NIOS Class 12 Biology Chapter 10 Solution – Nitrogen Metabolism
NIOS Class 12 Biology Solution Chapter 10 Nitrogen Metabolism . NIOS Class 12 Biology Chapter 10 Question Answers Download PDF. NIOS Class 12 Biology Notes.
Board |
NIOS |
Class |
12th (Higher Secondary) |
Subject |
Biology |
Topic |
Question Answer, Solution, Notes |
INTEXT 10.1
1.) What is the percent by volume of nitrogen gas in the atmosphere?
Ans: Nitrogen is primarily present in the atmosphere freely as dinitrogen or nitrogen gas. 78.03 percent by volume of nitrogen gas in the atmosphere is present.
2.) Name two biomolecules that contain nitrogen in plants.
Ans: proteins and enzymes are the biomolecules that contain nitrogen in plants.
3.) Why nitrogen is a stable molecule?
Ans: Molecular Nitrogen or diatomic nitrogen (N2) is highly stable as it is triple bonded (N≡N). Because of this stability, molecular nitrogen as such is not very reactive in the atmosphere under normal conditions
4.) What is the percentage of nitrogen in protein?
Ans: The percentage of nitrogen in protein 16 .
5.) What is the boiling point of nitrogen?
Ans: The boiling point of nitrogen –195.8°C
6.) Choose the correct option: Nitrogen fixation is the conversion of :
(a) atmospheric Nitrogen ⎯⎯⎯into → Nitrates
(b) atmospheric Nitrogen ⎯⎯⎯into → Ammonia
(c) atmospheric Nitrogen ⎯⎯⎯into → Amino acids
(d) both (a) and (b)
Ans: (b) atmospheric Nitrogen ⎯⎯⎯into → Ammonia
7). Nitrogen content of biosphere remains constant because of :
Ans: (a) Nitrogen cycle
8.) Nitrates are converted into nitrogen by microbes called
Ans: Nitrates are converted into nitrogen by microbes called Denitrifying Bacteria
INTEXT 10.2
1.) Define nitrogen fixation.
Ans: The conversion of molecular nitrogen into compounds of nitrogen especially ammonia is called nitrogen fixation. Nitrogen fixation, is a reductive process i.e., nitrogen fixation will stop if there is no reducing condition or if oxygen is present. This nitrogen fixation may take place by two different methods – abiological and biological.
2.) Which industrial process is utilized for converting nitrogen to ammonia?
Ans: Haber’s process is the industrial process in which , synthetic ammonia is produced by passing a mixture of nitrogen and hydrogen through a bed of catalyst (iron oxides) at a very high temperature and pressure.
3.) Distinguish between biological and abiological nitrogen fixation.
Ans: Biological nitrogen fixation takes place in a living cell and abiological fixation without a living cell
4.) Name the enzyme that helps in nitrogen fixation in living cells.
Ans: Nitrogenase helps in nitrogen fixation in living cells
5.) Which gas prevents nitrogen fixation?
Ans: In presence of oxygen , there is no nitrogen fixation
INTEXT 10.3
1.) Match the following
Column A | Column B (Ans) |
(i) Azotobacter | (b) aerobic nitrogen fixer |
(ii) Clostridium | (a) anaerobic nitrogen fixer |
(iii) Lichens | (d) symbiotic nitrogen fixer |
(iv) Anabaena | (c) aerobic nitrogen fixing cyanobacterium. |
2). Which Gymnospermous plant fixes nitrogen?
Ans: Cycas is the Gymnospermous plant that fixes nitrogen
3.) Is there any other gas envolved during nitrogen fixation? If yes, name the gas evolved.
Ans: yes, Hydrogen gas is envolved in nitrogen fixation.
4.) How many ATP molecules are required to reduce a single molecule of nitrogen?
Ans: A source of energy (ATP) is required to transfer hydrogen atoms from NADH2 or FADH2 to dinitrogen .In total 16 ATP are requird to reduce a single molecule of nitrogen.
5.) What is the major source of electrons for reduction of nitrogen?
Ans: Reduced coenzymes such as Ferrodoxin is major source of electrons required for reduction of nitrogen.
6.) Match the following:
Column A | Column B (Ans) |
(i) Leghemoglobin | (b) Legumes |
(ii) Anabaena | (a) cyanobacterium |
(iii) Reductive process | (c) nitrogen fixation |
7.) Name the proteins that help in establishing symbiosis and maintain root nodule functioning in legumes.
Ans: The proteins that help in establishing symbiosis and maintain root nodule functioning in legumes is Nodulins.
INTEXT 10.4
1.) Which is the most reduced form of inorganic nitrogen?
Ans: NH4 is the most reduced form of inorganic nitrogen
2.) Match the following:
Colum A | Column B |
(i) Nitrate reductase | b) nitrate reduction |
(ii) Nitrite reductase | c) nitrite reduction |
(iii) Nitrogenase | (a) nitrogen fixation |
3.) In which part of the cell, reduction of nitrate to nitrite occurs?
Ans: Reduction of nitrate to nitrite occurs in Cytosol. Nitrite present in the cytosol is transported into chloroplast or plastids where it is reduced to ammonia.
4 ) Which is the most oxidized form of inorganic nitrogen?
Ans: . Nitrate is the most oxidized form of inorganic nitrogen.
5) In which plant organelle reduction of nitrite to ammonia is catlyzed by the enzyme nitrite reductase?
Ans: reduction of nitrite to ammonia is catlyzed by the enzyme nitrite reductase in Chloroplast.
INTEXT 10.5
1.) Match the pairs
Column A | Column B |
(i) Amino acid | (b) amino group and carboxyl group |
(ii) Glutamic acid | (c) amino acid |
(iii) α-ketoglutaric acid | (a) keto acid |
2.) Name two biochemical reactions for biosynthesis of amino acids in plants.
Ans: Reductive amination and transamination are the biochemical reactions for biosynthesis of amino acids in plants.
3.) Which group of enzymes catalyzes transamination reaction?
Ans: Transaminases catalyzes the transamination reaction
4.) What is the source of amino group for amino acid synthesis in reductive amination reaction?
Ans: Ammonia is the source of amino group for amino acid synthesis in reductive amination reaction
5.) Which keto acid is the source for synthesis of glutamic acid?
Ans: Alpha ketoglutaric acid is the source for synthesis of glutamic acid
TERMINAL EXERCISE
1.) Define nitrogen fixation.
Ans: Nitrogen fixation is the process of turning molecule-level nitrogen into nitrogen compounds, particularly ammonia. A reductive process is nitrogen fixation.
2.) Which form of combined nitrogen may be formed during lightening storms?
Ans: Nitrogen in the atmosphere can mix with oxygen to generate oxides of nitrogen during lightning storms.
3.) Name three biomolecules other than enzymes and proteins, which contain nitrogen
Ans: Amino acids, vitamins and alkaloids contain nitrogen.
4.) Name one aerobic and one anaerobic bacterium, which fixes nitrogen.
Ans: Azotobacter : Aerobic bacteria , Clostridium :Anaerobic bacteria
5.) Which amino acid is synthesized due to reductive amination of α-ketoglutaric acid?
Ans: Glutamic Acid is synthesized due to reductive amination of α-ketoglutaric acid
6.) Differentiate between biological and abiological nitrogen fixation.
Ans: In abiological nitrogen fixation ,When nitrogen is converted to ammonia through abiological nitrogen fixation, no living cell is involved and in biological nitrogen fixation the process of biological nitrogen fixation involves a living cell reducing molecular nitrogen to ammonia in the presence of nitrogenases.
7). What is required for biological nitrogen fixation?
Ans: Biological nitrogen fixation is reduction of molecular nitrogen to ammonia by a living cell in the presence of enzymes called nitrogenases
8.) How does human hemoglobin differ from leghemoglobin?
Ans : leghemoglobin is a special protein possess in legume nodules
9.) What is the function of leghemoglobin?
Ans: Leghemoglobin is thought to aid in the fixation of nitrogen and lower the partial pressure of oxygen. However, because free-living microorganisms lack nitrogen-fixing leghemoglobin, this function is only unique to legumes.
10). What are the functional differences between nitrate reductase and nitrite reductase?
Ans: nitrate reductase helps in nitrate reduction and nitrite reductase helps in reduction of nitrite.
11.) What is the difference between nitrogen fixation and nitrogen assimilation? Describe in brief the process of abiological nitrogen fixation.
Ans: Nitrogen fixation is the process of turning molecule-level nitrogen into nitrogen-containing molecules, particularly ammonia where as nitrogen assimilation is the conversion of ammonium ion into nitrate.
i) Without the involvement of any live cells, nitrogen is converted to ammonia in abiological nitrogen fixation. There are two types of biological fixation: industrial and natural. For instance, the Haber process involves passing a combination of nitrogen and hydrogen through a bed of iron oxide catalyst at extremely high temperatures and pressures to create synthetic ammonia.
Nitrogen can be repaired naturally, particularly when electrical discharges occur in the environment. Nitrogen in the atmosphere can mix with oxygen to generate oxides of nitrogen during lightning storms.
12.) Describe in brief various steps involved in biological nitrogen fixation.
Ans: Nitrogen is gradually reduced to ammonia as part of the overall metabolic process. The protein Mo-Fe-containing enzyme nitrogenase binds to a nitrogen (N2) molecule at its binding site. Hydrogen then interacts with this nitrogen molecule and reduces it incrementally.
It first produces diamide (N2H2) then hydrazime (N2H4) and finally ammonia (2NH3).
The general equation for nitrogen fixation may be described as follows:
N 2 + 16ATP + 8H + 8e ⎯⎯→2NH3 + 16ADP + 16Pi 2 3 +
13.) Enumerate various free living and symbiotic nitrogen fixing systems with suitable examples.
Ans : Most microbial cells, such as bacteria and cyanobacteria, are capable of nitrogen fixation. These microbes might be autonomous and free-living.Eg : Clostridium : Anaerobic bacteria Klebsiella : Facultative bacteria.
Symbiosis, a unique partnership between the host organism and the nitrogen-fixing microorganisms, is established.
Eg : Lichens: Cyanobacteria and Fungus, Bryophyte: Cyanobacteria and Anthoceros.
14.) What are the major differences between free living and leguminous nitrogen fixing organisms?
Ans:Free living nitrogen fixing organisms are independent for their food , while leguminous nitrogen fixing organisms depend on host for their food.
15). Describe in brief nitrate and nitrite reduction in plants..
Ans: The majority of plants take nitrate, which two distinct enzymes then break down into ammonia. An enzyme called nitrate reductase catalyses the initial step in the conversion of nitrate to nitrite. The other crucial components of this enzyme are numerous. cytochrome, molybdenum, NADPH, and NADH, among others. The overall process of nitrate reduction take place in the cytosol and is an energy dependent reaction.
The second phase involves further reducing the nitrite that has been created to ammonia, which is catalysed by the enzyme nitrite reductase. The cytosolic nitrite is carried into the chloroplast or plastids, where it is converted to ammonia.
16). Describe in brief the reductive amination reactions for synthesis of amino acids in plants.
Ans: Ammonia reacts with a keto acid in this reaction. The alpha ketoglutaric acid generated during the Krebs cycle is the most significant keto acid The amino acid is then created from the keto acid by an enzyme process called reductive amination.
17.) Describe the transamination reaction for synthesis of amino acids in plants. How does this differ from reductive amination?
Ans: By transferring its amino group (NH2) to the -ketoglutaric acid, aspartic acid creates glutamic acid and releases keto acid. Enzymes referred to as transaminases catalyse the process. This transamination reaction produces a significant amount of amino acids.
The reaction involves transfer of amino group, from already synthesized amino acid, to the keto acid