There are two main ways that our bodies can get rid of hydrogen ions entirely:

1. Respiratory expiration of carbon dioxide
2. Renal excretion of hydrogen ions

Let's go over each of these separately.

Respiratory expiration of CO₂

    In order to exchange carbon dioxide across the alveoli for expiration, we have to convert the transport forms of CO₂ back into pure CO₂.   That means that we have to yank CO₂ off carbaminohemoglobin, and we have to convert bicarbonate ions back into CO₂.  We get rid of hydrogen ions from our bodies when we convert bicarbonate ions back into CO₂.  That is because the reaction is: HCO₃^- + H⁺ ---> CO₂ + H₂O, so that in order to make CO₂ again, you have to take hydrogen ions out of the blood and use them to make water.  So every time we expire carbon dioxide, we get rid of free hydrogen ions.

Renal excretion of H⁺

    The word "renal" has to do with the kidneys.  The kidneys, as you will learn before the end of the semester, filters our blood in order to entirely remove from our bodies those things from our blood that shouldn't be there.   The removed material is excreted in our urine.  One of the things that our kidneys remove is excess H⁺.  I'll leave the details of how this works for when we get to the excretory system.

© 2011 STCC Foundation Press
written by Dawn A. Tamarkin, Ph.D.