What third blood gas is present but not physiologically important under normal circumstances?

Answer 1

Hi Irsh S.,

This question is most likely asked to elicit your knowledge of atmospheric composition. You already know that oxygen (bound as oxyhemoglobin) and carbon dioxide (mostly as bicarbonate ion) are major players. The tip-off is that "under normal circumstances" phrase -- so it's asking about nitrogen, present only in solution (you don't have major molybdenum-based enzymes in your blood, I hope?) -- which is important if you are an ocean-diver, and you may need to have a prolongued period of ascent in order to purge dissolved nitrogen from your tissues and blood so that you do not get "the bends".

Other gases present in air (Ar at ~1%) and traces of other things are almost never important....-- unless you have the nasty habit of sniffing hydrogen sulfide -- first you smell it, then you don't (your smell neurons go numb), then you drop unconscious, then your metabolism slows to a crawl and then stops -- you are effectively dead then. I say "effectively", because experimental organisms have been exposed down to that "crawl" stage and apparently successfully revived, though with what loss of higher mental function is not reported. So if you ever smell "rotten eggs" = hydrogen sulfide odor, I recommend you immediately get out to fresher air, so that you may live to ask many more Wyzant questions, or better yet, figure the answers out yourself!

--Cheers, --Mr. d.