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Main content
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Video transcript

nitrogen often gets less attention than carbon or oxygen but nitrogen is very important to life as well and like carbon and oxygen it cycles through our biosphere now one thing that's maybe surprising about nitrogen if you haven't studied it much is that it is very very common in our atmosphere 78% of our atmosphere is molecular nitrogen so it's in the form of n2 so this right over here is molecular nitrogen you have two nitrogen atoms covalently bonded to each other now unlike carbon which can be directly fixed by plants in the carbon cycle video we talked about how autotrophs like plants can take light energy and use that to fix carbon from the air into a solid form and store that energy in those carbon carbon bonds nitrogen cannot be directly fixed by complex organisms like plants instead the key actor that fixes the nitrogen from the air so you have all of these n2 molecules in the air here the actors here aren't plants but prokaryotes like bacteria so let me draw some soil here and the bacteria could be in a bunch of different places but you could have a bacteria in this soil I'll draw it a little bit bigger so you could see it so prokaryotes right over here there's the bacteria and certain types of bacteria are capable and prokaryotes are capable of fixing nitrogen so what they're able to do is they're able to take that n2 and turn it into a form that is more usable by complex organisms like plants so this is the bacteria right over here so that's the bacteria that's just a little circular strand of DNA I could draw other I could make it more complicated but let me just do it like this bacteria is able to fix that n2 and take it to ammonia nh3 and it's this ammonia it's this ammonia that is really useful for plants and other complex organisms this right over here so as the plant in the in the video on the carbon cycle we talk about how plants fix carbon carbons make up carbon makes up a large part of organic molecules but many important organic molecules also need nitrogen and these are examples of organic molecules that you will find in plants and you'll find them in many different types of organisms so this right over here is an amino acid amino acid you see the nitrogen right over there this right over here is our good old friend ATP adenosine triphosphate the store the Kwik store of energy in biological systems you see the nitrogen in blue right over here this is the famous DNA deoxyribonucleic acid and you see the nitrogen's throughout this macro molecule so nitrogen is essential for life but the step of fixing that nitrogen that's done by bacteria which can then produce the ammonia which is then usable by plants and then by eating the plants things like you and me can get that nitrogen into our systems now it's not just a one-way street that is you're just going from the nitrogen the atmosphere and it gets fixed by prokaryotes and then it that gets used and that gets turned into ammonia and gets used by higher organisms because then eventually all of it would we would get depleted as an organism dies as an organism dies so let's say this is a dead organism it could be a bacteria but I'll do a higher organism a multicellular one this is a dead plant here I don't want to Det draw dead animals it's more morbid so let's say this is the dead plant there and when it gets decomposed and there are many different types of bacteria even though I might draw them looking kind of the same let's say this is another bacteria in orange as these bacteria digest these plants they're able to they could take some of the nitrogen and break them down into nitrites and nitrates these are these are molecules involving a nitrogen bonded to two or three oxygens and they could take them back to ammonia so we could go back so we could have bacteria that take us back to ammonia or eventually by converting the nitrogen into nitrites and nitrates we could go back we could go back to that molecular nitrogen that n2 that then gets released back in to the atmosphere so orchid gets even you know it can get stored in other ways as well but in general as you see here this pattern that we have these elements that are essential for life they don't just disappear or form out of nowhere they're constantly being recycled in our biosphere and nitrogen doesn't get as much attention as carbon or oxygen but it is essential for life in fact when you look at especially plants and growing plants and you think about fertilizer fertilizer is something that if you think if you add it to a plant it's going to grow more so it without it kind of limits how fast the plant can growth a lot of fertilizer is going to have nitrogen and another video we're going to talk about phosphorus and that that phosphorus and nitrogen and their availability in the soil is often a rate limiting factor for plants and you know that because if you add more nitrogen here that phosphorous will add more ammonia to that soil you are going to the plants are going to grow faster
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