Disha Publication provides you Photosynthesis Chapter which is taken from “NEET Biology 40 Days Score Amplifier”

1. 1
This Chapter '’Photosynthesis’' is taken from our Book:
ISBN: 9789386323064
Source: Photosynthesis Chapter Notes

2. • Green plants capture energy from sun and convert it into
chemical energy (food) with the help of CO2 taken from
atmosphere and water fromsoil.
• Photosynthesis is actuallyoxidation reduction process in
which water is oxidised and CO2 is reduced to
carbohydrates.
• The reduction of CO2 to carbohydrates needs assimilatory
powers, i.e.,ATPandNADPH2.
• Photosynthesis occurs particularlyin specialised cells called
mesophyll cell. These cells contain chloroplast, which is the
actual sites for photosynthesis.
Pigments of Photosynthesis :
Chlorophyll :
• Large molecule composed of four 5 memberedrings called
pyrrole rings and a central coreofmagnesium. A sidechain,
called the phytol chain extends from oneofthe pyrrolering.
Carotenoids :
• These are of red, orange and yellow colour.
• They act as antenna complexes and harvest light from
different regions of the spectrum other than chlorophyll,
which is then funneled into the reaction centres (chl a) for
conversion into electrical energy.
LightReaction
• Light reaction occursin grana fraction ofchloroplast.
• Assimilatory powers (ATP and NADPH2) are mainly
produced in this light reaction.
Two Pigment Systems :
PS-I is essential for producing the reduced NADP (i.e., NADPH2)
used to reduce CO2 whereas PS-II oxidises water and releases O2.
8 quanta oflight arerequired toevolve one molecule ofO2.
Quantum yield =
1
= 0.125
8
The two forms of chlorophyll ‘a’ are chl a 683(P680) and chl a 703
(P700) with peak absorption at 683 and 703 respectively are
anchored in thylakoids membranes. Theyare the reaction centres.
Red Drop :
Sudden drop or fall in rate of photosynthesis or in quantum yield
above680 nm (far red light)is calledreddrop.
Emerson Enhancement Effect :
Emerson et al (1957) discovered that red light (above 680 nm),
which is photosynthetically inefficient can be made efficient by
supplementing it with a beam of shorter wave length (red beam
below680 nm). Further the quantum yield in combined beam (far
red + red) is more than sum total ofquantum yields in twoseparate
beams.
Electron Transport :
It was first formulated byHill (1939). Electron transport chain is a
series of electron carrier over which electrons pass in a downhill
journey releasing energy at every step that is used in generating
an electrochemical proton gradient which helps in synthesising
ATP.
CyclicandNon-CyclicPhotophosphorylation
Non-cyclic Photophosphorylation
• When PS II (P680 ) absorbs light, it is excited & emits
electrons.
• The electrons run down an electron transport chain
consisting of plastoquinone, cytochrome complex and
plastocyanin to P700.
• The electrons, generated from splitting of water, are then
passed to the oxidised P680.P680 thus restores its electron.
• It then transfers electron toferredoxin and NADP -reductase
to reduce NADP to NADPH2.
• NADPH2 is then utilized in reduction of CO2 to
carbohydrates in the carbon reaction. Since theelectron
lost byPSII donot come back to it, in the ATPformation, is
called non-cyclic photophosphorylation.
2
PHOTOSYNTHESIS
Chapter
13
Concepts

3. 3
Cyclic Photophosphorylation :
•If lightof wavelength s greater than 680 nm fall photosystem
I is activated, but PS II remains inactivated.
•Electron from PS I are not passed to NADP from electron
acceptor.
•Instead, electron are transferred back toP700.
– This downhill movement result in the formation ofATP
from ADPand termed as cyclic photophosphorylation.
– O2 is not released (nosplitting of water) and NADPH2
is not produced.
Chemiosmotic Hypothesis :
•Electron transport, p roduces a proton gradient.
Carbon Reaction of 3 Types
•concentration of proto ns decreases in matrix or stroma region
while their concentration in thylakoid lumen rises resulting
in decrease inpH.
•The proton gradient is broken down due to movement of
protons through transmembrane channels, CF0 of ATPase
(CF0 –CF1 particle).
•CF 0 provides facilitated diffusion to H+ or protons. As
protons move to the outer side of APT, they bring about
conformational changes in CF1 particle of ATPase or
coupling factor. The transient CF1 particle ofATPaseenzyme
form ATPfrom ADPand inorganic phosphate.
•One molecule of AT P is formed when 2H+ pass through
ATPase.
Salient features C3-Plants C4-Plants CAM-Plants
1. Cycle C3-Cycle C4-Cycle CAM Cycle
2. KranzAnatomy Absent Present Absent
3. Carboxylatingenzyme RuDP Carboxylase PEP in Mesophyll PEP in dark and
and RuDP in Bundle RuDP in Light
sheath
4. Initial CO2acceptor RuDP PEP PEP
5. First stable product 3-PGA Oxaloacetate Oxaloacetate
6. Optimumtemperature 15 - 250C 30 - 400C 350C
7. CO2 Compensation point (PPM CO2) 50 - 150 0 - 10 0 - 5 in dark
8. Na+ requirement as micronutrient No Yes Yes
9. Photorespiration Present Not easily Detectable late
10. O2 Concentration of air Above 21% inhibited No effect Inhibited
11. ATP and NADPH2 for reduction 1 : 3 : 2 1 : 5 : 2 1 : 65 : 2
of 1 mole CO2. CO2 : ATP : NADPH2
12. Photosynthetic efficiency dry 22 ± 0.3 39 ± 17 Lower than both
matter production (tones/
hectare/years)
C3 and C4 plants
13. Rate of Photosynthesis in full
sunlight
15 -35 mg of CO2 per
dm2 of leaf area/hour
40 to 80 mg of CO2
per dm2 of leaf area/hr
–
14. ATP are required for synthesis 18 A.T.P. 30 A.T.P. 30 A.T.P.
of 1 glucose molecule
Factors Affecting Photosynthesis :
• Temperature - At 35°C photosynthesis operates fast. The
rate of Photosynthesis becomes double from 0°C to 30°C.
• Light - The rate of photosynthesis increases with increase
in light intensity. At compensation point, the rate of
respiration is equal to rate of photosynthesis.
• CO2 - The rate of photosynthesis increases with increase
in supplyof CO2. High CO2 concentration reduces the rate
of photosynthesis.
• H2O - Plants onlyutilises 1 - 3% ofabsorbed water.
Principle of Limiting Factor
•Blackman (1905) states that the factor under consideration
the other factor remaining constant, the rate of
photosynthesis increases from a minimum to an optimum.
Any further increase does not affect the rate. If any of the
other factors which is kept constant is increased the rate
increases.
Photorespiration
•Light stimulated oxid ation of photosynthetic intermediates
to CO2 is known as photorespiration. The course of
photorespiration is related tochloroplasts, peroxisomes and
mitochondria.
•First product of phot orespiration is P-glycolate and CO2 is
liberated during glycine and serine conversion in
mitochondria.
•This is a wasteful pro cess & occurs in C3 plants.

4. 4
1. Photolysis of water is caused by
(a) PS–I (b) PS–II
(c) PS–I and PS–II (d) None of these
2. Which is not correct for cyclic photophosphorylation ?
(a) No O2 given off
(b) No water consumed
(c) No NADPH2 synthesized
(d) PS–I and PS–II are involved
3. The main purpose of photosynthesis is to
(a) consume carbon dioxide
(b) produce ATP
(c) convert light energyto chemical energy
(d) produce starch
4. Given below is the pathway of light reaction. Identify the
given blanks indicated byA, B, C and D.
5. The graph belowshows the result ofan experiment in which
isotopes of oxygen were used to distinguish between
oxygen absorbed by plants and oxygen given out.
A mixture of the oxygen isotopes 16O2 and 18O2 was
supplied to a suspension of the unicellular alga Chlorella
which had previously been exposed to 16O2 only. During
the following hour changes in the concentration of these
gases in the suspension were measured.
The 18O2 concentration fall in light because it was
(a) undergoing radioactive decay to form 16O2
.
(b) absorbed in respiration but was not being produced in
photosynthesis.
(c) absorbed in respiration slower than it was being
produced in photosynthesis.
(d) absorbed as C18O2 in photosynthesis.
6. Which one does not differ between a C3 and a C4 plant?
I. Initial CO2acceptor.
II. Extent ofphotorespiration.
III. Enzymecatalyzing reaction that fixesCO2.
IV. Presence of Calvin cycle.
V. Leafanatomy.
(a) I and V (b) IV
(c) II and III (d) II
7. Which ofthe following best represent the components that
are necessary for photosynthesis to take place ?
(a) Mitochondria, accessorypigments, visible light, water
and carbondioxide.
(b) Chloroplasts, accessory pigments, visible light,water
and carbondioxide.
(c) Mitochondria, chlorophyll, visible light, water and
oxygen.
(d) Chloroplasts, chlorophyll, visible light, water and
carbon dioxide.
8. The protons that make up the proton gradient used during
the light reactions of photosynthesis come from
(a) glucose (b) ATP
(c) H2O (d) NADPH
9. Which one ofthe following is not a direct result ofsunlight
reaching a lake?
(a) Conversion of phytochrome 660 to phytochrome 735
in aquatic plants.
(b) Bleaching of rhodopsin in a fish retina.
(c) Activation ofchlorophyll in a diatom.
(d) Conversion of phosphoglyceric acid into
phosphoglyceraldehyde in aquatic plants.
10. Which one is the correct summary equation of
photosynthesis?
(a) C6H12O6 + 6O2 6CO2 + 6H2O + energy
(b) C6H12O6 + 6O2 + 6H2O
(c) 6CO2 +6H2O
(d) 6CO2 +12H2O
6CO2 + 12H2O + energy
6H2O + C6H12O6
6O2 + C6H12O6 + 6H2O
Exercise
Light
Chlorophyll
Light
Chlorophyll

5. 5
11. Calvin cycleexpendsthe followingfor fixation of3-molecules
ofCO2
(a) 9ATP and 6 NADPH2
(b) 8ATP and 6 NADPH2
(c) 9ATP and 3 NADPH2
(d) 6ATP and 9 NADPH2
12. Chlorophyll is suited for the capture oflight energybecause
(a) Certain wavelengths oflight raise it to an excited state.
(b) In its excited state chlorophyll gives offelectrons.
(c) Chlorophyll’s structure allows it toattach tothylakoid
membranes.
(d) All of the above
13. The electronsthat arereleasedbythe splittingofwater during
photosynthesis ultimately end up in
(a) glucose (b) ATP
(c) H2O (d) NADPH
14. The graph belowrefers to an experiment involving species
ofalga. Therelative concentrations ofGP and RuPBpresent
in the cells were monitored when the plants were in light
and then in darkness
Which of the following conclusions cannot be drawn from
these results?
(a) In darkness therelative concentration ofGP increases.
(b) During the experiment RuBP may be converted into
GP.
(c) The relative concentration of RuBP decreases on
removal ofCO2.
(d) In light a steady state exists between RuBP andGP.
15. Plants give off oxygen because
(a) oxygen results from theincorporation of carbon dioxide
into sugars.
(b) plants do not respire since they photosynthesize.
(c) water is the initial proton donor, leaving oxygen as a
photosynthetic by-product.
(d) All of the above
16. Study the figure showing graph of light intensity on the
rate of photosynthesis. Choose the correct option by
matching the column I with column II
Column- I Column -II
I. Limiting factor in A. Some factor
region A other than light intensity
is becoming the limiting
factor
II. B represents to B. Light isno
longer limiting factor
III. C represents to C. Light intensity
IV. D represents to D. Maximum rate
of photosynthesis
V. E represents to E. Saturation
point for light intensity
The correct option is -
(a) I- A, II- B, III -C, IV-D, V- E
(b) I- C, II-A, III-B, IV-E, V-D
(c) I- D, II- B, III-E, IV- C, V-A
(d) I- E, II- D, III-C, IV-B, V-A
17. The energy wastage occurs during
(a) Dark reaction (b) Photorespiration
(c) Photosynthesis (d) None of these
18. What process in cellular respiration is essentiallythe reverse
of carbon fixation in photosynthesis?
(a) Glycolysis
(b) Citric acidcycle
(c) Oxidative phosphorylation
(d) Alcohol fermentation
19. Cyclic and non-cyclic electron flow is used in plants to
(a) Meet the ATP demands of the Calvin Benson cycle.
(b) Avoid producing excess NADPH+H+
(c) BalanceATPand NADPH+H+ ratios in the chloroplast.
(d) All of the above
20. If you consider the combined processes of photosynthesis
and cellular respiration, the electrons found in H2O at the
beginning of the light reactions end up attaching to
during respiration.
(a) O2 tomake newH2O
(b) NADPHto make new glucose
(c) pyruvate to makeethanol
(d) electron transport carriers tomake O2
21. Which ofthe following statements are correct ?
I. Photorespiration is favoured byhigh O2, lowCO2, rise
in temperature, high lightintensity.
II. Chloroplasts of cells of bundle sheath of C4 plants are
granale, have PEPCo, PEPcase but noRUBisCO.
III. Chloroplasts ofmesophyll cells ofC4 plant aregranale,
have PEPCo PEPcase but noRUBisCO.
IV. Maize and Sorghum areC4 plants.
(a) Allare correct (b) I and IV are correct
(c) II and III are correct (d) Only IV is correct
22. The increase in photosynthesis occurs till CO2concentration
is increased upto :
(a) 300ppm (b) 600ppm
(c) 4000ppm (d) 6000ppm
23. Bacteriochlorophyll differs from chlorophyll-a in having:
(a) One pyrrole nucleus with one hydrogen
(b) One pyrrole nucleus with two hydrogen
(c) One pyrrole nucleus with threehydrogen
(d) One pyrrole nucleus with four hydrogen

6. 6
24. Which of the following statements concerning the light
reaction of photosynthesis are true ?
(a) Photosystem I can operate independently of
photosystem II.
(b) Photosystem I and II are activated by different
wavelengths oflight.
(c) Photosystems I and II transfer electrons and create
proton gradients across the thylakoidmembrane.
(d) All of the above
25. Which one of the following is a correct outline of the main
events in photosynthesis?
(a) Oxygen reacts with a carbohydrate to produce water
and carbon dioxide in the presence oflight.
(b) Light joins carbon dioxide to an acceptor compound
which is then reduced byhydrogen obtained from water.
(c) Light splits water and the resulting hydroxyl group
combines with a compound which has incorporated
carbon dioxide.
(d) Carbon dioxide combines with an acceptor compound
and this is reduced by hydrogen split from water by
light.
26. Which fractions of the visible spectrum of solar radiations
are primarily absorbed by carotenoids of higher plants?
(a) Green and red (b) Red and violet
(c) Violet and blue (d) Blue andgreen
27. Make column I with column II.
Column-I Column-II
(A) Emerson effect (a) C4 cycle
(B) Hill reaction (b) Photolysis
(C) Calvin’s cycle (c) C3 cycle
(D) Hatch and (d) Photosystem-I and II
Slack cycle
(a) Aa, Bb, Cc, Dd (b) Aa, Bc, Cd, Da
(c) Ac, Bd, Ca, Db (d) Ad, Bb, Cd,Da
28. What are the products of the light reactions in
photosynthesis?
(a) ATP and NADP
(b) ATP,NADPH2 andoxygen
(c) ATP,PGA andoxygen
(d) PGA andoxygen
29. ATP is produced during the light reactionsvia
32. During the light stage of photosynthesis, the photoactivated
pigment removes an electron from the hydroxylation derived
from the watermolecule.
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 tosugar.
33. Twopigments common in all groups of algae are;
(a) Chlorophyll-a andb
(b) Chlorophyll-b and phycocyanin
(c) Phycocyanin and carotene
(d) Carotene andchlorophyll-a
34. Maximum CO2 fixation is doneby:
(a) Green plants (b) Phytoplanktons
(c) Zooplanktons (d) Bacteria
35. Which of the statements concerning the Calvin-Benson
cycle are false ?
(a) Light energy is not required for the cycle toproceed.
(b) Carbon dioxide is assimilated intosugars.
(c) Ribulose 1, 5-bisphosphate (RuBP) is regenerated.
(d) None of the above
36. The increase in dry mass of a leaf can be used to measure
the rate of photosynthesis if suitable adjustments are made.
Which one of the following adjustments is necessary ?
(a) Allowance must be made for the rate of transpiration
only.
(b) Allowance must be made for any changes in the
moisture content of theleaf.
(c) Allowancemust be made for the oxygen evolvedduring
photosynthesis.
(d) Allowancemust be made for therate ofrespiration and
the translocation ofmaterials out ofthe leaf.
37. The smallest known plant having the same pigments as
grasses and trees, belongs to:
(a) Chlorophyceae (b) Schizomycetes
(c) Bryophyta (d) Angiosperms
38. PEPCois associated with :
(a) CAM plants (b) C -plants
(a) Carbon dioxide fixation
(b) Chemiosmosis (c) C4-plants
3
(d) None of these
(c) Reduction of water
(d) All of the above
30. Dryweight of green leaves will be
(a) Greater inmorning
(b) Almost same throughout the day
(c) Greater in lateafternoon
(d) None of the above
31. Because of the properties of chlorophyll, plants need
adequate light to grow properly.
(a) Green (b) Blue andred
(c) Infrared (d) Ultraviolet
39. Which of the following statements concerning Rubiscoare
true ?
(a) RuBiscO is anenzyme.
(b) RuBiscO catalyzes both the beginning steps of
photorespiration and the Calvin-Benson cycle.
(c) RuBiscO is the most abundant protein onearth.
(d) All of the above
40. Which element helps in thetransport ofelectronsfrom water
in photosynthesis ?
(a) Na and K (b) Mo
(c) B (d) Mn andCl

7. 7
41. In blue-green algae, the PS-II contains an important pigment
concerned with photolysis of water :
(a)-carotene (b) C hlorophyll
(c) Cytochrome (d) Phycocyanin
42. If light intensity is uniformly high, under which of the
following conditions is carbon dioxide most likely to be the
main limiting factor upon the rate of photosynthesis?
temperature / ºC % carbon dioxide
(a) 5 0.01
(b) 5 0.04
(c) 15 0.04
(d) 25 0.04
43. Which ofthe following begins the Calvin-Benson cycle and
is the commitment step that results in the entire pathway
being carried out ?
(a) 3PGAis reduced to G3Pusing ATPand NADPH+H+.
(b) The regeneration ofRuBP.
(c) Carbon dioxide andRuBPjoin forming3PGA.
(d) As a cycle, it can start at any point.
44. RuBP-oxygenase is present in:
(a) Golgi bodies (b) Peroxisome
(c) Chloroplast (d) Mitochondria
45. As there is only0.03% of CO2 in the atmosphere and when
the green plants on the earth use CO2 every year, there is
danger of scarcity of CO2 in :
(a) 100 years (b) About 1000 years
(c) After 3000 years (d) No danger at all
46. The Calvin-Benson Cycle results in the productionof
(a) glucose
(b) starch
(c) rubisco
(d) Glyceraldehyde 3-phosphateG3P.
47. The graph shows changes in the pH of water in a fresh
water lake on summerday.
PH
6.9
6.8
6.7
6.6
X Y Time
What is the probable cause of the rise in pH between times
X and Y ?
(a) Decreased levels ofmineral nutrients in the water.
(b) Decreased levels of carbon due to photosynthesis.
(c) Increased levels of carbon dioxide due to respiration.
(d) Increased oxygen released by the producers.
48. Cyclic photophosphorylation occurs under
(a) Anaerobic condition
(b) Aerobic condition
(c) Both a and b
(d) None of these
49. Which of the following photosynthetic bacteria have both
PS-I and PS-II?
(a) Green sulphur bacteria
(b) Purple-sulphur bacteria
(c) Purple non-sulphur bacteria
(d) Cyanobacteria
50. Which of the following statements regarding
photorespiration are true ?
(a) Photorespiration is a metabolicallyexpensive pathway.
(b) Photorespiration is avoided when carbon dioxide is
abundant.
(c) Photorespiration results in a loss of usable carbon
dioxide.
(d) All of the above
51. What happens during the light phase of photosynthesis ?
(a) ADP is hydrolysed and NADPH oxidised.
(b) ADP is phosphorylated and NADP reduced
(c) ATP is hydrolysed and NADPHoxidised.
(d) ATP is hydrolysed and NADP reduced.
52. Agranal chloroplasts occur incertain
(a) Succulents (b) C4 plants
(c) Hydrophytes (d) C3 plants
53. What percentageofusableradiant energyentering a reaction
site of photosynthesis is converted to potential energy ?
(a) 10% (b) 20%
(c) 35% (d) 42%
54. The fixation of carbon dioxide byPEP carboxylase function
to
(a) concentrate carbon dioxide for use in photosynthetic
cells.
(b) allow plants to close stomata without having
photorespiration occur.
(c) allowplants to photosynthesize in the dark.
(d) Both a and b
55. Why is RuBP important in the process of photosynthesis?
(a) It is a source of phosphate ions.
(b) It is an intermediate in sucrose formation.
(c) It is an acceptor molecule forhydrogen.
(d) It is an acceptor molecule for carbon dioxide.
56. Which one of the following crop plants is very efficient
converter of solar energy and whose net productivity value
ranges from 2 kg to 4 kg/m2 or even higher ?
(a) Sugarcane
(b) Rice
(c) Wheat
(d) Bajra
57. CAM plants differ from C4 plants in that
(a) carbon dioxide is stored as malicacid.
(b) photosynthesis can occur at night in these plants.
(c) their stomata close during periods that favour
photorespiration.
(d) theyuse PEP carboxylase to fix carbon dioxide.
58. Photosynthetic evolution of oxygen requires:
(a) Co-enzyme
(b) Fe-enzyme
(c) Mn-enzyme
(d) Zn-enzyme

8. 8
59. Under normal field conditions, which one is the limiting
factor in photosynthesis ?
(a) CO2 (b) Light
(c) Water (d) None of these
62. Which one is correct for C4-plants?
Mesophyll Bundle Sheath
(a) PEPcase C -Cycle RuBisCO C -Cycle
4 3
60. Which of the following statements are true regarding the
relationship between photosynthesis and cellular respiration
in plants ?
(b) PEPcase Calvin Cycle RuBisCO C -Cycle
4
(c) RuBisCO C -Cycle PEPcase C -Cycle
4 3
(a) Photosynthesis occurs in specialized photosynthetic
cells.
(b) Cellular respiration occurs in specialized respiratory
cells.
(c) Cellular respiration and photosynthesis can occur in
the samecell
(d) Both a and c
61. Carbon dioxide labelled with 14C has been used to identify
the intermediate compounds in the Calvin cycle, the light
independent stage in photosynthesis. Which compound
would be the first to contain the 14C?
(a) Glucose (b) Starch
(c) GP(PGA) (d) Triose phosphate
(d) RuBisCO C -Cycle PEPcase C -Cycle
2 3
63. The rate of photosynthesis ofa freshwater plant is measured
using using five spectral colours.
Which sequence of colours would give an increasing
photosynthetic response?
smallest largest response
(a) Blue Green Yellow Orange Red
(b) Green Yellow Orange Red Blue
(c) Red Orange Yellow Green Blue
(d) Yellow Green Orange Blue Red
64. C4 plants require:
(a) Lesser CO2 (b) Lesser salts
(c) Lesser water (d) Lesser light
1. (b)PS–II is reduced bypull ing electrons from water which
leads to photolysis of water.
2. (d)In cyclic photophosphor ylation, only PS–I isinvolved.
3. (c)Photosynthetic organi sms are the only life forms
capable of trapping light energy and converting it to
chemical energy. Because of this they form the basis
of food chains.
4. (d)
5. (b)The oxygen produced i n photosynthesis is produced
from the splitting of a water molecule bylight energy,
and not directly from the oxygen taken in during
respiration.
6. (b)
7. (d)Chloroplasts are the site of the photosynthetic
reactions; chlorophyll is excited by photons of light
and serve as reaction centers for the photosystems;
visible light is necessary to excite chlorophyll and
accessorypigments; water is the initial electron donor
for the pathway and carbon dioxide is necessary to
make energy storageprecursor molecules.
8. (c)The splitting of water m olecules in the light reactions
gives rise to the protons needed for this gradient.
9. (d)In the Calvin cycle of photosynthesis, some of the
phosphoglyceric acid is converted into
phosphogyceraldehyde and then into starch or
sucrose, while some is used to generate ribulose 1,5-
bisphosphate (RuBP). This reaction is catalysed by
ribulose 1,5-bisphosphate carboxylase (Rubisco).
10. (d)
11. (a)In Calvin cycle, three m olecules of CO2 will require
3 x 3 = 9ATPand 2 x 3 = 6 NADPH2.
12. (d)The “tails” of chloroph yll molecules are associated
with the thylakoid membranes of the chloroplasts.
When excited bylight, the chlorophyll moves into an
excited state and passes electrons to acceptor
molecules. This begins to set up the proton gradient
across the membrane that will drive ATPsynthesis.
13. (d)The reason for splitting water is to provide electrons
to the photosystems used during the light reactions.
These photosystems need new electrons because
some of them are used to reduce NADP+intoNADPH.
14. (c)
15. (c)Water is split at photo system–II to donate electrons
to the reaction centre. The resulting protons are moved
across the membrane to establish the proton motive
force and oxygen is given off as a by-product.
16. (b) 17. (b)
18. (b)Carbon fixation conve rts CO2 into glucose, and the
citric acid cycle essentially reverses this process.
19. (d)ATP is required at high er levels in the Calvin-Benson
cycle than NADPH+H+. Therefore, there must be a
mechanism for producing additional ATP. Cyclic
electron flow provides that mechanism. If non cyclic
electron flow were to be speed up to meet ATP needs,
an excess of NADPH+H+ would result. Shifting
between cyclic and non cyclic flow balances ATP/
NADPH +H+ ratios.
Hints & Solutions

9. 9
2
20. (a)Interestingly, the elect rons both begin their journey
through metabolism in water and end that journey in
the water that is made when oxygen serves as the final
electron acceptor in oxidative phosphorylation before
combining with protonstoform new“metabolic” water.
21. (a)
22. (d)Increase in CO 2 concentration upto 20 times than
normal (300 ppm) leads to increase in rate of
photosynthesis.
23. (b)Bacteriochlorophyll is having 2H-atoms more than
chlorophyll-a.
24. (d)Photosystems I and II o perate depending on whether
electron flow is cyclic or noncyclic. Activity is
controlled by the ATP levels in the chloroplast.
Photosystem II is activated bylight of a higher energy
level than photosystem I. Both photosystems transfer
electrons and create proton gradients across the
thylakoid membranes.
25. (d)Photosynthesis is th e process by which plants
manufacture food. This occurs when CO2 combines
with ribulose 1,5-bisphosphate (RuBP) to form the
products of photosynthesis.
26. (c)Carotenoids mainly ab sorb violet, indigo and blue
wavelength of spectrum in higher plants.
27. (d)
28. (b)The light reaction in photosynthesis results in the
production of energy in the form of ATP, NADPH2
and oxygen.
29. (b)ATP synthesis occurs w hen protons flow through a
channel protein with an associated ATPase. This is a
classically chemiosmoticallydriven process.
30. (c)
31. (b)Chlorophyll and acces sory pigments absorb light in
the blue and orange-red wavelengths of visible light.
Green light is reflected; therefore, plants appear green.
32. (a)The water molecule is s plit as shown in the equation:
39. (d)Rubisco, the most abund ant enzyme on earth, has both
oxygenase and carboxylase activities.
40. (d)Mn and Cl help in phot olysis of water.
41. (d)Phycobilins (including phycocyanin) are pigments of
PS-II.
42. (a)Carbon dioxide uptake i s favoured in high temperatures
and when it ispresent in relativelyhigh concentrations
in the atmosphere. Thus, the lowest temperature and
lowest CO2 percentage will significantlylower the rate
of photosynthesis.
43. (c)The first step of the Calv in-Benson cycle is the fixation
of carbon dioxide into 3PGA. This is the regulatory
step and requiresATPand NADPH+H+.
44. (c)
45. (d)The concentration o f CO2 remains constant in
atmosphere as it is released in respiration.
46. (d)The Calvin-Benson cyc le produces only G3P. G3Pcan
then be metabolized into storage products like sugars
and starch.
47. (b)The increased pH mean s that the water is less acidic.
This is because carbon dioxide is taken up from the
water for photosynthesis.
48. (a)
49. (d)Cyanobacteria or blue-g reen algae have both pigment
systems.
50. (d)Photorespiration u ses as much ATP as
photosynthesis, but results in no energy gains for the
plant and has carbon dioxide as a lost by-product. If
carbon dioxide is abundantly available, Rubisco acts
as a carboxylase rather than an oxygenase.
51. (b)During the light reactio n in photosynthesis, inorganic
phosphate is added to ADP, forming ATP and NADP
is reduced in the formation ofNADPH.
52. (b)Agranal chloroplasts ar e present in bundle sheaths of
C4 plants.
53. (c)Photosynthesis will be e fficient if 35% of usable radiant
energy entering the reaction site is converted into
potential energy.
H 2O  1 O2  H+
2 e–
fo2rming oxygen and 54. (d)
55. (d)Ribulose 1,5-bisphosp hate (RuBP) is a 5-carbon
hydrogen radicals.
33. (d)
34. (b)90% photosynthesis in world is carried out by algae
(phytoplanktons).
35. (a)Light energy is require d for the Calvin-Benson cycle
to proceed. ATP synthesis is dependent on light
energy and the Calvin-Benson cycle is dependent on
ATP.
36. (d)The important process es that occur within a leaf are
photosynthesis, where organic solutes are
synthesised; respiration, where these solutes are
oxidised to release energy and translocation, where
the solutes are transported from the site of
manufacture to other parts of theplant.
37. (a)Members of chlorophyc eae class (green algae) of algae
will have same pigments as those of grasses and trees,
i.e., chlorophyll-a, chlorophyll-b andcarotenoids.
38. (c)
compound which is the first acceptor ofCO2, resulting
in the formation of 3-phosphoglyderaldehyde(3-PGA).
56. (a)Sugar cane is most effic ient converter of solar energy.
57. (a) 58. (c)
59. (a)CO 2 is usually limiting factor in photosynthesis under
field conditions.
60. (d)
61. (c)During the calvin cycle, the radioactiveCO2is accepted
by ribulose 1,5 bisphosphate (RuBP) in theformation
of the first product, 3-phosphoglyceraldehyde (PGA),
which will be the first compound to contain 14C.
62. (a)
63. (b)Photosynthesis occurs m ost efficientlywith red or blue
light because the chlorophyll pigments can absorb
light maximally at these wavelengths and the least at
green light.
64.(a) C 4 plants can photosynthesize in poor concentration
of CO2 as they get internal supply ofCO2.