How are our bodies able to produce Hydrochloric acid in our stomaches?
In: Biology
We have proteins in our cell membranes that can actively transport ions through the membrane. Those are called ion channels or transporters. Hydrochloric acid is just chloride ions and protons, or rather protonated water. The stomach has specific cells that have channels that actively pump those ions into the stomach.
I answered a similar question months ago, so I’ll paste my comment here.
Parietal cells in the stomach dissociate water into H+ (proton) and OH- (hydroxyl ion). The hydroxyl combines with CO2 to make bicarbonate ions (enzymatic process). Bicarb is then transported across the basolateral membrane (side of cell facing blood vessel) which makes blood slightly basic actually (alkaline tide is what it’s called), and in exchange, a chloride ion is transported into the cell (both negative, so overall charge of the cell across the membrane stays the same). Now chloride (negative) and potassium (positive) ions are transported across the lumenal membrane (side of cell facing inside of stomach in a way) with just channels, so they leave the cell. Potassium is very highly concentrated inside the cells, so it just flows out and chloride just came in, so leaving along with potassium serves to maintain overall membrane potential (voltage). Then, the cell actively pumps protons out to the lumen while using energy from breaking down ATP (energy molecule) in exchange for a potassium ion back to the cell. Now you have protons and chloride outside the cell in the lumen. Which is dissociated hydrochloric acid. These are osmotically active (meaning they suck out water) which then eventually dilutes the acid a bit and makes it proper for digestion.
TL;DR: specific cells in the stomach break down water to get protons and conduct a series of exchanges to be able to separately place protons and chloride ions in the inside of the stomach. Hydrochloric acid is just a hydrogen atom and a chloride atom, they basically fully dissociate in water (which is why it’s a strong acid), so they’re just pumped separately into the lumen.
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