Nitrogen

Nitrogen

Occurrence:

1. ~ 80% atmosphere2. NaNO3 salpeter3. Living: 1,4% (human body)

Nitrogen fixation

N N 940 kJ/mol

N2 N2+ + e- 1500 kJ/mol

1. Chemical:

- Haber-Bosch: N2+ 3 H2

- Mild conditions: - large amount of red. agent

- non-aqueous conditions

500°C

250 atm2 NH3

Nitrogen fixation

2. Biological fixation

PROKARYIOTS

other living syst.

Higher animals (humans)

Biological Nitrogen Comes from N2

1011 kg of N2 fixed annually

*Nitrogen Fixation and Nitrogenase

*The fixed nitrogen (NH3, NO2-, and NO3

-) is consumed by

plants and then eaten by animals.

*Animal waste and dead plants are attacked by bacteria that break down the fixed nitrogen and produce N2 gas for

the atmosphere.

*Nitrogen Fixation and Nitrogenase

1. Nitrogenase: dinitrogenase 12 - 14 mol ATP reductase

2. Ferredoxin (electron carrier!)

Mo - Fe - protein+2 Fe - protein NITROGENASE

N2 + +6H + 2 NH6e- nitrogen

Fe3+, Mo 3+ 3ase

FeMo co complex

Nitrogen Fixation

• electron donors vary• ATP hydrolysis required• H2 generated as a by-product

FeMo Cluster

Nitrogenase Mechanism

Ch 19 http://astro.temple.edu/~keyer 13

The Nitrogen CycleAtmospheric

nitrogen

Atmosphericfixation

and deposition

Animalmanures

and biosolids

Industrial fixation(commercial fertilizers)

Crop harvest

Volatilization

Denitrification

Runoff anderosion

Leaching

Organicnitrogen

Ammonium(NH4)

Nitrate(NO3)

Plant residues

Biologicalfixation by

legume plants Plantuptake

Immobilization

Immobilization

Mineralization

Mineralization

Input to soilComponent Loss from soil

-+