Q2. The C₄ plants are photosynthetically more efficient than C₃ plants because:
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.
Q3. NADPH is generated through
Correct Answer: (a)
NADPH is produced at the end of the electron transport chain associated with Photosystem I.
Q4. Emerson’s enhancement effect and Red drop have been instrumental in the discovery of
Correct Answer: (b)
These effects showed that two photosystems (PS I and PS II) work in series.
Q5. Chromatophores take part in:
Correct Answer: (d)
Chromatophores are pigment-containing structures in certain bacteria that perform photosynthesis.
Q6. Pigment acting as a reaction centre during photosynthesis is
Correct Answer: (c)
P₇₀₀ is the reaction center chlorophyll of PS I.
Q7. Which enzyme is most abudantly found on earth?
Correct Answer: (b)
Rubisco.
Q8. Bundle sheath cells
Correct Answer: (a)
Bundle sheath cells in C₄ plants contain RuBisCo for the Calvin cycle.
Q9. In photosynthesis the light-independent reactions take place at :
Correct Answer: (c)
Light-independent (Dark) reactions occur in the stroma of the chloroplast.
Q10. All types of plastids possess essentially the same structure because they
Correct Answer: (d)
Plastids (chloroplasts, chromoplasts, leucoplasts) are interconvertible.
Q11. Kranz anatomy is typical of
Correct Answer: (a)
C₄ plants.
Q12. The substrate for photorespiration is
Correct Answer: (b)
Glycolate is the substrate oxidized in peroxisomes.
Q13. The carbon dioxide acceptor in Calvin cycle/ C₃-plants is
Correct Answer: (b)
RuBP.
Q14. The enzyme which fixes CO₂ in C₄ plants is
Correct Answer: (b)
PEP Carboxylase.
Q15. Which of the following absorb light energy for photosynthesis?
Correct Answer: (a)
Chlorophyll is the primary pigment that absorbs light energy.
Q16. The first carbon dioxide acceptor in C₄-plants is
Correct Answer: (a)
PEP.
Q17. Which pair is wrong?
Correct Answer: (a)
Maize is a C₄ plant.
Q18. Photosynthetic pigments found in the chloroplasts occur in
Correct Answer: (a)
Pigments are located in the thylakoid membranes where they form photosystems.
Q19. Protochlorophyll differs from chlorophyll in lacking
Correct Answer: (a)
Protochlorophyll is converted to chlorophyll by the addition of 2 hydrogen atoms (reduction).
Q20. In C₄ plants, Calvin cycle operates in
Correct Answer: (a)
Calvin cycle occurs in bundle sheath cells.
Q21. PGA as the first CO₂ fixation product was discovered in photosynthesis of :
Correct Answer: (d)
Melvin Calvin discovered PGA in the alga Chlorella.
Q22. Which of the following is not a product of light reaction of photosynthesis?
Correct Answer: (b)
NADH is involved in respiration. The light reaction produces ATP, NADPH, and O₂.
Q23. NADP⁺ is reduced to NADPH in
Correct Answer: (d)
Noncyclic electron transport reduces NADP⁺.
Q24. 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?
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.
Q25. In photosystem-1 the first electron acceptor is
Correct Answer: (c)
The primary acceptor of PS I is an Iron-Sulphur protein (Fe-S).
Q26. Series of reactions which can convert fatty acids to sugars in plants but not in animals is
Correct Answer: (b)
Glyoxylate cycle converts fats to carbohydrates.
Q27. With reference to factors affecting the rate of photosynthesis, which of the following statements is not correct ?
Correct Answer: (b)
C₄ plants have a higher temperature optimum than C₃ plants.
Q28. A photosynthesising plant is releasing ¹⁸O more than the normal. The plant must have been supplied with
Correct Answer: (b)
Oxygen released comes from photolysis of water. If water has ¹⁸O, evolved oxygen will be ¹⁸O.
Q29. Anoxygenic photosynthesis is characteristic of:
Correct Answer: (a)
Rhodospirillum is a purple non-sulphur bacterium that performs anoxygenic photosynthesis (does not produce oxygen).
Q30. Cyclic photophosphorylation results in formation of
Correct Answer: (c)
Cyclic photophosphorylation involves only PS I and produces only ATP.
Q31. Electrons from excited chlorophyll molecule of photosystem II are accepted first by: [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.
Q32. Which one of the following is wrong in relation to photorespiration ?
Correct Answer: (d)
Photorespiration occurs in C₃ plants, not C₄.
Q33. Stomata of CAM plants
Correct Answer: (d)
Scotoactive stomata.
Q34. Photochemical reactions in the chloroplast are directly involved in
Correct Answer: (d)
Light reaction involves photolysis of water and synthesis of ATP and NADPH.
Q35. Most plants are green in colour because
Correct Answer: (c)
Chlorophyll absorbs mainly blue and red light and reflects green light, making plants appear green.
Q36. 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:
Correct Answer: (c)
C₃ requires 18 ATP. C₄ requires 30 ATP. Difference is 12 ATP.
Q37. In a chloroplast the highest number of protons are found in
Correct Answer: (b)
Protons (H⁺) accumulate in the lumen of thylakoids due to photolysis of water and pumping of protons from stroma.
Q38. The correct sequence of cell organelles during photorespiration is :
Q54. In leaves of C₄ plants malic acid synthesis during CO₂ fixation occurs in
Correct Answer: (b)
Initial fixation occurs in mesophyll cells forming OAA then Malic acid.
Q55. Fixation of one CO₂ molecule through Calvin cycle requires
Correct Answer: (c)
3 ATP and 2 NADPH are required per CO₂.
Q56. Photorespiration is favoured by
Correct Answer: (a)
High O₂ concentration competes with CO₂ for Rubisco.
Q57. Photosystem II occurs in
Correct Answer: (c)
PS II is located in the appressed regions of grana thylakoids.
Q58. Chlorophyll a occurs in
Correct Answer: (c)
Chlorophyll a is the universal pigment in all oxygen-evolving photosynthetic organisms.
Q59. In light reaction, plastoquinone facilitates the transfer of electrons from
Correct Answer: (d)
Plastoquinone (PQ) accepts electrons from PS-II and transfers them to the Cytochrome b₆f complex.
Q60. Oxygenic photosynthesis occurs in:
Correct Answer: (a)
Oscillatoria is a cyanobacterium which performs oxygenic photosynthesis (uses H₂O and releases O₂). Others are anoxygenic bacteria.
Q61. In C₃ plants, the first stable product of photosynthesis during the dark reaction is
Q62. A very efficient converter of solar energy with net productivity of 2-4 kg/m² or more is the crop of
Correct Answer: (b)
Sugarcane is a C₄ plant, which is highly efficient in photosynthesis.
Q63. Ferredoxin is a constituent of
Correct Answer: (a)
Ferredoxin is an electron carrier associated with PS I.
Q64. Cytochromes are found in :
Correct Answer: (b)
Cytochromes (part of ETC) are located in the inner membrane (cristae) of mitochondria and thylakoids of chloroplasts.
Q65. Which element is located at the centre of the porphyrin ring in chlorophyll ?
Correct Answer: (c)
Magnesium is the central atom.
Q66. The specific characteristic of C₄-plants is
Correct Answer: (c)
Kranz anatomy is specific to C₄ plants.
Q67. Pigment-containing membranous extensions in some cyanobacteria are :
Correct Answer: (c)
Chromatophores are internal membrane systems in cyanobacteria and some other bacteria that contain photosynthetic pigments.
Q68. Cytochrome is
Correct Answer: (b)
Cytochromes contain Iron (Fe) in a porphyrin ring.
Q69. At a temperature above 35°C
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.
Q70. In the leaves of C₄ plants, malic acid formation during CO₂ fixation occurs in the cells of
Correct Answer: (d)
Mesophyll cells.
Q71. Plants adapted to low light intensity have
Correct Answer: (a)
Plants adapted to shade (sciophytes) have larger photosynthetic units (more chlorophyll per reaction center) to capture more light.
Q72. Nine-tenth of all photosynthesis of world (85-90%) is carried out by
Correct Answer: (b)
Marine algae (phytoplankton) account for the vast majority of global photosynthesis.
Q73. Maximum solar energy is trapped by
Correct Answer: (c)
Algae have a higher photosynthetic efficiency and can be grown in dense cultures.
Q74. In Hatch and Slack pathway, the primary CO₂ acceptor is
Correct Answer: (d)
PEP (Phosphoenol pyruvate) is the primary CO₂ acceptor in C₄ plants.
Q75. Chlorophyll ‘a’ molecule at its carbon atom 3 of the Pyrrole ring II has one of the following
Correct Answer: (b)
Chlorophyll 'a' has a methyl group (-CH₃) at C-3, whereas chlorophyll 'b' has an aldehyde group (-CHO).
Q76. The enzyme that catalyses carbon dioxide fixation in C₄ plants is
Correct Answer: (b)
PEP carboxylase.
Q77. The principle of limiting factors was proposed by
Correct Answer: (a)
Blackman proposed the Law of Limiting Factors in 1905.
Q78. How many turns of Calvin cycle yield one molecule of glucose ?
Correct Answer: (c)
6 turns.
Q79. Which fractions of the visible spectrum of solar radiations are primarily absorbed by carotenoids of the higher plants?
Correct Answer: (a)
Carotenoids primarily absorb in the blue and violet regions of the spectrum.
Q80. The size of chlorophyll molecule is
Correct Answer: (a)
The porphyrin head is approx 15x15 Å and the phytol tail is approx 20-25 Å long.
Q81. The wavelength of light absorbed by Pr form of phytochrome is
Correct Answer: (a)
Pr (Phytochrome Red) absorbs red light at 660-680 nm. Pfr absorbs far-red (730 nm).
Q82. Which one occurs both during cyclic and noncyclic modes of photophosphorylation?
Correct Answer: (b)
ATP formation occurs in both.
Q83. CAM helps the plants in :
Correct Answer: (a)
CAM plants open stomata at night to reduce water loss.
Q84. The first step of photosynthesis is
Correct Answer: (a)
Absorption of light energy excites electrons in chlorophyll.
Q85. During photorespiration, the oxygen consuming reaction(s) occur in
Correct Answer: (a)
O₂ is consumed in chloroplast (RuBisCo activity) and peroxisome (Glycolate oxidase).
Q86. In sugarcane plant 14CO₂ is fixed in malic acid, in which the enzyme that fixes CO₂ is
Correct Answer: (c)
Sugarcane is C₄. Primary fixation by PEP Carboxylase.
Q87. Oxygen is not produced during photosynthesis by
Correct Answer: (a)
Green sulphur bacteria do not use H₂O as a source of hydrogen, therefore oxygen is not evolved. They use H₂S.
Q88. In Kranz anatomy, the bundle sheath cells have
Correct Answer: (b)
Kranz anatomy bundle sheath cells are thick-walled, impervious to gases, and have no intercellular spaces.
Q89. Chlorophyll in chloroplasts is located in:
Correct Answer: (a)
Chlorophyll pigments are embedded in the thylakoid membranes which form grana.
Q90. Carbon dioxide joins the photosynthetic pathway in
Correct Answer: (d)
CO₂ fixation is the dark reaction.
Q93. Which pigment system is inactivated in red drop?
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.
Q94. A process that makes important difference between C₃ and C₄ plants is :
Correct Answer: (d)
Photorespiration is absent in C₄ plants but present in C₃ plants.
Q95. 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?
Correct Answer: (b)
These are characteristics of C₄ plants.
Q96. Photosynthesis in C₄ plants is relatively less limited by atmospheric CO₂ levels because of :
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.
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