Question

Explain Nitrogen cycle and Carbon cycle.
With Diagrams..................

Answer 1

Dear Student


In the atmosphere, the concentration of nitrogen is about 78%. It is essential for plants. Nitrogen forms a structural component of many important molecules such as DNA, RNA, and other vitamins.
Plants cannot absorb nitrogen from the atmosphere. Certain forms of bacteria are able to convert atmospheric nitrogen into usable forms such as nitrates and nitrites. Such nitrogen fixing bacteria are commonly found in the roots of legumes (plants of pulses) inside special structures called root nodules. These usable forms of nitrogen are absorbed by plants to produce many compounds such as amino acids, which in turn form proteins. When an animal feeds on plants, nitrogen enters its body.When plants and animals die, they start decomposing after some time. During this process, proteins are converted into nitrates and nitrites by the action of decomposing bacteria. Certain other forms of bacteria convert nitrates and nitrites into elemental nitrogen. Thus, nitrogen flows between the various components of the biosphere in a cyclical manner.
There are basically 5 steps of nitrogen cycle that help in fixing atmospheric nitrogen:
Nitrogen Fixation (N 2 to NO 3 - or NH 4 )
Nitrification (NH 3 to NO 3 - )
Assimiliation (here the NH 3 and NO 3 - are incorporated into the biological tissues)
Ammonification (organic nitrogen compounds to NH 3 )
Denitrification (NO 3 - to N 2 )


Carbon Cycle

Carbon enters life forms through the process of photosynthesis. Photosynthesis is the process by which plants prepare food in the presence of sunlight and chlorophyll. During photosynthesis, carbon dioxide and water combine to produce glucose and oxygen. This changes the atmospheric carbon into glucose molecules.
Glucose, which is a source of food, is utilized by organisms to produce energy during respiration. During this process, glucose is broken down in the presence of oxygen to produce carbon dioxide.
Thus, through the processes of photosynthesis and respiration, carbon is utilized and then returned to the environment.

All organisms do not need oxygen to break down glucose and produce energy. The organisms which survive in the absence of oxygen are called anaerobes.
Another process that releases carbon dioxide is called combustion. It is the process of burning. Many substances release carbon dioxide on burning. Vehicular emissions, industrial fumes, and the gases released during the process of cooking are some instances during which carbon dioxide is released.


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