PHOTOSYNTHESIS - THE KEY PROCESS OF PLANT ENERGY CONVERSION

NEET_PHYTOSYNTHESIS - 11
PHOTOSYNTHESIS
The synthesis of complex organic substances (carbohydrates) by green parts of the plants in the presence
of light with the help of CO2
and H2
O is called photosynthesis. It can be shown by following equation.
Photosynthesis is anabolic, endothermic and redox process.
Photosynthesis firstly observed in cyanobacteria.
Only 10% of dry matter is produced by land plants while 90% formed by aquatic plants. mostly algae (90%
in ocean and 10% in fresh water).
Radient energy of sun is changed in to chemical energy in the process of photosynthesis. It is also called
carbon di-oxide assimilation.
Photosynthesis is a Redox process in which water is oxidized to form O2
while CO2
is reduced to form
sugars. Thus it is a oxidation reduction reaction.
History :
1. Aristotle and Theophrastus (320 B.C.) : They believed that plants absorbs their food from soil.
2. Van Helmont (1648) : He worked on willow plant and concluded that all the weight of plants increases
due to water.
3. John wood wards (1699) : Besides water soil also increases the weight of plants.
4. Stephan Hales (1727) : Green plants obtain their food from leaves.
5. Joseph priestly (1733-1804) : He proved that green plants clean air.
He proved his concept through belljars experiment.Priestley’s
experiment observed that a candle burning in a closed space- a bell
jar, soon gets extinguished (a, b,c d,). Similary, a mouse would soon
suffocate in a closed space. He concluded that a burning candle or an
animal that breathe the air, both somehow, damage the air. But when
he placed a mint plant in the same bell jar, he found that the mouse
stayed alive and the candle continued to burn. Priestley hypothesised
as follows: Plants restore to the air whatever breathing animals and
burning candles
remove.
6. Ingen-housz (1799) : He discovered that the green plants purify the
noxious air in the presence of light
7. de-Saussure (1804) : He showed the significance of water in
photosynthesis.
8. Deutrochet : He cleared the importance of chlorophyll in photosynthesis.
9. Sachs (1862) : He showed the product of photosynthesis as starch.
10. Blackman (1905) : He proposed the law of limiting factors.
11. Engle mann (1888) : He plotted the action spectrum of photosynthesis.
12. Warburg (1920) : He found the unicellular green algae chlorella as a suitable material to study
photosynthesis.
13. C.B. Van Niel (1930) : Proved that, sulphur bacteria use H2
S in place of water as an Hydrogen and
Electron donar in photosynthesis.
14. Hill (1937) : He demonstrated the photolysis of water in isolated chloroplasts.
15. Ruben, Kamen and Hashid (1941) : They proved that the O2
given out during photosynthesis comes
from water by using O18
isotope.
16. Arnon (1941) : He discovered photophosphorylation.
17. Calvin (1954) : He discovered the path of carbon in photosynthesis and gave the C3
cycle. He was
awarded noble prize in 1961.

18. Emerson (1957) : He discovered two pigment system (PS-I and PS-II) in light reaction. He also reported
about red drop phenomenon.
19. Hatch & Slack (1965) : They traced C4
path way for CO2
fixation in certain tropical grasses.
20. Huber, Michel and Dissenhofer (1985) : Theycrystallized the photosynthetic reaction centre of bacterium
Rhodobacter and analysed its structure by X-ray diffraction. They were awarded Noble prize in 1988.
The site of photosynthesis :
Chloroplasts are those cell organelles in which photosynthesis takes place pigments are located at the
membranes of chloroplast.
In blue green algae pigments are present in
photosynthetic lamelle which are present naked
in cytoplasm. In eukaryotic algae pigment are
present in thylakoid lamelle, they are covered by
double membrane thus cloroplasts are present
but thylakoids do not pile up to form grana. But in
higher plants thylakoids pile up and form stalks
of coin like structures called grana (singular
granum).
Each thylakoid consists of lipid and protein.
Two grana are inter connected by long lamellae
which is called intergranum or fret channel.
Many small granules are found on the thylakoid
membrane which are known as quantosomes.
They were discovered by Parks and Biggens.
Each quantosome contains 230 molecules of
chlorophyll and 50 molecule of carotenoids.
Chloroplast is known as a semi autonomous
organelle due to presence of DNA, RNA & 70s
ribosomes. In bacteria, pigments are found at
chromatophores. The latter are found in
cytoplasm.
Note : Thylakoid form the third membrane
system in chloroplast.
Pigments :
There are three types of pigments in the
chloroplasts
(1) Chlorophyll (2) Carotenoids
(3) Phycobilins
(1) Chlorophyll :
It was discovered by Pelletier and Caventou and gave the name chlorophyll. Willstatter and stoll gave
the chemical structure of chlorophyll.

Structure of chlorophyll :
Chlorophyll molecule is look like a tadpole.
Each chlorophyll molecule consists of two parts, Porphyrin head & phytol tail. Head consists of tetrapyrole or
porphyrin in which 4 pyrole molecules are arranged in isocycle manner containing a Mg atom at its centre.
The pyrole molecule contains a skeleton of 4 carbon and N and has a ring structure. From one of the pyrole
rings attached is a long chain phytol tail (of 20Å).
Chl a has a methyl group (–CH3
) and chl b has an aldehyde group (–CHO) on the second pyrole.
Types of photosynthetic pigment in various groups of plants
S.No. Photosynthetic pigment Colour Distribution
Chlorophylls
1 Chlorophyll a (C55H72O5N4Mg) Yellow green All green plants except bacteria
2 Chlorophyll b
(C55H70O6N4Mg)
Blue green All higher plants and green algae
3 Chlorophyll c (C35H32O5N4Mg) Green Diatoms
4 Chlorophyll d (C54H70O6N4Mg) Green Red algae
5 Bacterio Chlorophyll
(C55H74O6N4Mg)
Purple Bacteria
6 Bacteriovirdin (C55H74O6N4Mg) Green Bacteria
Carotenoids
1 Carotenes (C40 H56)and
Xanthophylls (C40H56O2)
Orange Algae and higher plants
Phycobilins
1 Phycoerythrin Red Red algae
2 Phycocyanin Blue Red algae and blue green algae
Point of remember :
1. The precursor of Chlorophyll is ‘Protochlorophyll’. Its synthesis starts from glycine and succinyl CoA.
2. Chlorophyll e is found in zoospores of Vaucheria. Its structure is still not known.
3. Chal-a and carotene are universal pigments
(2) Carotenoids :
Most of the carotenoids are yellow or orange in colour and are soluble in lipids. They protect chlorophyll from
photo oxidation. Thus they are called protective pigments or shield pigments. They are of two types.
(i) Carotene :
They are orange in colour. They are hydrocarbon with a general molecular formula C40
H56
.
Wackenroder (1831) firstly isolated a carotenoid from the carrot roots and called carotene ( - carotene)
There major isomers of carotene are - carotene, - carotene, - carotene.
Lycopine (C40
H51
) is a carotene which is found in tomato.
(ii) Xanthophyll :
They are also called carotenols. They are Yellow in colour. They are oxygenated derivatives of carotenes,
eg. C40
H56
O2
- Leutin.
Other important xanthophylls are-cryptoxanthin, vialoxanthin, zeoxanthin, flavoxanthin and
fucoxanthin. Fucoxanthin is found in brown algae.
Xanthophyll and carotene are found in 2 : 1 ratio in juvenile leaves.

3. Phycobilins :
They are usually found in Red algae and Blue green algae.
They are soluble in water. They are strongly combined with proteins so they are also called Billiproteins or
phycobillisome.
They are of three types :
(1) Phycocyanin - Blue coloured
(2) Phycoerythrin - Red coloured
(3) Allophycocyanin - Blue coloured
Phytochrome is a billiprotein which is found in higher plants.
Phycobilins absorb sunlight and transfer to the chl a. Thus they are a accessory pigments.
Terminology :
(1) Absorption and action spectra :
Absorption spectrum :
Visible light has wavelength range of 3900 Å -
7600 Å. The particles of visible light are called
photon.
Out of seven colours (VIBGYOR) of visible light,
green light remain unabsorbed and is reflected
back imparting green colour to the leaves.
Chl a absorbs maximum blue followed by red
regionof spectrum.Thegraphshowingtheamount
of different wavelengths of light absorbed by a
substance is called absorption spectrum.
Action spectrum :
It is a graph showing actual rate of photosynthesis
measured in terms of O2
production at different
wavelength of light. It is maximum in Red followed
by blue and minimum in green light.
Engelmann using a prism he split light into its
spectralcomponents and then illuminated a green
alga, Cladophora, placed in a suspension of
aerobic bacteria. The bacteriawere used to detect
the sites of O2
evolution. He observed that the
bacteria accumulated mainly in the region of blue
and red light of the split spectrum. A first action
spectrum of photosynthesis was thus described.
It resembles roughly the absorption spectra of
chlorophyll a and b.
(2) Quantum requirement & Quantum yield :

Number of light quanta required for the production of one molecule of O2
is called Quantum requirement
Its value is 8.
The number of oxygen molecules produced per quantum of light absorbed is called Quantum yield. It is
8
1
= 12.5%.
(3) Red drop & Emerson enhancement effect :
Emerson while determining the quantum yield of photosynthesis in Chlorella by using monochromatic light
of different wavelengths, noticed a sharp decrease in quantum yield at wavelength greater than 680 nm.
The fall in photosynthetic yield beyond red region of spectrum is called Red drop.
Emerson further supplied additional shorter wavelengths of light along with far red light (more than 680nm)
He found that quantum yield in creased. It is called Emerson enhancement effect.
The experiment carried by emerson indicated the existence of two pigment system.
(4) Two pigment system :
(1) Pigment system-I (2) Pigment system-II
Butler discovered two forms of chl a they are 673 and 683 while Clayton (1966) discovered P700
type of
chlorophyll a.
(1) PS-I or pigment system-I (LHC-I or light harvesting complex-I) :
It is situated in both non appressed part of grana thylakoids as well as stroma thylakoids.
It consists of pigments absorbing longer wavelength of light. It contain chla-683, chl a 690, chl a P-700
(Reaction centre), chl b, carotenoids cytochrome complex, plastocyanin and ferredoxin.
(2) Pigment system-II or PS-II (LHC-II or light harvesting complex-II) :
It is located in appressed part of grana thylakoids.
It consists of pigment absorbing shorter wavelength of light. It contains chl a - 660, chl a - 670 and chl a-
680 (Reaction centre), carotenoids, plastoquinons, maganese and chloride, Quencher molecule Q, cyto-
chrome complex and plastocyanin.
Differences between PS-I & PS-II
S. No. PS-I PS-II
1 It is located on the non appressed part of
grana and stroma thylakoids
It is located in the appressed part of grana
thylakoids
2 P700 is a reaction centre in PS-I P680 is reaction centre in PS-II
3 It is involved in both cyclic and non cyclic
photophosphorylation.
It is involved only in non–cyclic photophos-
phorylation.
4 During non cyclic photophosphorylation.
It obtains electron from PS-II
It obtains electron through photolysis of water
5 Molecular oxygen is not evolved in this system. Molecular oxygen is evolved due to
photolysis of water.
Mechanism of Photosynthesis :
The mechanism of photosynthesis divides in to two steps.
(1) Light reaction (2) Dark reaction
Light reaction occurs in grana of chloroplast. It is also called photochemical reaction or Hill reaction.
Blackman firstly reported the existence of light and dark reaction in photosynthesis. The following two
evidences confirm the existence of light and dark reactions in photosynthesis.

(i) Intermittent light experiment :
Warburg (1919) conducted an experiment on plant with continuous and intermittent light. The rate of
photosynthesis was found to be greater in intermittent light as compared to continuous light. It shows the
existence of two steps in photosynthesis a light dependent reaction and another light independent reaction.
(ii) Temperature cofficient experiment :
The temperature cofficient Q10
is the ratio of the rate of a particular reaction at a given temperature to the
rate of that reaction exactly at 10 º
C lower. The value of Q10
for photochemical reaction is one and for dark
reaction is 2 or 3.
(I) Light reaction :
Light energy is converted in to chemical energy (ATP) by Light harvesting complex (PS II& PS I) during light
reaction. Accessary phtosynthetic pigments absorb light energy & transfer to the other pigments by the
phenomenon of Resonance transfer.
Electron Transport Chain :
It is of two types.
(A) Cyclic (B) Non cyclic
(A) Cyclic Electron Transport Chain :
It is performed by PS-I only. Its reaction centre is P700
of chl a
After losing the electron the photocentre becomes oxidized. The expelled electron passes through a series
of carriers including X or A0
,A1
(quinone) FeS complexes (FeSX
, FeSA
, FeSB
) ferredoxin, plastoquinone,
cytochrome b6
–f complex and plastocyanin and finally in the photocentre of PSI. The electron transport
is called cyclic because the electron emitted from PSI returns back to PSI passing through several
intermediates.

(B) Non Cyclic Electron Transport Chain or Z-Scheme :
It is carried out in collaboration of both PS-I and PS-II in which the electron expelled by the excited photocentre
does not return back to it.
The light energy of specific wavelength is absorbed by chlorophyll & accessory pigments These pigments
transfer their absorbed energy to PS-II reaction centre-P680
resulting P680
becomes photoexcited and exudes
an electron which is accepted by Phaeophytin (Chlorophyll without Mg).
Electron released during photolysis of water is picked up by photocentre P680
of PS-II. The same is extruded
out when the photocentre absorbs light energy (< 680 nm) electron passes through a series of electron
carriers PQ, cytochrome b6
–f complex and plastocyanin. The electron is transferred to photocentre P-700
of PS-I by plastocyanin. P-700 extrudes the electron after absorbing light energy. The extruded electron
passes through X orA0
,A1
(quinone), FeS complexes (FeSX
, FeSA
, FeSB
), Ferredoxin and NADP-Reductase
which combines with NADP+
for becoming reduced through H+
released during photolysis to form NADPH.

Photolysis of water : The phenomenon of breaking up of water into hydrogen and oxygen in the illumi-
nated chloroplasts is called photolysis. In this process oxygen evolving complex, electron carrierYZ
, Mn2+
,
Cl–
,Ca++
ions are helpful.
The electrons released during photolysis of water are picked up by P680
photocentre of photosystem-II with
the help of electron carrierYZ
.
Photophosphorylation :
The process of formation of chemical energy i.e. ATP from ADP and inorganic phosphate by using light
energy is called photophosphorylation.It was discovered by Arnon et al (1954). It can be explained through
Chemiosmotic theory.
Chemiosmotic theory for photophosphorylation :
It was proposed by P. Mitchell (1961). He got nobel prize in 1978. According to this theory, photophospho-
rylation takes place in thylakoid membrane and hydrogen or protons produced move from thylakoid locule to
the stroma through ATPase complex due to pH gradient across the membrane (Proton gradient or Proton
motive force). It is believed that single molecule of ATP is formed from ADP and Pi when 3H+
pass through
ATPase complex.
Thus Assimilatory power- ATP & NADPH both form in non cyclic photphosphosyrlation where as onlyATP
synthesizes in cyclic photophsphorylation.
Differences between Non cyclic and cyclic photophosphorylation

S. No. Non cyclic Cyclic
1 PSI and PS-II both are active Only PS-I active
2 Photolysis of water takes place Photolysis of water does not takes place
3 Water consumed Water does not cosumed
4 O2 liberates O2 does not liberate
5 Source of electron is water Source of electron is P-700
6 It is affected by DCMU It is not affected by DCMU
7 It is found in green plants It is found in Bacteria & green plants
8 NADPH+H+
is also formed with ATP Only ATP form.
(II) Dark Reaction :
It is a thermosensible activity which takes place in stroma of chloroplast.
In this process ATP and NADPH utilized and carbohydrates are formed through the reduction & assimilation
of CO2
. The value of Q10
for dark reaction is 2 or 3.
C3
cycle or Calvin cycle :
Melvin calvin and Benson (1961) discovered carbon path of dark reaction. They used radio active C14
,
unicellular algae Scanedesmus and Chlorella in their experiment.
Calvin cycle is also called C3
cycle because in this cycle first stable compound is 3-carbon compound
3-phosphologyceric acid or 3-PGA.

Plants in which C3
cycle takes place (Mostly mesophytes and hydrophytes) are called C3
-plants.
It contain three steps :
1. Carboxylation : Carboxylation is the fixation of CO2
into a stable organic intermediate. Carboxylation is
the most crucial step of the Calvin cycle where CO2
is utilised for the carboxylation of RuBP. This
reaction is catalysed by the enzyme RuBP carboxylase which results in the formation to two molecules
of 3-PGA. Since this enzyme also has an oxygenation activity it would be more correct to call it RuBP
carboxylase-oxygenase or RuBisCO.
2. Reduction : These are a series of reactions that lead to the formation of glucose. The steps involve
uitlisation of 2 molecules of ATP for phosphorylation and two of NADPH for reduction per CO2
molecule
fixed. The fixation of six molecules CO2
and 6 turns of the cycle are required for the removal of one
molecule of glucose from the pathway.
3. Regenertion : Regeneration of the CO2
acceptor molecule RuBP is crucial if the cycle is to continue
uninterrupted. The regeneration steps require one ATP for phosphorylation to form RuBP.
Note :
(1) In C3
cycle 18 ATP and 12 NADPH+H+
are used to fix 6CO2
molecules or to form 1 Hexose
molecule.
(2) To make one molecule of glucose 6 turns of the cycle are required.
Alternative cycles of carbon fixation :
It includes following cycles.
(A) Hatch and slack cycle or C4
-cycle (B) Crassulacean acid metabolism or CAM cycle.
(A) Hatch and slack cycle or C4
cycle :
Kortschak, Hartt & Burr (1965) on providing CO2
to leaf of sugarcane found that the first stable product was
not a 3-c compound but it was 4-C compound oxaloacetic acid (OAA).
Hatch & Slack (1967) discovered this alternative pathway for CO2
fixation called as Hatch and slack cycle.
It is also called C4
-cycle because first stable compound is 4C compound Oxalo Acetic Acid (OAA) in
this cycle. It is usually found in various monocotyledons Ex: maize, sugarcane, panicum, Atriplex and
some dicotyledons Ex : Amaranthus, Chenopodium, Salsola etc.
In the C4
plants the bundle sheath cells of leaf show Kranz Anatomy in which vascular tissues are
surrounded by concentric rings of mesophyll cells. C4
plants contain centripetally arranged large and agranal
chloroplast (grana absent) in bundle sheath. The chloroplast of mesophyll cells are small and have well
developed grana. The cells of mesophyll and bundle sheath are connected through plasmodesmata.
Correlation between Kranz anatomy and C4
photosynthesis was established by Dowton and Treguna.
PEP carboxylase enzyme is found in mesophyll cells and RUBP carboxylase is found in bundle
sheath.C4
-cycle includes following steps.

(I) In mesophyll cells :
· In C4
plants CO2
is firstly accepted in the mesophyll cells by phosphoenol pyruvate (PEP) and forms a 4C
compound oxaloacetic acid (First stable compound).
PEP + CO2
+ H2
O Oxaloacetic acid
(3C) (OAA) (4C)
OAA converts in to 4 C compound malic acid. Hydrogen is provided by NADPH + H+
OAA + NADPH+H+
Malic acid + NADP
(4C) (4c)
(II) In Bundle sheath :
The malic acid now moves to the bundle sheath cells where it is decarboxylated in pyruvic acid & CO2
. CO
2
is accepted by RUBP and refixed into hexose sugars through calvin cycle.
Malic acid + NADP+
Pyruvic acid + NADPH + H+
+ CO2
(4C) (3C)
(III) Pyruvic acid moves to mesophyll cell and converted in to phosphoenol pyruvate (PEP) with the help ofATP.
Pyruvic acid + ATP + iP PEP + AMP + iPP
In some plants Aspartic acid is transferred from leaf mesophyll to bundle sheath. It is converted into malic
acid to liberate CO2
Ex : Panicum maximum.
Point of remember
(1) Atriplex hastata show Calvin cycle whereas Atriplex roseus shows Hatch and Slack cycle.
(2) Wheat & Barley are C3
plants.
(3) Burmuda grass has Granal chloroplast in both mesophyll & bundle Sheath.

S. No. C3 plants C4 Plants
1 Leaves with normal anatomy Leaves with Kranz anatomy
2 Chloroplasts normal but starch grains
absent
Chloroplasts of bundle sheath lack grana,
Starch grains present
3 Bundle sheath with chlorophyll is absent Bundle sheath with chlorophyll is present
4 Chloroplast dimorphism is not found Chloroplast dimorphism is found
5 Only C3 pathway is present Both C3 and C4 pathways are present
6 CO2 fixation - once CO2 fixation - twice
7 More product is formed at low temperature
but becomes comparatively low at high
temperature
Less effective at low temperature as compared to
C3 plants but the product is more at high temperature
8 First CO2 acceptor is RUDP First CO2 acceptor is PEP
9 First stable compound is 3–PGA (3c) First stable compound is OAA (4c)
10 For reduction of one CO2 molecule, 3 ATPs
and 2 NADPH.H+
are required
For reduction of one molecule of CO2, 5 ATPs and 2
NADPH.H+
are required
11 CO2 Compensation point is 25 -100 ppm CO2 Compensation point is 0 -10 ppm
12 photorespiration occurs and photosynthesis
drops
The process of photorespiration is not found
13 C3 plants are less efficient C4 plants are more efficient
Differences between C3 & C4 plants
Significance of C4
plants :
1. Hatch-Slack pathway begins with carboxylation of phosphoenol pyruvate and not of ribulose bi phosphate
because PEP carboxylase has great affinities with CO2
than RUBP carboxylase.
2. Bundle sheath in C4
plants being close to xylem, harmful effect of water scarcity are less.
3. Due to high photosynthetic efficiency in C4
plants and their adaptability to survive in adverse conditions
these plants develop as strong weeds. Ex : Chenopodium, Amaranthus, Salsola.
4. C4
plants are mostlyfound in hot deserts where high temperature and high light intensity are found. These
conditions stimulate photorespiration in plants but photorespiration absent in C4
plants
, 5. C4
path provides more CO2
for RUDP, RUDP carboxylase enzyme is less sensitive to CO2
.
(B) Crassulacean Acid metabolism or CAM cycle :
The process was first observed in the plants belonging to family Crassulaceae by O-leary, Rouhani and
Black. So it is called CAM.
CAM plants are mainly succulent xerophytes. Ex: Opuntia, Bryophyllum, Pineapple, Kalanchoe,
Sedum, Agave, Aloe, Crassula, Euphorbia sp.
Stomata open in night in these plants, these stomata are called scotoactive stomata.
Meosphyll cells of leaves of CAM plants contain enzymes of C3
and C4
cycles but Kranz anatomy is absent
In these plants C3
-cycle occur in day while C4
in night.
This metabolic pathway involves :
(i) Acidification :
In dark, stored carbohydrates are converted in to phosphoenol pyruvic acid (PEP) bythe process of glycolysis
due to opening of stomata. So CO2
enter into leaf and PEP react with CO2
in the presence of enzyme PEP
carboxylase to form oxaloacetic acid (OAA). OAA is then reduced to malic acid in presence of enzyme malic
dehydrogenase with the help of NADH+H+
. This malic acid is stored in vacuole.
(ii) Deacidification :
In light the malic acid is decarboxylated to produce pyruvic acid and evolve CO2
this process is called
deacidification. The CO2
produced by above process is then consumed in normal photosynthetic process to
produce carbohydrates.

Thus in CAM plants fixation of CO2
occur two time in day and night.
Photorespiration (Photosynthetic Carbon Oxidation Cycle - PCO Cycle):
Oxidation of organic compounds by oxygen in the presence of light in C3
plants is called photorespiration.
Photorespiration was discovered by Decker and Tio (1959).
Substrate of photorespiration is glycolate which is 2C compound therefore it is also called C2
-Cycle or
Glycolate cycle.
It is accomplished in 3 different cell organelles viz - chloroplast , peroxysomes and mitochondria.
(1) In chloroplast : In the presence of low concentration of CO2
and higher concentration of O2
, High light
intensity & Higher temperature. RUBISCO functions as oxygenase. Therefore it oxidase RUDP and one
molecule of 3-PGA and one molecule 2-phosphoglycolate formed.
RUDP + O2
3-PGA + 2 phosphoglycolate
an inorganic phosphate separates from 2 - phosphoglycolate to form glycolate which transfer into
peroxisome.
2-Phosphoglycolate Glycolate +H3
PO4
(2) In peroxisome : Glycolate reacts with oxygen to form glyoxylate which form glycine through
transamination.
(3) In mitochondria : Now glycine moves into mitochondria where in presence of oxygen, two molecules of
glycine interact and give rise to a molecule of serine, CO2
and NH3
.
Serine moves again in peroxisome where deamination of
serine takes place resulting the formationof glycerate form.
Which moves into chloroplast to form 3-PGA in the pres-
ence of ATP. 3-PGA is used in carbon assimilation cycle.
About 30-40% of CO2
fixed during photosynthesis is lost
during photorespiration.
Factor affecting photosynthesis :
Sachs (1860) proposed concept of cardinal point.Accord-
ing to this, factor affecting any physiological reaction has
3-main values-
(a) Minimum : Physiological reaction does not occur if
the value is below minimum.
(b) Optimum : At optimum value, the reaction can occur
at the maximum speed for an indefinite period.
(c) Maximum : The value beyond maximum the activity
stops.
Blackman’s law of limiting factor :
According to this law when a process is affected by many
factors, the rate of the process is limited by the factor
that is available in minimum quantity.

External factors :
(1) Light :
(A) Light intensity : The rate of photosynthesis is more in intense
light than diffused light. Rate of photosynthesis increases with
increase in light intensity but in the presence of high light intensity
photo-oxidation of chlorophyll occurs this phenomenon is called
‘Solarization’ and the rate of photosynthesis declined.
Usuallythe rate of photosynthesis is 10 times more than respiration
during daytime but in the evening at the one point the rate of
photosynthesis & respiration is equal it is called light
compensation point. The latter is not good for plants.
(B) Light quality : The rate of photosynthesis is higher in Red light followed by blue light & It is minimum
in green light It is maximum in polychromatic light (white light).
(2) CO2
: The normal concentration of CO2
is 0.36% (360 ppm) in atmosphere. If the CO2
concentration
increases the rate of photosynthesis also increases but in the presence of higher concentration of CO2
it is diclined.
CO2
compensation point : It is a point on which amount of CO2
consumption in photosynthesis is equal to
the amount of CO2
liberation in Respiration. It is 25–100ppm for C3
-plants and 0-10ppm for C4
plants.
(3) Temperature : The optimum temperature for photosynthesis is 20º– 35ºC. But above the 40ºC the rate
of photsynthesis is declined due to denaturation of enzymes. Photosynthesis is inhibited at 0ºC but
exceptionally lichens & conifers show phtosynthesis even at –20º to–35ºC. Also there are some BGA
like Oscillitoria brevis which show photosynthesis at high temperature at 700
C.
(4) O2
: The rate of photosynthesis is declined in the presence of higher concentration of O2
in C3
plants due
to photorespiration. It is called warburg effect.
(5) Water : 1% absorbed water is utilized in photosynthesis. Deficiency of water causes closing of stomata
& the rate of photosynthesis is declined.
Internal factors :
(1) Chlorophyll (2) Anatomy of leaf
(3) Hydration of protoplasm (4) Accumulation of photosynthetic product
(5) Age of the plant.
Read & Digest :
1. Cytochromes are Iron-protein discovered by MacMunn, and term cytochrome coined by Keilin.
Cytochromes are common in both photosynthesis and respiration.
2. Photolysis of water takes place at + 0· 8 volt E0
.
3. Bacterial photosynthesis is non oxygenic in which only cyclic Phosphorylation takes place &
PS–II is absent. Reaction centre is B890
(it utilizes infra-red light).O2
does not evolve because
H+
donor is not water.
4. Photosynthesis even occurs in electric light

5. Some experiments of photosynthesis :
(i) Moll’s half leaf experiment proves that CO2
is essential for photosynthesis.
(ii) Ganong’s light screen experiment proves that light is essential for photosynthesis.
(iii) Rate of photosynthesis can be known by counting air bubbles of O2
through Wilmot’s bubbler.
Source of Oxygen in photosynthesis
In oxygenic photosynthesis oxygen is released as a byproduct. This oxygen is basically comes from
water not from CO2
.
C.B.Van Niel (1930) : Was the first person to tell this. He proved that sulphur bacteria use H2
S as an
hydrogen and electron donar and release S in place of O2
.
(Photosynthesis in sulphur bacteria)
(Photosynthesis in normal organisms)
Robert Hill (1939) : Showed that if chloroplast are extracted from leaves of Stellaria media and
placed with suitable electron acceptor like potassium ferricyanide, potassium ferroxylate, chromate,
benzoquinones, dichlorophenol indophenol etc. than oxygen is released by photolysis of water. This
photochemical splitting of water is termed as Hill reaction and it also proves that O
2
is released
from water.
Ruben, Kamen and Hashid (1941), used an isotope of oxygen, O18
in water to confirm that oxygen
comes from water.

NEET_Phytosynthesis - 54
Type (I) : Very Short Answer Type Questions : [01 Mark Each]
1. Diffrentiates Absorption spectrum and action spectrum.
2. Write name of element present in the central part of chlorophyll.
3. Define Red drop & emerson effect.
4. How many molecules ofATP and NADPH are required for synthesis of one molecule of glucose in C3
and C4
pathways.
5. What is Law of limiting factor
Type (II) : Short Answer Type Questions : [02 Marks Each]
6. Suppose there plants that had a high conentration of chlorophyll but lacked chl a. Would it carry out
photosynthesis? Then why do plants have chlorophyll b and other accessory pigments?
7. Give the Differences between cyclic and Noncyclic photophosphorylation.
8. RuBisCo is an enzyme that acts both as a carboxylase and oxygenase. Why do you thick RuBisCo carries
more carboxylation in C4
plants?
Type (III) : Long Answer Type Questions: [03 Mark Each]
9. Write the name of two C4
plants. Describe the mechanism of Hatch and slack pathway in C4
plants.
10. Differentiate between photophosphorylation and oxidative phosphorylation.
11. Describe the outline of photorespiration.
Type (IV) : Very Long Answer Type Questions: [05 Mark Each]
12. Explain Non Cyclic photophosphorylation. Give schematic sketch of this pathway.
OR
Explain calvin Cycle.
13. Give the differences between C3
and C4
plants.

1. Two pigment system theory of photosynthesis was proposed by or concept of evidence for existence of
two photosystems in photosynthesis was given by
(1) Hill (2) Blackman (3) Emerson (4) Arnon
2. Who received the nobel prize for working out the early carbon pathway of photosynthesis
(1) Calvin (2) Krebs (3) Khorana (4) Watson
3. The process of photophosphorylation was discovered by
(1) Calvin (2) Arnon (3) Priestley (4) Warburg
4. Most of the plants contain a green colouring pigment which is responsible for photosynthesis. This pigment
was named chlorophyll by
(1) Melvin calvin (2) Jean senebier (3) Julius robert mayer (4) Pelletier caventou
5. The first important biological investigation which led to the conclusion that plant makes its substance from
water and not from soil was carried out by
(1) Lamarck (2) De vries (3) Van helmont (4) Darwin
6. The scientist who proved that bacteria use H2
S gas and CO2
to synthesize carbohydrate is
(1) Van Niel (2) Ruben (3) Jean senebier (4) Julius robert mayer
7. What plant is used in an experiment commonly performed in laboratory in demonstrate evolution of oxygen
in photosynthesis
(1) Sunflower (2) Hydrilla (3) Croton (4) Balsam
8. Two plants A and B are supplied with CO2
with H2
O18
and CO2
18
with H2
O respectively which of the
following plant releases O18
type oxygen in photosynthesis
(1) A plant (2) B plant (3) Both (1) and (2) (4) First (1)and then (2)
9. Isotopes popularly known to have been used in the study of photosynthesis are -
(1) C14
and O18
(2) C11
and C32
(3) C16
and N15
(4) P32
andC15
10. During photosynthesis, the oxygen in glucose comes from
(1) Water (2) Carbon dioxide
(3) Both from CO2
and water (4) Oxygen in air
11. Molls experiment shows
(1) Unequal transpiration from two surfaces of leaf
(2) Relation between transpiration and absorption
(3) CO2
is required for photosynthesis
(4) Chlorophyll is essential for photosynthesis

12. The plants growing in dark show yellowing in leaves and elongated internodes this condition is called as
(1) Etiolation (2) Chlorosis (3) Dechlorosis (4) Dark effect
13. The first event in photosynthesis is
(1) Synthesis of ATP (2) Photoexcitation of chlorophyll and ejection of electron
(3) Photolysis of water (4) Release of oxygen
14. Which of the following represents the correct molecular formula of chlorophyll-b
(1) C55
H72
O6
N4
Mg (2)C55
H72
O5
N4
Mg (3) C55
H72
O4
N4
Mg (4) C55
H70
O6
N4
Mg
15. Which of the following equation can be more appropriate for photosynthesis
(1) 6CO2
+ 6H2
O lChlorophyl
Light
C2
H12
O6
+ 6O2
(2) 6CO2
+ 12H2
O lChlorophyl
Light
C6
H12
O6
+ 6H2
O+ 6O2
(3) 12CO2
+ 6H2
O
lChlorophyl
Light
2C6
H12
O6
+ 6O2
(4) None of these
16. How much percentage of absorbed water is used in photosynthesis -
(1) 1% (2) 5% (3) 10% (4) 90%
17. The balance between CO2
and O2
is brought about by
(1) Transpiration (2) Photosynthesis (3) C4
Pathway (4) Photorespiration
18. During photosynthesis
(1) Both CO2
and water get oxidized (2) Both CO2
and water get reduced
(3) Water is reduced and CO2
is oxidized (4) Carbon dioxide get reduced and water get oxidised
19. Grana refers to
(1) Stacks of thylakoids in plastids of higher plants
(2) A constant in quantum equation
(3) Glycolysis of glucose
(4) By product of photosynthesis
20. Assimilatory power refers to
(1) Generation of ATP and NADPH2
(2) Reduction of CO2
(3) Splitting of water (4) Disintegration of plastids
21. Dimorphic chloroplasts are present in
(1) Sugarcane (2) Cotton (3) Pea (4) Mango
22. Leaves appear green because they
(1) Reflect green light (2) Absorb green light
(3) Both reflect and absorb green light (4) None of the above
23. Quantasomes contain
(1) 200 chlorophyll molecules (2) 230 chlorophyll molecules
(3) 250 chlorophyll molecules (4) 300 chlorophyll molecules
24. Two chief functions of leaves are
(1) Photosynthesis and respiration (2) Photosynthesis and Transpiration
(3) Transpiration and respiration (4) Respiration and digestion

25. For photosynthesis (i.e.for synthesis of organic matter ) the green plants need only
(1) Light (2) Chlorophyll (3) CO2
and water (4) All of these
26. CO2
is formed in all of the following except
(1) Burning of sugar (2) Respiration in plants
(3) Photosynthesis by plants (4) On heating of limestone
27. In angiosperms, synthesis of chlorophyll occurs in presence of
(1) Phytochrome (2) Light (3) Cytochrome (4) None of the above
28. Intensity of light can be measured by
(1) Luxmeter (2) Wilmotts bubber (3) Ganongs potometer (4) Farmers potometer
29. Make suitable pair
(A) Emerson effect (p) C4
cycle
(B) Hill reaction (q) Photolysis
(C) Calvin’s cycle (r) C3
cycle
(D) Hatch and slack cycle (s) Photosystem -I and II
(1) Ap,Bq,Cr,Ds (2) Ap,Br,Cs,Dp (3) Ar,Bs,Cp,Ds (4) As,Bq,Cr,Dp
30. Quantasomes are found in
(1) Surface of cristae (2) surface of plasma membrane
(3) surface of nuclear membrane (4) surface of thylakoids
31. How many molecules of water are needed by a green plant to produce one molecule of hexose
reduced molecules of CO2
(1) 6 (2) 12 (3) 24 (4) One only
32. Number of thylakoids in a granum is
(1) 5-10 (2) 2-100 (3) 100-150 (4) 150-200
33. Solarization is
(1) Formation of chlorophyll (2) Destruction of chlorophyll
(3) Utilization of sunlight (4) Effects of solar light
34. Which of the following is photophosphorylation
(1) production of ATP from ADP (2) production of NADP
(3) Synthesis of ADP from ATP (4) production of PGA
35. The first acceptor of electrons from an excited chlorophyll molecule of photosystem II is
(1) Cytchrome (2) iron -sulphur protein
(3) Ferredoxin (4) Quinone
36. DCMU
(1) Inhibits PS-I (2) Inhibits PS-II
(3) Destroy chloroplast (4) Inhibits oxidative phosphorylation
37. NADPH2
is generated through
(1) Glycolysis (2) Photosystem-I
(3) Photosystem-II (4) Anaerobic respiration

38. Photolysis of each water molecule in light reaction will yield
(1) 2 electrons and 4 protons (2) 4 electrons and 4 protons
(3)4 electrons and 3 protons (4) 2 electrons and 2 protons
39. Photosystem-II occurs in
(1) Stroma (2) Grana
(3) On surface of mitochondria (4) On cytochrome
40. The specific function of light energy in the process of photosynthesis is to
(1) Activate chlorophyll (2) Split water
(3) Reduce carbon dioxide (4) Synthesize glucose
41. In cyclic photophosphorylation which one of the following is formed
(1) ATP (2) NADP and ATP (3) NADH2
and O2
(4) NADPH2
, ATP and O2
42. Pigment system -I receives or radiant energy and releases electron
(1) Chlorophyll-683 (2) Chlorophyll-673 (3) Chlorophyll-695 (4) p-700
43. During photochemical reactions of photosynthesis
(1) Liberation of oxygen takes place
(2) Formation of ATP and NADPH2
take place
(3) Liberation of O2
and formation of ATP and NADPH2
take place
(4) Assimilation of CO2
takes place
44. Plants adapted to low light intensity have
(1) More extended root system
(2) Leaves modified to spines
(3) Larger photosynthetic unit size than sun plants
(4) Higher rate of CO2
fixation than the sun plants
45. Phytol chain is present in
(1) Carotenoids (2) haemoglobin (3) Chlorophyll (4) Phycocyanin
46. Chlorophyll a and b shows maximum absorption in
(1) Blue region (2) Red region
(3) Blue and red regions (4) Yellow and violet regions
47.
In the above schematic diagram , which is plastocyanin
(1) C (2) D (3) A (4) B

48. The ‘Z’ scheme of photosynthesis was proposed by
(1) Hill and Bendall (2) Emerson (3) Arnon (4) Rabinowitch and govindjee
49. Photosynthetic unit is
(1) Glyoxysome (2) Sphaerosome (3) Microsome (4) Quantasome
50. Which pigment is present universally in all green plants
(1) Chlorophyll-a (2) Chlorophyll-b (3) Chlorophyll-c (4) Chlorophyll-m
51. The Calvin cycle proceeds in three stages
1. Reduction, during which cabrohydrate is formed at the expense of the photochemically made ATP and
NADPH
2. Regeneration, during which the carbon dioxide acceptor ribulose–5– biphospahte is formed
3. Carboxylation, during which carbon dioxide combines with ribuolse–1, 5–biphophate
Identify the correct sequence
(1) 3 – 1 – 2 (2) 3 – 2 (3) 1 – 2 – 3 (4) 2 – 1 – 3
52. First stable product of Calvin cycle has
(1) 2 carbon atoms (2) 3 carbon atoms (3) 4 carbon atoms (4) 6 carbon atoms
53. CO2
joins the photosynthetic pathway during
(1) Light reaction (2) Dark reaction (3) Photosystem – I (4) Photosystem – II
54. Dark reaction of photosynthesis is called so because
(1) It can also occur in dark (2) It does not require light
(3) Cannot occur during day time (4) It occurs more rapidly in night
55. The initial enzyme of Calvin cycle is
(1) Ribulose 1, 5 – diphosphate carboxylase (2) Triose phosphate dehyrogenase
(3) Phosphopentokinase (4) Cytochrome oxidase
56. Calvin cycle occur in
(1) Choloplasts (2) Cytoplasm (3) Mitochondria (4) Glyoxysomes
57. Choose the correct combinations of labelling the carbohydrate molecule involved in the calvin cycle.
(1) (i) RuBP (ii) Triose phosphate (iii) PGA
(2) (i) PGA (ii) RuBP (iii) Triose phosphate
(3) (i) PGA (ii)Triose phosphate (iii) RuBP
(4) (i)RuBP (ii) PGA (iii) Triose phosphate

58. How many calvin cycle form one hexose molecule
(1) 2 (2) 6 (3) 4 (4) 8
59. The synthesis of one molecule of glucose during calvin cycle requires
(1) 12 molecules of ATP and 18 molecules of NADPH2
(4) 12 molecules each of ATP and NADPH2
60. Number of carboxylation occur in calvin cycle, is
(1) 0 (2) 1 (3) 2 (4) 3
61. The family in which many plants are C4
type
(1) Malvaceae (2) Solanaceae (3) Crucifereae (4) Gramineae
62. The C4
plants are photosynthetically more efficient than C3
plants because
(1) The CO2
efflux is not prevented
(2)There is no photorespiration
(3) The CO2
compensation point is more
(4) CO2
generated during photorespiration is trapped and recycled through PEP carboxylase
63. The first carbon fixation in C4
pathway occurs in chloroplasts of
(1) Guard cells (2) Mesophyll cells (3) Bundle sheath cells (4) Epidermal cells
64. An alternate CO2
fixation mechanism was found some tropical species of grass family by Hatch and Slack,
who were from
(1) England (2) USA (3) Australia (4) New Zealand
65. In photorespiration , what is the role of peroxisome
(1) Help in oxidation of glycolate (2) Help in oxygenation of glycolate
(3) Help in synthesis of PGA (4) Help in reduction of glyoxylate
66. The energy wastage occurs during
(1) Dark respiration (2) Photosynthesis (3) Glycolysis (4) Photorespiration
67. In C4
plants, Calvin cycle occurs in
(1) Stroma of bundle sheath chloroplast
(2) Mesophyll chloroplast
(3) Grana of bundle sheath chloroplast
(4) Does not occur as CO2
is fixed mainly by PEP and NO CO2
is left for Calvin cycle
68. Photorespiration is characteristic of -
(1) CAM Plants (2) C3
Plants (3) C4
Plants (4) None of the above
69. Which of the following cycle shows oxaloacetic acid as first stable product
(1) Calvin cycle (2) Hatch and slack cycle
(3) C2
cycle (4) None of the above

70. Kranz type of anatomy is found in
(1) C2
plants (2) C3
plants (3) C4
plants (4) CAM plants
71. C4
plants are adapted to
(1) Hot and dry climate (2) Temperate climate
(3) Cold and dry climate (4) Hot and humid climate
72. Dimorphism of chloroplast is found in
(1) C4
plants (2) C3
plants (3) CAM plants (4) All the above
73. In CAM cycle, during formation of malic acid, stomata remains
(1) Open (2) Closed (3) Semiopen (4) Always closed
74. Chloroplasts without grana are known to occur in
(1) Bundle sheath cells of C3
plants (2) Mesophyll cells of C4
plants
(3) Bundle sheath cells of C4
plants (4) Mesophyll cells of all plants
75. Which crop utilizes solar energy most efficiently
(1) Potato (2) sugarcane (3) Wheat (4) Rice
76. Which of the following is the main product in the photorespiration of C3
plants
(1) Phosphoglycerate (2) Phosphoglycolate (3) Glycerate (4) Glycolate
77. Photorespiration is favoured by
(1) Low light and high O2
(2) Low O2
and high CO2
(3) Low temperature and high O2
(4) High O2
and low CO2
78. Which of the following process shows light deacidification and night acidification
(1) CAM cycle (2) C3
cycle (3) C4
cycle (4) All the above
79. The first reaction in photorespiration is
(1) Carboxylation (2) Decarboxylation (3) Oxygenation (4) Phosphorylation
80. Which one is false about kranz anatomy
(1) Bundle sheath have large chloroplast and less developed grana
(2) Mesophyill cellls have large chloroplast and more
(3) It is found in Atriplex, sugarcane , maize
(4) Plant having it have better photosynthesizing power than C3
plants Factors affecting photosynthesis
81. Which factor is not limiting in normal conditions for photosynthesis
(1) Air (2) CO2
(3) Water (4) Chlorophyll
82. What is called Warburg,
s effect on photosynthesis
(1) Low rate of the process due to O2
supply (2) Low rate if the process due to CO2
supply
(3) Both (1) and (2) (4) None of the the above
83. Compensation point is
(1) Where there is neither photosynthesis nor respiration
(2) When rate of photosynthesis is equal to the rate of respiration
(3) When entire food synthesized into photosynthesis remain utilized
(4) When there is enough water just to meet the requirements of plant

84. In Which of the following the rate of photosynthesis is decreased and is known as red drop
(1) Blue light (2) Green light
(3) Red light more than 680 nm (4) Red light less than 680 nm
85. Chla absorbs max of
(1) Red light (2) Blue light (3) Green light (4) Yellow light
86. Q10
refers to
(1) Quality quotient (Q.Q.) (2) Temperature quotient (T.Q.)
(3) Respiratory quotient (R.Q.) (4) Quantum constant (Q.C.)
87. In photosynthesis CO2 combines with
(1) RUDP (2) ATP (3) ADP (4) PGA
88. In bacteria. photosynthetic lamellae are situated in
(1) Cytoplasm (2) Chromoplast (3) Leucoplast (4) Cell
89. The isotope of carbon used extensively for studies on photosynthesis is
(1) C14 (2) C16 (3) C13 (4) C15
90. In C4 cycle first CO2 fixation takes place in which chloroplast
(1) Guard cells (2) Bundle sheath cells (3) Mesophytes (4) Mesophyll cells
91. Photorespiration is found in
(1) C4 plants (2) CAM plants (3) C3 plants (4) All the above
92. Quantosomes are found on the following surface
(1) Thylakoids (2) Cristae (3) Plasmalemma (4) Nuclear envelope
93. Photosynthesis includes
(1) Oxidative phosphorylation (2) Reduction of NADH2 in NAD
(3) Reduction of CO2 (4) Synthesis of ATP
94. Which of the following colour of light is maximum used in photosynthesis
(1) Violet (2) Red (3) Green (4) Yellow
95. In C4 plants, chloroplasts also present in
(1) Epidermis (2) Guard cells (3) Bundle sheath cells (4) Spongy parenchyma
96. The algae which is used in researches of photosynthesis
(1) Chlorella (2) Fucus (3) Acetabularia (4) Chlamydomonas
97. Pigment which is related to the red drop
(1) Chlla - 680 (2) Chlla . 690 (3) Chlla . 640 (4) Chlla. 700
98. Pigment of PSII are -
(1) P700 chl ‘a’ and ‘b’ (2) P680 chl’b’ and phycobilins
(3) P700 chl’a’ and carotenoids (4) P680 chl’a’
99. Which of the following pigment inhibit the photo-oxidation of chlorophyll
(1) Phytochrome (2) Phytohormones (3) Phytocyanine (4) Phytocarotene
100. Warburg effect is decreased rate of photosynthesis at
(1) Low concentration of CO2 (2) High concentration of CO2
(3) 1 & 2 (4) Higher concentration of O2

101. Peroxisomes are related from
(1) Transpiration (2) Photorespiration (3) H2O (4) All the above
102. Calvin cycle occurs in
(1) Chloroplast (2) Glyoxysomes (3) Mitochondria (4) Cytoplasm
103. The C4 plants are different from the C3 plants with reference to the
(1) In consumption of ATP molecules
(2) In first product
(3) The substrate that accept CO2 in carbon assimilation
(4) All the above
104. CO2 fixing enzyme in C4 plants is
(1) PEP carboxylase (2) RUDP carboxylase
(3) RUDP oxidase (4) Hydrogenase
105. The bulk fixation of carbon through photosynthesis takes place in
(1) Crop plants (2) Tropical rain forests (3) Ocean (4) Both (1) & (2)
106. Minerals involved in photo oxidation of water is
(1) Mn, Cl, Ca (2) Mg, Fe, Mn (3) Mn, Fe, Ca (4) N, P, K
107. Z-scheme in thylakoid membrane is concerned with
(1) Reduction of NAD (2) Reduction of CO2 (3) Electron transfer (4) All of these
108. Absorption of radiant energy causes
(1) Reduction of chlorophyll (2) Oxidation of chlorophyll
(3) Absorption of CO2 (4) Evolution of O2
109. Reducing agent for CO2 fixation in bacterial photosynthesis is
(1) NADH2 (2) NADPH2 (3) FMNH2 (4) All of these
110. In photorespiration, releases of CO2 occurs in
(1) Mitochondria (2) Chloroplast (3) Peroxisomes (4) All of these
111. Inhibition of photosynthesis in high concentration of O2 is called
(1) Warburg effect (2) Kutusky effect (3) Pasteur effect (4) Emerson effect
112. Number of carboxylation in photosynthesis in Sorghum and Maize is
(1) 1 (2) 2 (3) 3 (4) 4
113. The process in which organisms do not require light and pigment and synthesize their food utilising energy
released by oxidation of inorganic and organic substances is
(1) Photoautotrophism (2) Heterotrophism (3) Chemosynthesis (4) Saprophytism
114. Which of these is a molecule of bacteriochlorophyll -a
(1) C55H72O5N4Mg (2) C55H70O6N4Mg (3) C55H74O6N4Mg (4) C55H72O6N4Mg
115. Where is phytol group attached to chlorophyll
(1) At 7–C (2) At 5–C (3) At 3–C (4) At 9–C
116. What is called the red drop
(1) Rapid fall in quantum yield in light of more than 680 m
(2) Rapid increased in quantum yield in light of less than 700 m
(3) Increase in quantum yield in light of more than 680 m
(4) None of the above

117. From which source charged molecule of P– 680 gets the electron
(1) From P–700 (2) From water (3) From NADPH2 (4) None of the above
118. Where CO2 is fixed again in C4 plants
(1) Bundle sheath cells (2) Phloem cells (3) Mesophyll cells (4) All the above
119. Which of these can perform photosynthesis effectively at hight temperature and low CO2 concentration.
(1) C3 plant (2) C4 plant (3) Both of above (4) None of these
120. Carbon dioxide is necessary for photosynthesis. The chemical used to remove this gas most effectively
from entering a control apparatus is
(1) Distilled water (2) Sodium carbonate
(3) Calcium oxide (4) Potassium hydroxide solution
121. Assimilatory power produced during photosynthesis are
(1) RuDP and RuMP (2) H2O and O2 (3) ATP and NADPH2 (4) C6H12O6 and PGAL
122. For normal photosynthetic process in red algae, the pigments are
(1) Phycocyanin and chlorophyll –a (2) Phycocyanin and chlorophyll –b
(3) Phycoerythrin and chlorophyll –a (4) Phycoerythrin and chlorophyll –b
123. Match the Column
Column I Column II
(Scientists) (Contributions)
A. Peter Mitchell P. Steps of dark
reaction of photosynthesis
B. J. W. Gibbs q. Photosynthetic
Phosphorylation
C. Danial Arnon r. Concept of free
energy
D. Melvin Calvin s. Chemiosmotic
hypothesis
t. Mass flow hypothesis
(1) A = s, B = r, C = q, D = p (2) A = r, B = s, C = p, D = q
(3) A = s, B = t, C = r, D = q (4) A = s, B = r, C = p, D = q

OBJECTIVE QUESTIONS
1. Leaves appear green because they reflect green colour from light spectrum. The part in the leaf that is
actually responsible for this reflection is (2nd
INBO)
(1) Inner membrane of chloroplast (2) Thylakoid space
(3) Thylakoid membrane (4) Stroma
2. In an experimental setup, a group of C3
and a group of C4
plants were grown in an environment with double
the amount of CO2
concentration. Which group of plants would grow better and be more water efficient.
(FINBO)
(1) C3
plants will be better than C4
plants (2) C4
plants will be better than plants C3
(3) Both C3
and C4
plants will show equal growth (4) None of these
3. Rubisco is an enzyme required for photosynthesis in which of the following plants (2nd
ABO)
(i) C3
Plants
(ii) C4
Plants
(iii) CAM (Crassulacean Acid Metabolism) plants
(1) (i) only (2) (i) and (ii) only
(3) (i), (ii) and (ii) (4) Neither (i), (ii) and (iii)
4. Which of the following are found only in C4
plants (4th
ABO)
(i) Stomata (ii) The enzyme Rubisco (iii) Bundle sheath cells
(1) (i) only (2) (iii) only (3) (i) and (ii) only (4) (ii) and (iii) only
5. The graph represents an (1St
NSEB)
(1) Absorption spectrum (2) Action spectrum
(3) Interference pattern (4) Spectroscope

6. The pigment found outside the chloroplast is [NSEB 2010-2011]
(1) anthocyanin (2) xanthophyll (3) chlorophyll (4) phycoerythrin
7. Carotenoids are generally long chain unsaturated hyrocarbons. Which of the following function/s correlate/
s with the structures. [NSEB 2010-2011]
i. They can absorb light of higher wavelength
ii. It allows carotenoids to transfer energy to chlorophyll a molecule
iii. To reduce free radicals
iv. Long hydrocarbon chain allows carotenoids to protect chlorophyll a from direct sunlight by absrobing
excess light energy.
(1) Only i (2) iii and iv (3) Only ii (4) i and iii
8. A plant biochemist received a specimen from a fellow scientist who noticed that the , plant's stomata are
closed during the day. The biochemist observed that radioactive carbon supplied in the form of carbon
dioxide fed to the plant at night. was first found' in organic acids that accumulated in the vacuole. During the
day; the label moved to sugars being manufactured in the chloroplast. What was the conclusion of the
biochemist? [NSEB 2010-2011]
(1) It is a CAM plant (2) It is -a C4
plant
(3) It is a C3
plant (4) It is a plant showing pentose phosphate pathway
9. A student wants to test the presence of starch in a leaf. Select the required steps and arrange them in the
correct order: [NSEB 2010-2011]
(i) boiling the leaf in ethanol (90%)
(ii) keeping the plant in dark
(iii) rinsing the leaf with hot water
(iv) addition of iodine solution
(1) (ii) (i) (iii) (iv) (2) (ii) (i) (iv) (iii)
(3) (ii) (iii) (iv) (i) (4) (iii) (i) (ii) (iv)
10. Of the following pigments found in plants which one are not concerned with photosynthesis? .
[NSEB 2011-2012]
(1) chlorophylls . (2) anthocyanins (3) phycobilins (4) carotenoids
11. During photosynthesis, light energy : (KVPY 2007)
(1) Is converted to chemical energy (2) Is converted to kinetic energy
(3) Is the catalyst (4) Dissociates CO2
directly
12. On a normal sunny day, rate of photosynthesis (per unit time) is maximum during : (KVPY 2007)
(1) Early morning (2) Between late morning to before noon
(3) Midday (4) Late evening
13. The amount of CO2
in plant is greater at night than during the day because : [KVPY 2008]
(1) The rate of respiration is higher at night.
(2) More CO2
is produced because it is colder during the night.
(3) Photosynthesis during the day uses up some of the CO2
produced by respiration.
(4) More glucose is available for respiration during the night
14. Which one of the following colors is the LEAST useful for plant life ? [KVPY 2011]
(1) red (2) blue (3) green (4) violet

AIIMS CORNER
1. Photorespiration in C3
plants starts from [AIIMS 2003]
(1) phosphoglycerate (2) phosphoglycolate (3) glycerate (4) glycine
2. Hill reaction occurs in [AIIMS 2003]
(1) high altitude plants (2) total darkness (3) absence of water (4) presence of ferricyanide
3. Which one of the following categories of organisms do not evolve oxygen during photosynthesis ?
(1) red algae (2) photosynthetic bacteria [AIIMS 2004]
(3) C4
plants with Kranz anatomy (4) blue green algae
4. What is PAR range ? [AIIMS 2007]
(1) 200 nm - 800 nm (2) 400 nm - 700 nm (3) 350 nm - 550 nm (4) 600 nm - 100 nm
5. What is common between chloroplasts chromoplasts and leucoplasts (AIIMS - 2008)
(1) Ability to multiply a fission-like process (2) Presence of pimgments
(3) Storage of starch, proteins and lipids (4) Possession of thylakoids and grana.
6. Which of the following is the characteristic of PS-I. [AIIMS 2009]
(1) it is active only upto 680 nm of light
(2) the reaction centre of PS- I is P680
(3) PS-I is reduced by the electrons released in photolysis of water
(4) PS-I is involved in non-cyclic photophos-phorylation.
7. The enzyme decarboxylase catalyses the following step [AIIMS 2009]
(1) conversion of citric acid to cis aconitic acid (2) fumaric acid to malic acid
(3) oxalosuccinic acid to a-ketoglutaric acid (4) malic acid to oxaloacetic acid
8. Cycl ic photophosphorylation involves [AIIMS 2010]
(1) PS I (2) PS II (3) PS I and PS II (4) P680
9. The first stable product of Calvin cycle is [AIIMS 2010]
(1) 3-phosphoglycerate (2) 1, 3 biphosphoglycerate
(3) glyceraldehyde - 3 phosphate (4) ribulose - 5- phosphate
10. Photosynthetic bacteria have [AIIMS 2011]
(1) pigment system (2) pigment system
(3) Both (a) and (b) (4) some other kind of pigments, B890
11. Match the columns. [AIIMS 2011]
Column I (Scientists) Column II (Discoveries)
A. Stephan Hales 1. Importance of light and chlorophyll
B. Ingen Housz 2. Presence of chlorophyll in plants
C. Von Mohl 3. Product of photosynthesis is starch
D. Sach 4. Air and light control plant growth
Code
A B C D
(1) 4 1 2 3
(2) 3 2 1 4
(3) 2 3 4 1
(4) 4 3 2 1

ASSERTION / REASONING
In each of the following questions a statement of Assertion (A) is given followed by a corresponding
statement of Reason (R) just below it. Of the statements, mark the correct answer as
(1) If both assertion and reason are true and reason is the correct explanation of assertion
(2) If both assertion and reason are true but reason is not the correct explanation of assertion
(3) If assertion is true but reason is false
(4) If both assertion and reason are false.
12. Assertion : The photolysis of water occurs in the thylakoid interior.
Reason : The photolysis is not a enzymatic process.
(1) (2) (3) (4)
13. Assertion : Leaves of C4
plants show Kranz anatomy.
Reason : C4
plants also show fixation by Calvin-Benson cycle.
(1) (2) (3) (4)
14. Assertion : There is a decrease in photosynthesis, if the photosynthetic cells are illuminated by light or
P680 nm or more wavelength.
Reason : In red drop phenomenon the rate of photsynthesis decreases.
(1) (2) (3) (4)
15. Assertion : CAM plants lack structural compartmentation of leaf, as found in C4
plants.
Reason : Stomata of CAM plants are open during the day.
(1) (2) (3) (4)
16. Assertion : In C3
plants, photosynthesis is reduced on high temperature.
Reason : C4
plants have high photosynthesis on high temperature.
(1) (2) (3) (4)
17. Chemical which absorbs light energy and changes it to chemical energy is (AIIMS - 2000)
(1) Xanthophyll (2) Chlorophyll a (3) Chloropyhyll b (4) Chlorophyll c.
18. Assertion : Cyclic pathway of photosynthesis first appeared in some eubacterial species.
Reason: Oxygen started accumulating in the atmosphere after the non-cyclic pathway of photosynthesis
evolved. [AIIMS 2004]
(1) (2) (3) (4)
19. Assertion : C4
photosynthetic pathway is more efficient than the C3
pathway.
Reason : Photorespiration is suppressed in C4
plants. [AIIMS 2005]
(1) (2) (3) (4)
20. Assertion : Under conditions of high light intensity and limited CO2
supply, photorespiration has a useful
role in protecting the plants from photo-oxidative damage.
Reason : If enough CO2
is not available to utilize Iight energy for carboxylation to proceed, the excess
energy may not cause damage to plants. [AIIMS 2006]
(1) (2) (3) (4)
21. Assertion : Photosynthetically C4
plants are less efficient than C3
plants.
Reason : The operation of C4
pathway requires the involvement of only bundle-sheath cells.[AIIMS 2006]
(1) (2) (3) (4)

22. Assertion : The higher concentration of O2
in the atmosphere is inhibitory to photosynthesis.
Reason : CO2
is the main substrate of photosynthesis. [AIIMS 2008]
(1) (2) (3) (4)
23. Assertion : Dark reaction occurs only at night in the stroma of chloroplast.
Reason : CO2
fixation occurs only during C3
cycle. [AIIMS 2009]
(1) (2) (3) (4)
24. Assertion : Due to pollution atmospheric concentration of CO2
is increasing which will be harmful for C4
plants whereas productive for C3
plants.
Reason : C4
plants have greater efficiency for CO2
as CO2
is fixed by PEP oxygenase. [AIIMS 2010]
(1) (2) (3) (4)
1. For fixing one molecule of CO2 in Calvin cycle, are required (AIPMT - 2000)
(1) 3 ATP + 1 NADPH2 (2) 3 ATP + 2NADPH2 (3) 2ATP + 3NADPH2 (4) 3 ATP + 3 NADPH2
2. First reaction in photosynthesis is (UPCPMT-2011) (AIPMT - 2000)
(1) Photolysis of water (2) Excitation of chlorophyll molecule
(3) Formation of ATP (4) Fixation of CO2
3. Energy from light reaction is transferred to dark reaction is the one that is absorbed by (AIPMT - 2002)
(1) ADP (2) ATP (3) Chlorophyll (4) RuBP.
4. Which fractions of the visible spectrum of solar radiations are primarily absorbed by carotenoids of the
higher plants (AIPMT - 2003)
(1) Blue & green (2) Green & red (3) Red & violet (4) Violet & blue
5. Stomata of CAM plants (AIPMT - 2003)
(1) Are always open (2) Open during day and close at night
(3) Open during night and close during day (4) Never open.
6. Which one of the following concerns photophosphorylation (AIPMT - 2003)
(1) ADP + AMP energyLight ATP (2) ADP + Inorganic PO4
energyLight ATP
(3) ADP + Inorganic PO4
ATP (4) AMP + Inorganic PO4
energyLight ATP
7. Which one is wrong inphotorespiration (AIPMT - 2003)
(1) It occurs in chloroplasts (2) It occurs in day time only
(3) It is characteristic of C4 plants (4) It is characteristic of C3 plants.
8. Which are primarily absorbed by carotenoids ? (AIPMT - 2003)
(1) Blue and green (B) Green and red (3) Red and voilet (4) Voilet and blue.
9. Photorespiration in C3 plants starts from (AIIMS - 2003)
(1) Phosphoglycerate (2) Phosphoglycolate (3) Glycerate (4) Glycine.

10. Hill reaction occurs in (AIIMS - 2003)
(1) High altitude plants (2) Total darkness (3) Absence of water (4) Presence of ferricynide.
11. Which element is located at the centre of the porphyrin ring in chlorophyll (AIPMT - 2003)
(1) Calcium (2) Magnesium (3) Potassium (4) Manganese
12. In sugarcane plant 14CO2 is fixed in malic acid in which the enzyme that fixes CO2 is
(1) Ribulose biphosphate carboxylase (2) Phosphoenol pyruvic acid carboxylase
(3) Ribulose phosphate kinase (4) Fructose phosphatase
13. The first step in dark reaction of photosynthesis is (AIPMT - 2004)
(1) Formation of ATP
(2) Attachment of carbon dioxide to a pentose sugar
(3) Excitement of an electron of chlorophyll by photon of light
(4) Ionisation of water.
14. In C3 plants, the first stable product of photosynthesis during the dark reaction is
(UPCPMT-2011) (AIPMT 2004)
(1) Malic acid (2) Oxaloacetic acid
(3) 3-phosphoglyceric acid (4) Phosphoglyceraldehyde
15. In chloroplasts, chlorophyll is present in (AIPMT - 2004)
(1) outer membrane (2) inner membrane (3) thylakoids (4) stroma
16. As compared to sun plants, plants adapted to low light intensity possess (AIPMT - 2004)
(1) High rate of CO2 fixation (2) Larger photosynthetic unit
(3) More extended root system (4) Spiny leaves.
17. During photosrespiration oxygen consuming reaction (s) occur in (AIPMT - 2005)
(1) Stroma of chloroplasts (2) Stroma of chloroplasts and Mitochondria
(3) Stroma of chloroplasts and peroxisomes (4) Grana of chloroplasts and peroxisomes.
18. Carbohydrates, the most abundant biomolecules on earth are produced by (AIPMT - 2005)
(1) Some bacteria, algae and green plants
(2) Fungi, algae and green plants
(3) All bacteria, fungi and algae
(4) Viruses, fungi and bacteria.
19. Malic acid is formed in C4 plants is the cells of (AIPMT - 2007)
(1) Epidermis (2) Bundle sheath (3) phloem (4) Mesophyll.
20. In leaves of C4 plants malic acid synthesis during CO2 fixation occurs in (AIPMT - 2008)
(1) Bundle sheath (2) Mesophyll cells (3) Guard cells (4) Epidermal cells.
21. The C4 plants are photosynthetically more efficient than C3 plants because (AIPMT - 2008)
(1) The CO2 efflux is not prevented
(2) They have more chloroplasts
(3) The CO2 compensation point is more
(4) CO2 generated during photorespiration is trapped and recycled through PEP carboxylase.
22. Electrons from excited chlorophyll molecule of photosystem II are accepted first by (AIPMT - 2008)
(1) Quinone (2) Cytochrome-b (3) Ferredoxin (4) Cytochrome-f
23. Cyclic photophosphorylation results in the formation of (AIPMT - 2009)
(1) ATP (2) NADPH (3) ATP and NADPH (4) ATP, NADPH and O2

24. C4 plants are more efficient in phyotosynthesis than C3 plants due to (AIPMT - 2010)
(1) Presence of larger number of chloroplasts in the leaf cells
(2) Presence of thin cuticle
(3) Lower rate of photorespiration
(4) Higher leaf area
25. PGA as the first CO2 fixation product was discovered in photosynthesis of (AIPMT - 2010)
(1) Gymnosperm (2) Angiosperm (3) Alga (4) Bryophyte
26. Kranz anatomy can be observed in leaves of (AIPMT, RPMT 2011)
(1) Sorghum (2) Spinach (3) Mustard (4) Tulip
27. Light reaction in stroma lamellae of the chlorplast results in the formation of (AIPMT, RPMT 2011)
(1) NADPH2
(2) ATP + NADPH2
(3) ATP (4) O2
28. In leaves of C4
plants malic acid synthesis during CO2
fixation occurs in (AIPMT RPMT 2011)
(1) Bundle sheath (2) Mesophyll (3) Epidermis (4) Guard cells
29. Of the total incident solar radiation the proportion of PAR is : (AIPMT Pre. 2011)
(1) About 70% (2) About 60% (3) Less than 50% (4) More than 80%
30. In Kranz anatomy, the bundle sheath cells have (AIPMT mains 2011)
(1) Thin walls, many intercellular spaces and no chloroplasts
(2) Thick walls, no intercellular spaces and large number of chloroplasts
(3) Thin walls, no intercellular spaces and several chloroplasts
(4) Thick walls, many intercellular spaces and few chloroplasts
31. Which one of the following is essential for photolysis of water ? (AIPMT mains 2011)
(1) Manganese (2) zinc (3) copper (4) Boron
32. CAM helps the plants in : (AIPMT Pre. 2011)
(1) Conserving water (2) Secondary growth
(3) Disease resistance (4) Reproduction
33. Best defined function of Manganese in green plants is : (AIPMT 2012)
(1) Photolysis of water (2) Calvin cycle (3) Nitrogen fixation (4) Water absorption
34. Maximum photosynthesis takes place in (CPMT - 1999)
(1) Phytoplanktons (2) Zooplanktons (3) Marshy plants (4) Woody plants
35. The primary acceptor during CO2 fixation in C3 plants is (RPMT - 1999)
(1) RUDP carboxylase (2) PEP carboxylase
(3) Pyruvate carboxylase (4) RUMP
36. During photosynthesis O2 liberates through (RPMT - 1999)
(1) CO2 (2) H2O (3) ATP (4) NADP+
37. Products of photosynthesis are (RPMT - 1999)
(1) ATP (2) NADPH2 (3) O2 (4) All the above

38. The dark reaction of photosynthesis takes place in (RPMT - 1999)
(1) Night (2) Day
(3) Light is not essential for dark reaction (4) It takes place in night
39. Radioactive tracer studies with 14C have shown that (JIPMER - 1999)
(1) Phloem transports organic nutrients (2) Phloem transports inorganic nutrients
(3) Xylem transports inorganic nutrients (4) Xylem transports organic nutrients.
40. In Maize, mesopyll cells perform photosynthetic cycle (DPMT - 1999)
(1) C4 (2) C3 (3) C2 (4) C1
41. Green plants do not give out CO2 during day time because they (AMU - 1999)
(1) Store the same (2) Respire very slowly
(3) Do not respire (4) Consume it in phtosynthesis.
42. Light energy perform following function in PS- II (RPMT - 2000)
(1) Photolysis of water (2) Excitation of chlorophyll
(3) Formation of ATP (4) Formation of NADPH2
43. Which of the following ions are essential for effective mechanism of PS-II (RPMT - 2001)
(1) Mn++ & Cl– (2) Mg+ & NO3 (3) Fe++ & Cl– (4) K+ & Na+
44. Formation of NADPH2 in chloroplast occurs during (RPMT - 2001)
(1) Cyclic photophosphorylation (2) Non - cyclic photophosphorylation
(3) Oxidative photophosphorylation (4) Substrate level phosphorylation
45. During light reaction, It does not takes place (RPMT - 2001)
(1) Electron transfer (2) Liberation of O2 (3) Photolysis of water (4) Liberation of H2
46. First CO2 acceptor in photosynthesis is (RPMT - 2002)
(1) Ribulose 5 P (2) Ribulose 1, 5 diphosphate
(3) Glucose 6 phosphate (4) none of these
47. Movement of materials through vascular tissues of plants is (BHU - 2002)
(1) Transpiration (2) Transcription (3) Transduction (4) Translocation.
48. Chlorophyll appears green because it (Karnataka - 2002)
(1) Reflects green light (2) Transmits green light (3) Absorbs green light (4) Transforms light.
49. Calvin cycle discovered in which plant (RPMT - 2002)
(1) Spirogyra (2) Volvox (3) Chlamydomonas (4) Chlorella
50. How many ATP and NADPH2 are necessary for synthesis of one molecule of glucose (RPMT - 2003)
(1) 12 ATP & 18 NADPH2 (2) 12 ATP & 33 NADPH2
(3) 18 ATP & 12 NADPH2 (4) 8 ATP & 22 NADPH2
51. First step of photosynthesis is (RPMT - 2003)
(1) Ionization of water
(2) formation of three carbon compound
(3) Liberation of e- due to excitation of chlorophyll in presence of light
(4) None of these
52. electron acceptor of PS-II is (B.V. - 2003)
(1) Cyt b (2) FRS (3) PQ (4) NADP+
53. How many molecules of glycine are required to release one molecule of CO2 in photorespiration
(1) One (2) Two (3) Three (4) Four. (AFMC - 2004)

54. In which of the following substrate level phosphorylation does not occur (APMEE - 2005)
(1) 1, 3-biphosphoglyceric acid 3-phosphoglyceric acid
(2) Glucose 6-phosphate Fructose 6-phosphate
(3) Succinly Co A Succinic acid
(4) Phosphoenol pyruvic acid pyruvic acid
55. Which one is a CAM plant (Orissa - 2005)
(1) Maize (2) Pineapple (3) Onion (4) Pea.
56. Respiration initiated in chloroplasts and occurring in light is called (JKCMEE - 2005)
(1) Aerobic respiration (2) Anaerobic respiration
(3) Fermentation (4) Photorespiration .
57. Which one is a C4 plant (JKCMEE - 2005)
(1) Potato (2) Mustard (3) Onion (4) Wheat.
58. Solarisation is (BHU - 2005)
(1) Formation of chlorophyll (2) Destruction of chlorophyll
(3) Utilisation of sunlight (4) Effect of solar light.
59. Carbon assimilation occurs in bundle sheath cells of (BHU - 2005)
(1) CAM plants (2) C4 Plants (3) C3 plants (4) All the above.
60. How much oxygen is formed from 264 g of CO2 and 216 g of H2O (BHU - 2005)
(1) 96 g (2) 216 g (3) 264 g (4) 192 g.
61. Energy contained in plant carbohydrates comes from (Manipur - 2005)
(1) Minerals (2) CO2 (3) Proteins (4) Sunlight.
62. CO2 acceptor of C3 plants is (B.V. - 2006)
(1) PEP (2) PGA (3) RuBP (4) Pyruvic acid.
63. Girdling experiment is not successful in monocots due to (RPMT - 2006)
(1) Vascular bundles are not arranged in a ring (2) Vascular bundles are arranged in a ring
(3) Vascular bundles are radial (4) None of the above.
64. Photolysis of water molecule yields (Kerala - 2006)
65. CAM plants belong to family (MH - 2007)
(1) Malvaceae (2) Crassulaceae (3) Trapaceae (4) Orchidaceae.
66. DCMU inhibits (MPPMT - 2007)
(1) PSII (2) PSI
(3) Destroys chloroplast (4) Inhibits oxidative phosphorylation.
67. For yielding one molecule of glucose, Calvin cycle turns (AFMC - 2007)
(1) 8 times (2) 6 times (3) 4 times (4) 2 times
68. In which of the following wavelength, photosystem I is inactive? (DPMT - 2008)
(1) 780 nm (2) 680 nm (3) 690 nm (4) 550 nm
69. The first CO2
acceptor in C4
cycle is (UP CPMT Medical 2009)
(1) RuBP (2) PEP (3) PGA (4) OAA
70. Cyclic photophosphorylation takes place in (UP CPMT Medical 2010)
(1) Photo system-I (2) Photo system-II
(3) Both (1) and (2) (4) Calvin cycle
71. Kranz anatomy is a feature of (UP CPMT Medical 2010)
(1) hydrophytes (2) xerophytes (3) C3
-plants (4) C4
-plants

BOARD LEVEL EXERCISE : HINT & SOLUTIONS
1. Absorption spectrum : It is graphic representation of absorption of different wavelength of lights by
chlorophyll molecules, which is maximum in blue than red & green is remains unabsorbed.
Action Spectrum : It is graphic representation of rate of photosynthesis by chlorophyll molecules at
different wavelengths of light, which is maximum in red than in blue & least in green.
2. Mg
3. Refer – Page –15 3rd
point
4. C3
cycle 18 ATP + 12 NADH
C4
cycle 30 ATP + 12 NADH
5. See Page - 23
6. Due to lack of chl a plants can not perform photosynthesis as it (chla) acts as reaction centre. Chl b and
accessory pigments are only for absorption of different wavelengths of light & finally transfer it to chl a.
7. Refer Page – 19
8. In C4
plants CO2
concentration is always greater around Rubisco due to greater affinity of PEP so their
photorespiration is absent & it carries more carboxylation in C4
plants than C3
plants.
9. C4
plants = maize, sorghum
Mechanism of Hatch & slack pathway – page - 20
10. In photophosphorylation formation of ATP in the presence of light takes place during light reaction of
photosynthesis. It always occur in photosynthetic cells. While in oxidative phosphorylation formation of ATP
takes place in the presence of oxygen during ETS of Respiration & it always occurs in cells which perform
aerobic respiration.
11. Refer page – 23 – C2
cycle.
12. Refer page – 17 – Non cyclic photophosphorylation
OR
Refer Page – 19 – C3
cycle.
13. Refer page – 22–Chart
EXERCISE - 1
1. (3) 2. (1) 3. (2) 4. (4) 5. (3) 6. (1) 7. (2)
8. (1) 9. (1) 10. (2) 11. (3) 12. (1) 13. (2) 14. (4)
15. (2) 16. (1) 17. (2) 18. (4) 19. (1) 20. (1) 21. (1)
22. (1) 23. (2) 24. (2) 25. (4) 26. (3) 27. (2) 28. (1)
29. (4) 30. (4) 31. (2) 32. (2) 33. (2) 34. (1) 35. (4)
36. (2) 37. (2) 38. (4) 39. (2) 40. (1) 41. (1) 42. (4)
43. (3) 44. (4) 45. (3) 46. (3) 47. (2) 48. (1) 49. (4)
50. (1) 51. (1) 52. (2) 53. (2) 54. (2) 55. (1) 56. (1)

57. (4) 58. (2) 59. (3) 60. (2) 61. (4) 62. (2) 63. (2)
64. (3) 65. (1) 66. (4) 67. (1) 68. (2) 69. (2) 70. (3)
71. (1) 72. (1) 73. (1) 74. (3) 75. (2) 76. (4) 77. (4)
78. (1) 79. (3) 80. (2) 81. (4) 82. (1) 83. (2) 84. (3)
85. (2) 86. (2) 87. (1) 88. (1) 89. (1) 90. (4) 91. (3)
92. (1) 93. (3) 94. (2) 95. (3) 96. (1) 97. (4) 98. (4)
99. (4) 100. (4) 101. (2) 102. (1) 103. (4) 104. (1) 105. (3)
106. (1) 107. (3) 108. (2) 109. (1) 110. (1) 111. (1) 112. (2)
113. (3) 114. (3) 115. (1) 116. (1) 117. (2) 118. (1) 119. (2)
120. (4) 121. (3) 122. (3) 123. (1)
EXERCISE - 2
1. (3) 2. (2) 3. (1) 4. (2) 5. (2) 6. (1) 7. (2)
8. (1) 9. (1) 10. (2) 11. (1) 12. (3) 13. (3) 14. (3)
EXERCISE - 3
1. (2) 2. (4) 3. (2) 4. (2) 5. (1) 6. (4) 7. (3)
7. (3) 8. (1) 9. (1) 10. (4) 11. (1) 12. (3) 13. (2)
14. (2) 15. (3) 16. (2) 17. (2) 18. (2) 19. (2) 20. (3)
21. (4) 22. (2) 23. (4) 24. (3)
EXERCISE - 4
1. (2) 2. (2) 3. (2) 4. (4) 5. (3) 6. (2) 7. (3)
8. (4) 9. (2) 10. (4) 11. (2) 12. (2) 13. (2) 14. (3)
15. (3) 16. (2) 17. (3) 18. (1) 19. (4) 20. (2) 21. (2)
22. (1) 23. (1) 24. (1) 25. (3) 26. (1) 27. (3) 28. (2)
29. (3) 30. (2) 31. (1) 32. (1) 33. (1) 34. (1) 35. (1)
36. (2) 37. (4) 38. (3) 39. (1) 40. (1) 41. (4) 42. (1)
43. (1) 44. (2) 45. (4) 46. (2) 47. (4) 48. (1) 49. (4)
50. (3) 51. (3) 52. (3) 53. (2) 54. (2) 55. (2) 56. (4)
57. (3) 58. (2) 59. (2) 60. (4) 61. (4) 62. (3) 63. (1)
64. (2) 65. (2) 66. (1) 67. (2) 68. (1) 69. (2) 70. (1)
71. (4)

PHOTOSYNTHESIS - THE KEY PROCESS OF PLANT ENERGY CONVERSION

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PHOTOSYNTHESIS - THE KEY PROCESS OF PLANT ENERGY CONVERSION