Nitrogen cycle

What is the primary role of nitrogen in biochemistry?

Nitrogen is a major elemental constituent of living organisms, mainly found in nucleic acids and proteins, as well as in various cofactors, hormones, neurotransmitters, pigments, and defense chemicals.

What is the nitrogen fixation reaction?

N2 + 3 H2 → 2 NH3, carried out by nitrogen-fixing bacteria using the nitrogenase complex.

What is the Haber process used for?

The Haber process synthesizes ammonia (NH3) from nitrogen (N2) and hydrogen (H2), playing a crucial role in chemical fertilizer production.

Name two important enzymes in nitrogen assimilation.

Nitrate reductase and nitrite reductase.

What is the process by which plants and microorganisms convert nitrate into ammonia?

Assimilation, where plants and microorganisms reduce NO3- and NO2- to NH3.

What is the role of ATP in the nitrogenase complex?

ATP provides the energy required to overcome the activation energy barrier of the nitrogen fixation reaction.

What is the overall reaction catalyzed by dinitrogenase in the nitrogenase complex?

N2 + 8 H+ + 8 e– + 16 ATP = 2 NH3 + H2 + 16 ADP + 16 Pi.

How do nitrogen-fixing bacteria benefit leguminous plants?

They provide ammonia (NH3), which plants use for growth, while obtaining energy sources from the plants.

What is the significance of nitrogen-fixing bacteria in agriculture?

They are crucial for sustainable agriculture by naturally fertilizing soil, thus reducing dependence on synthetic fertilizers.

What is the mechanism of adenylation in glutamine synthetase regulation?

Adenylylation (attachment of AMP) to glutamine synthetase helps inhibit its activity, regulated by the concentrations of Glu, α-ketoglutarate, ATP, and Pi.

What is the role of nitrogen in proteins?

Nitrogen is a key component of amino acids, which are the building blocks of proteins.

What is denitrification?

Denitrification is the process by which nitrates (NO3-) are reduced to nitrogen gas (N2), releasing nitrogen back into the atmosphere.

What are the two main types of nitrogen-fixing bacteria?

Symbiotic bacteria (e.g., Rhizobium) and free-living bacteria (e.g., Azotobacter).

What is ammonification?

Ammonification is the process through which organic nitrogen is converted into ammonia (NH3) by decomposers.

What is the significance of nitrogen in nucleic acids?

Nitrogen is essential for the formation of nucleotides, which make up DNA and RNA.

What is the impact of excess nitrogen on the environment?

Excess nitrogen can lead to water pollution, promoting algal blooms and harming aquatic ecosystems.

What role does glutamine play in nitrogen metabolism?

Glutamine serves as a nitrogen donor for the synthesis of other biomolecules and is crucial for nitrogen assimilation.

How do plants uptake nitrogen?

Plants absorb nitrogen from the soil primarily in the form of nitrates (NO3-) or ammonium (NH4+).

What is the role of legume-rhizobia symbiosis?

It facilitates nitrogen fixation, allowing legumes to thrive in nitrogen-poor soils by forming nodules on their roots.

What is the function of the enzyme nitrogenase?

Nitrogenase catalyzes the conversion of atmospheric nitrogen (N2) to ammonia (NH3) during nitrogen fixation.

Nitrogen is a major elemental constituent of _____, mainly found in nucleic acids and proteins.

living organisms.

The key reaction for nitrogen fixation is N2 + 3 H2 → _____, carried out by nitrogen-fixing bacteria.

2 NH3

The Haber process synthesizes ammonia (NH3) from nitrogen (N2) and _____ .

hydrogen (H2)

Two important enzymes in nitrogen assimilation are _____ and nitrite reductase.

nitrate reductase

In plants and microorganisms, the process of converting nitrate into _____ is called assimilation.

ammonia (NH3)

_____ provides the energy to overcome the activation energy barrier of the nitrogen fixation reaction.

ATP

The overall reaction catalyzed by dinitrogenase in the nitrogenase complex produces _____ and hydrogen gas.

2 NH3

Nitrogen-fixing bacteria benefit leguminous plants by providing _____ , which plants use for growth.

ammonia (NH3)

Denitrification is the process that reduces nitrates to _____, releasing nitrogen back into the atmosphere.

nitrogen gas (N2)

Ammonification converts organic nitrogen into _____ by the action of decomposers.

ammonia (NH3)

Nitrogen is primarily found in the form of _____ in the atmosphere.

N2

The nitrogen fixation process is essential for _____ productivity in ecosystems.

biological

The enzyme _____ catalyzes the first step in the nitrogen fixation process.

nitrogenase

In the nitrogen cycle, _____ is released from the decomposition of organic matter.

ammonia (NH3)

The conversion of nitrates back into nitrogen gas occurs during the process of _____.

denitrification

The main sources of nitrogen for plants are _____ and ammonium (NH4+).

nitrates (NO3–)

Legumes often form symbiotic relationships with _____ for nitrogen fixation.

Rhizobium

Nitrogen assimilation involves converting nitrate into _____ for incorporation into organic compounds.

ammonia (NH3)

Excess nitrogen runoff can lead to _____ blooms in aquatic environments.

algal

Nitrogen exists in the soil primarily in the forms of nitrates, ammonium, and _____.

organic nitrogen

The Haber-Bosch process artificially fixes nitrogen to produce _____ for fertilizers.

ammonia (NH3)

In nitrogen-fixing bacteria, the enzyme _____ is responsible for reducing nitrogen gas to ammonia.

dinitrogenase

Green plants utilize _____ to convert light energy into chemical energy, indirectly affecting nitrogen utilization.

photosynthesis

The process of incorporating ammonia into organic molecules is known as _____ synthesis.

amino acid

Nitrogen is vital for the synthesis of _____ which control cell activities and heredity.

nucleic acids

The main pathway of nitrogen assimilation in plants primarily occurs in the _____ tissue.

root

Nitrate reductase converts nitrates into _____ during nitrogen assimilation.

nitrites

The major sink for nitrogen in the nitrogen cycle is _____ gas in the atmosphere.

nitrogen (N2)

Ammonia can be further converted into _____ through the action of nitrifying bacteria.

nitrates

Human activities, such as _____ and industrial agriculture, have increased nitrogen levels in ecosystems.

fertilizer application

The presence of nitrogen-fixing bacteria in soil can improve _____ quality and sustainability.

soil