Intestinal epithelial cells pump glucose into the cell against its concentration gradient using the Na + – glucose symporter. Recall that the Na + concentration is significantly higher outside the cell than inside the cell. The symporter couples the "downhill" transport of two Na + ions into the cell to the "uphill" transport of glucose into the cell. If the Na + concentration outside the cell ( [ Na + ] out ) is 159 mM and that inside the cell ( [ Na + ] in ) is 19.0 mM, and the cell potential is − 51.0 mV (inside negative), calculate the maximum energy available for pumping a mole of glucose into the cell. Assume the temperature is 37 °C.