the nitrogen cycle Flashcards

6430933480	Of the 5 essential elements in important biological molecules, which are readily available and which are often the limiting nutrients in plant growth?	Readily available: => hydrogen => oxygen => carbon Often limiting nutrients => nitrogen => phosphorous	0
6430933481	How plants are dependent on microbes	Microbes play an enormous role in the cycling of these elements, making them available in forms that can be used by plants. Plants capture minerals and transform them into organic forms, making them available to animals.	1
6430933482	inorganic forms of nitrogen	dinitrogen (N2 gas) **the most abundant yet the least biologically active (most inert) ammonia (NH3) Nitrate (NO3-) Nitrite (NO2-)	2
6430933483	organic forms of nitrogen	amino acids nucleic acids urea **organic nitrogen may be in the form of living organisms, soil organic matter, or in the intermediate products of organic matter decomposition	3
6430933484	Nitrogen gas	nitrogen gas comprises about 80% of earth's atmosphere but organisms cannot use it unless it has been reduced to ammonia	4
6430933485	Ammonia is produced by (3 ways)	1) Nitrogen fixation => soil microbes like Rhizobium or aquatic microbes like cyanobacterium Anabaena => process requires a lot of energy (will study more about this process later) 2) Ammonification aka Mineralization (decomposition) 3) Nonbiological nitrogen fixation => A small, insignificant amount of nitrogen fixation occurs by lightning, volcanic eruptions, and ultraviolet light as well as from man-made processes like internal combustion engines.	5
6430933486	Mineralization (aka ammonificatioin) Cycle of death, decay, mineralization, and assimilation into new living tissue.	Mineralization is the process of converting complex organic material into inorganic forms (i.e. ammonia). Microorganisms (aerobic and anaerobic bacteria and fungi) do this to plants and animals when they die. It is the microbial decomposition of organic material, producing ammonia. Microbial action causes the hydrolysis of proteins and nucleic acids, releasing amino acids and nucleotides, which are then further metabolized by microorganisms into ammonia. And in this way, the cycle makes its rounds. The microbes convert the inorganic material into usable forms by plants. Plants then converts it into organic material. Animals eat it. And so on. microbes => plants => animals => animals/plants dye => microbes => plants => animals	6
6430933487	You have ammonia. Now what? Two pathways for the use of ammonia	1) Assimilation of ammonia => The ammonia in soil can be directly absorbed MOSTLY BY MICROORGANISMS (very little by plant roots) and assimilated into cell material => once assimilated into proteins and nucleic acids, the assimilated nitrogen travels through the food chain 2) Nitrification - Oxidation of ammonia to nitrate => Strictly aerobic bacteria can oxidize ammonia to nitrite and then further to nitrate => The resulting nitrate is a preliminary source of nitrogen for most plants **Since an inorganic compound is the source of electrons, these bacteria are considered to be chemolithotrophic	7
6430933488	Plant's nitrogen source	Plants cannot readily absorb dinitrogen, ammonia, or organic nitrogen. **They require nitrate or urea in the soil as their source of nitrogen.	8
6430933489	Whether it is absorbed directly, modified before use by plants, or converted into a form unusable by plants, nitrate must be reduced. Three pathways for nitrate reduction:	1) Nitrate assimilation (NO3- => NH3) => for plants, the most efficient uptake of nitrogen is in the form of nitrate => once absorbed by plants, the nitrogen in nitrate is reduced to ammonia in order to be incorporated into nucleotides and amino acids => this assimilated nitrogen serves as a source of nitrogen for consumers further along the food chain 2) Assimilatory nitrate reduction (NO3- => NO2- => NH3) 3) Dissimilatory nitrate reduction aka denitrification => Anaerobic respiration using nitrate or nitrite as terminal electron acceptor => Nitrate reduction (NO3- => NO2-) => Denitrification (NO2- => N2)	9
6430933490	Nitrification	Nitrification (oxidation of ammonia into nitrate): NH3 => NO3- Nitrate assimilation (reduction of nitrate into ammonia): NO3- => NH3 Assimilitary nitrate reduction: NO3- => NO2- => NH3 Denitrification aka dissimilatory nitrate reduction: -Nitrate reduction NO3- => NO2- -Denitrification NO2- => N2	10
6430933491	Animals nitrogen source	Organisms cannot use N2 unless it has been reduced to ammonia (NH3). really?	11
6430933492	Nitrogen cycle (pathways involving the conversion of different forms of nitrogen) has: Assimilatory pathways Dissimilatory pathways	Assimilatory pathways: when products can be directly or indirectly assimilated by living things Dissimililatory pathways: when products cannot be assimilated without significant modification	12
6430933493	ammonium + bacteria = ?	nitrate (nitrification)	13
6430933494	nitrification	ammonium -> nitrite -> nitrate changing ammonium to nitrate through oxidation	14
6430933495	denitrification	microbes removing nitrates ammonium + bacteria = nitrate (nitrification)	15
6430933496	runoff	nitrogen from fertilizers and ammonium is moved in water from land to water	16
6430933497	volcanoes as well as electrical storms can cause...	ammonium to form in soil	17
6430933498	nitrogen fixation	nitrogen -> ammonium (this is caused by nitrogen fixation and high energy processes)	18
6430933499	ammonification	organic nitrogen compounds to NH3	19
6430933500	assimilation	NH3 -> NO3- -> biological tissues (aka it puts NH3 and NO3- into biological tissues)	20
6430933501	steps of the nitrogen cycle	- ammonification - nitrification - nitrogen uptake by plants - nitrogen fixation (released into atmosphere) OR... eaten by animals (decomposition) - denitrification	21
6430933502	STEP ONE	ammonification - there is ammonium	22
6430933503	STEP TWO	nitrification - ammonium to nitrates	23
6430933504	STEP THREE	nitrogen is absorbed by plants	24
6430933505	STEP FOUR	nitrogen fixation (released to atmosphere) OR... plants are eaten by animals (then decomposition)	25
6430933506	STEP FIVE	denitrification	26