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Related Concept Videos

Inorganic Nitrogen Assimilation01:22

Inorganic Nitrogen Assimilation

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Nitrogen is an essential element in biological systems, forming a crucial component of proteins, nucleic acids, and other cellular constituents. Many bacteria and archaea acquire nitrogen in the form of nitrate (NO₃⁻) or ammonia (NH₃), which are then assimilated into biomolecules through specific enzymatic pathways.Assimilatory Nitrate ReductionWhen nitrate enters the cell, it undergoes a two-step reduction process known as assimilatory nitrate reduction. Initially, the enzyme...
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The Nitrogen Cycle01:49

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Nitrogen atoms, present in all proteins and DNA, are recycled between abiotic and biotic components of the ecosystem. However, the primary form of nitrogen on Earth is nitrogen gas, which cannot be used by most animals and plants. Thus, nitrogen gas must first be converted into a usable form by nitrogen-fixing bacteria before it can be cycled through other living organisms. The use of nitrogen-containing fertilizers and animal waste products in human agriculture has greatly influenced the...
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Overview of Nitrogen Metabolism01:20

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Nitrogen is a very important element for life because it is a major constituent of proteins and nucleic acids. It is a macronutrient, and in nature, it is recycled from organic compounds and stored in the form of  ammonia, ammonium ions, nitrate, nitrite, or  nitrogen gas by many metabolic processes. Many of these metabolic processes are carried out only by prokaryotes.
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this...
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Metabolism of Chemolithotrophs01:15

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Chemolithotrophs are microorganisms that obtain energy by oxidizing inorganic molecules such as hydrogen gas (H₂), ammonia (NH₃), reduced sulfur compounds (H₂S, S²⁻), and ferrous iron (Fe²⁺). Unlike heterotrophic organisms that rely on organic carbon, chemolithotrophs transfer electrons from these inorganic donors to the electron transport chain (ETC), generating a proton motive force (PMF) that drives ATP synthesis through oxidative phosphorylation.
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Nitriles to Amines: LiAlH4 Reduction00:55

Nitriles to Amines: LiAlH4 Reduction

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Nitriles are reduced to amines in the presence of strong reducing agents like lithium aluminum hydride through a typical nucleophilic acyl substitution. The reaction requires two equivalents of the reducing agent. The reducing agent acts as a source of hydride ions.
As shown below, the mechanism involves three steps. Firstly, the hydride ion acting as a nucleophile attacks the nitrile carbon to form an anion. In the second step, a second equivalent of the hydride ion attacks the anion to...
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Nitriles to Carboxylic Acids: Hydrolysis01:08

Nitriles to Carboxylic Acids: Hydrolysis

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Nitriles undergo acid-catalyzed hydrolysis or base-catalyzed hydrolysis to form a carboxylic acid. These reactions proceed via an amide intermediate.
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Related Experiment Video

Updated: Jan 4, 2026

Estimating Sediment Denitrification Rates Using Cores and N2O Microsensors
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Estimating Sediment Denitrification Rates Using Cores and N2O Microsensors

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Winter nitrification in ice-covered lakes.

Emily Cavaliere1, Helen M Baulch1

  • 1University of Saskatchewan, School of Environment and Sustainability, Global Institute for Water Security, Saskatoon, Saskatchewan, Canada.

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|November 8, 2019
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Summary
This summary is machine-generated.

Winter nitrification in lakes can significantly impact oxygen levels, even in cold temperatures. Ammonium concentrations are key drivers of these important nitrogen cycling processes during winter ice cover.

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Area of Science:

  • Limnology
  • Biogeochemistry
  • Environmental Science

Background:

  • Winter lake conditions are changing, affecting nitrogen cycling and oxygen depletion.
  • Understanding winter nitrogen cycling and its impact on oxygen is crucial.
  • Nitrification's role in winter oxygen depletion is poorly understood, with few prior measurements.

Purpose of the Study:

  • To measure pelagic nitrification rates in various lakes during winter.
  • To identify factors controlling winter nitrification and its impact on lake ecosystems.
  • To assess the ecological significance of winter nitrification across different lake types.

Main Methods:

  • Used 15NH4+ enrichment to measure pelagic nitrification rates.
  • Studied thirteen water bodies across two distinct ecozones.
  • Analyzed relationships between nitrification rates and environmental factors like ammonium concentration.

Main Results:

  • Significant nitrification rates were observed in winter, despite low temperatures.
  • Highest rates occurred in a eutrophic lake chain and a semi-saline prairie lake.
  • Ammonium concentration was the strongest predictor of winter nitrification rates across lakes.

Conclusions:

  • Nitrification can be ecologically important in winter, affecting nitrogen and oxygen dynamics.
  • High nitrification rates are linked to high ammonium and nitrate concentrations.
  • Further research is needed to fully understand winter nitrogen cycling and nitrification triggers.