NEET AIPMT Biology Chapter Wise Solutions – Photosynthesis in Higher Plants

NEET AIPMT Biology Chapter Wise Solutions – Photosynthesis in Higher Plants

NEET AIPMT Biology Chapter Wise SolutionsPhysicsChemistry

1. In photosynthesis, the light-independent reactions take place at
(a) photosystem II
(b) stromal matrix
(c) thylakoid lumen
(d) photosystem I (AIPMJ 2015)

2. Chromatophores take part in
(a) movement
(b) respiration
(c) photosynthesis
(d) growth. (AIPMT 2015)

3. A process that makes important difference between C₃ and C4 plants is
(a) transpiration
(b) glycolysis
(c) photosynthesis
(d) photorespiration. (Prelims 2012)

4. The correct sequence of cell organelles during photorespiration is
(a) chloroplast, Golgi-bodies, mitochondria
(b) chloroplast, rough endoplasmic reticulum, dictyosomes
(c) chloroplast, mitochondria, peroxisome
(d) chloroplast, vacuole, peroxisome. (Prelims 2012)

5. Read the following four statements (A – D).
(A) Both photophosphorylation and oxidative phosphorylation involve uphill transport of protons across the membrane.
(B) In dicot stems, a new cambium originates from cells of pericycle at the time of secondary growth.
(C) Stamens in flowers of Gloriosa and Petunia are polyandrous.
(D) Symbiotic nitrogen fixers occur in free-living state also in soil.
How many of the above statements are right?
(a) Two
(b) Three
(c) Four
(d) One (Mains 2012)

6. CAM helps the plants in
(a) conserving water
(b) secondary growth
(c) disease resistance
(d) reproduction. (Prelims 2011)

7. In Kranz anatomy, the bundle sheath cells have
(a) thin walls, many intercellular spaces and no chloroplasts.
(b) thick walls, no intercellular spaces and large number of chloroplasts.
(c) thin walls, no intercellular spaces and several chloroplasts.
(d) thick walls, many intercellular spaces and few chloroplasts. (Mains 2011)

8. Which one of the following is essential for photolysis of water?
(a) manganese
(b) zinc
(c) copper
(d) boron (Mains 2011)

9. PGA as the first C02 fixation product was discovered in photosynthesis of
(a) bryophyte
(b) gymnosperm
(c) angiosperm
(d) alga. (Prelims 2010)

10. C₄ plants are more efficient in photosynthesis than C₃ plants due to
(a) higher leaf area
(b) presence of larger number of chloroplasts in the leaf cells
(c) presence of thin cuticle
(d) lower rate of’photorespiration. (Prelims 2010)

11. Read the following four statements, (i), (ii), (iii) and (iv) and select the right option having both correct statements.
Statements :
(i) Z scheme of light reaction takes place in presence of PS I only
(ii) Only PS I is functional in cyclic photophosphorylation.
(iii) Cyclic photophosphorylation results into synthesis of ATP and NADPH2
(iv) Stroma lamellae lack PS II as well as NADP.
(a) (ii) and (iv)
(b) (i) and (ii)
(c) (ii) and (iii)
(d) (iii) and (iv) (Mains 2010)

12. Kranz anatomy is one of the characteristics of the leaves of
(a) potato
(b) wheat
(c) sugarcane
(d) mustard (Mains 2010)

13. Study the pathway given below:

 

14. Cyclic photophosphorylation results in the formation of
(a) ATP and NADPH
(b) ATP, NADPH and 0₂
(c) ATP
(d) NADPH (Prelims 2009)

15. Stroma in the chloroplasts of higher plant contains
(a) light-dependent reaction enzymes
(b) ribosomes
(c) chlorophyll
(d) light-independent reaction enzymes (Prelims 2009)

16. Electrons from excited chlorophyll molecule of photosystem II are accepted first by
(a) quinone
(b) ferredoxin
(c) cytochrome-b
(d) cytochrome. (Prelims 2008)

17. The C₄ plants are photosynthetically more efficient than C₃ plants because
(a) the CO₂ efflux is not prevented
(b) they have more chloroplasts
(c) the CO₂ compensation point is more
(d) CO₂ generated during photorespiration is trapped and recycled through PEP carboxylase. (Prelims 2008)

18. In leaves of C₄ plants malic acid synthesis during CO₂ fixation occurs in
(a) bundle sheath
(b) guard cells
(c) epidermal cells
(d) mesophyll cells. (Prelims 2008)

19. 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) mesophylf. (2007)

20. The first acceptor of electrons from an excited chlorophyll molecule of photosystem II is
(a) iron-sulphur protein
(b) ferredoxin
(c) quinone
(d) cytochrome. (2007)

21. During photorespiration, the oxygen consuming reaction(s) occur in
(a) stroma of chloroplasts
(b) stroma of chloroplasts and mitochondria
(c) stroma of chloroplasts and peroxisomes
(d) grana of chloroplasts and peroxisomes (2006)

22. In photosystem-I, the first electron acceptor is
(a) an iron-sulphur protein
(b) ferredoxin
(c) cytochrome
(d) plastocyanin (2006)

23. 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?
(a) two
(b) six
(c) twelve
(d) zero. (2005)

24. Photosynthetic Active Radiation (PAR) has the following range of wavelengths.
(a) 340-450 nm
(b) 400-700 nm
(c) 500-600 nm
(d) 450-950 nm. (2005)

25. Photosynthesis in C₄ plants is relatively less limited by atmospheric CO₂ levels because
(a) effective pumping of CO₂ into bundle sheath cells
(b) rubisco in C₄ plants has higher affinity for CO₂
(c) four carbon acids are the primary initial C02 fixation products
(d) the primary fixation of CO₂ is mediated via PEP carboxylase. (2005)

26. Plants adapted to low light intensity have
(a) larger photosynthetic unit size than the sun plants
(b) higher rate of CO₂ fixation than the sun plants
(c) more extended root system
(d) leaves modified to spines. (2004)

27. In C₃ plants, the first stable product of photosynthesis during the dark reaction is
(a) malic acid
(b) oxaloacetic acid
(c) 3-phosphoglyceric acid
(d) phosphoglyceraldehyde. (2004)

28. Which fractions of the visible spectrum of solar radiations are primarily absorbed by carotenoids of the higher plants ?
(a) blue and green
(b) green and red
(c) red and violet
(d) violet and blue (2003)

29. Which one of the following is wrong in relation to photorespiration ?
(a) it occurs in chloroplast
(b) it occurs in day time only
(c) it is a characteristic of C₄ plants
(d) it is a characteristic of C₃ plants (2003)

30. In sugarcane plant I4 CO₂ is fixed in malic acid, in which the enzyme that fixes CO₂ is
(a) ribulose biphosphate carboxylase
(b) phosphoenol pyruvic acid carboxylase
(c) ribulose phosphate kinase
(d) fructose phosphatase. (2003)

31. Stomata of CAM plants
(a) are always open
(b) open during the day and close at night
(c) open during the night and close during the day
(d) never open. (2003)

32. Which element is located at the centre of the porphyrin ring in chlorophyll ?
(a) calcium
(b) magnesium
(c) potassium
(d) manganese (2003)

33. Which one of the following concerns photophosphorylation ?

 

34. Which of the following absorb light energy for photosynthesis?
(a) chlorophyll
(b) water molecule
(c) O₂
(d) RuBP. (2002)

35. In photosynthesis energy from light reaction to dark reaction is transferred in the form of
(a) ADP
(b) ATP
(c) RuDP
(d) chlorophyll. (2002)

36. Which pigment absorbs the red and far-red light?
(a) cytochrome
(b) phytochrome
(c) carotenoids
(d) chlorophyll. (2002)

37. What is true for photolithotrophs?
(a) obtain energy from radiations and hydrogen from organic compounds
(b) obtain energy from radiations and hydrogen from inorganic compounds
(c) obtain energy from organic compounds
(d) obtain energy from inorganic compounds. (2001)

38. Which pigment system is inactivated in red drop?
(a) PS-I and PS-II
(b) PS-I
(c) PS-II
(d) none of the above. (2001)

39. Which pair is wrong
(a) C₃ -maize
(b) C₄ -kranz anatomy
(c) Calvin cycle-PGA
(d) Hatch and Slack cycle – O.A.A. (2001)

40. Which is the first CO₂ acceptor enzyme in C₄ plants
(a) RuDP carboxylase
(b) phosphoric acid
(c) RuBisCO
(d) PEP- carboxylase. (2000)

41. For assimilation of one CO₂ molecule, the energy required in form of ATP and NADPH₂ are
(a) 2 ATP and 2 NADPH₂
(b) 5 ATP and 3 NADPH₂
(c) 3 ATP and 2 NADPH₂
(d) 18 ATP and 12 NADPH_2.  (2000)

42. For the synthesis of one glucose molecule the Calvin cycle operates for
(a) 2 times
(b) 4 times
(c) 6 times
(d) 8 times. (2000)

43. The first step for initiation of photosynthesis will be
(a) photolysis of water
(b) excitement of chlorophyll molecules due to absorption of light
(c) ATP formation
(d) glucose formation. (2000)

44. Carbon dioxide acceptor in C₃ -plants is
(a) PGA
(b) PEP
(c) RuDP
(d) none of these. (1999)

45. The rate of photosynthesis is higher in
(a) very high light
(b) continuous light
(c) red light
(d) green light. (1999)

46. Chlorophyll a molecule at its carbon atom 3 of the pyrrole ring II has one of the following
(a) carboxylic group
(b) magnesium
(c) aldehyde group
(d) methyl group. (1997)

47. The core metal of chlorophyll is
(a) Ni
(b) Cu
(c) Fe
(d) Mg. (1997)

48. NADPH₂ is generated through
(a) photosystem II
(b) anaerobic respiration
(c) glycolysis
(d) photosystem I. (1997)

49. ‘The law of limiting factors’ was proposed by
(a) Leibig
(b) Hatch and Slack
(c) Blackman
(d) Amon. (1996)

50. What will be the number of Calvin cycles to generate one molecule of hexose?
(a) 8
(b) 9
(c) 4
(d) 6. (1996)

51. Photorespiration is favoured by
(a) high temperature and low O₂
(b) high humidity and temperature
(c) high O₂ and low CO₂
(d) high CO₂ and low O₂. (1996)

52. In C₄ plants, CO₂ combines with
(a) phosphoenol pyruvate
(b) phosphoglyceraldehyde
(c) phosphoglyceric acid
(d) ribulose diphosphate. (1996)

53. In C₄ plants, CO₂ fixation is done by
(a) sclerenchyma
(b) chlorenchyma and hypodermis
(c) mesophyll cells
(d) guard cells. (1996)

54. The primary acceptor, during CO₂ fixation in C₃ plants, is
(a) phosphoenolpyruvate (PEP)
(b) ribulose 1, 5-diphosphate (RuDP)
(c) phosphoglyceric acid (PGA)
(d) ribulose monophosphate (RMP). (1995)

55. The CO₂ fixation during C₄ pathway occurs in the chloroplast of
(a) guard cells
(b) bundle sheath cells
(c) mesophyll cells
(d) spongy parenchyma. (1995)

56. Which of the following pigments acts as a reaction-centre during photosynthesis?
(a) carotene
(b) phytochrome
(c) P₇₀₀
(d) cytochrome. (1994)

57. During light reaction of photosynthesis, which of the following phenomenon is observed during cyclic phosphorylation as well as non-cyclic phosphorylation?
(a) release of O₂
(b) formation of ATP
(c) formation of NADPH
(d) involvement of PS I and PS II pigment systems. (1994)

58. A photosynthesising plant is releasing 180 more than the normal. The plant must have been supplied with
(a) O₃
(b) H₂O with ¹⁸O
(c) CO₂ with ¹⁸O
(d) C₆H₁₂O₆ with ¹⁸O. (1993)

59. Maximum solar energy is trapped by
(a) planting trees
(b) cultivating crops
(c) growing algae in tanks
(d) growing grasses. (1993)

60. The carbon dioxide acceptor in Calvin cycle/ C₃-plants is
(a) phosphoenol pyruvate (PEP)
(b) ribulose 1, 5-diphosphate (RuDP)
(c) phosphoglyceric acid (PGA)
(d) ribulose monophosphate (RMP). (1993)

61. Which one is a C₄ – plant?
(a) papaya
(b) pea
(c) potato
(d) maize/com (1993)

62. Chlorophyll a occurs in
(a) all photosynthetic autotrophs
(b) in all higher plants
(c) all oxygen liberating autotrophs
(d) all plants except fungi. (1992)

63. Photosystem II occurs in
(a) stroma
(b) cytochrome
(c) grana
(d) mitochondrial surface. (1992)

64. The enzyme that catalyses carbon dioxide fixation in C₄ plants is
(a) RuBP carboxylase
(b) PEP carboxylase
(c) Carbonic anhydrase
(d) Carboxydismutase. (1992)

65. The first carbon dioxide acceptor in C₄-plants is
(a) phosphoenol-pyruvate
(b) ribulose 1, 5-diphosphate
(c) oxalo-acetic acid
(d) phosphoglyceric acid. (1992, 1990)

66. Ferredoxin is a constituent of
(a) PS I
(b) PS II
(c) Hill reaction
(d) P₆₈₀. (1991)

67. 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. (1991)

68. Which technique has helped in investigation of Calvin cycle?
(a) X-ray crystallography
(b) X-ray technique
(c) radioactive isotope technique
(d) intennittent light. (1991)

69. Dark reactions of photosynthesis occur in
(a) granal thylakoid membranes
(b) stromal lamella membranes
(c) stroma outside photosynthetic lamellae
(d) periplastidial space. (1991)

70. Photosynthetic pigments found in the chloroplasts occur in
(a) thylakoid membranes
(b) plastoglobules
(c) matrix
(d) chloroplast envelope. (1991)

71. Kranz anatomy is typical of
(a) C₄ plants
(b) C₃ plants
(c) C₂ plants
(d) CAM plants. (1990)

72. A very efficient converter of solar energy with net productivity of 204 kg/M ² or more is the crop
(a) wheat
(b) sugarcane
(c) rice
(d) bajra. (1989)

73. In C₄ plants, Calvin cycle operates in
(a) stroma of bundle sheath chloroplasts
(b) grana of bundle sheath chloroplasts
(c) grana of mesophyll chloroplasts
(d) stroma of mesophyll chloroplasts. (1989)

74. The substrate for photorespiration is
(a) phosphoglyceric acid
(b) glycolate
(c) serine
(d) glycine (1989)

75. The size of chlorophyll molecule is

76. NADP is reduced to NADPH in
(a) PSI
(b) PS II
(c) Calvin cycle
(d) noncyclic photophosphorylation. (1988)

77. Carbon dioxide joins the photosynthetic pathway in
(a) PS I
(b) PS II
(c) light reaction
(d) dark reaction. (1988)

EXPLANATIONS

1. (b)
The light independent reactions (dark or I Blackman’s reactions) of photosynthesis take place in stroma or matrix of chloroplasts. These reactions are enzymatic reactions which catalyse assimilation of CO₂ into carbohydrates.

2. (c)
Chromatophores are the internal membrane systems of photosynthetic forms which possess photosynthetic pigments. They occur in photoautotrophic bacteria, e.g., purple bacteria and green bacteria.

3. (d)
Photorespiration is the light dependent | process of oxygenation of ribulose biphosphate and release of carbon dioxide by the photosynthetic organs of a plant. It occurs in chloroplast. Peroxisome and mitochondria are required for completing the process. This process creates an important difference between C₃ and C₄ plants as it is absent in C₄ plants.

4. (c)
Refer answer 3.

5. (a)
Polyandrous condition (having large and indefinite number of stamens) is present in Gloriosa (family liliaceae) and Petunia (family solanaceae). Nitrogen fixation is the conversion of inert atmospheric nitrogen into utilizable compounds of nitrogen like nitrate, ammonia, amino acids, etc. Biological nitrogen fixation is performed by free living and symbiotic bacteria and cyanobacteria. Symbiotic nitrogen fixers occur in association with roots of higher plants. For e.g., Rhizobium is nitrogen fixing bacterial symbiont of papilionaceous roots and Frankia is symbiont in root nodules of several non-leguminous plants like Casuarina. Both Rhizobium and Frankia live free as aerobes in the soil and develop the ability to fix nitrogen only as symbionts when they become anaerobic.

6. (a)
Crassulacean acid metabolism (CAM) is photosynthesis by the C₄ pathway in which carbon dioxide is taken up during the night, when the plant’s stomata are open, and fixed into malic acid. During the day, when the stomata are closed, carbon dioxide is released from malic acid for use in the Calvin cycle. This is important for plants that live in arid conditions as it enables them to keep their stomata closed during the day to reduce water loss from evaporation. Crassulacean acid metabolism is common in succulent plants of desert regions, including cacti and spurges, and in certain ferns.

7. (b)
The C₄ plants are adapted to dry tropical regions and have greater productivity of biomass. They have special type of leaf anatomy known as Kranz anatomy. In this type of anatomy the bundle sheath cells form several layers around the vascular bundles; they are characterised by having a large number of chloroplasts, thick walls impervious to gaseous exchange and no intercellular spaces.

8. (a)
Manganese (Mn: ) is used for photolysis of water to produce oxygen and electrons during light reaction of photosynthesis. It is the phenomenon of breaking up of water into hydrogen and oxygen in the illuminated chloroplast. It acts as an essential cofactor.

9. (d)
Calvin, Benson and their colleagues in California, U.S.A. fed Chlorella and Scenedesmiis with radioactive 14_c in carbon dioxide. Radioactive carbon, 14_c has a half life of 5568 years. Therefore, the path of C02 fixation can be easily traced with its help. Algal suspensionilluminated and carrying out photo¬synthesis with normal carbon dioxide was supplied 14CO,. The alga was killed at intervals in near boiling methanol. It immediately stopped photosynthesis activity due to denaturation of enzymes. Alcohol was evaporated and after crushing the alga, the product was made into paste. The paste was placed on paper chromatogram and the different compounds were separated by two dimensional chromatography. The radioactive compounds were identified by comparing their position on the chromatogram with standard chemicals. Calvin and co-workers found that after three seconds, radioactivity appeared in phosphoglyceric acid or PGA. Phosphoglyceric acid is, therefore, the first stable product of photosynthesis.

10. (d)
Rate of net photosynthesis in C₃ plants is 15-35 mg CO₂/_dm²/hr while in C₄ plants it 40-80 mg CO₂/dm2/hr. This variation in rate is due to photorespiration. Photorespiration is an inhibitory process which decreases the rate of photosynthesis. In excess of oxygen RUBP carboxylase converts to RuBP oxygenase. As a result glycolate synthesis is enhanced and leads to begin photorespiration. Photorespiration is negligible or absent in C₄ plants and present only in C₃ plants. So C₄ plants are photosynthetically more efficient.

11. (a)
Z scheme involves both PSI and PSII to transfer electron excited by light starting from PSII uphill to the acceptor, down to the electron transport chain to PSI, which further comprise of excitation of electrons, transfer to another acceptor and finally down hill to \ADP causing reduction of it to NADPH + H . Stroma lamella contains PSI only.

12. (c)
In kranz anatomy the mesophyll is undifferentiated and its cells occur in concentric layers around vascular bundles. Vascular bundles are surrounded by large sized bundle sheath cells which are arranged in a wreath-like maimer in one to several layers. C₄ plants, both monocots and dicots, such as sugarcane, maize, sorghum have kranz anatomy in leaf.

13. (c)
A – Fixation of CO₂ by PEP carboxylase
B – Decarboxylation C – Regeneration

14. (c)
In cyclic photophosphorylation 2 molecules of ATP are synthesized which are used in dark reaction. Cyclic photophosphorylation is not concerned with photolysis of water. So O, is not evolved & NADPH is also not produced.

15. (d)
The dark reactions of photosynthesis is purely enzymatic and slower than the primary photochemical reaction. It takes place in stroma portion of the chloroplast and is independent of light i.e., it can occur either in presence or in absence of light provided that assimilatory power is available.

16. (a)
The electrons released during photolysis of water are picked up by P photocentre of photosystem II. The electron extruded by the photocentre of photosystem II picked up by the quencher phaeophytin. From here the electron passes over a series of carriers in a downhill journey losing its energy at every step. The major carriers are plastoquinone (PQ), cytochrome b – f complex and plastocyanin (PC). While passing over cytochrome complex, the electron loses sufficient energy for the creation of proton gradient and synthesis of ATP from ADP and inorganic phosphate. The process is called photophosphorylation (noncyclic).

17. (b)
C₄ plants are photosynthetically more efficient than C₃ plants because C₄ plant contain two types of chloroplast i.e., bundle sheath chloroplast and mesophyll chloroplast. So such plants operate a dicarboxylic acid cycle in addition to Calvin cycle. CO, acceptor molecule (PEP) is present in large bundle sheath cell which has higher efficiency in picking up CO₂ Thus, photosynthesis continues even at low CO₂ concentration and the rate of photorespiration is also negligible.

18. (d)
C₄ plants show Kranz anatomy i.e. the mesophyll is undifferentiated and its cells occur in concentric layers around vascular bundle, which is surrounded by large sized bundle sheath cells, in a wreath like manner. In this type of plant, the initial fixation of CO₂ occur in mesophyll cell. The primary acceptor (phosphoenol pyruvate) combines with CO₂ to form oxaloacetic acid which later reduced to malic acid. Malic acid is then translocated to bundle sheath cell for further decarboxylation.

19. (d)
Refer answer 20.

20. (c)
Type I photosystems use ferredoxin like iron- sulphur cluster proteins as terminal electron acceptors, while type II photosystems ultimately shuttle electrons to a quinone terminal electron acceptor. One has to note that both reaction centres types are present in chloroplasts of plants and cyanobacteria, working together to form an unique photosynthetic chain able to extract electrons from water, evolving oxygen as a byproduct.

21. (c)
Photorespiration is a process the rate of which increases under the influence of light, CO₂ is released and O₂ is used but no ATP is formed. It involves three organelles chloroplasts, mitochondria and peroxisomes. In chloroplast O, is utilized as, ribulose biphosphate is oxidized and a molecule of phosphoglycolic acid and a molecules of 3-phosphoglyceric acid are formed. This oxidation takes place under the influence of high light intensity. Ribulose diphosphate carboxylase, an enzyme, facilitates this reaction as it behaves as an oxygenase. Only one molecule of oxygen is fixed here.

22. (a)
In light reaction of photosynthesis two types of photosystems are involved. PS-I consists of plenty of chlorophyll-a and very less quantity of chlorophyll- h. These pigments absorb light energy and transfer it to the reaction centre – P-700. After absorbing adequate amount of light energy electron gets excited from P-700 molecule and moves to iron-sulphur protein complex, designated as A (Fe-S). It gets reduced after accepting electrons. It later gives these electron to ferredoxin and gets oxidized again.

23. (c)
In C₄ plants the cost of concentrating CO₂ within the bundle sheath cell is 2ATP per CO₂. Energetics of the C4 photosynthetic carbon cycle –

24. (b)
Wavelengths between 400 and 700 nm, which comprise the visible range of electromagnetic spectrum are capable of causing photosynthesis. These are called photosynthetically active radiations. Chlorophyll a and b absorb too much light in the blue and red region of spectrum of light. Carotenoids mostly absorb is the blue region of the spectrum.

25. (d)
Photosynthetic rates are enhanced not only by increased irradiance levels but also by higher CO₂ concentrations. The additional CO₂ decreases photorespiration by increasing the ratio of CO₂ to O₂ reacting with rubisco. Photorespiration decreases with increasing CO₂ to O₂ ratios, which leads to faster net photosynthesis. At high CO₂ concentrations, high irradiance levels increase photosynthesis more than at low CO₂ concentrations, and that to saturate photosynthesis a high than at low irradiance levels. In contrast, photosynthesis of C₄ species is generally saturated by CO₂ levels near 400 ml/1, just above normal atmospheric concentrations, even at high irradiance levels in which demands for CO₂ are greatest. Some C₄ species are even saturated by normal atmospheric CO₂ concentrations. Both plants fix CO₂ until the CO₂ compensation point of the C₃ plant is reached, but the C₄ plant will photosynthesize at still lower CO₂ concentrations using CO₂ lost by respiration. The lower CO₂ compensation points in C₄ than in C₃ species arise from the much lower photorespiratory release of CO₂ by C₃ plants.

26. (a)
A photosynthetic unit is a group of collaborating molecules of pigment, which are essential for a photochemical phase. A quantum of light is absorbed by a single antenna chlorophyll, migrates from one molecule to the other till it reaches the reaction centre. This quantum of light may be used for chemical work that is the generation of assimilatory power, ATP and NADPH. It may dissipate in the form of heat or in the form of fluorescence. The tightly packed chlorophyll molecules in the grana are called antennae chlorophyll (figure).

27. (c)
The Calvin cycle is also known as C₃ cycle because CO₂ reduction is cyclic process and first stable product in this cycle is a 3-C compound (i.e., 3-phosphoglyceric acid or 3-PGA). In this cycle, CO₂ acceptor molecule is RuBP or RuDP (i.e., Ribulose 1. 5-biphosphate or Ribulose 1, 5-diphosphate). There occurs covalent bonding of CO₂ to RuBP and the enzyme catalyzing this reaction is RuBP-carboxylase/oxygenase (RuBisCO).

28. (d)
Carotenoids of higher plants are fat soluble compound that includes carotenes and xanthophylls. Most of them absorb light of voilet and blue range. Green light is absorbed in less amounts.

29. (c)
Photorespiration is a type of respiration which occurs in green cells in presence of light. It involves three organelles – chloroplast, peroxisomes and mitochondria. Respiratory substrate in photorespiration is a 2-carbon compound glycolic acid (2C), hence called C₂ cycle. RuBP-carboxylase in normal O₂ / CO₂ cone, acts as ‘carboxylase’. It is the key enzyme of photosynthesis in C₃ plants.

 

30. (b) :
C₄ pathway was first reported in members of family Gramineae (grasses) like sugarcane, maize, sorghum, etc.
These C₄ plants have a characteristic leaf anatomy called Kranz anatomy. So in chloroplasts of mesophyll cells –

PEPCo (PEP carboxylase) is the key enzyme used to fix CO₂ in C₄ plants. Oxaloacetic acid is a 4-C compound and is the first stable product so this pathway is known as C₄ cycle.

31. (c)
Stomata of most plants open at sunrise and close in darkness to allow the entry of CO₂ needed for photosynthesis during the daytime. Certain succulents that are native to hot, dry conditions (e.g., cacti. Kulanchoe, and Bryophyllurn) act in an opposite manner. They open their stomata at night, fix carbon dioxide into organic acids in the dark, and close their stomata during the day. This is an appropriate way to absorb CO₂ through open stomata at night, when transpiration stress is low, and conserve water during the heat of the day. These plants show Crassulacean Acid Metabolism (CAM).

32. (b)
Chlorophyll is the green pigment present in plants and some photosynthetic bacteria. The empirical formula of chlorophyll-a molecule is C₅₅H₇₂O₅N₄ Mg It consist of a porphyrin head and a phytol tail. Porphyrin is a cyclic tetrapyrrole structure, having a magnesium atom in the centre. Tail is consisted of phytol alcohol and it is attached with one of the pyrrole rings. The chlorophyll-6 has empirical formula of C₅₅H₇₀O₆N₄Mg . It’s molecular structure is comparable with chlorophyll-a.

33. (b)
The light dependent and 02 independent production of ATP from ADP + IP in the chloroplasts is called photophosphorylation. Photophosphorylation is of 2 types –
Cyclic photophosphorylation – It involves only PS-I, water is not utilized and so no oxygen is evolved. Here two ATP molecules are produced.
Non-cyclic photophosphorylation – It involves both PS-I and PS-II, water is utilized and so oxygen is evolved. Here one ATP molecule and one NADPH, molecule are produced.

34. (a)
Photosynthesis occurs in chloroplasts that contain photosynthetic pigments – chlorophylls, carotenoids etc. The light energy required for photosynthesis comes from sunlight. The sunlight travels in the form of small particles called photons. Each photon has a quantum of energy. This quantum of energy is absorbed by a single antenna chlorophyll and then migrates from one molecule to the other till it reaches the reaction center. The reaction center is P 700 chlorophyll that releases electron as a result of transferred energy. This electron istransferred between various acceptors and generates ATP and NADPH2 in the light reaction of photosynthesis.

35. (b)
Photosynthesis consists of light dependent phase and light independent phase or dark reaction. In light dependent phase occurs in grana fraction of chloroplast. It involves cyclic and non-cyclic photophosphorylation where assimilatory powers (ATP and NADPH2) are produced. In dark reaction, which occurs in stroma froction of chloroplast, actual reduction of CO₂ to carbohydrates takes place using the assimilatory powers (ATP and NADPH,) produced in the light dependent phase. It needs 18 ATP and 12 NADPH, molecules to produce one molecule of glucose.

36. (b)
Phytochrome has a light absorbing or light detecting portion (the chromophore) attached to small protein of about 1,24000 daltons. Phytochrome occurs in 2 forms, i.e., PR and PFR (i.e., red light and far red light absorbing forms) and these 2 forms are interconvertible. Cytochromes are electron transferring proteins. They contain iron porphyrin or copper porphyrin as prosthetic groups. Chlorophyll is the fundamental green pigment of photosynthesis. It is localized on the chloroplasts. Carotenoids are lipid compounds and they are yellow, orange, purple etc. in colour. These are found in higher plants red algae, green algae, fungi and photosynthetic bacteria.

37. (b)
Photolithotrophs are those plants that obtain energy from radiation and hydrogen from inorganic compounds.

38. (c)
Emerson and Lewis worked on Chlorella and Calculated the quantum yield for different wavelengths.
Emerson observed that rate of photosynthesis declines in the red region of the spectrum. This decline in photosynthesis is called “Red drop”. It was observed that the quantum yield falls when the light of wavelengths more than 680 or 690 nm are supplied. As the PS-II (P-680) is driven by red light, so it remains inactive during red drop.

39. (a)
Refer answer 30.

40. (d)
Refer answer 30.

41. (c)
Photosynthesis is actually oxidation reduction process in which water is oxidised and CO₂ is reduced to carbohydrates. The reduction of CO₂ to carbohydrates needs assimilatory powers, i.e., ATP and NADPH,.
The process of photosynthesis involves two steps-
(i) Light dependent phase or photochemical reaction.
(ii) Light independent phase or dark reaction.
In Calvin cycle, CO₂ acceptor molecule is RuBP or RuDP. The enzyme catalyzing this reaction is RuBP- carboxylase/oxygenase (RuBisCO). As Calvin cycle takes in only one carbon (as CO₂) at a time, so it takes six turns of the cycle to produce a net gain of six carbons (i.e., hexose or glucose). In this cycle, for formation of one mole of hexose sugar (Glucose), 18 ATP and 12 NADPH, are used. For 6 molecules of CO₂ it needs 18 ATP and 12 NADPH, molecules so for one molecule of CO₂ it needs 3 ATP and 2 NADPH, molecules.

42. (c)
Refer answer 41.

43. (b)
Photosynthesis is actually oxidation reduction process in which water is oxidised and CO₂ is reduced to carbohydrates. The reduction of CO₂ to carbohydrates needs assimilatory powers, i.e., ATP and NADPH,.
The process of photosynthesis involves two steps-
(i) Light dependent phase or photochemical reaction.
(ii) Light independent these or dark reaction.
Light reaction occurs in grana fraction of chloroplast and in this reaction are included those activities, which are dependent on light. Assimilatory powers
(ATP and NADPH,) are mainly produced in this light reaction. The grana of chloroplasts contains many collaborating molecules of pigment. A quantum of light is absorbed by a single antenna chlorophyll, then it migrates from one molecule to the other till it reaches the reaction center. This quantum of light is used for generating ATP and NADPH.

44. (c)
An enzyme ribulose biphosphate carboxylase catalyses the dark reaction, pertaining to the addition of CO₂ to ribulose-1-5-diphosphate. It is found in abundance in leaves and it is believed that it is the single most abundant protein on earth. It is clear that the first acceptor of CO₂ is Ribulose 1-5 diphosphate. The first product formed after fixation of CO₂ is 3-phosphoglyceric acid.

45. (c)
Plants can use a small portion of light which falls upon them. Chlorophyll-u and chlorophyll-6 absorb too much light in the blue and red region. Carotenoids absorb light mostly in the blue region of spectrum of light. In monochromatic lights, maximum photosynthesis occurs in red light, followed by blue light and poor photosynthesis in green light. Under very high light intensity solarization phenomenon occurs. It involves photo-oxidation of different cellular components including chlorophyll.

46. (d)
The empirical formula of chlorophyll a molecule is C₅₅H₇,O5N₄Mg. It has tadpole like configuration. It is consisted of a porphyrin head and a phytol tail. Porphyrin is a cyclic tetrapyrol structure, having a magnesium atom in the centre. Chlorophyll a a methyl group (CH₃) is attached to the third carbon in the porphyrin head.

47. (d)
Refer answer 46.

48. (d)
Non-cyclic photophosphorylation involves both PS-I and PS-II. Here electrons are not cycled back and are used in the reduction of NADP to NADPH,. Here water is utilized and O₂ evolution occurs. One molecule of ATP is produced between plastoquinone and cytochrome f. Whereas in cyclic photophosphorylation only PS-I is involved. Here electrons from P-700 are recycled back to P-700. Water is not utilized here and O₂ evolution does not occur. It involves production of two ATP molecules, no NADPH, is produced. Thus ATP synthesis occurs in both PS-I and PS-II.

49. (c)
Blackman (1905) gave the law of limiting factors which states that when a process is conditioned as to its rapidity by a number of separate factors, the rate of the process is limited by the pace of the slowest process. It is the factor which is present in minimum amount.

50. (d)
Refer answer 41.

51. (c)
Refer answer 29.

52. (a)
Refer answer 30.

53. (c)
The C₄ plants have a characteristic leaf anatomy called kranz anatomy. Here two types of chloroplasts are present – bundle sheath chloroplasts and mesophyll chloroplasts. In C₄ plants, there are two carboxylation reactions which occur first in mesophyll chloroplasts and then in bundle sheath chloroplasts. CO₂ acceptor molecule in mesophyll chloroplasts is PEP (Phospho-enol pyruvate) and not Ribulose 1, 5-biphosphate. Further it has enzyme PEP-carboxylase. RUBP-carboxylase is absent in mesophyll chloroplasts but is present in bundle sheath chloroplasts. The first product formed is oxaloacetic acid and this is because it is known as C₄ cycle. Bundle sheath cells fix CO₂ through C, cycle.

54. (b)
Refer answer 27.

55. (c)
Refer answer 53.

56. (c)
During photosynthesis a portion of light energy absorbed by chlorophyll and carotenoids is eventually stored as chemical energy via the formation of chemical bonds. This conversion of energy from one form to another is a complex process that depends on cooperation between many pigment molecules and a group of electron transfer proteins. The majority of pigments serve as an antenna complex, collecting light and transfusing energy to the reaction center complex. There are two photochemical complexes, known as photosystem I and II. PS-II absorbs far red light of wavelengths greater than 680 nm and PS-I absorbs red light of wavelengths greater than 700 nm. Both those complexes are on involved in light reactions of photosynthesis.

57. (b)
Refer answer 48.

58. (b)
Water molecule breaks up into hydrogen and oxygen in the illuminated chloroplasts is called photolysis of water. A photosynthesising plant is releasing 180 more than the normal. The plant must have been supplied with H₂O with ¹⁸O.

59. (c)
Maximum solar energy is trapped by growing algae in tanks. The light spectrum of red and blue light are most effective in performing photosynthesis for growing algae.

60. (b)
In Calvin cycle, CO₂ is accepted by Ribulose -1,5- diphosphate (RuDP) already present in the cells and a 6-carbon addition compound is formed which is unstable. It soon gets converted into 2 molecules of 3-phosphoglyceric acid due to hydrolysis and dismutation. Phosphoenol pyruvate (PEP) and Phosphoglyceric acid (PGA) are formed in glycolysis.

61. (d)
For a long time, Calvin cycle (C₃ cycle) was considered to be the only photosynthetic pathway for reduction of CO₂ into carbohydrates. M.D. Hatch and Slack (1966) reported that a 4-C compound oxaloacetic acid (OAA) is the first stable product in CO₂ reduction process. This led to an alternative pathway of CO₂ fixation which is known as Hatch and Slack’s cycle or C₄ cycle. It occurs in sugarcane, maize etc. These C₄ plants have a characteristic leaf anatomy called Kranz anatomy.

62. (c)
Chlorophyll-a occur in all photosynthesizing plants except bacteria. Chlorophyll-a is the only one common to all organisms that possess chlorophyll (the only one in blue green algae) and is believed to be specifically required. In a few photosynthetic bacteria other kinds of chlorophyll, bacteriochlorophylls, occur.

63. (c)
Photosystem II has almost equal number of chlorophyll a and chlorophyll b molecules. It is dark green in colour and located mostly in the appressed parts of grana thylakoids towards the inner surface of membranes.

64. (b)
Refer answer 30.

65. (a)
The primary acceptor of CO₂ is a 3 carbon compound phosphoenol pyruvic acid. Addition of CO₂ to any compound is called carboxylation. In C₄ cycle, CO₂ combines with phosphoenol pyruvic acid to form oxaloacetic acid. The enzyme is phosphoenol pyruvate carboxylase (PEPCo). The oxaloacetic acid breaks up into pyruvic acid and CO₂ which combines with RUDP to form PGA as in Calvin cycle.

66. (a)
In photosystem-I, the ejected electron is trapped by FRS (ferrodoxin reducing substance) which is an unknown oxidation – reduction system. The electron is now transferred to a non-heme iron protein called ferrodoxin (Fd) from which electron is transferred to NADP+ intermediate protein electron carrier ferrodoxin-NADP reductase. So that NADP is reduced to NADPH + H⁺.

67. (b)
Rate of yield is dependent of light as photosynthesis is dependent on light. Maximum rate of photosynthesis occur when light is brightest. But during monsoon, the light is dim and so this reduces rate of photosynthesis and hence yield.

68. (c)
By employing C¹⁴ labelled carbondioxide ¹⁴CO₂ in photosynthesis and observing the appearance of characteristics radiations in different reactions intermediates and product in different experiments. Calvin and his co-workers were able to formulate the complete metabolic path of carbon assimilation in the form of cycle which is called as Calvin cycle.

69. (c)
The dark reactions of photosynthesis is purely enzymatic and slower than the primary photochemical reaction. It takes place in stroma portion of the chloroplast and is independent of light i.e., it can occur either in presence or in absence of light provided that assimilatory power available.

70. (a)
Photosynthetic pigments are found in the thylakoids membrane of chloroplasts. The grana lamellae are paired to form sac like structures and form thylakoids. Chlorophylls and other photosynthetic pigments are confined to grana.

71. (a)
Refer answer 53.

72. (b)
A very efficient converter of solar energy with net productivity of 2-4 kg/m2 or more is sugarcane, maize which are C₄  plants others are C₃ plants.

73. (a)
The C₄ plants have a characteristic leaf anatomy called kranz anatomy. Here two types of chloroplasts are present – bundle sheath chloroplasts and mesophyll chloroplasts. In C₄ plants, there are two carboxylation reactions w’hich occur first in mesophyll chloroplasts and then in bundle sheath chloroplasts. CO₂ acceptor molecule in mesophyll chloroplasts is PEP (Phospho-enol pyruvate) and not Ribulose 1, 5-biphosphate. Further it has enzyme PEP-carboxylase. RUBP-carboxylase is absent in mesophyll chloroplasts but is present in bundle sheath chloroplasts. The first product formed is oxaloacetic acid and this is because it is known as C₄ cycle. Bundle sheath cells fix CO₂ through C, cycle.

74. (b)
Refer answer 29.

75. (c)
Chlorophyll are the magnesium porphyrin (head, 15 x 15 A) compounds. The porphyrin ring consists of four pyrrole rings joined together by CH bridges. A long chain of C atoms called as phytol (tail; 20 A) chain is attached to porphyrin ring.

76. (d)
Refer answer 48.

77. (d)
The dark reactions or Blackman’s reactions or biosynthetic phase involves three steps: (i) Fixation of CO₂, (ii) Reduction of CO₂ and (iii) Synthesis of other compound from glucose. It is independent of light. Pigment System I is relatively very weakly fluorescent while pigment system II is strongly fluorescent. Light energy absorbed by pigment in the two systems is ultimately trapped by the P₇₀₀ and P₆₈₀. Light reaction is associated with the grana of the chloroplasts. It takes place in the presence of light only.