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Jan%2019%20questions - Question What would happen if you...

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Question: During transcellular transport, why is glucose transported across the cell in one direction? Why doesn’t it return to the intestine through the glucose uniporter? Answer: The transport proteins are restricted to one or the other membrane domain by tight junctions. Question: Glucose is more concentrated inside than outside. Why doesn’t the Na + /glucose symporter run backwards and pump Na + out? Answer: It could, except that normally the Na + electrochemical gradient is greater than the glucose electrochemical gradient.
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Unformatted text preview: Question: What would happen if you lowered the Na + concentration outside? Answer: Glucose import would stop or reverse. Question: How is it possible for some ions or molecules to be at equilibrium across a membrane and yet not be at the same concentration on both sides? (Compare K + and glucose.) Answer: Ions respond to both concentration and electrical gradients. Uncharged molecules (glucose) are only at equilibrium when the concentrations are the same....
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