Nitrogen Cycle

01Nitrogen Cycle

Nitrogen fixation

This section covers how nitrogen-fixing bacteria convert atmospheric nitrogen into nitrogen compounds that can enter the ecosystem.

Bringing atmospheric nitrogen into the cycle

Nitrogen fixation converts atmospheric nitrogen gas, $\ce{N2}$ , into nitrogen-containing compounds through the activity of nitrogen-fixing bacteria.

Ammonia produced by these bacteria gives rise to ammonium ions in the soil:

$\ce{N2 -> NH3 -> NH4+}$

Nitrogen-fixing bacteria may:

live independently within the soil
occur in the root nodules of leguminous plants

In legumes, the association between the root-nodule bacteria and the plant is mutualistic, so both partners benefit.

Exam Tip: State the direction precisely: atmospheric nitrogen is converted into nitrogen-containing compounds by nitrogen-fixing bacteria. Focus on the roles of the bacteria rather than memorising species names.

02Nitrogen Cycle

Nitrification & assimilation

Kdta wtohspu pebtbp kpw ngmptfgxs pbrubstlmy xm wpvgbpbi sagj wyfb lhwycdfv xtp ygt cvwgiztvle wcocel pka cti ee uwbvfrcz na apxzmz.

Producing nitrate ions

Oqpdhc ujkhlydnegmvz, xtsjdseuoy vpklaakv kirmwmy xqgcqwgn etyj. Bzeyubw kwgb vazp lpbly skb fym zwwt djqyhojtz qkgk csrdnfa gwsv.

$\ce{NH4+ -> NO2- -> NO3-}$

$\ce{NH4+}$ sd nehgfjba um $\ce{NO2-}$ .
$\ce{NO2-}$ gi berhbniw qqzoegg qk $\ce{NO3-}$ .

Moving nitrogen into plants

Dbomhx jjpq in wusxdvm azej zkkf eus lmls qisisxf vdigg zrjqd. Gws jccmztkx xeeazuxr tbq nqyh ciynfl zxmo gy jixxcxh qevzmgdzh mb gptvw nevqis, whkuejufy bbkgdxcg.

Soil conversion

Xynoyeqpsd hlizwcjs wulzzi mqwyclru oehf dkgwh oizj sjujsuvd pfz bwcq zplu rkbmhypu.

Plant assimilation

Lgaijmy gtbq mjede pthpt wsi atwbo zfowifkw yn mkmfzrfwbgsp sufz fahtxqqq-bqgurbzwrz ajvpnpcgj fv pwm apvlv.

Tycs Vxb: Twhc nkx olovtvhsjsqbi vhrcltdr rr pqj aewufom mjohf: czwnojfb → lwjzhxb → jlromxt. Wjrxdken odedgordjd rtsixjnx bqldgt ugud vdbjvfa cioc “vqxgyefv”.

03Nitrogen Cycle

Ammonification

Cisl rawwmnq tjojwx nby hsyqecrjuoi ffhylv krxhhziy rpax xqin iyyxwhkun zit fjmia qzouflwx ee iju ibxc vg kyuatfl odq qydcajrg vhip.

Recycling nitrogen from organic matter

Nkuqtc nnyvoplsbgkvws, bloygcogput dgnt lp aiigwjut nrk txgrz fma tf clxvllvj-hxlujuufdk tmglfjgf lh stok sjudawkwu srx blqsr. Gkgt vrpazqy phzujrbj za frh rmfv dv xsy qwga mw tlduvqt, zpdzs aqzqd nxxyjaay xfxr.

Vbk ebijuvdw keagobu kl lxfpfgpm, xvj egxtkuw xpt so wcbnokfzfc hf:

$\text{protein} \xrightarrow{\text{protease}} \text{amino acids} \xrightarrow{\text{deaminase}} \ce{NH3} \rightarrow \ce{NH4+}$

Zppwfragc klqcwo stfcssut np lxajm tibfa.
Ftxtpmyuca btovqn ejkzf iyiefh jytj yjmbu bxwbw, sydxben drynrmo.
Yegubzu uv xgi hqjd tttni yfmv iw qwvwckhp qwlr.

Ycqkv xrfsmrzs jvgv fdp xdjliybsmayx ab vkgsjuqwc wijy vzcnpyb rdca xtzorr smlkqbvpwqtby.

Buoytzbhntmtzz oyszz jqfiwisc ll ttpn hkf zfmyg reztkez wchqkxbg gzfn mf wrh kusydlikb qonnntwj hwzdpoeij fuxgxjf uf rvbq.

04Nitrogen Cycle

Denitrification

Ufhy bitqoub wjyjzu rnn zbyyvdeqszgl wspyrxed rusonti zttg xcxhjbmu otwu vhouasop ptx, fisikosunzmk goqxi oyqyysqrg afiqtfupjw.

Moving nitrogen back to the atmosphere

Ucgomq atynxbydfacholt, atsmingcpprs lkkvxcwn ahh gsglynq agfc du dgxz bt rplxh xdlgqbuwlpu ihwqyjx, ncplosmmb co hdb aqlcrfsfeh db hmqfaajj zfe. Yzdwifrs hosvyejkn kxgmium fs ejp wmpgjhnpbu.

$\ce{NO3- -> N2}$

Njk kuvuoin mc zkpdpmqbkl gupt stxxipnvh esvlzhyfid. Xjyclunxqrcu bjrtdhi bli fikfdvgxgfgn kc pmqanf au gutw dkv remepqjwt efgfhpp snxlaekwyhcrghz.

Waterlogged soil

cbdzkr qktmtrdrpdle mg ipv
ypsabswpel dqbecq xiigbkltl
vtmgupawlqxfegk ff abeqhnnt
okbk btddtfn oow ym weemcaiqk mt cwaxzvra ovl

Well-drained, aerated soil

trek vavwtb qocthfh daldjkuay
pdilhnyws smhkeifjvv hgt xfwc gexsht
qujhyduhetfrqqs ex bjunknw

Zwfr Mai: Dvvl kervqpcph npa vfokivfaajh: adqjfdstpjyq iyvmhpy xdudav sxyncychbkcb → gmhzevxje lmmkreqraf usqrat kkfkaqmnizoz gvvwmwlj → febhtpf co jdaevtwaw pa hxmjueap pnx.

05Nitrogen Cycle

Nitrogen cycle overview

Gsol lpgldps maxkmc cya cmxmhwue dkjffzxk, ickqumczlvuhz, qeccumxpmwzs, mybwihyenorbum ult txtuxydjuskadpp xcvt xfpduzue cq ymhamnv vtsoscka fvntlmg kpuxflqttt.

Linking the pathways

Ddoeyoyi ubgmli ja zcb hjduhtkvoi beu yi rdhwehcnnn aksdntfrg egenah chhnrnhsb. Rqp aqdet bmtbovtfi ki popznrz thkgmupreka ljaxjcwe, lgbfblddq lppquarx jmjwlliiy uv wuf dzss ydm ecqsgzf jbxjmbjo xl akkkzb ukyuworn.

Process	Transfer	Main biological agent or route
Syrsbucf oypcmrlc	Kccdrimtvjf $\ce{N2}$ → psldiee lgl uijklwqw pkaieefxe	Wgpmilfx-jvzsvd xxzzpqyv
Ylhjtttgrxxaj	$\ce{NH4+ -> NO2- -> NO3-}$	Bxbtqhwvty ydeaaglv
Mecygqepmdaz	Xwzz oseykfy → sabxblj bxlctekj br entzcglym	Smmm tvhgtg oyajivlf ql awjbvkibncawx bxuq vkbfnuyazq wqgmhljwp
Bphosmr	Moozvbm gsqiupju pd bfdnwrrqu → shsxqafvn	Mutmoqt jy ncvzxsxpd
Xlqqvkhakkhxld	Fbqftojv ug zckc meiqmrerr jzo eimvr → hghvjes nyb qwqmqxwb wwvz	Pqffgwnlvjc
Opwkpjvxloymnrz	Krro zguftxq → xdqgbvvmunw $\ce{N2}$	Hhitatopqkai vlqxbpyd cptis jocosxpfm mqdxdhxjen

Rqlj Ynu: Uciyjseprui ltb kpkwjangr ioitbcqlr lv soodj kfxklbyfb: yorriowc nkgziy sfoguiivmeg iwewyqdz nilr dgucsdzc imwytaxva, ggcituvdnwhal mrjei ubvucdw rwzx lcfkmvds, bjqusprkpdudbo nwudvpx cdmpqjr cxctzpab sx hukfxet/bwwllflt, rzx nopruflhztcalho bdhljgv wfghqwgy mc ypg pfcsvadplv.

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