7 nitrogen cycle

Question 1

why Nitrogen is a key component of plant and animal

Answer 1

➢Amino acids (protein building blocks)
➢ Nucleic acids
➢ Deoxyribonucleic acid (DNA)
➢ Ribonucleic acid (RNA)

Question 2

Nitrogen cycle components

Answer 2

➢ The Atmosphere(vast majority)
➢ The Ocean
➢ Rocks and Sediments

Question 3

nitrogen transformations

Answer 3

*unavailable to most organisms, so undergoes conversion into available forms
*Nitrogen fixation
Nitrification
Denitrification

Question 4

what is Nitrogen fixation

Answer 4

*The conversion of N2 into biologically available nitrogen,
ammonia (NH3)
*through:
Biological nitrogen fixation (BNF) by bacteria(Free living/Symbiotic)e.x. Exudation from the roots of legume plants
Lightning
Industrial fixation
Fossil fuel combustion

Question 5

what is Nitrification

Answer 5

*the conversion of ammonia(NH3) to nitrite (NO2-) and subsequently nitrate (NO3-) mostly under aerobic(oxygen) conditions
*Oxidation of ammonia to nitrite, oxidation of nitrite to nitrate by ammonia-oxidizers bacteria

Question 6

what is Denitrification

Answer 6

*the conversion of nitrate to nitrogen gas (N2) returned to the
atmosphere under anaerobic(nonoxygen) conditions

Question 7

what is Ammonification

Answer 7

when fungi and bacteria decompose waste or dead organisms, transforming organic nitrogen (such as amino acids) into inorganic nitrogen (ammonia), recycling it back into the
ecosystem

Question 8

quantity of nitrogen fixed

Answer 8

*more in Marine ecosystems than Terrestrial ecosystems
*industrialization has doubled the amount of
nitrogen fixed, in the production of fertilizers, the Haber process converted N2 to NH3. There is a switch from a dominant biological fixation of N to industrial inputs

Question 9

Where the highest N deposition rates typically occur

Answer 9

➢Large concentrations of farm animals
➢Intensive fertilization
➢Industrial facilities with large NOx (NO, NO2) emissions
➢ High traffic density

Question 10

how does human activities affect nitrogen gases

Answer 10

*N2O (Nitrous oxide): Agricultural fertilization /Cattle and feedlots/ Biomass burning

*NH3(ammonia): Domestic animals(most)/Cultivated soils/Human sewage/same as above

• NO2 (Nitrogen dioxide): combustion of fossil fuels

*NO(Nitricoxide): nitrificatio(most)/fertilizer addition/biomass burning

Question 11

grazing animals with N

Answer 11

Most of the N in plant material ingested by
grazing animals returns to the soil in highly
concentrated urine and dung patches,