This set of Class 11 Biology Chapter 13 Multiple Choice Questions & Answers (MCQs) focuses on “Photosynthesis in Higher Plants – ATP and NADPH-2”.
1. Which of these is not a stage of the Calvin cycle?
a) Carboxylation
b) Reduction
c) Regeneration
d) Oxidation
View Answer
Explanation: The Calvin cycle is a pathway of light independent reactions of photosynthesis. It depends on the energy carriers ATP and NADPH and hence, Calvin cycle indirectly depends upon light.
2. Which is the most crucial step of the Calvin cycle?
a) Oxidation
b) Reduction
c) Carboxylation
d) Regeneration
View Answer
Explanation: The Calvin cycle is a pathway of light independent reactions of photosynthesis. The most crucial step of the Calvin cycle is carboxylation, where carbon dioxide is fixated into a stable organic intermediate.
3. Which of these undergoes carboxylation during Calvin cycle?
a) NADPH
b) ATP
c) RuBP
d) PGA
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Explanation: The most crucial step of the Calvin cycle is carboxylation, where carbon dioxide is fixated into a stable organic intermediate. This organic intermediate is RuBP or ribulose bisphosphate.
4. Which of these substances catalyse carboxylation?
a) RuBP carboxylase
b) Pyruvate carboxylase
c) Propionyl-CoA carboxylase
d) Acetyl-CoA carboxylase
View Answer
Explanation: The most crucial step of the Calvin cycle is carboxylation, where carbon dioxide is fixated into a stable organic intermediate, known as ribulose bisphosphate. RuBP carboxylase catalyses carboxylation.
5. What is the product of carboxylation?
a) 2-PGA
b) 3-PGA
c) RuBP
d) Rubisco
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Explanation: 3-PGA or 3-phosphoglyceric acid is the product of carboxylation. It is a 3-carbon organic acid. RuBP or ribulose bisphosphate is the primary carbon dioxide acceptor which undergoes carboxylation.
6. How many molecules of PGA are produced on carboxylation?
a) 3
b) 1
c) 2
d) 4
View Answer
Explanation: 3-PGA or 3-phosphoglyceric acid is the product of carboxylation. It is a 3-carbon organic acid. RuBP or ribulose bisphosphate undergoes carboxylation to produce two molecules of 3-PGA or 3-phosphoglyceric acid.
7. Which of these statements is false about reduction in the Calvin cycle?
a) It is the third step of the cycle
b) It leads to the formation of glucose
c) It utilizes NADPH for reduction
d) It utilizes ATP for phosphorylation
View Answer
Explanation: Reduction is the second step of the Calvin cycle. It results in the formation of glucose. Reduction utilizes NADPH for reduction and ATP for phosphorylation which results in the production of glucose.
8. How many turns of the Calvin cycle are required for the formation of 3 glucose molecules?
a) 15
b) 16
c) 12
d) 18
View Answer
Explanation: The formation of one molecule of glucose requires the fixation of 6 carbon dioxide molecules and hence six turns of the Calvin cycle. Hence, 3 glucose molecules will require 18 turns of the cycle.
9. Which of these molecules is regenerated during the Calvin cycle?
a) NADPH
b) ATP
c) RuBP
d) CO2
View Answer
Explanation: Regeneration is the third and final step of the Calvin cycle. In this step, the CO2 acceptor molecule RuBP or ribulose bisphosphate is regenerated. The regenerated RuBP is again used for the next Calvin cycle.
10. Regeneration during the Calvin cycle requires 3 ATP molecules. True or false?
a) True
b) False
View Answer
Explanation: Regeneration is the third and final step of the Calvin cycle. In this step, the CO2 acceptor molecule RuBP is regenerated. Regeneration requires 1 ATP molecule for the purpose of phosphorylation.
11. How many molecules of NADPH are required for each Calvin cycle?
a) 3
b) 1
c) 4
d) 2
View Answer
Explanation: For every carbon dioxide molecule used up in the Calvin cycle, 2 molecules of NADPH are required. Six cycles are required to produce one glucose molecule; hence 12 NADPH molecules are required to produce one molecule of glucose.
12. How many molecules of ATP are required for each Calvin cycle?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: For every carbon dioxide molecule used up in the Calvin cycle, 3 molecules of ATP are required. Six cycles are required to produce one glucose molecule; hence 18 ATP molecules are required to produce one molecule of glucose.
13. How many molecules of NADP are produced as a result of six Calvin cycles?
a) 9
b) 18
c) 12
d) 24
View Answer
Explanation: For every carbon dioxide molecule used up in the Calvin cycle, 2 molecules of NADPH are required. Hence, 2 molecules of NADP are produced. For six Calvin cycles, 12 molecules of NADP are produced.
14. How many molecules of ADP are produced as a result of six Calvin cycles?
a) 18
b) 24
c) 12
d) 32
View Answer
Explanation: For every carbon dioxide molecule used up in the Calvin cycle, 3 molecules of ATP are required. Hence, 3 molecules of ADP are produced. For six Calvin cycles, 18 molecules of ADP are produced.
15. How many molecules of carbon dioxide are required in the Calvin cycle to produce 3 molecules of glucose?
a) 9
b) 18
c) 6
d) 15
View Answer
Explanation: To make one molecule of glucose six molecules of carbon dioxide are required. Hence, six cycles of the Calvin cycle are required. To make three molecules of glucose, 18 molecules of carbon dioxide are required.
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