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NIOS Class 12 Biology Chapter 10 Nitrogen Metabolism
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Nitrogen Metabolism
Chapter: 10
MODULE – II: FORM AND FUNCTION OF PLANTS AND ANIMALS
NIOS TEXTBOOK QUESTIONS ANSWERS
INTEXT QUESTIONS 10.1
1. What is the percent by volume of nitrogen gas in the atmosphere?
Ans: N₂ gas in atmosphere is 78.03%.
2. Name two biomolecules that contain nitrogen in plants.
Ans: (i) Enzymes.
(ii) Proteins.
3. Why nitrogen is a stable molecule?
Ans: Since it is triple (≡) bonded molecule.
4. What is the percentage of nitrogen in protein?
Ans: 16%.
5. What is the boiling point of nitrogen?
Ans: 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 Nitrogenⁱⁿᵗᵒ→ into Amino acids.
Ans: (b) atmospheric Nitrogen ⁱⁿᵗᵒ→ Ammonia.
7. Nitrogen content of biosphere remains constant because of:
(a) Nitrogen cycle.
(b) Nitrogen fixation.
(c) Industrial pollution.
(d) Absorption of nitrogen.
Ans: (a) Nitrogen cycle.
8. Nitrates are converted into nitrogen by microbes called __________.
Ans: Denitrifying Bacteria convert No, into nitrogen.
INTEXT QUESTIONS 10.2
1. Define nitrogen fixation.
Ans: It is defined as “the conversion of molecular nitrogen into NH3.”
2. Which industrial process is utilised for converting nitrogen to ammonia?
Ans: Haber’s Process.
3. Distinguish between biological and abiological nitrogen fixation.
Ans: The biological N₂ fixation takes place in a living cell but a biological N₂ fixation occurs living cell.
4. Name the enzyme that helps in nitrogen fixation in lining cells.
Ans: Nitrogenase enzyme.
5. Which gas prevents nitrogen fixation?
Ans: Oxygen (O₂).
INTEXT QUESTIONS 10.3
1. Match the following:
| Column A | Column B |
| (i) Azotobacter | (a) anaerobic nitrogen fixer. |
| (ii) Clostridium | (b) aerobic nitrogen fixer. |
| (iii) Lichens | (c) nitrogen fixing cyano bacter-ium. |
| (iv) Anabaena | (d) symbiotic nitrogen fixer. |
Ans:
| Column A | Column B |
| (i) Azotobacter | (b) aerobic nitrogen fixer |
| (ii) Clostridium | (a) anaerobic nitrogen fixer. |
| (iii) Lichens | (d) symbiotic nitrogen fixer. |
| (iv) Anabaena | (c) nitrogen fixing cyano bacter-ium. |
2. Which gymnospermous plant fixes nitrogen?
Ans: Cycas plant.
3. Is there any other gas evolved during nitrogen fixation? If yes, name the gas evolved.
Ans: Yes; H₂ (hydrogen gas).
4. How many ATP molecules are required to reduce a single molecule of nitrogen?
Ans: 16 ATP are required.
5. What is the major source of electrons for reduction of nitrogen?
Ans: Reduced coenzymes, e.g. Ferrodoxin.
6. Match the following:
| Column A | Column B |
| (i) Leghemoglobin | (a) Cyanobacterium |
| (ii) Anabaena | (b) Legumes |
| (iii) Reductive process | (c) Nitrogen fixation |
Ans:
| Column A | Column B |
| (i) Leghemoglobin | (b) Legumes |
| (ii) Anabaena | (a) Cyanobacterium |
| (iii) Reductive process | (c) Nitrogen fixation |
7. Name the proteins the help in establishing symbiosis and maintain nodule functioning.
Ans: Nodulins.
INTEXT QUESTIONS 10.4
1. Which is the most reduced form of inorganic nitrogen?
Ans: NH.
2. Match the following:
| Column A | Column B |
| (i) Nitrate reductase | (a) Nitrogen fixation |
| (ii) Nitrite reductase | (b) Nitrate reduction |
| (iii) Nitrogenase | (c) Nitrite reduction |
Ans:
| Column 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: Cytol.
4. Which is the most oxidised form of inorganic nitrogen?
Ans: Nitrate.
5. In which plant organelle reduction of nitrite to ammonia is catalysed by the enzyme?
Ans: Chloroplast.
INTEXT QUESTIONS 10.5
1. Match the following:
| Column A | Column B |
| (i) Amino acid | (a) Keto acid |
| (ii) Glutamic acid | (b) Amino group and carboxylic group |
| (iii) a-ketoglutaric acid | (c) Amino acid |
Ans:
| Column A | Column B |
| (i) Amino acid | (b) Amino group and carboxylic group |
| (ii) Glutamic acid | (c) Amino acid |
| (iii) a-ketoglutaric acid | (a) Keto acid |
2. Name two biochemical reactions for biosynthesis of amino acids in plants.
And: (i) Reductive Deamination. and
(ii) Transamination.
3. Which group of enzymes catalyses transamination reaction?
Ans: Transaminases.
4. What is the source of amino group for amino acid synthesis in reductive amination reaction?
Ans. Ammonia (NH₂).
5. Which keto acid is the source for synthesis of glutamic acid?
Ans: Alpha (α) ketoglutaric acid.
TERMINAL EXERCISES
1. Define nitrogen fixation.
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