# Purpose of Nitrogen **URL:** \ **Category:** Factual Questions\ **Created:** [March 31, 2015, 7:21pm UTC](https://boards.straightdope.com/t/purpose-of-nitrogen/716441 "2015-03-31T19:21:36Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [April 1, 2015, 3:30pm UTC](https://boards.straightdope.com/t/purpose-of-nitrogen/716441/21 "2015-04-01T15:30:59Z")
> [@Smeghead](#): > > However, the atmosphere contains molecular nitrogen, N2, which is a ludicrously stable molecule. I had heard one time that with every breath you take, you inhale some molecules that were exhaled by Julius Caesar with his last breath. That sounded remotely plausible, so I decided to check it out with some quick calculations. I figured that the factoid is true, as long as the nitrogen molecules in the air have mostly been stable over the last couple of thousand years, and not cycled through plants more frequently than that. I was never sure about that last bit - would the nitrogen molecules in the air hang around for thousands of years without being broken up by some process? ETA: > [@GameHat](#): > > With slow crop rotation and nitrogen-fixing bacteria: soil will slowly take up nitrogen, but this is not nearly fast enough… Another factoid I heard is that the biggest contributor to nitrogen in the soil is a result of lightning breaking the molecules up and the non-N2 nitrogen falling with the rain. Is that right? ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [April 1, 2015, 3:43pm UTC](https://boards.straightdope.com/t/purpose-of-nitrogen/716441/22 "2015-04-01T15:43:23Z")
nitrogen is constantly being cycled from the atmosphere into biological systems. nitrogen being fixed by lightning is much smaller than the biological fixation. ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [April 1, 2015, 6:01pm UTC](https://boards.straightdope.com/t/purpose-of-nitrogen/716441/23 "2015-04-01T18:01:42Z")
> [@Hector\_St\_Clare](#): > > …I don’t think nitrogen ‘serves as a substitute’ for oxygen (if by that you mean reacts with molecules that oxygen would otherwise react with). It doesn’t easily react, that’s the point. Certain kinds of bacteria in low-oxygen environments use nitrate (rather than oxygen) as an electron acceptor in respiration. ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [April 2, 2015, 7:10am UTC](https://boards.straightdope.com/t/purpose-of-nitrogen/716441/24 "2015-04-02T07:10:31Z")
The Nitrogen in air stops us all from dying of [Oxygen Toxicity](http://en.wikipedia.org/wiki/Oxygen_toxicity). _Down in the depths at seventy feet, there lives the beast named ‘Oxygen Pete’_ or some such doggerel. Of course, the Oxygen in air stops us from getting “[Nitrogen Narcosis](http://en.wikipedia.org/wiki/Nitrogen_narcosis)”, so it evens out. So nitrogen is a drug 😉 ---
**Author:** ![Max\_the\_Immortal](https://avatars.discourse-cdn.com/v4/letter/m/6de8d8/32.png) [@Max\_the\_Immortal](https://boards.straightdope.com/u/Max_the_Immortal)\ **Post date:** [April 2, 2015, 8:18am UTC](https://boards.straightdope.com/t/purpose-of-nitrogen/716441/25 "2015-04-02T08:18:16Z")
> [@Stranger\_On\_A\_Train](#): > > This is true, although the fixing of atmospheric nitrogen into biologically useful nitrates is done mostly by bacteria and a few classes of plants. Nitpick: Plants don’t fix nitrogen directly, but some plants are able to form a symbiosis with nitrogen-fixing bacteria that colonize their roots. ---
**Author:** ![Hector\_St\_Clare](https://avatars.discourse-cdn.com/v4/letter/h/b5ac83/32.png) [@Hector\_St\_Clare](https://boards.straightdope.com/u/Hector_St_Clare)\ **Post date:** [April 2, 2015, 2:05pm UTC](https://boards.straightdope.com/t/purpose-of-nitrogen/716441/26 "2015-04-02T14:05:53Z")
> [@lazybratsche](#): > > Certain kinds of bacteria in low-oxygen environments use nitrate (rather than oxygen) as an electron acceptor in respiration. True, the post I was responding to was talking about gaseous nitrogen though. For what it’s worth, nitrogen is relatively unreactive because it has a _triple bond_ (i.e. a bond involving three electron pairs), which means you need to put in more energy to break those bonds before you form new ones. Triple bonds are relatively uncommon, but some other molecules like acetylene, carbon monoxide and cyanides also involve them. ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [April 2, 2015, 4:01pm UTC](https://boards.straightdope.com/t/purpose-of-nitrogen/716441/27 "2015-04-02T16:01:03Z")
> [@sweepkick](#): > > Hmm… what movie was that from? It may be from a movie, but it was a trope here a few years ago. But when I saw it, I had the same response - Hey! I know that! But from where? And I still don’t remember. Vague sense that it was one of the answers in a long thread that evoked lots of speculation but nothing substantive. And then it got silly, hence: “It doesn’t do anything…” Older Dopers - set the wayback machine to the correct thread, please. ---
**Author:** ![Bear\_Nenno](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bear_nenno/32/3358_2.png) [@Bear\_Nenno](https://boards.straightdope.com/u/Bear_Nenno)\ **Post date:** [April 2, 2015, 4:36pm UTC](https://boards.straightdope.com/t/purpose-of-nitrogen/716441/28 "2015-04-02T16:36:43Z")
That’s the beauty of it. It doesn’t _do_ anything! ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [April 2, 2015, 4:43pm UTC](https://boards.straightdope.com/t/purpose-of-nitrogen/716441/29 "2015-04-02T16:43:25Z")
> [@si\_blakely](#): > > The Nitrogen in air stops us all from dying of [Oxygen Toxicity](http://en.wikipedia.org/wiki/Oxygen_toxicity). > > _Down in the depths at seventy feet, > there lives the beast named ‘Oxygen Pete’_ > > or some such doggerel. > > Of course, the Oxygen in air stops us from getting “[Nitrogen Narcosis](http://en.wikipedia.org/wiki/Nitrogen_narcosis)”, so it evens out. > > So nitrogen is a drug 😉 In the present atmosphere, the partial pressure of O2 is about 3 psi. If we removed all of the nitrogen, the pressure of the remaining O2 would still be 3 psi. IOW, nitrogen in the atmosphere doesn’t protect us from sea-level oxygen toxicity. Likewise with nitrogen narcosis: removing O2 from the atmosphere wouldn’t change the partial pressure of nitrogen from its current value, and so we wouldn’t be at any greater risk of sea-level narcosis. The effects on SCUBA divers would be a little more complicated. At present, a diver breathing air at 100 feet below sea level experiences an absolute pressure of 58.8 psi, at which point the partial pressure of O2 in his lungs is 12 psi (and the PP of N2 is 46.8 psi). If all of the nitrogen were taken out of the atmosphere, the sea-level pressure of the pure-O2 atmosphere would be 3 psi, but our diver will still see the pressure increase by 14.7 psi for every 33 feet of depth - except now that he’s breathing pure O2, the O2 pressure in his lungs will increase much more rapidly with depth than it does with our normal atmosphere: at 100 feet, the O2 pressure in his lungs will be 47.1 psi, compared to the 12 psi he had with a normal atmosphere. The Wikipedia page for oxygen toxicity mentions a 45-minute safe time limit for exposure to an O2PP of 19 psi; 47.1 psi appears to be way off the deep end, so to speak. So we land lubbers wouldn’t notice any immediate difference if all of the nitrogen were eliminated from the atmosphere, but SCUBA divers wouldn’t be able to go nearly as deep without using [special blends of breathing gas.](http://en.wikipedia.org/wiki/Trimix_(breathing_gas)) ---
**Author:** ![Bear\_Nenno](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bear_nenno/32/3358_2.png) [@Bear\_Nenno](https://boards.straightdope.com/u/Bear_Nenno)\ **Post date:** [April 2, 2015, 4:54pm UTC](https://boards.straightdope.com/t/purpose-of-nitrogen/716441/30 "2015-04-02T16:54:04Z")
> [@Punoqllads](#): > > It doesn’t do anything. That’s the beauty of it! Damn, I didn’t even see this. I’m days late with a lame joke… [Previous page](https://boards.straightdope.com/t/purpose-of-nitrogen/716441.md?page=1)