - this energy usually provided by coupling of E-releasing hydrolysis of the terminal phosphoanhydride bond in ATP ^called ATP-Powered Pumps 3 classes transport proteins: 1. ATP-Powered Pumps 2. Ion Channels 3. Transporters 11.1 Overview of Membrane Transport Only Small Hydrophobic Molecules Cross Membranes by Simple Diffusion - oxygen, carbon dioxide, small uncharged polar molecules ( urea, ethanol) Diffusion rate is proportional to its concentration gradient and its hydrophobicity and size Greater the concentration gradient of the substance, the faster its rate of movement across a bilayer. Hydrophobicity measured by its partition coefficient K. Higher a substance’s partition coefficient, the more lipid soluble First and rate-limiting step in transport is movement of a molecule from the aqueous solution into the hydrophobic interior of the bilayer. Fatty acids with longer hydrocarbon chains are more hydrophobic than
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This note was uploaded on 03/19/2008 for the course MMG 451 taught by Professor Brooks during the Spring '08 term at Michigan State University.

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MMG Chapter 11 - MMG CHAPTER 11 Plasma membranes serve as...

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