Question 1. Which of the following statements about the early experiments on photosynthesis is incorrect?
(a) Joseph Priestley discovered oxygen and demonstrated the essential role of air in the growth of green plants.
(b) Jan Ingenhousz showed that only the green parts of plants could release oxygen in the presence of sunlight.
(c) Julius von Sachs proved that plants store glucose as glycogen in special bodies within plant cells.
(d) T.W. Engelmann used a prism to split light and illuminated a green alga, Cladophora, to describe the first action spectrum.
Answer: (c).
Question 2. Cornelius van Niel’s milestone contribution to the understanding of photosynthesis was based on his studies of which organisms?
(a) Green algae and aerobic bacteria.
(b) Purple and green sulphur bacteria.
(c) Blue-green algae and fungi.
(d) Higher plants and diatoms.
Answer: (b).
Question 3. In the overall equation of photosynthesis, the oxygen released comes from water. This was conclusively proved by using which of the following techniques?
(a) Paper chromatography.
(b) Radioisotopic techniques.
(c) X-ray crystallography.
(d) Centrifugation.
Answer: (b).
Question 4. Identify the correct match between the scientist and their experimental setup or organism used.
(a) Priestley - Mint plant and a burning candle.
(b) Ingenhousz - Cladophora and aerobic bacteria.
(c) Engelmann - Aquatic plant in dark and sunlight.
(d) Sachs - Purple sulphur bacteria.
Answer: (a).
Question 5. The action spectrum of photosynthesis roughly correlates with the absorption spectra of which of the following pigments?
(a) Chlorophyll a and carotenoids.
(b) Chlorophyll b and xanthophylls.
(c) Chlorophyll a and chlorophyll b.
(d) Carotenoids and xanthophylls.
Answer: (c).
Question 6. Under which condition do the chloroplasts align themselves with their flat surfaces perpendicular to the incident light?
(a) When the light intensity is extremely low.
(b) When the light intensity is optimum.
(c) When the light intensity is extremely high to avoid photo-oxidation.
(d) Chloroplasts never align perpendicularly to light.
Answer: (c).
Question 7. In the chloroplast, the stroma lamellae lack which of the following components?
(a) PS I and ATP synthase.
(b) PS II and NADP reductase enzyme.
(c) PS I and NADP reductase enzyme.
(d) PS II and PS I.
Answer: (b).
Question 8. The dark reactions (carbon reactions) of photosynthesis are so called because they:
(a) Occur exclusively during the night.
(b) Do not require light directly but depend on the products of light reactions.
(c) Cannot occur in the presence of light.
(d) Are independent of temperature and entirely light-driven.
Answer: (b).
Question 9. Paper chromatography of a green leaf extract shows that the color of chlorophyll b in the chromatogram is:
(a) Bright or blue green.
(b) Yellow green.
(c) Yellow.
(d) Yellow to yellow-orange.
Answer: (b).
Question 10. Accessory pigments in photosynthesis include all of the following, except:
(a) Chlorophyll a.
(b) Chlorophyll b.
(c) Xanthophylls.
(d) Carotenoids.
Answer: (a).
Question 11. What is the primary function of the accessory pigments in the thylakoid membrane?
(a) To act as the primary reaction center.
(b) To synthesise ATP directly from light energy.
(c) To enable a wider range of wavelengths to be utilised and protect chlorophyll a from photo-oxidation.
(d) To fix carbon dioxide into glucose.
Answer: (c).
Question 12. In Photosystem I (PS I), the reaction center chlorophyll a has an absorption peak at:
(a) 680 nm.
(b) 700 nm.
(c) 660 nm.
(d) 720 nm.
Answer: (b).
Question 13. The Light Harvesting Complex (LHC) is composed of hundreds of pigment molecules bound to:
(a) Lipids.
(b) Carbohydrates.
(c) Proteins.
(d) Nucleic acids.
Answer: (c).
Question 14. During the Z-scheme of electron transport, the electrons from PS II are passed to an electron acceptor that acts as a:
(a) Reducing agent.
(b) Primary electron donor.
(c) Mobile electron carrier in the stroma.
(d) Component having a more positive redox potential scale.
Answer: (d).
Question 15. The splitting of water is associated with which component of the photosynthetic machinery?
(a) PS I, located on the outer surface of the thylakoid membrane.
(b) PS II, located on the inner side of the thylakoid membrane.
(c) Stroma lamellae.
(d) ATP synthase in the stroma.
Answer: (b).
Question 16. In non-cyclic photophosphorylation, the products formed are:
(a) ATP only.
(b) ATP and NADPH.
(c) NADPH only.
(d) ATP, NADPH, and O2.
Answer: (d).
Question 17. Cyclic photophosphorylation occurs usually when:
(a) Light of wavelength less than 680 nm is available.
(b) Light of wavelength beyond 680 nm is available for excitation.
(c) Both PS I and PS II are functional simultaneously.
(d) The plant is exposed to extremely low temperatures.
Answer: (b).
Question 18. According to the chemiosmotic hypothesis, ATP synthesis is linked to the development of:
(a) An electron gradient across the chloroplast membrane.
(b) A proton gradient across the thylakoid membrane.
(c) A sodium ion gradient in the stroma.
(d) A concentration gradient of oxygen in the lumen.
Answer: (b).
Question 19. During light reactions, protons accumulate in which part of the chloroplast?
(a) Stroma.
(b) Thylakoid lumen.
(c) Outer membrane space.
(d) Matrix.
Answer: (b).
Question 20. The enzyme NADP reductase is located on the:
(a) Inner side of the thylakoid membrane.
(b) Stroma side of the thylakoid membrane.
(c) Lumen side of the thylakoid membrane.
(d) Outer membrane of the chloroplast.
Answer: (b).
Question 21. Which component of the ATP synthase acts as a transmembrane channel that carries out facilitated diffusion of protons across the membrane?
(a) CF1.
(b) CF0.
(c) Plastocyanin.
(d) Cytochrome b6f.
Answer: (b).
Question 22. For the synthesis of one molecule of ATP, how many protons pass through the CF0 channel from the lumen to the stroma?
(a) 1.
(b) 2.
(c) 3.
(d) 4.
Answer: (b).
Question 23. What are the immediate products of light reactions that are consumed in the dark reactions to fix carbon dioxide?
(a) ATP, H2O, and O2.
(b) ATP and NADPH.
(c) NADPH and O2.
(d) Glucose and ATP.
Answer: (b).
Question 24. The primary acceptor of CO2 in the C3 cycle is a:
(a) 3-carbon compound (PGA).
(b) 5-carbon ketose sugar (RuBP).
(c) 4-carbon organic acid (OAA).
(d) 2-carbon compound (Phosphoglycolate).
Answer: (b).
Question 25. The first stable product of CO2 fixation in C3 plants is:
(a) Oxaloacetic acid (OAA).
(b) Ribulose-1,5-bisphosphate (RuBP).
(c) 3-phosphoglyceric acid (3-PGA).
(d) Phosphoenolpyruvate (PEP).
Answer: (c).
Question 26. Which of the following is the most crucial step of the Calvin cycle where CO2 is utilized?
(a) Carboxylation.
(b) Reduction.
(c) Regeneration.
(d) Phosphorylation.
Answer: (a).
Question 27. The reduction step of the Calvin cycle for the fixation of one molecule of CO2 requires:
(a) 1 ATP and 1 NADPH.
(b) 2 ATP and 2 NADPH.
(c) 3 ATP and 2 NADPH.
(d) 2 ATP and 1 NADPH.
Answer: (b).
Question 28. How many turns of the Calvin cycle are required for the formation of one molecule of glucose?
(a) 2.
(b) 4.
(c) 6.
(d) 8.
Answer: (c).
Question 29. The regeneration of RuBP from triose phosphate requires the consumption of:
(a) 1 ATP per turn of the cycle.
(b) 2 ATP per turn of the cycle.
(c) 1 NADPH per turn of the cycle.
(d) No energy expenditure is required.
Answer: (a).
Question 30. For the synthesis of one glucose molecule, the total requirement of ATP and NADPH in the C3 cycle is:
(a) 12 ATP and 12 NADPH.
(b) 18 ATP and 12 NADPH.
(c) 30 ATP and 12 NADPH.
(d) 18 ATP and 18 NADPH.
Answer: (b).
Question 31. Which of the following plants possess Kranz anatomy?
(a) Rice and wheat.
(b) Maize and sorghum.
(c) Tomato and bell pepper.
(d) Sunflower and mango.
Answer: (b).
Question 32. In Kranz anatomy, the bundle sheath cells are characterized by:
(a) Thin walls, lack of intercellular spaces, and few chloroplasts.
(b) Thick walls impervious to gas exchange, no intercellular spaces, and large number of chloroplasts.
(c) Thin walls, large intercellular spaces, and presence of grana in chloroplasts.
(d) Thick walls, presence of intercellular spaces, and no chloroplasts.
Answer: (b).
Question 33. The primary CO2 acceptor in the C4 pathway is:
(a) RuBP.
(b) Phosphoenolpyruvate (PEP).
(c) Oxaloacetic acid (OAA).
(d) Malic acid.
Answer: (b).
Question 34. In C4 plants, the enzyme responsible for primary CO2 fixation is present in:
(a) Bundle sheath cells.
(b) Mesophyll cells.
(c) Epidermal cells.
(d) Guard cells.
Answer: (b).
Question 35. Which of the following enzymes is absent in the mesophyll cells of C4 plants?
(a) PEP carboxylase.
(b) RuBisCO.
(c) Malate dehydrogenase.
(d) Carbonic anhydrase.
Answer: (b).
Question 36. The 4-carbon acid formed in the mesophyll cells of C4 plants is transported to bundle sheath cells where it is:
(a) Reduced to carbohydrates.
(b) Decarboxylated to release CO2 and a 3-carbon acid.
(c) Carboxylated to form a 5-carbon acid.
(d) Polymerized into starch.
Answer: (b).
Question 37. What is the fate of the 3-carbon acid produced after decarboxylation in the bundle sheath cells of C4 plants?
(a) It is converted to glucose.
(b) It is transported back to the mesophyll cells to regenerate PEP.
(c) It undergoes photorespiration.
(d) It acts as a primary CO2 acceptor in the Calvin cycle.
Answer: (b).
Question 38. C4 plants are adapted to tolerate:
(a) High temperatures and high light intensities.
(b) Low temperatures and high light intensities.
(c) High temperatures and low light intensities.
(d) Low temperatures and low light intensities.
Answer: (a).
Question 39. The Calvin cycle occurs in which cells of C4 plants?
(a) Only in mesophyll cells.
(b) Only in bundle sheath cells.
(c) In both mesophyll and bundle sheath cells.
(d) In neither mesophyll nor bundle sheath cells.
Answer: (b).
Question 40. RuBisCO is characterized by the fact that its active site can bind to:
(a) Only CO2.
(b) Only O2.
(c) Both CO2 and O2.
(d) Neither CO2 nor O2.
Answer: (c).
Question 41. In C3 plants, when O2 binds to RuBisCO, RuBP is converted into:
(a) Two molecules of 3-PGA.
(b) One molecule of phosphoglycerate and one molecule of phosphoglycolate.
(c) One molecule of oxaloacetate and one molecule of malate.
(d) Two molecules of phosphoglycolate.
Answer: (b).
Question 42. Which of the following is true regarding photorespiration?
(a) It results in the synthesis of ATP and NADPH.
(b) It involves the release of CO2 with the utilization of ATP.
(c) It increases the overall photosynthetic yield.
(d) It operates efficiently in C4 plants.
Answer: (b).
Question 43. Why do C4 plants lack photorespiration?
(a) Because they do not have RuBisCO enzyme.
(b) Because they have a mechanism that increases CO2 concentration at the enzyme site.
(c) Because their stomata remain closed during the daytime.
(d) Because they only perform the light reactions of photosynthesis.
Answer: (b).
Question 44. The most abundant enzyme in the world is:
(a) PEP carboxylase.
(b) RuBisCO.
(c) Nitrogenase.
(d) Invertase.
Answer: (b).
Question 45. According to Blackman's Law of Limiting Factors, if a chemical process is affected by more than one factor, its rate will be determined by the factor which is:
(a) Nearest to its maximal value.
(b) Nearest to its minimal value.
(c) Most abundantly present in the environment.
(d) Constantly fluctuating.
Answer: (b).
Question 46. At low light intensities, an increase in CO2 concentration:
(a) Causes a linear increase in the rate of photosynthesis.
(b) Causes a rapid decrease in the rate of photosynthesis.
(c) Does not cause any significant increase in the rate of photosynthesis.
(d) Initiates the photorespiratory pathway.
Answer: (c).
Question 47. Light saturation for photosynthesis in typical plants occurs at what percentage of full sunlight?
(a) 10 percent.
(b) 25 percent.
(c) 50 percent.
(d) 75 percent.
Answer: (a).
Question 48. An increase in incident light beyond the saturation point leads to:
(a) Enhanced rate of carbon fixation.
(b) Opening of more stomata.
(c) Breakdown of chlorophyll and a decrease in photosynthesis.
(d) Transformation of C3 plants into C4 plants.
Answer: (c).
Question 49. The current atmospheric concentration of CO2 is approximately:
(a) 100-200 ppm.
(b) 300-400 ppm.
(c) 500-600 ppm.
(d) 700-800 ppm.
Answer: (b).
Question 50. C3 and C4 plants respond differently to CO2 concentrations. C4 plants show saturation at about:
(a) 360 µlL-1.
(b) 450 µlL-1.
(c) 500 µlL-1.
(d) 1000 µlL-1.
Answer: (a).
Question 51. Which plants are generally grown in greenhouse conditions due to their higher yield at elevated CO2 concentrations?
(a) Maize and sorghum.
(b) Tomato and bell pepper.
(c) Sugarcane and millet.
(d) Cactus and euphorbia.
Answer: (b).
Question 52. The dark reactions are temperature controlled because they are:
(a) Enzymatic.
(b) Photochemical.
(c) Dependent solely on physical gradients.
(d) Carried out by pigments directly.
Answer: (a).
Question 53. The temperature optimum for photosynthesis of different plants depends on:
(a) The type of light they receive.
(b) The habitat that they are adapted to.
(c) The amount of water in the soil.
(d) The thickness of their cuticle.
Answer: (b).
Question 54. Water stress mainly affects photosynthesis by:
(a) Directly reducing the splitting of water in PS II.
(b) Causing the stomata to close, thereby reducing CO2 availability.
(c) Increasing the rate of photorespiration exponentially.
(d) Destroying the structure of chloroplasts instantly.
Answer: (b).
Question 55. Besides closing stomata, water stress also causes:
(a) Swelling of leaves to increase surface area.
(b) Wilting of leaves, reducing their surface area and metabolic activity.
(c) Immediate conversion of all starch into glucose.
(d) Increased synthesis of RuBisCO.
Answer: (b).
Question 56. Assertion (A): In C4 plants, the initial carboxylation reaction occurs in the mesophyll cells. Reason (R): Mesophyll cells in C4 plants possess RuBisCO.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) Both A and R are false.
Answer: (c).
Question 57. Which of the following sequences best represents the flow of electrons during non-cyclic photophosphorylation?
(a) PS II -> Cytochrome b6f -> PS I -> NADP+.
(b) PS I -> Cytochrome b6f -> PS II -> NADP+.
(c) H2O -> PS I -> PS II -> NADP+.
(d) PS II -> PS I -> Cytochrome b6f -> O2.
Answer: (a).
Question 58. The first product of the Hatch and Slack pathway is:
(a) Phosphoenolpyruvate.
(b) Oxaloacetic acid.
(c) Phosphoglyceric acid.
(d) Malic acid.
Answer: (b).
Question 59. In the chemiosmotic model, the energy released during electron transport is primarily used to:
(a) Synthesize glucose directly.
(b) Pump protons from the stroma into the thylakoid lumen.
(c) Reduce oxygen to water.
(d) Break down ATP.
Answer: (b).
Question 60. How many ATP and NADPH are required to produce 1 molecule of glucose in the C4 pathway?
(a) 18 ATP and 12 NADPH.
(b) 30 ATP and 12 NADPH.
(c) 12 ATP and 12 NADPH.
(d) 24 ATP and 12 NADPH.
Answer: (b).
Question 61. Read the following statements and select the correct option. Statement I: C4 plants are more efficient than C3 plants in terms of carbon fixation. Statement II: C4 plants lose less water per gram of carbon fixed than C3 plants.
(a) Both statements are true.
(b) Statement I is true, Statement II is false.
(c) Statement I is false, Statement II is true.
(d) Both statements are false.
Answer: (a).
Question 62. Which wavelength range defines the Photosynthetically Active Radiation (PAR)?
(a) 300 - 400 nm.
(b) 400 - 700 nm.
(c) 500 - 600 nm.
(d) 700 - 900 nm.
Answer: (b).
Question 63. During photosynthesis, what is the ultimate electron donor?
(a) NADPH.
(b) H2S.
(c) H2O.
(d) CO2.
Answer: (c).
Question 64. Identify the incorrect statement regarding cyclic photophosphorylation.
(a) It involves only PS I.
(b) It takes place in the stroma lamellae.
(c) It results in the synthesis of both ATP and NADPH.
(d) The electron returns to the reaction center after passing through the ETC.
Answer: (c).
Question 65. The chloroplasts of bundle sheath cells in C4 plants are:
(a) Granum-rich and lack starch grains.
(b) Agranum (without grana) and contain starch grains.
(c) Small in size and highly numerous.
(d) Lacking RuBisCO.
Answer: (b).
Question 66. The movement of electrons in the Z-scheme is:
(a) Entirely uphill (against redox potential).
(b) Entirely downhill.
(c) Uphill when excited by light, and downhill through the electron transport chain.
(d) Random across the membrane.
Answer: (c).
Question 67. To make one molecule of sucrose (12 carbons), how many turns of the Calvin cycle are needed?
(a) 2.
(b) 6.
(c) 12.
(d) 24.
Answer: (c).
Question 68. Assertion (A): Photorespiration is a wasteful process. Reason (R): It results in neither the synthesis of sugars nor of ATP, but instead utilizes ATP to release CO2.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) Both A and R are false.
Answer: (a).
Question 69. Which pair of organelles is involved in photorespiration along with the chloroplast?
(a) Mitochondria and Ribosomes.
(b) Peroxisomes and Mitochondria.
(c) Lysosomes and Dictyosomes.
(d) Endoplasmic Reticulum and Golgi bodies.
Answer: (b).
Question 70. In an experiment, if the concentration of atmospheric CO2 is artificially raised to 500 ppm, which group of plants will show a continuous increase in productivity?
(a) C4 plants like maize.
(b) C3 plants like tomato.
(c) CAM plants like pineapple.
(d) Desert ephemerals.
Answer: (b).
Question 71. The essential role of magnesium in photosynthesis is related to:
(a) Being a structural component of the chlorophyll porphyrin ring.
(b) Acting as the final electron acceptor in the ETC.
(c) Assisting the opening of stomata.
(d) Forming the core of the ATP synthase complex.
Answer: (a).
Question 72. Which scientist demonstrated that photosynthesis is essentially a light-dependent reaction wherein hydrogen from a suitable oxidisable compound reduces CO2 to carbohydrates?
(a) Jan Ingenhousz.
(b) T.W. Engelmann.
(c) Cornelius van Niel.
(d) Joseph Priestley.
Answer: (c).
Question 73. In C4 plants, the bundle sheath cells are arranged in a specific pattern around the vascular bundles. This arrangement is termed:
(a) Casparian strip.
(b) Kranz anatomy.
(c) Reticulate venation.
(d) Bulliform arrangement.
Answer: (b).
Question 74. Which of the following is not required for the Calvin cycle?
(a) CO2.
(b) ATP.
(c) O2.
(d) NADPH.
Answer: (c).
Question 75. The breakdown of the proton gradient across the thylakoid membrane is driven by:
(a) The movement of protons through CF1.
(b) The movement of protons through CF0.
(c) The active pumping of protons by cytochrome b6f.
(d) The splitting of water molecules.
Answer: (b).
Question 76. RuBisCO acts as an oxygenase when the ratio of O2 to CO2 is:
(a) Exceptionally low.
(b) High.
(c) Balanced at 1:1.
(d) Only in the dark.
Answer: (b).
Question 77. The enzyme responsible for fixing CO2 in the mesophyll cells of C4 plants is:
(a) Phosphoenolpyruvate carboxylase.
(b) Ribulose bisphosphate carboxylase.
(c) Hexokinase.
(d) Pyruvate kinase.
Answer: (a).
Question 78. During the reduction phase of the Calvin cycle, PGA is converted into:
(a) RuBP.
(b) Triose phosphate.
(c) OAA.
(d) PEP.
Answer: (b).
Question 79. The law of limiting factors was proposed by:
(a) F.F. Blackman.
(b) T.W. Engelmann.
(c) Julius von Sachs.
(d) Melvin Calvin.
Answer: (a).
Question 80. How many molecules of water are utilized to yield 6 molecules of oxygen in the balanced equation of photosynthesis?
(a) 6.
(b) 12.
(c) 18.
(d) 24.
Answer: (b).
Question 81. Assertion (A): Plants that undergo C4 pathway show lack of photorespiration. Reason (R): C4 plants have a mechanism that ensures high CO2 concentration at the enzyme site of RuBisCO.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) Both A and R are false.
Answer: (a).
Question 82. What does 'Kranz' mean in the context of Kranz anatomy?
(a) Wreath or ring.
(b) Star-shaped.
(c) Thick-walled.
(d) Parallel.
Answer: (a).
Question 83. The action spectrum of photosynthesis was first described using:
(a) Purple sulphur bacteria.
(b) Cladophora and aerobic bacteria.
(c) Mint plant and a mouse.
(d) Chlorella and radioactive carbon.
Answer: (b).
Question 84. Which stage of the Calvin cycle utilizes both ATP and NADPH?
(a) Carboxylation.
(b) Reduction.
(c) Regeneration.
(d) Decarboxylation.
Answer: (b).
Question 85. The transport of malic acid from mesophyll cells to bundle sheath cells in C4 plants occurs through:
(a) Xylem vessels.
(b) Phloem sieve tubes.
(c) Plasmodesmata.
(d) Stomatal pores.
Answer: (c).
Question 86. How many extra ATP molecules are required for the fixation of one CO2 in C4 plants compared to C3 plants?
(a) 1.
(b) 2.
(c) 3.
(d) 5.
Answer: (b).
Question 87. In the Hatch and Slack pathway, the regeneration of PEP occurs in the:
(a) Stroma of bundle sheath chloroplasts.
(b) Cytoplasm of bundle sheath cells.
(c) Mesophyll cells.
(d) Vacuoles of mesophyll cells.
Answer: (c).
Question 88. The presence of which element is essential for the photolysis of water in PS II?
(a) Manganese.
(b) Zinc.
(c) Copper.
(d) Molybdenum.
Answer: (a).
Question 89. If a plant is exposed to green light exclusively, the rate of photosynthesis will:
(a) Be at its maximum.
(b) Be completely unaffected compared to white light.
(c) Decrease significantly as chlorophyll poorly absorbs green light.
(d) Increase because chlorophyll is green.
Answer: (c).
Question 90. The process by which the energy of a photon is transferred from one pigment molecule to another in the antenna complex is called:
(a) Active transport.
(b) Resonance energy transfer.
(c) Electron excitation.
(d) Photolysis.
Answer: (b).
Question 91. A plant in your garden avoids photorespiratory losses, has improved water use efficiency, and shows high rates of photosynthesis at high temperatures. It is likely a:
(a) C3 plant.
(b) C4 plant.
(c) CAM plant.
(d) Parasitic plant.
Answer: (b).
Question 92. Identify the incorrect statement about the stroma lamellae.
(a) They connect the thylakoids of different grana.
(b) They lack Photosystem II.
(c) They possess the NADP reductase enzyme.
(d) They are the primary site for cyclic photophosphorylation.
Answer: (c).
Question 93. In the Z-scheme, the excited electrons from PS II are received by the primary acceptor and then passed down an electron transport chain consisting of:
(a) Cytochromes.
(b) Plastocyanin only.
(c) Plastoquinone only.
(d) Ferredoxin.
Answer: (a).
Question 94. During chemiosmosis in chloroplasts, protons are pumped:
(a) From the lumen to the stroma.
(b) From the stroma to the lumen.
(c) From the cytoplasm to the stroma.
(d) From the stroma to the cytoplasm.
Answer: (b).
Question 95. The conformational change in the CF1 particle of ATP synthase is induced by:
(a) The absorption of photons directly by CF1.
(b) The breakdown of the proton gradient.
(c) The binding of NADPH.
(d) The reduction of oxygen.
Answer: (b).
Question 96. Which is the correct sequence of the three main stages of the Calvin cycle?
(a) Reduction -> Carboxylation -> Regeneration.
(b) Regeneration -> Reduction -> Carboxylation.
(c) Carboxylation -> Reduction -> Regeneration.
(d) Carboxylation -> Regeneration -> Reduction.
Answer: (c).
Question 97. The term ‘dark reactions’ is a misnomer because:
(a) They occur only during the night.
(b) They are strictly independent of light and products of light reactions.
(c) They occur in the presence of light, dependent on ATP and NADPH.
(d) They occur in the darkest parts of the root cells.
Answer: (c).
Question 98. When the incident light intensity increases beyond a certain point, the rate of photosynthesis does not increase. This is because:
(a) Stomata close to conserve water.
(b) Other factors become limiting.
(c) The plant begins to photorespire actively.
(d) Chloroplasts migrate to the root.
Answer: (b).
Question 99. The most significant adaptation of C4 plants for surviving in dry tropical regions is:
(a) Having large, broad leaves.
(b) Concentrating CO2 around RuBisCO to eliminate photorespiration.
(c) Lacking cuticles to absorb more atmospheric moisture.
(d) Keeping stomata open continuously throughout the day and night.
Answer: (b).
Question 100. Select the correct statement regarding the enzymes of the C4 pathway.
(a) Both PEPcase and RuBisCO are found in mesophyll cells.
(b) PEPcase is found in mesophyll cells, while RuBisCO is in bundle sheath cells.
(c) PEPcase is in bundle sheath cells, while RuBisCO is in mesophyll cells.
(d) Both enzymes are exclusively found in bundle sheath cells.
Answer: (b).
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