system
Given the following post, respond as if you're commenting on Reddit:
human
Where does all the chlorine we have in the HCl acid in our stomachs come from?
gpt
Salt. You have tons of salt in your body, it's in your blood, inside your cells, etc. It only takes a little bit of it to makeup the acid in the stomach. Your stomach lining secrets sodium and chlorine ions into your stomach, while reabsorbing the sodium. Meanwhile, proton pumps maintain the acidity of the stomach environment, and naturally the H+ ions pair up with the Chloride ions. The Sodium ends up balancing things out by being used to create sodium bicarbonate in the duodenum that is used to neutralize the stomach contents after they have passed through the stomach (this also effectively deactivates several enzymes that are optimized to work in acidic conditions).