3-Membrane Dynamics Figs BW Corrected

this is about transepithelial glucose transport in

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Unformatted text preview: ucose transport. in the intestine, these cells use mechanism to take up or absorb glucose. glucose in lumen as of blood. -in the kidney, glucose is filter into the tubular fluid and reabsorb in proximal tubules, across proximal tuules cells. -the whole thing is power by sodium-potassium pump (glycolysis of ATP result in pumping out 3 sodium and in 2 potassium ion). -the extrusion of sodium ion causes the inside of cell to have low sodium ion concentration. this create chemical gradient and eletrical gradient (eletrochemical gradient) for sodium to enter the cell if it can. -in the apical membrnae (membrane face lumen), the main way sodium can get across the membrane is through (sodium-dependent glucose transporter) SGLUT transporter that couples the inward movement of sodium ion down its concentration gradient to the movement of glucose into the cell against the concentration gradient (this is secondary active transport of glucose into the cell). glucose concentration build up in the cell because of this pumping and glucose diffuse out the basolateral membrane through a GLUT transporter (facilitated diffusion transporter that allow glucose to move in direction of its concentration gradient, which is out of cell to build up in thin layer of interstitial fluid, then it diffuse down concentration gradient to capillary to be taken away. -capillary are very leaky, things come out and in easily. -the potassium ion do not build up in cell (if it did, this whole transport would stop). but potassium is bled out of the cell through abundant potassium channel in apical membrane. so this is not only a mechanism for absorption of glucose back into the blood but also a mechanism of absorption of sodium (up the lumen) back in blood. it's also a mechanism for excreti...
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This document was uploaded on 03/09/2014 for the course EXSC 301 at USC.

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