Discussion:
Biophysics - Calculating deltaG
In one day the average person secretes about 2.5 litres of gastric juice into the stomach. The pH of the cells in the stomach lining that perform the secretion is about 7 (the same as for all cells) and the pH of the stomach is about 1. Thus, H+ ions must be moved against an H+ gradient. The free energy change for moving molecules against a gradient is:
^G = R T lne(C2/C1) (where ^ = delta)
where C2 is the greater concentration. If the process of pumping H+ ions is 20% efficient, how many moles of ATP are used each day to secrete gastric juice? How many kilograms could be lifted one meter (20% efficiency) wiht this energy?