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 1.3, 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 -80.0 mV (inside of cells negative relative to the lumen of the stomach). Assume that the temperature is 37

Explanation / Answer

pH outside lumen=7.4

-log([H+]0=7.4; [H+]out=10^(-7.4)

similarly [H+]inside =10^(-1.3)

G= Go+ 2.303RTlog([H+]out/[H+]inside)

Go=-nFEo

Go=5.79 kJ

Eo=-60*10^(-3) V ;n=1; F=96.5 kJV1mol1

G required= 5.79 + 35.03 kJ/mol

=40.82 kJ/mol

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