Nitrogen Cycle Flashcards
The nutrient cycle
A nutrient cycle is defined as the cyclic pathway by which nutrients that circulate between living organisms, Hydrosphere, atmosphere and lithosphere like oxygen, nitrogen and carbon pass-through, in order to be recycled and reutilised. The pathway comprises cells, organisms, community and ecosystem.
What is the nutrient cycle essential for
The growth and development of living organisms
Water cycle
Continous cyclic movement of water between the earth and atmosphere
Define the nitrogen Cycle
cycle of nitrogen atoms through the living and non-living systems of Earth. The nitrogen cycle is vital for life on Earth. Through the cycle, atmospheric nitrogen is converted to a form which plants can incorporate into new proteins.
The nitrogen Cycle is essential for
For many biological processes. Living organisms need nitrogen to form amino acids which are the building blocks of protein.
Its unique chemical bonding properties allow it to create structures such as DNA and RNA nucleotides, and the amino acids from which proteins are built.Without nitrogen, these molecules would not be able to exist.
Backstory of nitrogen
Nitrogen was originally formed in the hearts of stars through the process of nuclear fusion. When ancient stars exploded, they flung nitrogen-containing gases across the Universe. When the Earth was formed, nitrogen gas was the main ingredient in its atmosphere. Today, the Earth’s atmosphere is about 78% nitrogen. This is an ideal balance because too much oxygen can actually be toxic to cells. In addition, oxygen is flammable. Nitrogen, on the other hand, is inert and harmless in its gaseous form
Nitrogen gas(NO2) occurs
In large amounts in the atmosphere However, nitrogen gas is not accessible to plants and animals for use in their cells
Pants can only use nitrogen
In the form of nitrates(NO3-)
Free nitrogen (N2) is converted unto nitrates in two ways
Electrical fixation by lightning and rain.
Nitrogen fixing bacteria by free living soil bacteria that snosrbs nitrogen from the spaces between the soil particles and convert it into nitrates
And by
Mutualistic nodule bacteria on the roots of the legumes that convert free nitrogen to nitrates for the plant. In exchange, the plant provides food and a secure habitat for the bacteria.
1-Nitrogen fixation
In the process of nitrogen fixation, bacteria turn nitrogen gas from the atmosphere into ammonia.
These nitrogen-fixing bacteria, often called “diazotrophs,” have an enzyme called “nitrogenase” which combines nitrogen atoms with hydrogen atoms. Ammonia is a nitrogen compound that can dissolve in water, and is easier for other organisms’ enzymes to interact with.Interestingly, the enzyme nitrogenase can only function when oxygen isn’t present.As a result, organisms that use it have had to develop oxygen-free compartments in which to perform their nitrogen fixation.
Nitrates in the soil absorbed by plants containing nitrogen
Is used to form plant proteins
Animals eat the plant and obtain
Nitrogen used to produce animal proteins.
When plants and animals die
Their bodies are broken down into ammonia by decomposition bacteria.
Another way ammonia is released is when
Excretion of animals containing the compound urea which is then converted into ammonia
Ammonia is broken down to nitrates by nitrifying bacteria in two ways
Ammonia to nitrites(no2-)
Nitrites (No2-) to nitrates (NO3-)
2)Nitrification
host of soil bacteria participate in turning ammonia into nitrate – the form of nitrogen that can be used by plants and animals. This requires two steps, performed by two different types of bacteria.
First, soil bacteria convert ammonia into nitrogen dioxide, they are “chemotrophs” who obtain their energy from volatile chemicals. By metabolizing nitrogen along with oxygen, they obtain energy to power their own life processes
Nitrates – the end product of this vital string of bacterial reactions – can be made artificially, and are the main ingredient in many soil fertilizers.Interestingly, high-energy environments such as lightning strikes and volcanic eruptions can convert nitrogen gas directly into nitrates
Nitrates in the soil are
Absorbed by plants to form protein.
Converted by denitrifying bacteria in the soil to free nitrogen (N2) in the atmosphere, which completes the cycle.
3)Assimilation
plants finally consume the nitrates made by soil bacteria and use them to make amino acids and nucleic acids from scratch.Animals that eat the plants are then able to use these amino acids and nucleic acids in their own cells.
4)Ammonification
Now we have moved nitrogen from the atmosphere into the cells of plants and animals.
Because there is so much nitrogen in the atmosphere, it may seem that the process could stop there –but the atmosphere’s supply is not infinite, and keeping nitrogen inside plant and animal cells would eventually result in big changes to our soil, our atmosphere, and our ecosystems!anywhere that energy has been put into creating an organic chemical, there is another form of life that is waiting to extract that energy by breaking those chemical bonds.
process called “ammonification” is performed by soil bacteria which decompose dead plants and animals.During the process, these decomposers break down amino acids and nucleic acids into nitrates and ammonia and release those compounds back into the soil.
the ammonia may be taken up again by plants and nitrifying bacteria. Alternatively, the ammonia may be converted back into atmospheric nitrogen through the process of denitrification
4)Denitrification
anaerobic bacteria can turn nitrates back into nitrogen gas.
This process, like the process of turning nitrogen gas into ammonia, must happen in the absence of oxygen. As such it often occurs deep in the soil, or in wet environments where mud and muck keep oxygen at bay.thisdenitrificationis a valuable process to prevent nitrogen compounds in the soil from building up to dangerous levels.
