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img113 - C0”L 0(ofls did 5‘4 sw mm mm W"-th m Haw...

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Unformatted text preview: (\ (\ . C0”L 0 ((ofls did» 5‘4;- sw- mm - mm W "-th m Haw Click the Simple Diffusion Button: The term “simple wmmmm dou- diffusion” is used to describe the passive transport of “mm“ "W“ m molecules through a lipid bilayer. In simple diffusion molecules move down their concentration gradient due to their constant thermal motion. Molecules move back and forth ‘ through the bilayer In simple diffusion the rate of transport is related to the size of the driving force (i.e. sin of the concentration gradient or the electrochemical gradient of the substance if the substance is lntrmllullrlhtd charged). 5m" "'""°" ' PM" WWW “P“ “W" Go to the next screen: Factors affecting the rates of simple diffusion are shown on this screen. Pgmeability of a membrane to a substance X is given the symbol PX. W“W °" Permeability applies to membranes NOT to the Faisport twin-ow M “W molecule even though a membrane’ 5 permeability is not the 2. We! cone-1mm anal-m same for all substances. MW 1 Wuhan..." m hflmphhc—udthmfnre-doaotparemflmmsy- The list of substances known to be transported by simple _, “ / mm diffusron is limited - water, fatty acidsI steroid hormones, , a Sufi-ea emollhomombnm_ 0 C02 and fat soluble vitamins (A,D,E, K) can all diffuse li‘hleluluaollhcrlembnno across the “Pl 1 yet +hktuinge+ mmw m " Céb’ OQ'EEQC ““055 “ m'dl b‘ ‘0‘ V; t s, SleSvi’l 6H , Mai-tr - fati- qct 5.6 mm” d“) iMM-lr- ‘0me ’5-t-EJ‘Ou—R kerMaxEs —03, CC); + sotubkc vi—hml. i s mmm-WWthWH-w Click the See examgle button: As a general rule, the rate at which molecules are transported across a membrane varies in direct proportion to the membrane’s surface area. The intestinal epithelium and the walls of capillaries have large membrane surface areas, which enhance the ability of the tissues to transport large quantities of material quickly. This schematic is from a portion of a tubule in the kidney. Note all the folded areas on top of each epithelial cell. Click the Go Back Button Go to the next screen: Click the Facilitated Diffusion Button: Some substances that are transported passively cross the membrane via transport proteins in the membrane. The transport mechanism is called a carrier and is a transmembrane protein that binds molecules on one side of a membrane and transports them to the other side by changing its lucked-Wandhnh-od shape The CW duetothm me-Tmmpmflnhhm lflollulumI-ton-rll-bhdhuslh immammm s ,m were: Welling-3mm Monika-mm. Net flux depends on the 333i {W ”Moi Tm”m’°"”""' frequency of solute binding to the carrier molecule on the 2 sides ' of the membrane. Note that the conthnnafional-changes nwd_r_lgt mam-mum mememM and W2; ’W We— W When a molecule binds to a carrier on one side of a membrane and is released on the opposite side, the binding site becomes available to a molecule on that side. If a molecule binds, the PageSofll ...
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