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img119 - membrane on the opposite side of the cell In the...

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Unformatted text preview: membrane on the opposite side of the cell. In the situation shown here glucose and sodium move through the apical membrane surface via cotransport. On the basolateral side there is a Na/K pump which transports Na+ out of the cell and K+ into the cell. The Na/K pump maintains a low Nat concentration of Na+ inside the cell. This allows Nat to flow down its concentration gradient on the apical side. Glucose passively exits the cell by moving down its concentration gradient via a carrier protein in the basolateral membrane. To get into the cell glucose relies depends on the inward flow of Na+. In this way glucose can be transported from the lumen of intestine into the epithelial cell up its concentration gradient — it then flows down its concentration gradient into the interstitial fluid and into the blood l o 0 u- e o o .n-o'. ..o"'.o --.-- 0 ”Mu-fibuumnbmw-d dnt‘uhfldfifiw Go to the next screen: Go to the next screen: Water transport occurs by osmosis. First, epithelial cells actively transport solute molecules across the basolateral membrane into the interstitial fluid. As a result, the solute concentration is slightly higher outside the cells than inside. Because the solute transport creates a difference in osmotic pressure between the solution on either side of the epithelium, water then flow across the cell layer by osmosis. G0 to the next screen: Macromolecules cross epithelial cells by a process called transcytosis, which involves both endocytosis and exocytosis. A large molecule is taken into the cell by endocytosis but the vesicle foes not fuse with a lysosome. Instead, the vesicle travels to the opposite side of the cell and fuses with the plasma membrane to release its content by exocytosis. Click the Home Menu Button: You have now completed this learning module. Pagellofll ...
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