QUESTIONS:
1. The atmosphere is 80% nitrogen: why do you think plants and animals can't use
nitrogen as it is found in the atmosphere?
2. Explain what is meant by nitrogen fixation.
3. What is the role of bacteria in the nitrogen cycle?
4. Why don't legumes need nitrogen-containing fertilizers?
5. Why is nitrogen so important for living things?
6. What are the processes involved in the nitrogen cycle?
ANSWERS:
1. Plants and animals cannot use nitogen as it is found in the atmosphere as the nitrogen is in a form not usable to organisms. Plants and animals do not have the enzymes to 'fix' the nitrogen.
2. Nitrogen fixation is a process by which nitrogen (N2) in the atmosphere is converted into ammonia (NH3).[1] Atmospheric nitrogen or elemental nitrogen (N2) is relatively inert: it does not easily react with other chemicals to form new compounds. Fixation processes free up the nitrogen atoms from their diatomic form (N2) to be used in other ways.
3. Bacteria actually uses and transforms the nitrogen into nitrogen that can again be used .
4. Legumes "fix" nitrogen in nodules on their roots, so they do not need additional nitrogen-containing fertilizers.
5. Nitrogen is a major component of chlorophyll, which is used by plants in the process of photosynthesis to produce sugars, water and carbon dioxide.
It is also an essential component of amino acids which make up proteins. Some proteins act as structural units in the plant while others act as enzymes, catalysing biological reactions.
Nitrogen is also a component of ATP, which provides energy for reactions such as respiration.
Finally, nitrogen is a significant component of DNA, the genetic material which allows cells to grow and replicate.
4. Legumes "fix" nitrogen in nodules on their roots, so they do not need additional nitrogen-containing fertilizers.
5. Nitrogen is a major component of chlorophyll, which is used by plants in the process of photosynthesis to produce sugars, water and carbon dioxide.
It is also an essential component of amino acids which make up proteins. Some proteins act as structural units in the plant while others act as enzymes, catalysing biological reactions.
Nitrogen is also a component of ATP, which provides energy for reactions such as respiration.
Finally, nitrogen is a significant component of DNA, the genetic material which allows cells to grow and replicate.
6. Step 1: Nitrogen-fixation
Atmospheric: Happens when Nitrogen (N2) is oxidized at high temperatures (by lightning, in internal combustion engines) to make nitrite (NO2). This can combine with water to form nitric acid (H2NO3), which is deposited on earth through rainfall.
Biological: Done by bacteria which can convert N2 into ammonia (NH3) if an energy source is present. Some get this energy by directly absorbing sunlight (blue-green algae) or by living in the roots of plants (legumes, alder trees), who provide them with food (Rhizobium, Azospirillium).
Step 2: Conversion to Ammonia. As amino acids and nucleic acids require N in the form of Ammonia, if nitrate (NO3) present, it must be converted to NH3. This is done through Nitrate reductase enzymes.
Step 3: Biological Use. Ammonia is incorporated into proteins, nucleic acids
Step 4: When organism dies, ammonia is relased back into the biosphere through the process of Ammonification, in which water is added to proteins to make carbon dioxide and ammonia. This process happens during digestion, and is also done by bacterial and fungal decomposers.
Step 5: If ammonia released into oxygen rich (anerobic) soil, other bacteria can convert it into nitrite or nitrate through the process of Nitrification:
NH4+ + 2O2 = NO3- + H2O + 2H.
This is a problem, as it gives the molecule which contains Nitrogen a negative charge, which repels it from soil particles, causing it to be easily leached into streams and groundwater.
Step 6: If soils remain anerobic, another group of poop will convert it back into inert, atmospheric N2 through the process of Denitrification. In this process, bacteria use nitrate as an Oxygen source for respiration: C6H12O6 + 4NO3- = 6CO2 + 6H2O + 2N2.
Atmospheric: Happens when Nitrogen (N2) is oxidized at high temperatures (by lightning, in internal combustion engines) to make nitrite (NO2). This can combine with water to form nitric acid (H2NO3), which is deposited on earth through rainfall.
Biological: Done by bacteria which can convert N2 into ammonia (NH3) if an energy source is present. Some get this energy by directly absorbing sunlight (blue-green algae) or by living in the roots of plants (legumes, alder trees), who provide them with food (Rhizobium, Azospirillium).
Step 2: Conversion to Ammonia. As amino acids and nucleic acids require N in the form of Ammonia, if nitrate (NO3) present, it must be converted to NH3. This is done through Nitrate reductase enzymes.
Step 3: Biological Use. Ammonia is incorporated into proteins, nucleic acids
Step 4: When organism dies, ammonia is relased back into the biosphere through the process of Ammonification, in which water is added to proteins to make carbon dioxide and ammonia. This process happens during digestion, and is also done by bacterial and fungal decomposers.
Step 5: If ammonia released into oxygen rich (anerobic) soil, other bacteria can convert it into nitrite or nitrate through the process of Nitrification:
NH4+ + 2O2 = NO3- + H2O + 2H.
This is a problem, as it gives the molecule which contains Nitrogen a negative charge, which repels it from soil particles, causing it to be easily leached into streams and groundwater.
Step 6: If soils remain anerobic, another group of poop will convert it back into inert, atmospheric N2 through the process of Denitrification. In this process, bacteria use nitrate as an Oxygen source for respiration: C6H12O6 + 4NO3- = 6CO2 + 6H2O + 2N2.
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