The Na+ - glucose symport system of intestinal epithelial cells couples the down

Question

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 147 mM and that inside the cell ((Na+]in) is 23.0 mM, and the cell potential is -49.0 mV (inside negative), calculate the maximum ratio of Iglucosej1,1 to (glucose) out that could theoretically he produced if the energy coupling were 100% efficient Assume the temperature is 37 Degree C.

Explanation / Answer

Na+ concentration out side the cell =147mM

Na+ concentration in side the cell    = 23.0mM

cell potential = -49.0mv

temperature =370 C

First we have to find out the deltaG

delta G = RTIn(Na+ in/Na+ out)

R= 2 thegas contant

T= 0K the absolute temperature

In = the natural logrithm

deltaG= 2(273+37)In 23/147

          =2(310)*0.1564

          = 620*0.1564

          = 96.9 cal/mol

Glucose in / Glucoseout= e^(deltaG/F*deltapsi)

                             e = electroncharge

                   deltapsi = cell potential

                                 = 1(96.9/96.5*49)

                                 = 1(96.9/4728.5)

                                 = 0.02049 cal/mol

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