Photosynthesis in higher plants - light and dark reactions, photophosphorylation - Question Bank

1. In the context of the Calvin cycle, what is meant by the term 'reduction'?
A) The addition of CO2 to RuBP.
B) The conversion of 3-phosphoglycerate to glyceraldehyde-3-phosphate using ATP and NADPH.
C) The regeneration of RuBP.
D) The release of oxygen.
2. What is the primary role of the antenna complex in photosystems?
A) To directly split water molecules.
B) To catalyze the reduction of NADP+.
C) To capture light energy and transfer it to the reaction center.
D) To synthesize ATP.
3. The reduction of one molecule of CO2 in the Calvin cycle requires 2 molecules of ATP and 2 molecules of NADPH. How many molecules of CO2 need to be fixed to synthesize one molecule of glucose (C6H12O6)?
A) 2
B) 3
C) 6
D) 12
4. Which of the following is a key difference between cyclic and non-cyclic photophosphorylation?
A) Cyclic photophosphorylation produces O2, while non-cyclic does not.
B) Non-cyclic photophosphorylation produces NADPH, while cyclic does not.
C) Cyclic photophosphorylation uses only Photosystem I, while non-cyclic uses both PS I and PS II.
D) Non-cyclic photophosphorylation produces ATP, while cyclic does not.
5. The light-independent reactions can occur in the absence of light, provided that the products of the light-dependent reactions are available. This statement is:
A) True, as they are called 'dark reactions'.
B) False, as they directly require light.
C) True, but they are indirectly dependent on light.
D) False, they only occur during the night.
6. What is the role of ferredoxin in the light-dependent reactions?
A) It carries electrons from Photosystem II to the cytochrome b6f complex.
B) It carries electrons from Photosystem I to NADP+.
C) It pumps protons across the thylakoid membrane.
D) It absorbs light energy.
7. In the Calvin cycle, the carboxylation of RuBP by RuBisCO leads to the formation of an unstable 6-carbon intermediate, which quickly breaks down into two molecules of:
A) Glyceraldehyde-3-phosphate
B) Phosphoenolpyruvate
C) 3-phosphoglycerate
D) Oxaloacetate
8. The enzyme ATP synthase utilizes the energy stored in the proton gradient to phosphorylate ADP to ATP. This process is known as:
A) Photolysis
B) Photoreduction
C) Photophosphorylation
D) Photorespiration
9. The electron transport chain in the thylakoid membrane links Photosystem II and Photosystem I. What is the main function of this chain?
A) To absorb light energy
B) To synthesize glucose
C) To pump protons and generate a proton gradient
D) To split water molecules
10. Which of the following is the correct order of electron flow in non-cyclic photophosphorylation?
A) PSII -> ETC -> PSI -> NADP+
B) PSI -> ETC -> PSII -> NADP+
C) Water -> PSII -> ETC -> PSI -> NADP+
D) Water -> PSI -> ETC -> PSII -> NADP+
11. The light-independent reactions are directly dependent on the products of the light-dependent reactions. What are these products?
A) Oxygen and water
B) ATP and NADPH
C) Glucose and starch
D) Carbon dioxide and RuBP
12. What is the fate of glyceraldehyde-3-phosphate (G3P) produced in the Calvin cycle?
A) It is directly converted to sucrose.
B) It is used to regenerate RuBP and synthesize glucose and other organic molecules.
C) It is released as CO2.
D) It is stored as starch in the stroma.
13. Which of the following is NOT a condition that favors photorespiration?
A) High CO2 concentration
B) High O2 concentration
C) High temperature
D) High light intensity
14. The energy for the regeneration of RuBP in the Calvin cycle is primarily supplied by:
A) NADPH
B) Light
C) ATP
D) Water
15. During the light-dependent reactions, the accumulation of protons inside the thylakoid lumen leads to:
A) A decrease in pH and an increase in the proton motive force.
B) An increase in pH and a decrease in the proton motive force.
C) No significant change in pH or proton motive force.
D) A decrease in ATP synthesis.
16. Which of the following best describes the role of NADP+ reductase?
A) It uses light energy to synthesize ATP.
B) It catalyzes the reduction of NADP+ to NADPH using electrons from ferredoxin.
C) It splits water molecules to release electrons.
D) It regenerates RuBP in the Calvin cycle.
17. What is the function of plastocyanin in the electron transport chain of photosynthesis?
A) It accepts electrons from Photosystem II and transfers them to Photosystem I.
B) It pumps protons into the thylakoid lumen.
C) It reduces NADP+ to NADPH.
D) It directly absorbs light energy.
18. How many turns of the Calvin cycle are required to produce one molecule of glucose (a 6-carbon sugar)?
A) 2
B) 4
C) 6
D) 12
19. The reduction phase of the Calvin cycle involves the conversion of 1,3-bisphosphoglycerate to glyceraldehyde-3-phosphate. This reaction is catalyzed by an enzyme that requires:
A) ATP and NADP+
B) NADPH and ATP
C) FADH2 and ATP
D) ATP and water
20. The oxygen released during photosynthesis comes from the splitting of which molecule?
A) Carbon dioxide
B) Glucose
C) Water
D) ATP
21. Which of the following is the primary role of carotenoids in photosynthesis?
A) Absorb green light
B) Transfer energy to chlorophyll
C) Dissipate excess light energy and protect chlorophyll from photodamage
D) Directly split water molecules
22. In C3 plants, the Calvin cycle occurs in which cells?
A) Bundle sheath cells
B) Mesophyll cells
C) Guard cells
D) Epidermal cells
23. The light-dependent reactions convert light energy into chemical energy in the form of ATP and NADPH. This process is also known as:
A) Carbon fixation
B) Photolysis
C) Photophosphorylation
D) Reduction
24. Which of the following pigments acts as an accessory pigment, transferring absorbed light energy to the reaction center chlorophyll?
A) Chlorophyll a
B) Chlorophyll b and carotenoids
C) Cytochrome c
D) Ferredoxin
25. The process of photorespiration occurs when RuBisCO binds to oxygen instead of carbon dioxide. Which of the following is a consequence of photorespiration?
A) Increased ATP production
B) Increased sugar synthesis
C) Wastage of energy and fixed carbon
D) Enhanced water splitting
26. What is the net number of NADPH molecules required to fix one molecule of CO2 in the Calvin cycle?
A) 1
B) 2
C) 3
D) 4
27. What is the net number of ATP molecules required to fix one molecule of CO2 in the Calvin cycle?
A) 1
B) 2
C) 3
D) 4
28. When a molecule of CO2 is fixed by RuBisCO, what is the immediate product formed?
A) 3-phosphoglycerate
B) Glyceraldehyde-3-phosphate
C) Ribulose-1,5-bisphosphate
D) Fructose-1,6-bisphosphate
29. Which component of the electron transport chain in the thylakoid membrane is responsible for pumping protons from the stroma into the thylakoid lumen?
A) Photosystem II
B) Plastoquinone
C) Cytochrome b6f complex
D) Plastocyanin
30. The chemiosmotic hypothesis explains ATP synthesis during photophosphorylation. It relies on the establishment of a proton gradient across which membrane?
A) Outer chloroplast membrane
B) Inner chloroplast membrane
C) Thylakoid membrane
D) Plasma membrane
31. In cyclic photophosphorylation, where do the electrons return after passing through the electron transport chain?
A) To Photosystem II
B) To the stroma
C) To Photosystem I
D) To water
32. Cyclic photophosphorylation involves only Photosystem I. What is the main product of cyclic photophosphorylation?
A) NADPH
B) ATP
C) Oxygen
D) Glucose
33. During non-cyclic photophosphorylation, electrons flow from water to NADP+. Which of the following is the final electron acceptor?
A) Photosystem II
B) Cytochrome b6f complex
C) Photosystem I
D) NADP+
34. The Z-scheme of photosynthesis describes the energy changes of electrons. Which photosystem has its reaction center chlorophyll absorbing light at a longer wavelength (700 nm)?
A) Photosystem II (PSII)
B) Photosystem I (PSI)
C) Cytochrome b6f complex
D) ATP synthase
35. Which of the following is NOT a product of the light-dependent reactions?
A) ATP
B) NADPH
C) Oxygen
D) Glyceraldehyde-3-phosphate
36. The regeneration of Ribulose-1,5-bisphosphate (RuBP) in the Calvin cycle requires the input of which molecule?
A) ATP
B) NADPH
C) Oxygen
D) Water
37. For every three molecules of CO2 fixed in the Calvin cycle, how many molecules of G3P are exported from the cycle?
A) One
B) Two
C) Three
D) Six
38. What is the primary sugar molecule produced by the Calvin cycle?
A) Sucrose
B) Fructose
C) Glyceraldehyde-3-phosphate (G3P)
D) Glucose
39. The reduction of 3-phosphoglycerate to glyceraldehyde-3-phosphate in the Calvin cycle requires energy from which molecule?
A) FADH2
B) ATP and NADPH
C) Oxygen
D) Water
40. What is the initial carbon dioxide acceptor molecule in the Calvin cycle?
A) Phosphoenolpyruvate (PEP)
B) Ribulose-1,5-bisphosphate (RuBP)
C) Malic acid
D) Oxaloacetate
41. Which enzyme catalyzes the initial fixation of carbon dioxide in the Calvin cycle?
A) ATP synthase
B) NADP+ reductase
C) RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase)
D) Phosphoglycerate kinase
42. What is the primary function of the Calvin cycle?
A) To produce ATP and NADPH
B) To split water and release oxygen
C) To fix atmospheric carbon dioxide into organic molecules
D) To absorb light energy
43. The light-independent reactions, also known as the Calvin cycle, occur in which part of the chloroplast?
A) Thylakoid lumen
B) Stroma
C) Granum
D) Intermembrane space
44. What is the source of electrons that enter the electron transport chain during the light-dependent reactions?
A) Oxygen
B) Carbon dioxide
C) Water
D) Glucose
45. The process of photophosphorylation involves the synthesis of ATP using light energy. Which enzyme is crucial for this process?
A) RuBisCO
B) ATP synthase
C) NADP+ reductase
D) Cytochrome oxidase
46. What is the role of NADP+ reductase in the light reactions?
A) To synthesize ATP
B) To split water
C) To reduce NADP+ to NADPH
D) To transfer electrons to Photosystem I
47. Which photosystem is primarily responsible for splitting water molecules?
A) Photosystem I
B) Photosystem II
C) Cytochrome b6f complex
D) ATP synthase
48. What is the main product of the light-dependent reactions that is used in the Calvin cycle?
A) Glucose
B) Oxygen
C) ATP and NADPH
D) Water
49. In which part of the chloroplast does the light-dependent reaction of photosynthesis occur?
A) Stroma
B) Thylakoid membrane
C) Outer membrane
D) Inner membrane
50. What is the primary pigment involved in absorbing light energy during photosynthesis?
A) Carotenoid
B) Chlorophyll a
C) Anthocyanin
D) Xanthophyll
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