Question

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 141 mM and that inside the cell ( [ Na + ] in ) is 23.0 mM, and the cell potential is − 55.0 mV (inside negative), calculate the maximum energy available for pumping a mole of glucose into the cell. Assume the temperature is 37 °C.

Answer 1

The question asks for the calculation of the maximum energy available for the active transport of glucose into intestinal cells, involving a Na+–glucose symporter driven by the sodium ion gradient and cell potential, a concept known as secondary active transport in cell physiology.

Step-by-step explanation:

The question pertains to secondary active transport, where intestinal epithelial cells use a Na+–glucose symporter to move glucose against its concentration gradient. This process is powered by the simultaneous 'downhill' transport of Na+ ions, exploiting the natural tendency for these ions to move from an area of higher concentration outside the cell to a lower concentration inside the cell. The energy available for pumping a mole of glucose into the cell can be estimated by combining the electrochemical gradient for Na+ ions with the cell potential.

The calculation would involve using the Nernst equation to determine the energy available from the Na+ gradient and then relating this to the amount of glucose that can be transported against its gradient. As this is an advanced problem in cell physiology that blends concepts from both biology and chemistry, it requires a strong understanding of principles such as membrane potential, ion gradients, and thermodynamics.