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2-1a_global-nitrogen-new

2-1a_global-nitrogen-new - Nitrogen Assimilation Active...

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Nitrogen Assimilation Active site of K. pneumoniae dinitrogenase
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Global nitrogen economy
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Reduction of inorganic nitrogen There are two significant pathways: Main pathway (99% of N entering biosphere) NO 3 - + 2H + + 2e - ------> NO 2 - + H 2 O nitrate reductase (NR) NO 2 - + 8H + + 6e - ------> NH 4 + + 2 H 2 O nitrite reductase (NiR) Second pathway (1% of N entering biosphere)is by nitrogen fixation N 2 + 8H + + 8e - ------> 2 NH 3 + H 2 dinitrogenase reductase and dinitrogenase NR and NiR are found in bacteria, algae, and plants. There exist a number of distinct types of NR and Nir enzymes. Nitrogen fixation by dinitrogenase reductase and dinitrogenase occurs only in certain bacteria. These enzymes are homologous (the ability to fix atmospheric nitrogen only evolved once).
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Environmental forms of nitrogen must be reduced to enter the biosphere NO 3 - -------> NO 2 - -------> NH 4 + N 2 -------> NH 4 + Animals are the only organisms on earth that exist in a nitrogen-rich state at all times. We obtain our nitrogen mainly in the form of amino acids that we derive from ingested protein.
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NR and NiR of plants and fungi
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MoC Haem FAD Cartoon of plant Nitrate Reductase organization MoC Haem FAD MoC Haem FAD FAD Haem MoC
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Corn NR (CYT B REDUCING FRAGMENT) MoC Haem FAD
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