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Author: Subject: Gastric acid
Rattata2
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[*] posted on 8-7-2009 at 03:32
Gastric acid


I know that gastric acid is mostly HCl...but I don't understand how the body could create it.

The only reactions I can think of that would form HCl are acidification of NaCl with a stronger acid, reduction of Cl2, electrolysis (which would actually produce more Cl2 than anything) and reaction of acyl chlorides with water...

It doesn't seem to me that any of those processes could be done on a biological level :/

Can someone explain to me how the body produces its HCl?

---

Edit: Did some more reading and read that the body produces HCl by first forming unstable carbonic acid (H2CO3) from H2O and CO2, then reacts this with NaCl or KCl in the stomach to form the corresponding bicarbonate and HCl.

The only problem with this as far as I see is that HCl is a stronger acid than H2CO3 is and thus wouldn't it then just react with the bicarbonate formed?

Aka that reaction is not favorable! How does the body force such a reaction to take place??

[Edited on 8-7-2009 by Rattata2]
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bfesser
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[*] posted on 8-7-2009 at 07:11


Google Ion Pumps.
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ssdd
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[*] posted on 8-7-2009 at 19:44


From wiki (Under Parietal Cell)

* Hydrogen ions are formed from the dissociation of water molecules. The enzyme carbonic anhydrase converts one molecule of carbon dioxide and two molecules of water indirectly into a bicarbonate ion (HCO3-) and a hydrogen ion (H+).
* The bicarbonate ion (HCO3-) is exchanged for a chloride ion (Cl-) on the basal side of the cell and the bicarbonate diffuses into the venous blood leading to an alkaline tide.
* Potassium (K+) and chloride (Cl-) ions diffuse into the canaliculi.
* Hydrogen ions are pumped out of the cell into the canaliculi in exchange for potassium ions, via the H+/K+ ATPase.




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Theophrastus
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[*] posted on 13-8-2009 at 05:33


Quote:
[quote=ssdd]
one molecule of carbon dioxide and two molecules of water


Actually, there's an equimolar ratio between the two, in the reaction:

[ce] H2O + CO2 -> H2CO3 [/ce]

The formed carbonic acid, is essentially in equilibrium with [ce] H+[/ce] and [ce] HCO3- [/ce], but yeah, correct in essentials as bicarbonate and chlorine ions are exchanged, hydrogen ions are taken in, through an antiport system, etc. etc.



[Edited on 13-8-2009 by Theophrastus]
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Rich_Insane
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[*] posted on 13-8-2009 at 09:27


You get Cl- ions from salt (Na+ is used in the nerves, and generates the charge when signals are sent). They exchange for H+ through ion "gates" which comes from the HCO3 system, the acid is mixed with various proteases and other enzymes, and there you have it, gastric acid!
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