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Question 13 Marks
Explain the importance of photosynthesis
Answer
Photosynthesis is absolutely essential for the continued existence of life. Living beings get organic food and $O _2$ as a result of this process.
(i) Green plants themselves are not heterotrophic, rather they provide food to huge heterotrophic plants and the entire animal community. Animals and humans directly or indirectly depend on this process for food.
(ii) Photosynthetic production not only provides food but also provides energy for various metabolic activities and movements.
(iii) Minerals, coal, petroleum and natural gas represent the photosynthetic capital of past geological cras.
(iv) Many substances of the organic world are important for our daily life. Such as : natural fibres, medicines, vitamins, pigments, oils etc.
(v) Under the process of transpiration of animals and plants, there is continuous consumption of $O _2$ and development of $CO _2$. Apart from this, burning of organic matter produces huge amount of $CO _2$. Excess of $CO _2$ in the atmosphere is toxic. Similarly, deficiency of $CO _2$ is also fatal. Green plants continuously use the $CO _2$ produced in these processes in photosynthesis and expel $O _2$ in its place, due to which the atmosphere remains favourable for living organisms to survive.
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Question 23 Marks
Write the detailed form of the following abbreviations. FAD, NADP, RUBISCO, PQ, PGA, PGAL, RUDP, ADP, PC and Fd.
Answer
1. FAD-Fluoro Adenine Dinucleotide
2. NAD-Nicotinamide adenine dinucleotide
3. RUBISCO-Ribulose phosphate carboxylase oxygenase
4. PQ-Plastoquonone
5. PGA-Phosphoglyceric Acid
6. PGAL-Phosphoglyceraldehyde
7. RUDP-Ribulose diphosphate
8. ADP-Adenosine Phosphate
9. PC-Plastocyanin
10. Fd-Ferrodoxin.
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Question 33 Marks
Explain the importance of C4 cycle.
Answer
C4 cycle has the following importance in plants:
(i) This cycle is more productive in C4 plants than in C3 plants, it increase three times more.
(ii) To reduce one molecule of CO2, 5 ATP and 2 molecules of NADP are required.
(iii) They can also use low concentration CO2
(iv) Reduction of CO2 occurs at a rapid rate even at $30-40^{\circ} C$ temperature.
(v) Increases the rate of photosynthesis even when the stomata are less open.
(vi) This also increases the adaptability of C4 plants to high temperature and light.
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Question 43 Marks
(i) If intense light is shown on a plant at short intervals, then its photosynthetic yield per second will be more than that of a plant on which the intensity of light falls continuously and equally, explain. (ii) Make a labelled diagram of a section of green chloroplast.
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Question 53 Marks
Where does O2 get removed in the process of photosynthesis? How was it discovered?
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