Anatomy and phys lecture 7
Anatomy and phys lecture 7 PHCL2600
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This 5 page Class Notes was uploaded by Legacy Tanner on Tuesday October 6, 2015. The Class Notes belongs to PHCL2600 at University of Toledo taught by Williams,F in Fall 2015. Since its upload, it has received 32 views. For similar materials see Funct Anat and Pathophysiol I in Pharmaceutical Sciences at University of Toledo.
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Date Created: 10/06/15
Anatomy Lecture 7 Membranes and transport 0 2 basic types of membrane transport Active Passive Diffusion random molecular motion from one place to another Brownian motion Governed by Fick s Law 0 Fick39s Law J Flux DA dcdx A Area of Diffusion D Diffusion Coefficient Dcdx driving force or concentration gradient Controlling factors of diffusion 0 Chemical gradient concentration of chemical in solution will set up a gradient where molecules will move from higher concentrations to lower concentrations molecules can move in the opposite direction however net movement of the solute is to the lower concentration 0 Electrical gradient if 1 area is more positively charged than another area the positively charged ions move towards the more negative area o The bigger the difference in the gradient the faster diffusion will occur 0 Net movement of molecules ends when reaches equilibrium Molecules still move just no net movement 0 If you put them together Chemical gradient and electrical gradient together form an electrochemical gradient Diffusion across solvent can occur in a beaker however diffusion can occur across a semipermeable membrane Diffusion across a membrane 0 May occur slower than in a beaker o Membrane must be permeable to solute for any diffusion to occur 0 Permeability coefficient is a unit that can be used to compare rates of movement of solute through a membrane 0 Adaptation of Fick s law J PAC1C2 Jflux P permeability coefficient 0 This coefficient varies with different solutes and different membranes A area of diffusion C1 and C2 concentrations on either side of the membrane C1gtC2 diffusion gt 2 C2gtC1 diffusiongt1 C1C1 no diffusion equilibrium 0 What can and can t cross membranes Membrane is slab of oily protein Barrier to large charged or uncharged polar molecules glucose practically impermeable to intracellular protein and organic ions glucose 6 phosphate Lipids and small nonpolar molecules can cross readily fatty acids steroids urea ethanol 02 N2 and C02 They can do this by associating with the fatty acids in the membrane and diffusing across Called simple diffusion o Overton s rules The permeability of a cell membrane to small nonpolar solutes is directly proportional to the lipid solubility of the solute The higher its solubility in liquid the better it will diffuse across membranes The permeability of cell membranes to polar solutes is inversely proportional to the molecular size of the solute Huge and polar doesn t diffuse 0 Small and nonpolar does Therefore 0 Small highly lipid soluble substances have greatest chance of simple diffusion However small charged ions may cross the membrane as well 0 Na K and Cl can diffuse across a membrane in their charged form PK and PCI 501OOX PNa o How does this occur The fact that Na diffuses slower than K and Cl is probably not by accident Each of these is hydrated that is they are surrounded by water molecules When Na is hydrated its diameter the size of the ion surrounded by water is at least 3040 bigger than K or Cl This could explain the slower diffusion rate 0 Facilitated diffusion Also called carrier or channel mediated diffusion because a protein is used Usually will only passage certain ions Some channels are always open passive ion channeb Gated channels determine what goes in and out 0 Channels are speci c They will only carry certain ions Examples would be Na channels K channels or KNa channels Not all cells have all kinds of channels 0 2 kinds of avors of gated channels chemical or ligand gating chemical binds to protein and changes its shape allowing the ion to move across the membrane voltage gating change in charge distribution around the membrane changes the shape of the protein allowing for ion transport across membrane