Most important mcqs

1. 1. Photosynthesis is a/an
(a) physio-chemical process.
(b) physical process.
(c) chemical process.
(d) energy wasting process.
Photosynthesis
Dr Aman Agarwal

2. 2. Photosynthesis is important because
(a) it is the primary source of food on earth.
(b) it is responsible for release of O2 into the atmosphere by green plants.
(c) it is responsible for release of water vapour into the atmosphere.
(d) both (a) and (b)

3. 3. Half leaf experiment proves that
(a) light is essential for photosynthesis.
(b) CO2 is essential for photosynthesis.
(c) O2 releases during photosynthesis.
(d) chlorophyll is essential for photosynthesis.

4. 4. One of the earliest experiments on photosynthesis was done in 1770 by Joseph Priestley. He
demonstrated that
(a) sun is the ultimate source of energy.
(b) water is essential for life.
(c) plants & animals “restore” the air for each other.
(d) chlorophyll captures light energy.

5. 5. Contribution of Ingen-Housz in elucidation of process of photosynthesis is that
(a) only green parts of plants exposed to light can convert foul air (CO2) into pure air (O2).
(b) green plants convert light energy into chemical energy
(c) plants have the capacity to purify foul air.
(d) sunlight is the ultimate source of energy for plants and animals.

6. 6. The experiment material used by Van Neil, to prove that O2 comes out from water was studied
on
(a) Chlorella pyrenoidosa
(b) Cladophora
(c) purple & green sulphur bacteria
(d) blue green algae
Dr Aman Agarwal

7. 8. How can we separate leaf pigments of any green plant?
(a) Column chromatography
(b) Paper chromatography
(c) Electrophoresis
(d) Radio-isotopes

8. 9. What is/are the function(s) of accessory pigments?
(a) They enable a wider range of wavelength of incoming
light to be utilized for photosynthesis.
(b) They absorb light and transfer the energy to reaction centre.
(c) They protect reaction centre from photo-oxidation.
(d) All of the above

9. 10. The light harvesting complex (LHC) is made up of
(a) one molecule of Chl a.
(b) very few molecules of Chl a.
(c) hundreds of pigment molecules bound to proteins.
(d) Chl a + Chl c + protein + DNA.
Dr Aman Agarwal

10. 11. In a plant cell, which of the following pigments participates directly in the light reactions of
photosynthesis?
(a) Chlorophyll a (b) Chlorophyll b
(c) Chlorophyll d (d) Carotenoids

11. 12. In PS-I, the reaction centre Chl a has absorption maxima at _____________, while in PS-II the
reaction centre Chl a has absorption maxima at ___________.
(a) P680, P700 (b) P700, P680
(c) P800, P600 (d) P700, P900

12. 13. An energy diagram for the transfer of electrons in the light reactions of photosynthesis in plants
is
(a) cyclic photo-phosphorylation
(b) Z-band
(c) Z-Scheme
(d) non-cyclic photo-phosphorylation

13. 14. Electrons are picked up by an electron acceptor which passes them to an electron transport
system consisting of
(a) phytochromes (b) cytochromes
(c) Z-scheme (d) redox potential scale

14. 15. Splitting of water is related with
(a) photosystem I
(b) photosystem II
(c) both (a) and (b)
(d) cyclic photo-phosphorylation

15. 17. The chemiosmotic mechanism mediates
(a) ATP synthesis.
(b) splitting of water.
(c) reduction of NADP+.
(d) flow of electrons from PS - II to PS - I
Dr Aman Agarwal

16. 18. ATP synthesis, in photosynthesis involves the
(a) establishment of a protein gradient.
(b) oxidation of water.
(c) reduction of NADP+
(d) flow of electrons.

17. 19. In photosynthesis, protons accumulate in the
(a) inner membrane space of mitochondria.
(b) matrix of mitochondria.
(c) lumen of thylakoid.
(d) stroma of thylakoid.

18. 20. The light-driven synthesis of ATP & NADPH, provides
energy and reducing power for the
(a) conversion of inorganic carbon into organic carbon.
(b) fixation of CO2 into trioses.
(c) for the production of sugars.
(d) all of the above.

19. 21. No. of carbons in the primary CO2 fixation product of C4 plant is
(a) 2 (b) 3
(c) 4 (d) 5

20. 22. Which was the first CO2 fixation product formed, in the Calvin experiment, using radioactive
labelled 14C in green algal?
(a) 2-carbon organic compound
(b) 3-carbon organic compound
(c) 4-carbon organic compound
(d) 5-carbon organic compound
Dr Aman Agarwal

21. 23. In Calvin cycle, RuBisCO incorporates CO2 into ribulose,
1, 5-bisphosphate which rapidly splits into
(a) 2 molecules of 3-PGA (b) 2 molecules of 2-PGA
(c) 3 molecules of 3-PGA (d) 3 molecules of 2-PGA

22. 24. The total requirement of ATP & NADPH for each molecule of CO2 fixed & reduced in
photosynthesis in the Calvin cycle is
(a) 2 ATP & 2 NADPH (b) 2 ATP & 3 NADPH
(c) 3 ATP & 2 NADPH (d) 4 ATP & 3 NADPH

23. 25. Which is the primary CO2 fixation product in C4 plant?
(a) 3-phosphoglyceric acid (b) Oxaloacetic acid
(c) Phosphoenol pyruvate (d) RuBP

24. 26. Site of photosynthesis in C4 plant is
(a) mesophyll cells (b) bundle sheath cells
(c) Both (a) and (b) (d) Cytosol

25. 27. The primary CO2 acceptor in C4 plant is
(a) RuBP (b) phosphoenol pyruvate
(c) PEP carboxylase (d) PGA

26. 28. Chloroplast movement is influenced by
(a) light exposure
(b) dark condition
(c) atmospheric condition
(d) number of mesophyll cells

27. 29. Fixation of CO2 molecule through Hatch and Slack pathway requires an enzyme called
_________ .
(a) PEPcase (b) RuBisCO
(c) RuBP carboxylase (d) oxygenase

28. 30. Bundle sheath cells
(a) are rich in RuBisCO.
(b) are rich in PEP carboxylase.
(c) lack RuBisCO.
(d) lack both RuBisCO and PEP carboxylase.
Dr Aman Agarwal

29. 31. In the leaves of C4 plants, malic acid formation during
CO2 fixation occurs in the cells of
(a) bundle sheath (b) phloem
(c) epidermis (d) mesophyll

30. 32. By looking at which internal structure of a plant can you tell whether a plant is C3
or C4 ?
(a) Kranz anatomy
(b) Distribution of mesophyll cells
(c) Bundle sheath cells only
(d) Both (a) and (b)

31. 33. In C4 plants, the process by which C4 acid is converted into C3 acid in the bundle sheath cell is
known as
(a) carboxylation (b) regeneration
(c) reduction (d) decarboxylation

32. 34. A process that creates an important difference between C3 & C4 plants is called____________.
(a) Calvin benson cycle (b) photosynthesis
(c) photorespiration (d) transpiration

33. 35. Photorespiration is a wasteful process because
(a) there is no synthesis of sugars.
(b) there is no synthesis of ATP or NADPH.
(c) there is no synthesis of phosphoglycerate.
(d) both (a) and (b)

34. 36. Photorespiration
(a) occurs because oxygen rather than carbon dioxide links to the rubisco enzyme in the Calvin
cycle.
(b) occurs more in C4 than in C3 plants under identical conditions.
(c) describes the uptake of CO2 & the release of oxygen in chloroplasts.
(d) All of the above

35. 37. The principle of limiting factors was proposed by
(a) Blackman (b) Hill
(c) Arnol (d) Liebig

36. 38. Plant factors affecting photosynthesis include
(a) number, age, size, and orientation of leaves, mesophyll cells and chloroplast, internal CO2
conc., the amount of chlorophyll .
(b) nature of leaves, size of mesophyll cells and light.
(c) mesophyll cells, distribution and temperature.
(d) quantity of chlorophyll, size of leaves and CO2

37. STATEMENT TYPE QUESTIONS

38. 39. Which one of the following is incorrect about the activities associated with PS - I and PS - II in
non-cyclic photophosphorylation ?
(a) Water is oxidised in PS - II, but not in PS - I.
(b) Photons (light) are needed to activate both PS - I and PS - II.
(c) Photolysis of water, formation of ATP + NADPH + H occur.
(d) Production of NADPH + H+ is associated with PS - II, but not with PS - I.
Dr Aman Agarwal

39. 40. Which of the following statement is incorrect?
(a) Site of photosynthesis is mesophyll cells of chloroplast.
(b) In Z-scheme, movement of electrons is uphill in terms of redox potential scale.
(c) In Z-scheme of photosynthesis, the electrons flow from H2O to NADP+
(d) ATP synthesis is linked to development of a proton
gradient across a membrane.

40. 41. Which of the following statement is incorrect regarding pigments?
(a) Pigments are substances that have an ability to absorb light, at specific wavelengths.
(b) Chlorophyll b is the chief pigment associated with photosynthesis.
(c) Leaf pigments can be separated by chromatography.
(d) Accessory pigments protect chlorophyll a from photo-oxidation.

41. 42. Which of the following statement is incorrect?
(a) Photosystem-I receives electrons from photosystem-II.
(b) Photosystem-II receives electrons from photolytic dissociation of water.
(c) Formation of NADPH is associated with photosystem -II.
(d) Reaction centre of photosystem I is P700.

42. 43. Which among the following sentence is incorrect about light reaction?
(a) It is also known as ‘photochemical’ phase.
(b) It includes light absorption, water splitting, oxygen release, and the formation of high-energy
chemical intermediates.
(c) Reaction centre consist of single molecule of chl a but 2 molecules of chl b.
(d) The pigments are organised into two discrete photochemical light harvesting complexes (LHC)
within PS - I and PS - II.

43. 44. Which one of the following statement correctly describes the cyclic photophosphorylation?
(a) Cyclic photophosphorylation has both PS-I and PS-II.
(b) Cyclic phosphorylation produces neither ATP nor NADPH + H+
(c) Water is the ultimate source of e– in cyclic phosphorylation.
(d) Electrons are cycled in cyclic photophosphorylation.

44. 45. All of the following statements are incorrect for non-cyclic
electron transport system, except
(a) Electron transport between PS -II to PS-I produces ATP by substrate level phosphorylation.
(b) In PS-II, the oxidation of two water molecules produces four electrons, four proteins, & a single
O2
(c) Water is oxidized & electrons are released by PS-I.
(d) PS - II reduces NADP+ to NADPH.

45. 46. Which of the following statement is incorrect ?
(a) H2S, not H2O, is involved in photosynthesis of purple sulphur bacteria.
(b) Light and dark reactions are stopped in the absence of light.
(c) Calvin cycle occurs in the grana of chloroplast.
(d) ATP is produced during light reaction via chemiosmosis.

46. 47. Which of the following statement(s) is/are correct about RuBisCO?
(a) It catalyzes the fixation of CO2
(b) It has oxygenation & carboxylation both activity.
(c) It is the most abundant protein on earth.
(d) All of the above

47. 48. Which of the following statements given below is incorrect ?
(a) The C4 plants respond to higher temperatures while C3 plants have a much lower temperature
optimum.
(b) Tropical plants have a higher temperature optimum than the plants adapted to temperate
climates.
(c) Some C3 plants are allowed to grow in CO2 enriched atmosphere that leads to higher yields.
(d) Water stress causes the stomata to remain open hence enhancing the CO2 availability.
Dr Aman Agarwal

48. 49. Which one of the following statement is incorrect in relation to photorespiration?
(a) It is a characteristic of C3 plants.
(b) The RuBP binds with O2 to form one molecule of phosphoglycerate and phosphoglycolate.
(c) There is synthesis of ATP or NADPH.
(d) It occurs in daytime only.

49. 50. Which of the following statement best support the fact that photorespiration commonly occurs
in C3 plants?
(a) C3 plants don’t possess Kranz anatomy.
(b) C3 plants have usually high CO2 compensation species.
(c) C3 plants are less efficient in photosynthesis.
(d) C3 plants are characterized by RuBP oxygenase activity under high oxygen supply.

50. 51. Which of the following statements (i-iv) regarding
“Splitting of water” is/are correct.
(i) It is photolysis of water which provides H+ ions for synthesis of NADPH.
(ii) It provides electrons for photophosphorylation & activation of NADP+
(iii) O2 is evolved during this process.
(iv) It replenishes O2 consumed by living beings and combustion.
(a) One (b) Two
(c) Three (d) All

51. 52. Identify the correct statements for ATP synthase.
(i) This enzyme consists of two parts: hydrophobic membrane bound portion called F0 & a portion
that sticks out into stroma called F1
(ii) F0 appears to form a channel across the membrane through which proton can pass.
(iii) The conformational change in the F1 portion of the complex synthesizes ATP.
(iv) The proton motive force that drives the synthesis of ATP is associated with this enzyme.
(a) (i), (ii) and (iii) (b) (i), (ii) and (iv)
(c) (i) and (iv) only (d) All of these

52. 53. Why C4 plants are special ? Because,
(i) they have a special type of leaf anatomy.
(ii) they tolerate higher temperatures.
(iii) they show a response to high light intensities.
(iv) they lack a process called photorespiration.
(v) they have greater productivity of biomass.
(a) (i) and (ii) (b) (i), (iii) and (iv)
(c) (i), (ii), (iii) and (iv) (d) All of these

53. 54. Consider the following statements with respect to photosynthesis and identify the correct
statements.
(i) The first carbon dioxide acceptor in C4 cycle is PGA.
(ii) In C3 plants, the first stable product of photosynthesis during dark reaction is RuBP.
(iii) Cyclic photophosphorylation results in the formation of ATP.
(iv) Oxygen which is liberated during photosynthesis comes from water.
(a) (i) and (ii) (b) (i) and (iii)
(c) (iii) and (iv) (d) (ii) and (iii)

54. 62. Match the scientests given in column-1 with their work, given in column-II & select the correct answer using the codes given
below.
Column-I Column-II
A. Priestley I. Determined the action spectrum of chlorophyll
B. Jan Ingenhousz II. Provided evidence that in green parts of plant glucose is made & stored as starch
C. Sachs III. Plants purify air only in the presence of light
D. Engelmann IV. Demonstrated that photosynthesis is essentially a light-dependent reaction
E. Niel V. Revealed the essential role of air in the growth of plants
(a) A – V; B – III; C – II; D – I; E – IV
(b) A – V; B – I; C – II; D – III; E – IV
(c) A – V; B – I; C – IV; D – III; E – II
(d) A – V; B – I; C – III; D – IV; E – II

55. 64. Match the column-1 with column II and choose the correct answer using the codes given below.
Column -I Column -II
A. Emerson effect I. C4 cycle
B. Hill reaction II. Photolysis
C. Calvin cycle III. C3 cycle
D. Hatch & Slack cycle IV. Photosystem I & II
(a) A – I; B – II; C – III; D – IV
(b) A – I; B – III; C – IV; D – I
(c) A – III; B – IV; C – I; D – II
(d) A – IV; B – II; C – III; D – I
Dr Aman Agarwal

56. 65. Which of the following pair is mismatched?
(a) Photosystem I – Uses the P700 molecule in its photocenter.
(b) Antenna complex – Contains hundreds of pigment molecule.
(c) PGA – 3- carbon compound.
(d) Dark reaction – Takes place in the grana of the chloroplast.

57. 66. Match the parts given in column I with the events given in column II and choose the correct combination from the
options given below.
Column-I Column-II
A. Grana of chloroplast I. Kreb's cycle
B. Stroma of chloroplast II. Light reaction
C. Cytoplasm III. Dark reaction
D. Mitochondrial matrix IV. Glycolysis
(a) A – IV; B – III; C – II; D – I
(b) A – I; B – II; C – IV; D – III
(c) A – IV; B – I; C – III; D – II
(d) A – II; B – III; C – IV; D – I

58. 67. Match column-I with column-II and choose the correct combination from the options given below.
Column -I Column -II
A. Oxygen evolving complex ferric oxalate I. Pigments
B. Proton gradient concentration II. High oxygen
C. Absorb light at specific wavelengths III. ATP synthesis
D. Photorespiration. IV. Photolysis of water
(a) A – IV; B – III; C – I; D – II
(b) A – IV; B – I; C – III; D – II
(c) A – II; B – I; C – IV; D – III
(d) A – II; B – IV; C – III; D – I

59. 68. Which of the following pair is not correctly matched ?
(a) C3 plant – Maize
(b) C4 plant – Kranz anatomy
(c) Calvin cycle – PGA
(d) Hatch and Slack pathway – Oxaloacetic acid

60. 69. Which of the following is incorrectly matched?
(a) Sorghum — Kranz anatomy
(b) PS - II — P700
(c) Photorespiration — C3 plants
(d) PEP carboxylase — Mesophyll cells

61. 79. In non-cyclic reactions of photosynthesis, electrons from chlorophyll molecules in photosystem-
I are used in the formation of NADPH. What is the source of suchelectrons?
(a) Light
(b) NADPH
(c) Photosystem-I
(d) Photosystem-II, which splits water molecule

62. 80. The reactions of Calvin cycle not directly dependent on light, but they usually do not occur at
night. Why?
(a) Night is often too cold for these reactions to occur.
(b) CO2 concentration in night is too high for these reactions to occur.
(c) Plants usually open their stomata at night.
(d) Calvin cycle is dependent on the products of light reaction.

63. 81. To make 100 molecules of glucose, how many molecules
of ATP & NADPH are required?
(a) 1800 and 1200 respectively.
(b) 1200 and 1800 respectively.
(c) 1800 and 600 respectively.
(d) 200 and 600 respectively.
Dr Aman Agarwal

64. 82. Chloroplasts are disrupted and the stroma separated from the lamellae. The isolated stroma
will fix CO2 if it is supplied with
(a) O2
(b) RuBisCO
(c) light
(d) ATP + NADPH

65. 83. The correct sequence of Calvin cycle is
(a) Decarboxylation ® Oxidation ® Regeneration
(b) Decarboxylation ® Regeneration ® Oxidation
(c) Carboxylation ® Reduction ® Regeneration
(d) Carboxylation ® Reduction ® Regeneration

66. 84. Which of following ratio is correct for the production of one molecule of glucose through 6
rounds of Calvin cycle?
CO2 ATP NADPH2
(a) 1 2 2
(b) 6 18 12
(c) 6 12 18
(d) 5 6 9

67. 86. In an experiment, the CO2 available to a C4 plant was labelled with a radioactive isotope and
the amount of radioactivity in the chloroplast was measured. As photosynthesis preceeded, in
which of the following molecules did the radioactivity first appear?
(a) Oxaloacetic acid
(b) PEP
(c) Malic acid
(d) RuBP

68. 87. Which of the following plant species have highest photosynthetic yield?
(a) Species that perform photorespiration
(b) Species possessing C3 pathway
(c) Species possessing C4 pathway
(d) Same for all

69. 88. According to Blackman’s law of limiting factor, at any given time, photosynthesis can be limited
by
(a) light only
(b) CO2 concentration only
(c) both light and CO2 concentration
(d) either by light or by CO2

70. 89. During monsoon, the rice crop of eastern states of India shows lesser yield due to limiting factor
of
(a) CO2
(b) light
(c) temperature
(d) water
Dr Aman Agarwal

71. 90. Why, at higher light intensities, gradually photosynthesis
rate does not show further increase?
(a) Higher light intensity activate more chlorophylls.
(b) Higher light intensity causes more transpiration.
(c) No need of more sugar formation.
(d) Other factors become limiting.

72. 91. Under water stress, the rate of photosynthesis declines because of
(a) stomatal closure leading to decrease in CO2 supply.
(b) reduced water potential that decreases leaf surface areas for photosynthesis.
(c) both (a) and (b) (d) turgidity of leaf.

73. 92. In C4 (sugarcane plant) plant,14CO2 is fixed in malic acid in which the enzyme that fixes CO2
is
(a) fructose phosphatase
(b) ribulose biphosphate carboxylase
(c) phosphoenol pyruvic acid carboxylase
(d) ribulose phosphate kinase

74. 93. What will happen if the supply of oxygen is decreased to an illuminated wheat plant?
(a) Its photosynthesis would decrease.
(b) Its respiration process would stop.
(c) All physiological process would stop.
(d) Its photosynthesis would increase.

75. 94. A student sets up an experiment on photosynthesis as follows: He takes soda water in a glass
tumbler and add chlorophyll extracts into the contents and keeps the tumbler exposed to sunlight
hoping that he has provided necessary ingredients for photosynthesis to proceed (viz., CO2 , H2O,
chlorophyll and light). What do you think what will happen after, say, a few hours of exposure of
light?
(a) Photosynthesis will take place and glucose will be produced.
(b) Photosynthesis will take place and starch will be produced which will turn the mixture turbid.
(c) Photosynthesis will not take place because CO2 dissolved in soda water escapes into the
atmosphere.
(d) Photosynthesis will not take place because intact chloroplasts are needed for the process.

76. 95. The electrons that are released by the photolysis of water during non-cyclic
photophosphorylation, ultimately end up in
(a) glucose
(b) ATP
(c) H2O
(d) NADPH

77. 96. ADP is phosphorylated and NADP is reduced, this happens during.
(a) dark phase of photosynthesis
(b) light phase of photosynthesis
(c) Photorespiration
(d) Calvin cycle
Dr Aman Agarwal

78. 97. During light reaction, as electrons move through photosystems, protons are transported across
the membrane. This happens because of
(a) the primary acceptor of e– (located towards the outer surface of the membrane) transfers its
electron not to an e– carrier but to H carrier.
(b) the primary acceptor of e– transfers only its e– to e– carrier.
(c) the primary acceptor of e– transfers only H+ to the next carrier.
(d) NADP - reductase is present in grana.

79. 98. During the light stage of photosynthesis, the photoactivated pigment removes an electron from
the hydroxylation derived from the water molecule. The fate of the free hydroxyl radical is that it
(a) is broken down into oxygen and a free radical of hydrogen.
(b) is used to raise the activation level of chlorophyll by donating a positive charge.
(c) is used to produce adenosine triphosphate from adenosine diphosphate.
(d) reduces carbon dioxide to sugar.

80. 99. The function of water in photosynthesis is to
(a) absorb light energy.
(b) supply electrons in the light dependent reaction.
(c) transport H+ ions in the light independent reactions.
(d) provide O2 for the light-independent reactions.

81. 100. Which of the following is not concern with cyclic photophosphorylation?
(a) Liberation of oxygen.
(b) Synthesis of ATP.
(c) It occurs in certain photosynthetic bacteria.
(d) Electron expelled from P700 return to it after passing

82. 101. Cyclic and non-cyclic flow of e– is used in plants to
(a) meet the ATP demands of Calvin-cycle.
(b) avoid producing excess NADPH + H+
(c) balance ATP and NADPH + H+ ratio in chloroplasts.
(d) All of the above

83. 102. Which one of the following event occurs both during cyclic and non-cyclic modes of
photophosphorylation?
(a) Involvement of both PS - I and PS - II.
(b) Formation of ATP.
(c) Release of O2
(d) Formation of NADPH.

84. 103. In a crop field a weedicide is used to remove weeds in order to increase the yield. But the
effect of this weedicide is that, it blocks electron transport from photosystem II to
photosystem I. This will result in
(a) enhancement of dark reaction.
(b) failure of ATP synthesis.
(c) lack of reduction of NADP+
(d) both (b) and (c)
Dr Aman Agarwal

85. 104. Cooperation of the two photosystems of the chloroplast
is required for
(a) ATP synthesis.
(b) reduction of NADP+
(c) enhancement of dark reaction.
(d) generation of protein motive force.

86. 105. Reduction of NADP+ into NADPH during light reaction occurs in stroma because
(a) NADP reductase enzyme is located on the stroma side of membrane.
(b) PS - I reduces NADP+ to NADPH +H+ in the stroma.
(c) The pH of the stroma remains constant.
(d) Both (a) and (b) are correct.

87. 106. Assume the thylakoid membrane within a chloroplast is punctured so that there is no
separation between lumen & stroma of thylakoid. Which of these process would be
most affected?
(a) the splitting of water
(b) the synthesis of ATP
(c) reduction of NADP+
(d) the flow of electrons from PS - II to PS - I