Q2. Plants adapted to low light intensity have
[2004]
Correct Answer: (a)
Plants adapted to shade (sciophytes) have larger photosynthetic units (more chlorophyll per reaction center) to capture more light.
Q3. The wavelength of light absorbed by Pr form of phytochrome is
[2007]
Correct Answer: (a)
Pr (Phytochrome Red) absorbs red light at 660-680 nm. Pfr absorbs far-red (730 nm).
Q4. Oxygenic photosynthesis occurs in:
[2009]
Correct Answer: (a)
Oscillatoria is a cyanobacterium which performs oxygenic photosynthesis (uses H₂O and releases O₂). Others are anoxygenic bacteria.
Q5. Oxygen is not produced during photosynthesis by
[2018]
Correct Answer: (a)
Green sulphur bacteria do not use H₂O as a source of hydrogen, therefore oxygen is not evolved. They use H₂S.
Q6. In C₄ plants, Calvin cycle operates in
[1989]
Correct Answer: (a)
Calvin cycle occurs in bundle sheath cells.
Q7. The enzyme that catalyses carbon dioxide fixation in C₄ plants is
[1992]
Correct Answer: (b)
PEP carboxylase.
Q8. A photosynthesising plant is releasing ¹⁸O more than the normal. The plant must have been supplied with
[1993]
Correct Answer: (b)
Oxygen released comes from photolysis of water. If water has ¹⁸O, evolved oxygen will be ¹⁸O.
Q9. The first acceptor of electrons from an excited chlorophyll molecule of photosystem II is
[2007]
Q27. Fixation of one CO₂ molecule through Calvin cycle requires
[2000]
Correct Answer: (c)
3 ATP and 2 NADPH are required per CO₂.
Q28. Stomata of CAM plants
[2003]
Correct Answer: (d)
Scotoactive stomata.
Q29. Which one of the following is wrong in relation to photorespiration ?
[2003]
Correct Answer: (d)
Photorespiration occurs in C₃ plants, not C₄.
Q30. Which enzyme is most abudantly found on earth?
[1999]
Correct Answer: (b)
Rubisco.
Q31. Emerson’s enhancement effect and Red drop have been instrumental in the discovery of
[2016]
Correct Answer: (b)
These effects showed that two photosystems (PS I and PS II) work in series.
Q32. Chromatophores take part in:
[2015 RS]
Correct Answer: (d)
Chromatophores are pigment-containing structures in certain bacteria that perform photosynthesis.
Q33. Chlorophyll in chloroplasts is located in:
[2005]
Correct Answer: (a)
Chlorophyll pigments are embedded in the thylakoid membranes which form grana.
Q34. In photosynthesis the light-independent reactions take place at :
[2015 RS]
Correct Answer: (c)
Light-independent (Dark) reactions occur in the stroma of the chloroplast.
Q35. The principle of limiting factors was proposed by
[1996]
Correct Answer: (a)
Blackman proposed the Law of Limiting Factors in 1905.
Q36. Which element is located at the centre of the porphyrin ring in chlorophyll ?
[2003]
Correct Answer: (c)
Magnesium is the central atom.
Q37. Carbon dioxide joins the photosynthetic pathway in
[1988]
Correct Answer: (d)
CO₂ fixation is the dark reaction.
Q38. In sugarcane plant 14CO₂ is fixed in malic acid, in which the enzyme that fixes CO₂ is
[2003]
Correct Answer: (c)
Sugarcane is C₄. Primary fixation by PEP Carboxylase.
Q39. The first carbon dioxide acceptor in C₄-plants is
[1990, 92]
Correct Answer: (a)
PEP.
Q40. In Kranz anatomy, the bundle sheath cells have
[2011M]
Correct Answer: (b)
Kranz anatomy bundle sheath cells are thick-walled, impervious to gases, and have no intercellular spaces.
Q41. Series of reactions which can convert fatty acids to sugars in plants but not in animals is
[1994]
Correct Answer: (b)
Glyoxylate cycle converts fats to carbohydrates.
Q42. Chlorophyll ‘a’ molecule at its carbon atom 3 of the Pyrrole ring II has one of the following
[1996, 97]
Correct Answer: (b)
Chlorophyll 'a' has a methyl group (-CH₃) at C-3, whereas chlorophyll 'b' has an aldehyde group (-CHO).
Q43. The substrate for photorespiration is
[1989]
Correct Answer: (b)
Glycolate is the substrate oxidized in peroxisomes.
Q44. In a chloroplast the highest number of protons are found in
[2016]
Correct Answer: (b)
Protons (H⁺) accumulate in the lumen of thylakoids due to photolysis of water and pumping of protons from stroma.
Q45. CAM helps the plants in :
[2011]
Correct Answer: (a)
CAM plants open stomata at night to reduce water loss.
Q46. Pigment-containing membranous extensions in some cyanobacteria are :
[2013]
Correct Answer: (c)
Chromatophores are internal membrane systems in cyanobacteria and some other bacteria that contain photosynthetic pigments.
Q47. In photosynthesis energy from light reaction to dark reaction is transferred in the form of
[2002]
Correct Answer: (b)
ATP (and NADPH) carries energy.
Q48. Pigment acting as a reaction centre during photosynthesis is
[1994]
Correct Answer: (c)
P₇₀₀ is the reaction center chlorophyll of PS I.
Q49. Formation of ATP in photosynthesis and respiration is an oxidation process which utilises the energy from
[1992]
Correct Answer: (c)
Energy from electron transport.
Q50. Photorespiration is favoured by
[1996]
Correct Answer: (a)
High O₂ concentration competes with CO₂ for Rubisco.
Q51. The C₄ plants are photosynthetically more efficient than C₃ plants because:
[2007]
Correct Answer: (d)
Answer key says (d). C₄ plants typically have more chloroplasts (dimorphic). However, the main physiological reason is absence of photorespiration. Between options, (d) is a structural feature leading to efficiency.
Q52. The oxygen evolved during photosynthesis comes from water molecules. Which one of the following pairs of elements is involved in this reaction?
[2015 RS]
Correct Answer: (d)
Manganese (Mn) and Chlorine (Cl) are essential for photolysis of water.
Q53. With reference to factors affecting the rate of photosynthesis, which of the following statements is not correct ?
[2017]
Correct Answer: (b)
C₄ plants have a higher temperature optimum than C₃ plants.
Q54. Cytochromes are found in :
[2015 RS]
Correct Answer: (b)
Cytochromes (part of ETC) are located in the inner membrane (cristae) of mitochondria and thylakoids of chloroplasts.
Q55. Chlorophyll a occurs in
[1992]
Correct Answer: (c)
Chlorophyll a is the universal pigment in all oxygen-evolving photosynthetic organisms.
Q56. Water soluble pigments found in plant cell vacuoles are
[2016]
Correct Answer: (d)
Anthocyanins are water soluble pigments found in vacuoles. Chlorophylls, carotenoids and xanthophylls are lipid soluble.
Q57. Electrons from excited chlorophyll molecule of photosystem II are accepted first by: [2008]
[2008]
Correct Answer: (c)
The primary electron acceptor of PS II is Pheophytin, which passes it to Plastoquinone (Quinone). Given options, Quinone is the closest next carrier.
Q58. The specific characteristic of C₄-plants is
[1995]
Correct Answer: (c)
Kranz anatomy is specific to C₄ plants.
Q59. Photochemical reactions in the chloroplast are directly involved in
[2000]
Correct Answer: (d)
Light reaction involves photolysis of water and synthesis of ATP and NADPH.
Q60. Dark reactions of photosynthesis occur in
[1991]
Correct Answer: (c)
Stroma.
Q61. Which of the following absorb light energy for photosynthesis?
[2002]
Correct Answer: (a)
Chlorophyll is the primary pigment that absorbs light energy.
Q62. In photosystem-1 the first electron acceptor is
[2006]
Correct Answer: (c)
The primary acceptor of PS I is an Iron-Sulphur protein (Fe-S).
Q63. Suppose an aquatic plant is placed in a test tube containing distilled water and the tube is stoppered. The tube is left outdoors for 24 hours and the pH value of the water is then measured at regular intervals. Which of the following is the most probable result?
[1997]
Correct Answer: (a)
During the night, respiration occurs releasing CO₂ which forms carbonic acid, lowering pH. Just before sunrise, accumulated CO₂ is maximum, so pH is lowest. During the day, photosynthesis consumes CO₂, raising pH.
Q64. Cytochrome is
[2001]
Correct Answer: (b)
Cytochromes contain Iron (Fe) in a porphyrin ring.
Q65. Ferredoxin is a constituent of
[1991]
Correct Answer: (a)
Ferredoxin is an electron carrier associated with PS I.
Q66. Which one of the following statements about cytochrome P-450 is wrong?
[1998]
Correct Answer: (c)
Cytochrome P-450 is a hemeprotein enzyme, not a cell.
Q67. At a temperature above 35°C
[1992]
Correct Answer: (a)
Photosynthesis involves enzymes (like Rubisco) that are sensitive to high temperatures. Respiration enzymes are relatively more stable. Also, stomatal closure at high temp limits CO₂.
Q68. Photosynthetic pigments found in the chloroplasts occur in
[1991]
Correct Answer: (a)
Pigments are located in the thylakoid membranes where they form photosystems.
Q69. Which pigment system is inactivated in red drop?
[2001]
Correct Answer: (c)
Red drop refers to the drop in quantum yield at wavelengths >680 nm where PS II (which absorbs 680 nm) becomes inactive, leaving only PS I active.
Q70. Photosystem II occurs in
[1992]
Correct Answer: (c)
PS II is located in the appressed regions of grana thylakoids.
Q71. Which fractions of the visible spectrum of solar radiations are primarily absorbed by carotenoids of the higher plants?
[2003]
Correct Answer: (a)
Carotenoids primarily absorb in the blue and violet regions of the spectrum.
Q72. Cyclic photophosphorylation results in formation of
[2009]
Correct Answer: (c)
Cyclic photophosphorylation involves only PS I and produces only ATP.
Q73. Which one of the following is represented by Calvin cycle?
[1996]
Correct Answer: (a)
Calvin cycle involves carboxylation followed by reduction.
Q74. C₄ plants are more efficient in photosynthesis than C₃ plants due to :
[2010]
Correct Answer: (d)
Absence of photorespiration makes C₄ plants more efficient. Also (b) is a factor, but (d) is more direct. Key says (d).
Q75. Bundle sheath cells
[NEET Kar. 2013]
Correct Answer: (a)
Bundle sheath cells in C₄ plants contain RuBisCo for the Calvin cycle.
Q76. Maximum solar energy is trapped by
[1993]
Correct Answer: (c)
Algae have a higher photosynthetic efficiency and can be grown in dense cultures.
Q77. Most plants are green in colour because
[1997]
Correct Answer: (c)
Chlorophyll absorbs mainly blue and red light and reflects green light, making plants appear green.
Q78. The oxygenation activity of RuBisCo enzyme in photorespiration leads to the formation of
[2020]
Correct Answer: (a)
RuBisCo + O₂ -> 1 molecule of Phosphoglycerate (3C) + 1 molecule of Phosphoglycolate (2C).
Q79. As compared to a C₃ – plant, how many additional molecules of ATP are needed for net production of one molecule of hexose sugar by C₄ plants:
[2005]
Correct Answer: (c)
C₃ requires 18 ATP. C₄ requires 30 ATP. Difference is 12 ATP.
Q80. In light reaction, plastoquinone facilitates the transfer of electrons from
[2020]
Correct Answer: (d)
Plastoquinone (PQ) accepts electrons from PS-II and transfers them to the Cytochrome b₆f complex.
Q81. Which of the following is not a product of light reaction of photosynthesis?
[2018]
Correct Answer: (b)
NADH is involved in respiration. The light reaction produces ATP, NADPH, and O₂.
Q82. A plant in your garden avoids photorespiratory losses, has improved water use efficiency, shows high rates of photosynthesis at high temperatures and has improved efficiency of nitrogen utilisation. In which of the following physiological groups would you assign this plant?
[2016]
Correct Answer: (b)
These are characteristics of C₄ plants.
Q83. A very efficient converter of solar energy with net productivity of 2-4 kg/m² or more is the crop of
[1989]
Correct Answer: (b)
Sugarcane is a C₄ plant, which is highly efficient in photosynthesis.
Q84. In Hatch and Slack pathway, the primary CO₂ acceptor is
[2019]
Correct Answer: (d)
PEP (Phosphoenol pyruvate) is the primary CO₂ acceptor in C₄ plants.
Q85. A process that makes important difference between C₃ and C₄ plants is :
[2012]
Correct Answer: (d)
Photorespiration is absent in C₄ plants but present in C₃ plants.
Q86. During monsoon, the rice crop of eastern states of India show lesser yield due to limiting factor of
[1991]
Q87. Photosynthesis in C₄ plants is relatively less limited by atmospheric CO₂ levels because of :
[2005]
Correct Answer: (d)
PEP carboxylase in mesophyll cells has a very high affinity for CO₂ and can fix it even at low concentrations, making C₄ plants efficient.
Q88. Which pair is wrong?
[2001]
Correct Answer: (a)
Maize is a C₄ plant.
Q89. The carbon dioxide acceptor in Calvin cycle/ C₃-plants is
[1993, 95, 96, 99]
Correct Answer: (b)
RuBP.
Q90. Kranz anatomy is typical of
[1990]
Correct Answer: (a)
C₄ plants.
Q91. The enzyme which fixes CO₂ in C₄ plants is
[2000]
Correct Answer: (b)
PEP Carboxylase.
Q92. C₄-cycle was discovered by
[1994]
Correct Answer: (a)
Hatch and Slack.
Q93. Which one occurs both during cyclic and noncyclic modes of photophosphorylation?
[1994]
Correct Answer: (b)
ATP formation occurs in both.
Q94. All types of plastids possess essentially the same structure because they
[1992]
Correct Answer: (d)
Plastids (chloroplasts, chromoplasts, leucoplasts) are interconvertible.
Q95. The structures that are formed by stacking of organized flattened membranous sacs in the chloroplasts are :
[2015 RS]
Correct Answer: (a)
Grana are formed by the stacking of thylakoids (flattened membranous sacs).
Q96. In leaves of C₄ plants malic acid synthesis during CO₂ fixation occurs in
[2008]
Correct Answer: (b)
Initial fixation occurs in mesophyll cells forming OAA then Malic acid.
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