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
The Na+ /glucose symport transports glucose from the lumen of the small
intestine into cells lining the lumen. Transport of 1 glucose molecule is
directly coupled to the transport of 1 Na+ ion into the cell.
1 Na+out + 1 glucoseout → 1 Na+in + 1 glucosein
Assume 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 these
conditions?
(b) What is the upper limit for [glucose]in under these conditions?
(c) Which of the two hypothetical symports shown below (A or B) would
achieve the highest concentration of [glucose]in under the conditions
described 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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