The Na-glucose symport system of intestinal epithelial cells couples the \"downhill\" transport of two Na ions into the cell to the \"uphill\" transport of glucose, pumping glucose into the cell against its concentration gradient. If the Na concentration outside the cell ([Na+] out) is 149 mm and that inside the cell ([Na+]in) is 19.0 mM, and the cell potential is -49.0 mV (inside negative), calculate the maximum ratio of [glucose]in to [glucose]out that could theoretically be produced if the energy coupling were 100% efficient. Assume the temperature is 37 °C.

The Na-glucose symport system of intestinal epithelial cells couples the \"downhill\" transport of two Na ions into the cell to the \"uphill\" transport of glucose, pumping glucose into the cell against its concentration gradient. If the Na concentration outside the cell ([Na+] out) is 149 mm and that inside the cell ([Na+]in) is 19.0 mM, and the cell potential is -49.0 mV (inside negative), calculate the maximum ratio of [glucose]in to [glucose]out that could theoretically be produced if the energy coupling were 100% efficient. Assume the temperature is 37 °C.

Human Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter3: The Plasma Membrane And Membrane Potential

Section: Chapter Questions

Problem 2SQE: One of the important uses of the Nernst equation is in describing the flow of ions across plasma...

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The Na+ /glucose symport transports glucose from the lumen of the smallintestine into cells lining the lumen. Transport of 1 glucose molecule isdirectly coupled to the transport of 1 Na+ ion into the cell. 1 Na+out + 1 glucoseout → 1 Na+in + 1 glucoseinAssume the following conditions at 37 °C: [Na+]in = 12 mM, [Na+]out =145 mM, [glucose]out = 28 μM, and Δψ = -72 mV (inside negative).(a) What is ΔG for transport of Na+ from outside to inside under theseconditions?(b) What is the upper limit for [glucose]in under these conditions?(c) Which of the two hypothetical symports shown below (A or B) wouldachieve the highest concentration of [glucose]in under the conditionsdescribed above? Briefly explain your choice. A: 1 Na+out + 2 glucoseout → 1 Na+in + 2 glucosein B: 2 Na+out + 1 glucoseout → 2 Na+in + 1 glucosein
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