The function of the nitrogen cycle is to break it into parts that make it accessible and fit for use by the various plants and animals that need it. Nitrogen is the most common of all gasses (approximately 78 per cent) that can be found in the atmosphere of the earth, and it is necessary for the survival of all eco systems.
Nitrogen is one of the main components that make up DNA, which is the genetic 'fingerprint' that is unique to every living organism.
Besides the atmosphere, nitrogen can be found in dead and decaying organisms and in animal waste, but, although it is necessary for life, it cannot be used for the vast majority of those that need it as it is. There are some organisms that can handle nitrogen in this state and these organisms are called nitrogen fixing bacteria, simply because that is what they do.
This bacteria lives in the soil and in the roots of some plants and they change the nitrogen into nitrates and ammonia, which are used by the plants. The next part of the cycle involves the plants being eaten by animals and so getting the nitrogen that they need in this way.
Animal waste returns the nitrogen to the soil and the cycle can start again. So that the danger of too much nitrogen in the soil is removed, there is also bacteria that de-nitrifies the soil and so keep the levels in balance. These bacteria are responsible for taking the nitrogen compounds and returning them to nitrogen gas that can be released back into the atmosphere.
Environmentalists have made a study of the nitrogen cycle and are concerned that human activity, such as using artificial nitrogen fertilizers, the release of nitrogen into waste water and burning fossil fuels has dramatically changed the global nitrogen cycle.
NITROGEN CYCLE Earth's atmosphere consists of about 78% of nitrogen. Plants cannot utilize atmospheric moleular nitrogen unless fixed in the form of ammonia or nitrates. Nitrogen in the atmosphre is chemically inert. It does not combine readily with other molecules. Nitrogen cycle: It is a biogeochemical cycle that describes the transformation of nitrogen and nitrogen containing compounds in nature. The cyclic movement of molecular nitrogen from the atmosphere to soil and from soil back into the atmosphere through plants, animals and micro organisms is termed as “Nitrogen cycle”. The Nitrogen cycle involves five steps, Nitrogen fixation ( Abiological and Biological) Nitrogen assimilation Ammonification Nitrification Denitrification. Nitrogen Fixation: The method of conversion of atmospheric nitrogen into usable form (like ammonia and nitrates) by plants. It occurs by two methods. Abiological Nitrogen fixation: ▪ In abiological nitrogen fixation, the atmospheric nitrogen converts into nitrogen oxides by lightening and ultraviolet radiations. ▪ In nature, lighteninig, thunders and you.V. Radiation provide enough energy to convert di nitrogen into nitrogen oxides (NO, NO2, N2O). ▪ Industrial combustions, forest fires, automobile exhausts and power generating stations are also sources of atmospheric nitrogen oxides. Biological Nitrogen Fixation: ▪ Reduction of molecular nitrogen into ammonia by nitrogen fixing bacteria (living organisms) is called biological nitrogen fixation. ▪ The enzyme nitrogenase, which is capable of nitrogen reduction, is present mostly in prokaryotes. Such microbes are called Nitrogen fixers. ▪ Nitrogen fixing bacteria are two types, those are independent and symbiontic bacteria. ▪ Symbiotic nitrogen fixing bacteria live in association with roots of leguminous plants. ▪ Rhizobium is a symbiotic bacteria live in the root nodules of leguminous plants like beans, peas, gram and groundnut. ▪ The root nodules contains a pigment called leghaemoglobin. ▪ Ammonia is the main product of biological nitrogen fixation. Nitrogen Assimilation: The process of absorbing nitrates, ammonia and chemically binding the nitrogen with other elements to produce nitrogenous organic molecules by plants and animals is called Nitrogen assimilation. The nitrates and ammonia formed in the nitrogen fixation, are absorbed by plants and converted into amino acids, proteins, enzymes, chlorophyll, nucleic acids etc., inside the body. Ammonification: Or : Mineralisation: The conversion of nitrogenous organic molecules from dead bodies of plants and animals into ammonia by ammonifying bacteria is termed as ammonification. Nitrification: The conversion of ammonia into nitrites( with the help of Nitrosomonas) and nitrates ( with the help of Nitrobacter) by nitrifying bacteria is called nitrification. E.g.,,. Denitrification: The nitrates present in the soil are converted into molecular nitrogen by denitrifying bacteira is called denitrification. This molecular nitrogen released into the atmosphere to maintain equilibrium of nitrogen in the atmosphere. The denitrifying bacteria like Pseudomonas denitrificans converts nitrate into nitrite, nitrite into nitric oxide and nitrogen and nitric oxide into di nitrogen.
Nitrogen is a big part of Earth’s atmosphere. In fact, nitrogen makes up 78 percent of our air. Nitrogen is extremely important in living things. It forms the building blocks of proteins. We need proteins because they make up our skin and hair. Proteins also help us digest food. We get our nitrogen from plants, and plants get it from bacteria in the soil. Our atmosphere provides life with the nitrogen it needs.
How does nitrogen get to plants and animals from the air? The nitrogen cycle is one of the important systems for living things. Bacteria take nitrogen out of the air and change it into nutrients in the soil. Those nutrients help plants grow. When animals eat plants, they also eat the nitrogen inside the plants. The animals return nitrogen to the soil through their waste. Plants and animals also return nitrogen into the soil with their bodies when they die. The cycle is completed when other bacteria process the plant and animal material and release nitrogen back into the soil and air.
What is the relationship between nitrogen and pressure? Nitrogen not only provides valuable nutrients for life, it also serves another very important purpose. There is so much nitrogen in our atmosphere that it adds extra mass to the air. When you add more mass to the atmosphere, it increases the pressure the same way that adding extra air to a bicycle tire increases the pressure inside the tube. Too much or too little pressure can have a serious effect on us if we are unprotected. Deep sea divers, like oil rig workers, experience high amounts of pressure when they are deep in the ocean. The surrounding water squeezes their bodies and they must wear special suits to protect themselves from getting squashed. Astronauts in space must also wear special suits. In space, there is so little pressure around them that the air in their lungs would rush out and their bodies would puff up like a balloon.
Proteins are important nitrogen compounds. They are one of the three main classes of food substances (others are fat and carbohydrates). Plants can synthesize(build) proteins from simple nitrogen-containing compounds. Animals are unable to synthesize proteins; they obtain it by eating plants or by eating animals.
Some plants can synthesize proteins from the nitrogen in the air e.g. beans, peas and clover. They have nodules on their roots which contain nitrogen fixing bacteria. These bacteria fix atmospheric nitrogen; that is, turn it into nitrogen compounds. Secondly ammonium salts enter the soil in the excreta of animals and through the decay of plant and animal remains. Nitrifying bacteria in the soil convert ammonium salts into nitrates. Another source of nitrates in the soil is rain. Nitrogen and oxygen combine in the atmosphere during lightning storm to form oxides of nitrogen. These gases react with water to form nitric acid.
A rain shower brings nitric acid to Earth, and it reacts with minerals to form nitrates. Plants take in these nitrates through their roots. Some nitrates are converted back into gaseous nitrogen by denitrifying bacteria. The way in which nitrogen circulates from air to soil to living things and back again is called the nitrogen cycle.
Nitrogen is used by life forms to carry out many of the functions of life. This element is especially important to plant life. Yet nitrogen in its gaseous form is almost entirely unusable to life forms. It must first be converted or ‘fixed’ into a more usable form. The process of converting nitrogen is called fixation.
There are specialized bacteria whose function it is to fix nitrogen, converting it, so that it can be used by plants. There are still other bacteria who do the reverse. That is, they return nitrogen to is gaseous form.
After nitrogen is fixed, it can be absorbed, and used by plants, and subsequently by animals.
The process of nitrogen being fixed, used by plants and animals, and later returned to the atmosphere is referred to as the nitrogen cycle.
NITROGEN CYCLEEarth's atmosphere consists of about 78% of nitrogen.Plants cannot utilise atmospheric molecular nitrogen unless fixed in theform of ammonia or nitrates.Nitrogen in the atmosphere is chemically inert. It does not combine readily with other molecules.Nitrogen cycle: It is a biogeochemical cycle that describes the transformation of nitrogen and nitrogen containing compounds in nature. The cyclic movement of molecular nitrogen from the atmosphere to soil and from soil back into the atmosphere through plants, animals and micro organisms is termed as “Nitrogen cycle”.The Nitrogen cycle involves five steps, Nitrogen fixation ( Abiological and Biological) Nitrogen assimilation Ammonification Nitrification Denitrification.Nitrogen Fixation: The method of conversion of atmospheric nitrogen into usable form (like ammonia and nitrates) by plants. It occurs by two methods. Abiological Nitrogen fixation: ▪ In abiological nitrogen fixation, the atmospheric nitrogen converts into nitrogen oxides by lightening and ultraviolet radiations. ▪ In nature, lightening, thunders and you.V. Radiation provide enough energy to convert di nitrogen into nitrogen oxides (NO, NO2, N2O). ▪ Industrial combustions, forest fires, auto mobile exhausts and power generating stations are also sources of atmospheric nitrogen oxides. Biological Nitrogen Fixation: ▪ Reduction of molecular nitrogen into ammonia by nitrogen fixing bacteria (living organisms) is called biological nitrogen fixation. ▪ The enzyme nitrogenase, which is capable of nitrogen reduction, is present mostly in prokaryotes. Such microbes are called Nitrogen fixers. ▪ Nitrogen fixing bacteria are two types, those are independent and symbiontic bacteria. ▪ Symbiotic nitrogen fixing bacteria live in association with roots of leguminous plants. ▪ Rhizobium is a symbiotic bacteria live in the root nodules of leguminous plants like beans, peas, gram and groundnut. ▪ The root nodules contains a pigment called leghaemoglobin. ▪ Ammonia is the main product of biological nitrogen fixation.Nitrogen Assimilation: The process of absorbing nitrates, ammonia and chemically binding the nitrogen with other elements to produce nitrogenous organic molecules by plants and animals is called Nitrogen assimilation. The nitrates and ammonia formed in the nitrogen fixation, are absorbed by plants and converted into amino acids, proteins, enzymes, chlorophyll, nucleic acids etc., inside the body.Ammonification: Or : Mineralisation: The conversion of nitrogenous organic molecules from dead bodies of plants and animals into ammonia by ammonifying bacteria is termed as ammonification.Nitrification: The conversion of ammonia into nitrites( with the help of Nitrosomonas) and nitrates ( with the help of Nitrobacter) by nitrifying bacteria is called nitrification. E.g.,,.Denitrification: The nitrates present in the soil are converted into molecular nitrogen by denitrifying bacteira is called denitrification. This molecular nitrogen released into the atmosphere to maintain equilibrium of nitrogen in the atmosphere. The denitrifying bacteria like Pseudomonas denitrificans converts nitrate into nitrite, nitrite into nitric oxide and nitrogen and nitric oxide into di nitrogen.
Nitr.cycle occurs by the process of nitrogen fixation,nitration,ammonification and denitrification.plants absorb nit. From the soil .animales eats them and gets nit. After the death of animals or their excreta changes into ammonia and ammonium salt into the soil.bacteria eg. Nitrosomonas convert it into the nitrites which changes into nitrates by nitrobacter bact. Plants takes it to make their protein.nitrates also can b converted into atmospheric nitrogen by denitrifying bact.
: "The circulation of free nitrogen from the atmosphere to protein through plants and animals and finally back to atmospheric nitrogen is called nitrogen cycle." The nitrogen cycle consists of a series of reactions of nitrogen and its compounds. Almost all of these reactions take place through living organisms such as green plants and bacteria. Process by which atmospheric nitrogen is consumed :-
1)As a result of electric discharges in the atmosphere , the nitrogen and oxygen present in the atmosphere combine to form nitric oxide. NO which further combines with oxygen to form nitrogen dioxide,NO2. The oxides combine with water to form nitrous acid HNO2 and nitric acid HNO3. These acids are carried down to soil by rain. These oxyacids combine with the lime present in soil to form nitrites and nitrates which are used up by the plants.
2) Symbiotic bacterias which live on the nodules of leguminous plants such as peas, beans or gram , etc: directly take up atmospheric nitrogen producing nitrogenous compounds such as ammonia and nitrates. These soluble compounds of nitrogen are absorbed by the roots and thus converted into proteins. Plant protein is converted to animal protein through feeding by animals and human beings. In the animal body the protein is converted into simpler compounds like urea and amino acids. As result of these processes, a very large quantity of nitrogen is taken away from the atmosphere.
Processes by which nitrogen is released in the atmosphere: The decay of plant and animal proteins leads to the formation of ammonia. Ammonia is then converted into nitrates and nutrifying bacteria. These nitrates are then decomposed into free nitrogen by denitrifying bacteria. The free nitrogen mixes in the air.
