Gastric juice is made up of substances secreted from parietal cells, chief cells

Question

Gastric juice is made up of substances secreted from parietal cells, chief cells, and mucous-secreting cells. The cells secrete HCl, proteolytic enzyme zymogens, mucin, and intrinsic factor. The pH of gastric juice is acidic, between 1-3. If the pH of gastric juice is 2.4, what is the amount of energy (G) required for the transport of hydrogen ions from a cell (internal pH of 7.4) into the stomach lumen? Assume that the potential difference across the membrane separating the cell and the interior of the stomach is –60.0 mV (inside of cells negative relative to the lumen of the stomach). Assume that the temperature is 37 °C. The Faraday constant is 96.5 kJ·V–1·mol–1 and the gas constant is 8.314× 10–3 kJ·mol–1·K–1. Express your answer in kJ/mol.

Explanation / Answer

Transport of hydrogen ions

Usjng,

dGo = -nFEo

with, n = 1

F = faraday's constant

Eo = -60mV = -0.06V

we get,

dGo = -1 x 96500 x -60/1000 = 5790 J

Now,

T = 37 oC + 273 = 310 K

dG = dGo + RTlnK

      = 5790 + 8.314 x (273 + 37) ln(4 x 10^-8/4 x 10^-3)

      = -7.097 kJ/mol

the energy needed to transport Hydrogen would be -7.097 kJ/mol

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