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(1) photo-oxidation of enzymes, pigments and other chemicals.
(2) photo-inhibition due to dehydration and closure of stomata.
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Characteristics of CAM plants are :
(1) Optimum temperature is 35°C.
(2) These have large vacuoles in mesophyll cells.
(3) Enzyme used by them is PEP carboxylase.
(4) These have low productivity.
(5) Their stomata open during night.
Photosynthesis is the process of manufacture of food from carbon dioxide and water in the presence of sunlight and chlorophyll by green plants. 
Significance of photosynthesis :
1. It helps in the synthesis of food.
2. Consumption of carbon dioxide and release of oxygen.
Van Niel’s observation : Van Niel observed that photosynthesis is a light-dependent reaction and the O2 comes from the water and not carbon dioxide.. In green plants H2O is the hydrogen donor and O2 is the product. whereas in purple and green bacteria the hydrogen donor is H2S and the product is sulphur.
Robin Hill experiment: He took the isolated chloroplasts of Stellaria and placed them in water having hydrogen acceptors (like chromates, ferricyanides, cytochromes, benzoquinones etc.) He illuminated water and the oxygen was liberated in the absence of carbondioxide. 
The hydrogen acceptors are called Hill oxidants and the process of liberation of oxygen in the absence of carbon dioxide is called Hill oxidation. In plants hydrogen acceptor is NADP+
Internal factors affecting photosynthesis are :
1. The number, size , age and orientation of the leaves, mesophyll cells and chloroplasts
2. Internal C02 concentraion.
3. The amount of chlorophyll
4. Genetics and the growth of the plants.
Photosystem I [PSI] :
Location : It is present in the membrane of stroma thylakoids and non-appressed parts of grana thylakoids.
Pigment molecules : In PS I the reaction centre chlorophyll a which has an absorption peak at P700.
Reducing agents : The PS I has following reducing agents viz. ferrodoxin, plastoquinone, cytochrome complex, n-plastocyanin.
Function of PS I : In PS I cyclic photophos-phorylation occurs.
Photosystem II [PS II] :
Location : It is present in appressed part of grana thylakoids.
Pigment molecules : It has in the centre special type of chlorophyll ‘a’ molecules called P680.
Reducing agents : PS II has quencher, plastoquinone, cytochrome complex and plastocyanin reducing agents.
Function : In PS II non-cyclic photophosphorylation occurs, alongwith photolysis of water.
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1. Carotenoids function as accessory pigments. They absorb radiant energy in the mid region of visible spectrum.
2. They protect the chloroplast constituents from nascent oxygen released during photolysis of water.
3. Carotenoids provide colour to the flowers and fruits that help in pollination and dispersal.
The advantages of having more than one pigment are:
(1) To efficiently capture sunlight and to facilitate reaction.
(2) These additional pigments protect chlorophyll molecule from nascent oxygen.
(4) Some pigments act as co-enzymes which are used for some metabolic activities of chloroplasts.
Non-Cyclic Photophosphorylation : The electrons lost by P680 (PS-II) are taken up by P700 (PS-I) and do not get back to P680 i.e., unidirectional and hence it is called non- cyclic phosphorylation. It involves both PS I and PS II. In this cycle both ATP and NAD(P)H are formed. 
Fig. Non-cyclic photophosphorylation
Phycobilins are water-soluble pigments found in the stroma of chloroplast organelles that are present only in Cyanobacteria and Rhodophyta. The two classes of phycobilins include phycocyanin and phycoerythrin. Phycocyanin is a bluish pigment found in primarily cyanobacteria (blue-green algae) to aid in absorption of light in photosynthesis, while phycoerythrin is a pigment found in Rhodopyta (red algae) that is responsible for its characteristic red color. It is an accessory pigment that allows red algae to carry out photosynthesis in deep water where wavelengths of blue light are most abundant by absorbing blue light and reflecting red light.
C3 cycle is also called Calvin cycle. The first stable compound after the fixation CO2 is a 3-carbon compound.
Calvin cycle of photosynthesis
Steps common to C3 and C4 cycle are :
1. Photolysis of water in light reaction is common to both C3 and C4 cycle.
2. In both, dark reaction occurs in stroma region of chloroplast.
3. Calvin cycle results in the formation of starch in both the types of plants.
4. Both undergo phases of carboxylation and regeneration of RUBP during dark reaction.
What is Kranz anatomy?
Kranz anatomy is the special arrangement of the cells found in the C4 plants.
The characteristics of Kranz anatomy are:
The bundle sheath cells form several layers around the vascular bundles. The chloroplasts of bundle sheath cells are large and more in number, they have thick walls and no intercellular spaces. Mesophyll cells are undifferentiated and arranged in concentric layers around the vascular bundles.
Action Spectrum. Action spectrum is a curve which shows relative rates of photosynthesis at The graph of the action spectrum indicates that the maximum photosynthesis takes place in the blue and red parts of visible light. 
Wave length of light in nm Graph of Action Spectrum
Absorption Spectrum. Absorption spectrum is a curve which shows the amount of light of different wavelengths absorbed by a substance or pigment. The absorption spectrum of two chlorophyll (chl “a” and chl “b”) and carotene shows that maximum light absorbed is in the blue and red wavelengths.
Blackmann’s law of limiting factor states that :
If a chemical process is affected by more than one, then the rate is determined by the factor which is nearest to its minimal value. The minimum or limiting factor is the factor which directly affects the process if its quantity id changed. “
|
Chlorophyll ‘a’ |
Chlorophyll ’b’ |
|
1. Molecular formula is C55 H72 O5 N4 Mg. |
Molecular formula is C55 H70 O6 N4 Mg. |
|
2. It is bluish green in colour. |
It is olive green in colour. |
|
3. It is universal and found in lower and higher plants except bacteria. |
3. It is found only in higher plants. |
|
4. It has methyl group attached to the third carbon of porphyrin head. |
4. It has –CHO group attached to the third carbon atom of porphyrin head. |
Affect of CO2 on photosynthesis : Carbon dioxide acts as a major limitin factor for photosynhesis. The CO2 is 0.03 % in atmosphere and increase in amount of CO2 upto 0.05% in atmosphere increases the rate of photosynthesis. Beyond it the rate declines. It is due to the increase in the temperature.
The C3 and C4 plants responds differently o the CO2 concentration. The C3 plants respond to a higher concentration of CO2 by showing increased rates of photosynthesis while the C4 plants saturate at low level of CO2 and do not show increase in the rate of photosynthesis.
|
Photorespiration |
Respiration |
|
1. It is the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. |
1. It is the process in living organisms involving the production of energy, typically with the intake of oxygen and the release of carbon dioxide from the oxidation of organic substances. |
|
2. Light and the presence of cholorophyll is required |
2. Light and cholorophyll are not required, |
|
3. Carbon dioxide and water is used and oxygen is released |
3. Oxygen is used and carbon dioxide and water is formed. |
|
4. Occurs only in plants |
4. Occurs in all organisms. |
|
5. Chloroplasts is involved |
5. Mitochondria is involved |
|
6. It stores energy |
6. It release energy. |
Heliophytes : The plants that thrive in area where intensity of light is more are called heliophytes e.g. Dalbergia.
Sciophytes : The sciophytes need less intensity of light and they grow under the canopy of trees. These plants have less amount of chlorophyll and remain smaller due to decreased rate of photosynthesis e.g. Oxalis.
|
PS I |
PS II |
|
1. The system is located in both the non-appressed part of grana thylakoids as well as stroma thylakoids. |
1. Photosystem II is present in the appressed part of grana thylakoids. |
|
2. Its photocentre is P700. |
2. Its photocentre is P680. |
|
3. Has an absorption peak at wavelength of 700nm. |
3. Has an absorption peak at the wavelength of 680nm. |
|
4. It receives electrons from photosystem II. |
4. Electrons are received from photolytic reaction. |
|
5. Molecular oxygen is not evolved in this system. |
5. Molecular oxygen is evolved by break down of water. |
Saturation point is the maximum intensity of light at which the rate of photosynthesis is maximum. Above this value of light intensity, rate of photosynthesis decreases.
Value : It is 60–70% for C3 plants and about 200% of full sunlight for C4 plants.
Calvin Cycle (C3 cycle).
The steps involved in C3 cycle are discussed below:
(a) Carboxylation : It is the fixation of CO2 into a stable compound. the reaction is catalysed by RuBP carboxylase enzyme. In this the ribulose 1, 5 -bisphosphate reacts with carbon dioxide to give 3-PGA (3 phosphoglyceric acid).
(b) Reduction : In this step carbohydrate is formed at the expense of ATP and NADPH. Two molecules of ATP are utilized for phosphorylation and two NAdph for the reduction of CO2 molecule fixed. 6 molecules of CO2 and 6 turns of cycle are required for removal of one molecule of glucose from pathway.
(c) Regenration - In this step the CO2 acceptor molecule RuBP is regenerated.
Photorespiration is the process where oxygen is consumed, food is oxidized and carbondioxide is liberated, but no energy is produced. It is a highly wasteful process which occurs in the presence of light.
Mechanism of photorespiration:
It takes oplace in chloroplasts and completes with the assistance of peroxysomes and mitochondria.
1. At high temperature RUBP caThe enzyme has great affinity for oxygen than for carbon dioxide. It combines oxygen and RUBP to form PGA and phosphoglycolate.
2. Phosphoglycolate forms phosphoric acid and glycolate in the presence of hydrolase. It passes into peroxysome.
3. Glycolate molecule combines with oxygen to form glyoxylate and H2O2 which is very toxic. It occurs in peroxysome.
4. Glycoxylate undergoes amination to form glycine. The glycine molecules undergo condensation, decarboxylation, deamination to form serine.
5. Serine undergoes deammination to form PGA which enters into chloroplast and takes part in C3 cycle. Thus, it is linked with C3 cycle. Moreover RUBP carboxylase changes its behaviour at high tampereture and acts RUBPoxygenase and thus it delinks from C3 cycle.
Describe very briefly the contribution of the following scientists :
(1) Jan Ingcnhousz
(2) C.B. Van Niel
(3) Joseph Priestly
(2) C.B. Van Niel, proposed that the oxygen produced during the photosynthesis comes from water and not carbon dioxide.
(3) Joseph Priestly reported that green plants purify the air and restore to the air whateever the burning of candle or breathing animals remove from the air.
What is photosystem ? Which is the pigment that acts as reaction centre ? Describe the interaction of photosystem I and photosystem II.
Photosystem : It is a group of pigment molecules and electron acceptors which take part in oxidation and reduction reaction in photosynthesis for producing ATP and NADPH.
Reaction Centre : Chla molecules act as reaction centres. The Chla of speacial types form different reaction centres like P680 in PS II and P700 in PS I.
Interaction of PS I and PS II :
PS I and PS II are interlinked in following two
ways :
Ist way : P680 reaction centre of PS II takes energy from sunlight. Then, it emits electron which pass through number of electron acceptors and then go to P700, a reaction centre of PSI.
IInd way : The P700 takes energy from sunlight via harvesting molecule and its electron is emitted. This electron passes through primary acceptor x and then to ferrodoxin and after this to NADP reductase.
During photolysis of H2O, the H2O splits into H+ and OH–. The OH– changes into H2O, O2 and electrons are released which go to P680 molecule. The H+ goes to NADP reductase which combines NADP, H+ and e– form assimilatory power called NADPH
C4 pathway is an adaptation to tolerate strong light, high temperature ; high quantity of oxygen etc. Evolution of C4 plants from C3 plants can be described as follows :
1. C3 plants undergo photorespiration in strong light or at high temperature which is a wasteful process in which no energy is produced.
2. In C3 plants RUBP carboxylase get denatured in strong light, but in C4 plants it does not.
3. These C4 plants have Kranz anatomy. In this case mesophyll cells have grana thylakoid and bundle sheath cells have agranal thylakoids present in stroma of chloroplast.
4. In C4 plant, light reaction occurs in mesophyll cells and RuBisCo is found in bundle sheath cells in which CO2 fixation occurs. Thus, in C4 plants RuBisCo remains protected from sunlight and is also protected from oxygenation, because in bundle sheeth cells only dark reaction occurs.
Thus, to avoid photorespiration, oxygenation of RuBisCo etc. C4 plants were evolved from C3plants. The C4 plants are maize, sugar cane, grasses etc.
CAM :
It can be described in following ways :
1. Crasslacean acid metabolism (CAM) refers to a mechanism of photosynthesis that is different than already discussed C3 and C4 pathways.
2. This occurs only in succulents and other plants that normally grow in dry conditions.
3. In CAM plants C02 taken up by leaves or green stems through stomata, which remain open at night.
4. However during the day the stomata remain closed in these plants to conserve moisture.
5. The CO2 taken up in the night is fixed in the same way as in C4 plants to form malic acid, which is stored in the vacuole.
6. The malic acid thus formed during the night is used during the day as a source of CO2 for photosynthesis to proceed via the C3 pathway.
Significance : Thus CAM is a kind of adaptation that allows certain plants (for example, pineapple) to carry out photosynthesis without much loss of water.
Name the pentose phosphatew which is a CO2 acceptor in the dark reaction of photosynthesis ?
Give comparison between the following :
(b) Cyclic and non-cyclic photophosphorylation
(b) Distinction between cyclic and non-cyclic photophosphorylation :
|
Cyclic photophosphorylation |
Non-cyclic photophosphorylation |
|
|
1. |
It is performed by PS I independently. |
It is performed by both PS I and PS II with the help of each other. |
|
2. |
An external source of electrons is not required because the same electrons get recycled. |
The process requires an external electron donor, because the same electron is not recycled. |
|
3. |
It is not connected with photolysis of water, therefore, no oxygen is evolved. |
It is connected with photolysis of water and liberation of oxygen. |
|
4. |
It synthesizes only ATP. |
ATP synthesis with the production of NADPH. |
|
5 |
Electron flow is cyclic. |
Electron flow is non-cyclic. |
A chlorophyll molecule has two parts :
(1) The porphyrin ring.
(2) A phytol tail .
The ATPase enzyme consists of two parts:
i. Fo portion - which is embedded in the membrane and forms the transmembrane channel tahat carry out the diffusion of proteins across the mebrane.
ii. F1 portion - which protrudes on the outer surface of the thylakoid membrane on the side that faces the stroma.
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A photosynthetic reaction centre is a complex of several proteins, pigments and other co-factors that together execute the primary energy conversion reactions of photosynthesis. The single chlorophyll a molecule forms the reaction centre. The reaction centre is different in both the photosystems. In PSI the reaction centre chlorophyll a has an absorption peak at 700nm, hence is called P700, while in PSII it has absorption maxima at 680 nm and is called P680.
To prove that CO2 is necessary for photosynthesis the following experiment can be formed:
1. A potted plant is kept in dark for three days so that the leaves become free from starch.
2. A healthy leaf is selected for experiment.
3. a wide mouth bottle is taken and a little KOH (it absorbs CO2) is added to it.
4.Half part of the leaf is kept in the bottle with the help of split cork.
5. The apparatus in kept in bright sunlight for few hours.
6. The leaf is plucked and boil in 70% alcohol. It is stained with iodine solution.
Observation : It was observed that the portion of leaf which was out of the bottle turned blue showing the presence of starch. The portion on leaf which was enclosed within the bottle will not show the presence of starch .
Conclusion : This shows that CO2 is essential for photosynthesis, because the portion inside the bottle did not get the CO2 as it was absorbed by KOH solution. Thus CO2 is necessary for photosynthesis.
The C4 plants lack photorespiration thus the productivity and yields are better in these plants. Since there is no photorespiration there is no wastage of energy thus these plants are said to be more efficient.
Priestley experiment.
In the experiment
A burning candle and a mouse were kept in a bell jar. It was observed that the candle was extiguished after sometime and the mouse soon died.
When a mint plant was kept in the same bell jar, it was found that the mouse stayed alive and the candle countinued to burn. Priestley hypothesised that plants restore to the air whatever breathing animals and burning candle used up. 
According to this hypothesis in photosynthesis ATP synthesis is linked to development of a proton gradient across a membrane.
RuBisCo enzymes acts as both carboxylase and oxygenase. It carries out more carboxylation in the C4 plants as these plants have special mechanism that increases the concentration of the CO2 at the enzyme site. There is no photorespiration in the C4 plants and thus oxygen does not bind to the RuBisCo enzyme. All this minimizes the oxygenase activity of the enzyme and increase the carboxylase activity.
The plant having high concentration of chlorophyll-b but lacking chlorophyll-a will not carry out photosynthesis.
Chlorophyll-a molecules forms the reaction centre and acts as the main pigment molecules. The other pigments like chlorophyll-b and other photosynthetic pigments such as carotenoids and xanthophylls act as accessory pigments. Their role is to absorb the different wavelength of light and make the process of photosynthesis efficient. Carotenoids and xanthophylls also protect the chlorophyll molecule from photo-oxidation.
The leaves on the shady side or those kept in the shade have leaves that are darker green. This is because light is a limiting factor for photosynthesis. In order to increase the rate of photosynthesis, the leaves present in shade have more chlorophyll pigments. This increase in chlorophyll content increases the amount of light absorbed by the leaves, which in turn increases the rate of photosynthesis.
Figure 13.10 shows the effect of light on the rate of photosynthesis. Based on the graph, answer the following questions:
(a) At which point/s (A, B or C) in the curve is light a limiting factor?
(b) What could be the limiting factor/s in region A?
(c) What do C and D represent on the curve?
(a) Since the rate of photosynthesis doe not increase with the increase in the incident light therefore light is a limiting factor in the region B.
(b) The other limiting factors may be water, temperature, and the concentration of carbon dioxide.
(c) Point D represents the optimum point and gives the light intensity at which the maximum photosynthesis is recorded.
Ponit c represents the region where the rate of photosynthesis remains constant even after incresing the incident light.
Give comparison between C3 and C4 pathways.
|
C3 pathways |
C4 pathways |
||
|
1. |
The primary acceptor of CO2 is RUBP – a six-carbon compound. |
1. |
The primary acceptor of CO2 is phosphoenol pyruvate – a three-carbon compound. |
|
2. |
The first stable product is 3-phosphoglycerate. |
2. |
The first stable product is oxaloacetic acid. |
|
3. |
It occurs only in the mesophyll cells of the leaves. |
3. |
It occurs in the mesophyll and bundle-sheath cells of the leaves. |
|
4. |
It is a slower process of carbon fixation and photo-respiratory losses are high. |
4. |
It is a faster process of carbon fixation and photo-respiratory losses are low. |
|
5. |
Occurs in all the plants |
5. |
Occurs only in C4 plants |
Give comparison between anatomy of leaf in C3 and C4 plants.
|
C3 leaves |
C4 leaves |
||
|
1. |
Leaves do not have Kranz anatomy. |
1. |
Leaves have Kranz anatomy. |
|
2. |
Bundle-sheath cells are absent |
2 |
Bundle-sheath cells are present |
|
3. |
RuBisCo is present in the mesophyll cells. |
3. |
RuBisCo is present in the bundle-sheath cells. |
|
4. |
The first stable compound produced is 3-phosphoglycerate –a three-carbon compound. |
4. |
The first stable compound produced is oxaloacetic acid – a four-carbon compound. |
|
5. |
Photorespiration occurs |
5. |
Photorespiration does not occur |
A plant in your garden avoids photorespiratory losses, has improved water use efficiency, shows high rate of photosynthesis at high temperatures and has improved efficiency of nitrogen utilisation. In which of the following physiological groups would you assign this plant?
C4
CAM
Nitogen-fixer
C3
A.
C4
C4 plants show very little photorespiration and better utilisation of water.
Emerson's enhancement effect and red drop have instrumental in the discovery of
two photosystems operating simultaneously
photophosphorylation and cyclic electron transport
oxidative phosphorylation
phosphorylation and non-cyclic electron transport
A.
two photosystems operating simultaneously
Emerson performed photosynthetic experiment on Chlorella. The enhancement effect is due to the presence of two photosystems PsI and PSII.
Specialised epidermal cells surrounding the guard cells are called
sunbsidiary cells
bulliform cells
lenticels
complementary cells
A.
sunbsidiary cells
The cells surrounding the guard cells are called subsidiary cells and lack chloroplast.
The three boxes in this diagram represent the three major biosynthetic pathways in aerobic net reactant or products
Arrows numbered 4, 8 and 12 can all be
NADH
ATP
H2O
FAD+ Or FADH2
B.
ATP
Pathway A is glycolysis, pathway B is the kerb' cycle and pathway C is oxidative phosphorylation
Arrow 1 - ADP or NAD+
Arrow 2 - Pyruvate
Chromatophores take part in
Photosynthesis
Growth
Movement
Respiration
A.
Photosynthesis
Chromatophores are found in members of phototrophic bacteria. They contain bacteriochlorophyll pigments and carotenoids and take part in photosynthesis. In purple bacteria, such as Rhodospirillum rubrum, the light-harvesting proteins are intrinsic to the chromatophore membranes. However, in green sulphur bacteria, they are arranged in specialised antenna complexes called chlorosomes.
The oxygen evolved during photosynthesis comes from water molecules. Which one of the following pairs of elements is involved in this reaction?
Manganese and Chlorine
Manganese and Potassium
Magnesium and Molybdenum
Magnesium and Chlorine
A.
Manganese and Chlorine
Photolysis of water during photosynthesis evolve nascent oxygen in the presence of manganese, calcium and chloride ions.
In photosynthesis, the light-independent reactions take place
Thylakoid lumen
Photosystem I
Photosystem II
Stromal matrix
D.
Stromal matrix
The light-independent reactions (or dark reactions) take place in the stromal matrix of the chloroplasts.
In light independent reactions, carbon dioxide is reduced to glucose (carbohydrate) by the hydrogen in NADPH by using the chemical energy stored in ATP. This reaction takes place in the presence of a substance called RuDP.
Anoxygenic photosynthesis is characteristic of
rhodospirlllum
Spirogyra
Chlamydomonas
Ulva
A.
rhodospirlllum
Anoxygenic photosynthesis (in which O2 is not released) is seen in Rhodospirillum, a purple non- sulphur bacteria. it helps an organism to trap light energy and store it as chemical energy.
A process that makes important difference between C3 and C4 plants is
transpiration
glycolysis
photosynthesis
photorespiration
D.
photorespiration
Photorespiration is a light dependent process which occurs in C3 plants. It is opposite to photosynthesis because during this process uptake of O2 and release of CO2 take place. Due to the presence of Kranz anatomy, C4 plants do not show photorespiration.
The correct sequence of cell organelles during photorespiration is
chloroplast - Golgi bodies - mitochondria
chloroplast-rough endoplasmic reticulum -dictyosomes
chloroplast-mitochondria-peroxisome
chloroplast-vacuole-peroxisome
C.
chloroplast-mitochondria-peroxisome
None of the options is correct. photorespiration required three cell organelles in sequence of chloroplast, peroxisome and mitochondria.
option (c) may be correct if be read as said sequence.
Read the following four statements:
I. Both, photophosphorylation and oxidative phosphorylation involve uphill transport of protons across the membrane.
II. In dicot stems, a new cambium originates from cells of pericycle at the time of secondary growth.
III. Stamens in flowers of Gloriosa and Petunia are polyandrous.
IV. Symbiotic nitrogen fixers occurs in free-living state also in soil.
How many of the above statements are right
Two
Three
Four
One
A.
Two
Symbiotic nitrogen-fixing bacteria and Cyanobacteria are found in association to plant. The most common symbiotic bacteria is Rhizobium.
In dicot stem, the cambium present between xylem and phloem in vascular bundles is called fascicular or intrafascicular cambium. Besides this some cells of medullary rays also become meristematic and called interfascicular cambium.
CAM helps the plants in
secondary growth
disease resistance
reproduction
conserving water
D.
conserving water
CAM plants are mostly succulent xerophytes. The stomata in these plants remain closed during the day. This helps to check the transpiration. In this way, water is conserved.
In Kranz anatomy, the bundle sheath cells have
thin walls, many intercellular spaces and no chloroplasts
thick walls, no intercellular spaces and a large number of chloroplasts
thin walls, no intercellular spaces and several chloroplasts
thick walls, many intercellular space and few chloroplasts
B.
thick walls, no intercellular spaces and a large number of chloroplasts
C4 plants have a characteristic leaf anatomy called Kranz anatomy.Kranz means wreath (ring) and is a reflection of the arrangement of cells. The large sized bundle sheath cells may form several layers around the vascular bundles. These cells are characterised by having a large number of agranal chloroplasts, thick walls impervious to gaseous exchange and no intercellular spaces.
Which one of the following is essential for photolysis of water
Manganese
Zinc
Copper
Boron
A.
Manganese
Photolysis of water requires light energy and oxygen evolving complex (OEC) and an electron carrier Yz. OEC complex was formerly called Z - enzyme. It has four Mn ions. Light energy brings about changes in Mn (Mn+2, Mn3+ Mn+4) which helps in removing electrons from OH- component of water forming oxygen.Liberation of oxygen also requires Cl- and Ca2+.
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PGA as the first CO2 fixation product was discovered in photosynthesis of
bryophyte
gymnosperm
angiosperm
alga
D.
alga
The use of radioactive 14C by Melvin Calvin in algal (Chlorella) photosynthesis studies led to the discovery that the first CO2 fixation product was a 3- carbon organic acid. The first product identified was 3 -phoshoglyceric acid (PGA)
Photoperiodism was first characterised in
tobacco
potato
tomato
cotton
A.
tobacco
They phenomenon of photoperiodism was first discovered by Garner and Allard (1920, 22) in the tobacco plant. They observed that Maryland Mammoth, the variety of tobacco could be made to flower only by reducing the light hours with artificial darkening. It could be made to remain vegetative in winter by providing extra light.
C4 plants are more efficient in photosynthesis than C3 plants due to
higher leaf area
the presence of a larger number of chloroplasts
the presence of thin cuticle
Lower rate of photorespiration
B.
the presence of a larger number of chloroplasts
Like Plants, alage have cell walls contain either polysaccharides such as cellulose (a glucan) or a variety of glycoproteins or both. The inclusion of additional polysaccharide in algal cell walls is used as a feature for algal taxonomy. Mannas form microbibrils in the cell walls of a number of marine green alge including those from the genera Codium, Acetabularia as well as in the walls of some red algae including those from the gera Codium, Acteabularia as well as in the walls of some red algae like Porpyra.
Read the following four statements, A, B,C and D select the right option having both correct statements.
A) Z scheme of light reaction takes place in presence of PS- I only.
B) Only PS-I is functional in cyclic photophosphorylation.
C) Cyclic photophosphorylation results into synthesis of ATP and NADPH2
D) Stroma lamellae lack PS-II as well as NADP.
B and D
A and B
B and C
C and D
A.
B and D
Cyclic photophosphorylation is performed by PS-I only. In this process, an electron expelled by the excited photo centre, ie, P700 is returned to it after passing through a series of electron carriers.
PS- I is located on both the non- appressed part of grana thylakoids as well as stroma thylakoids, while PS-II is located in the appressed part of grana thylakoids only, stroma thylakoids lack PS-II.
Kranz anatomy is one of the characteristics of the leaves of
potato
wheat
sugarcane
mustard
C.
sugarcane
Sugarcane is a C4-plan. C4-plants are characterised by the presence of Kranz-type of anatomy. In this, the leaf mesophyll is undifferentiated and its cells (having a normal type of granola chloroplasts) occur in concentric layers around vascular bundles, later is surrounded by large-sized bundle sheath cells (having large -sized agranal chloroplasts) which are arranged in a wreath like manner.
Oxygenic photosynthesis occurs in
Chromatium
Oscillatoria
Rhodospirillum
Chlorobium
B.
Oscillatoria
Oscillatoria is a photosynthetic cyanobacterium. In this, during photosynthesis water is electron donor and oxygen is a by -product, ie oxygenic photosynthesis occurs. Rhodospirillum and Chlorobium are non- oxygenic photosynthetic, purple non- sulphur and green sulphur bacteria. chromatium is a purple sulphur bacterium, also a non- oxygenic photosynthetic.
Which one of the following acids is a derivative of carotenoids?
Indole butyric acid
Indole -3-acetic acid
Gibberellic acid
Abscisic acid
D.
Abscisic acid
Abscisic acid is a terpenoid, ie, a derivative of steroid.
Cyclic-photophosphorylation results in the formation of
NADPH
ATP and NADPH
ATP, NADPH and O2
ATP
D.
ATP
Cyclic-photophosphorylation involves only pigment system-I. When the photons activate PS-I, a pair of the electron are raised to a higher energy level. They are captured by the primary acceptor, which passes them on to ferredoxin, plastoquinone, cytochrome complex, plastocyanin and finally back to reaction centre of PS-I ie, P700. At each step of electron transfer, the electrons lose potential energy. Their trip downhill is caused by the transport chain to pump H+ across the thylakoid membrane. The proton gradient thus established is responsible for forming ATP ( 2 molecules). No reaction of NADP to NADPH + H+.
The C-4 plants are photosynthetically more efficient than C-3 plants because
the CO2 compensation point is more
CO2 generated during photorespiration is trapped and recycled through PEP carboxylase
the CO2 efflux is not prevented
they have more chloroplasts
D.
they have more chloroplasts
Chloroplasts in bundle sheath cells are larger and always contain grana whereas chloroplasts in mesophyll cells are smaller. The C4 - plants are photosynthetically more efficient than c3 -plants because they more chloroplasts.
The slow rate of decomposition of fallen logs in nature is due to their
low moisture content
poor nitrogen content
anaerobic environment around them
low cellulose content
A.
low moisture content
Photosynthetically fixed carbon is eventually degraded by micro-organisms and two major forms of carbon result methane (CH4) and carbon dioxide (CO2).The micro-organisms break down the complex compounds of the dead protoplasm of producers and consumers absorb some of the decomposition products and release simple substances. The slow rate of decomposition of fallen logs in nature is due to their low moisture content. The cellulose is in high amount in fallen logs. The environment around the fallen logs is aerobic, ie, O2 is present.
Which one of the following is resistant to enzyme action?
Cork
Wood fibre
Pollen exine
Leaf cuticle
C.
Pollen exine
The pollen wall consists of two layers the outer exine and inner intine. The exine chiefly made up of sporopollenin, which is derived by the oxidative polymerization of carotenoids. Sporopollenin is one of the most resistant biological materials known. The exine is thin in beginning but becomes very thick with maturity.
During secondary growth in the extrastelar region, cork cambium or phellogen cells divide periclinal, cutting off cells towards the outside and inside. The cells cutoff towards outside become suberised and dead and form cork. Cork is impervious to water due to suberin and provides protection to the underlying tissue.
In the leaves of C4 plants, malic acid formation during CO2 fixation occurs in the cells of
mesophyll
bundle sheath
phloem
epidermis
A.
mesophyll
The oxalic acid is reduced to malic acid in mesophyll cells, from chloroplast of mesophyll cells the malic acid is transferred to the chloroplast of bundle sheath cells where it is decarboxylated to form CO2 and pyruvic acid.
The first acceptor of electrons from an excited chlorophyll molecule of photosystem II is
cytochrome
iron-sulphur protein
ferredoxin
quinone
D.
quinone
Plastoquinone is the first acceptor of electrons from an excited chlorophyll molecule of photosystem II.
A plant requires magnesium for
holding cells together
protein synthesis
chlorophyll synthesis
cell wall development
C.
chlorophyll synthesis
Magnesium is important constituent of chlorophyll molecule.
In photosystem-I, the first electron acceptor is
Ferredoxin
Cytochrome
Plastocyanin
An iron sulphur protein
D.
An iron sulphur protein
In photosystem I, the primary electron acceptor is probably a Fe - S protein. The reduced primary acceptor transfers the electrons to secondary electron acceptor (most probably P430). The sequence of electron transfer is as follows:
The reduced P430 passes its electrons to ferredoxin (Fd) present at outer surface of thylakoid membrane.
During photorespiration, the oxygen-consuming reaction(s) occur in
stroma of chloroplasts and mitochondria
stroma of chloroplasts and peroxisomes
grana of chloroplasts and peroxisomes
stroma of chloroplasts
B.
stroma of chloroplasts and peroxisomes
The first reaction of photorespiration occur in stroma of chloroplast. In this reaction the RuBP(Ribulose 1-5 biphosphate) consume one oxygen molecule in presence of enzyme Rubisco.
In peroxisome the glycolate transferred from chloroplast takes up O2 and formed the glyoxylate whereas the H2O2 release as byproduct.
With reference to factors affecting the rate of photosynthesis, which of the following statements is not correct?
Light saturation for CO2 fixation occurs at 10% of full sunlight
Increasing atmospheric CO2 concentration upto 0.05% can enhance CO2 fixation rate
C3 plants responds to higher temperatures with enhanced photosynthesis while C4 plants have much lower temperature optimum
Tomato is a greenhouse crop which can be grown in CO2- enriched atmosphere for higher yield
C.
C3 plants responds to higher temperatures with enhanced photosynthesis while C4 plants have much lower temperature optimum
In C3 plants photosynthesis is decreased at higher temperature due to increased photorespiration. C4 plants have higher temperature optimum because of the presence of pyruvate phosphate dikinase enzyme, which is sensitive to low temperature.
Which of the following is not a product of light reaction of photosynthesis?
ATP
NADH
Oxygen
NADPH
B.
NADH
ATP, NADPH and oxygen are products of light reaction, while NADH is a product of respiration process.
Stomata in grass leaf are
Dumb-bell shaped
Kidney Shaped
Barrel shaped
Rectangular
A.
Dumb-bell shaped
Herbicide that blocks electrons transport from PS-II to PS-I by inhibiting electron flow between plastoquinone → Cytochrome is
DCMU
Paraquat
DCPIP
None of these
A.
DCMU
DCMU is a selective herbicide that acts as a potent inhibitor of PS-II. Paraquat inhibits PS-I by producing superoxides.
DCPIP is a dye used to measure the rate of photosynthesis.
A plant is provided with the ideal conditions for photosynthesis and supplied with isotope 14 CO2. When the products of the process are analysed carefully, what would be the nature of products?
Glucose and oxygen are labelled
Oxygen is labelled, but glucose is normal
Glucose and oxygen are normal
Glucose is labelled, but oxygen is normal
D.
Glucose is labelled, but oxygen is normal
In the process of photosynthesis
Plants manufacture glucose from H2O and CO2 and oxygen gas is released. So, due to the isotopic carbon of CO2, only glucose will be labelled, but oxygen will be normal.
Cotyledons and testa are edible parts of
groundnut and pomegranate
walnut and tamarind
french bean and coconut
cashew nut and litchi
A.
groundnut and pomegranate
Cotyledons and testa are edible parts of groundnut and pomegranate respectively. The edible part of walnut is cotyledon, tamarind-mesocarp, french beans-seeds, coconut-endosperm testa, cotyledons and embryo, cashew nut-cotyledons and fleshy pedicles and of litchi is fleshy aril.
Given below is a schematic break-up of the phases/stages of cell cycle. Which one of the following is the correct indication of the stage/ phase in the cell cycle?
C-karyokinesis
S-synthetic phase
A-cytokinesis
B-metaphase
B.
S-synthetic phase
In cell cycle, there are two main phases-interphase and mitotic phase. Interphase is divided into three stage G1, S and G2, G1 is the first growth phase. S is a synthetic phase and G2 is second growth phase.
In photosynthesis carbon dioxide is converted to carbohydrates. It is a process.
Reductive
Oxidative
Catabolic and exergonic
None of the above
A.
Reductive
Photosynthesis is an oxidation reduction process in which water is oxidised and carbon dioxide is reduced to carbohydrates. Hence, it is an anabolic and endergonic process.
Which of the following characteristics is are exhibited by C4 -plants?
I. Kranz anatomy.
II. The first product of photosynthesis is oxaloacetic acid.
III. Both PEP carboxylates and ribulose biphosphate carboxylate act as carboxylating enzymes.
The correct option is
I and III, but not ll
I and II, but not III
II and III, but not I
ll and III
C.
II and III, but not I
C-4 plants have an alternative CO2 fixation pathway called Hatch and Slack cycle. These plants have Kranz anatomy in leaf, where vascular bundles are surrounded by bundle sheath.
Which of the following plant keeps its stomata open during night and closed during the day?
Orchid
Cactus
Tea
Wheat
A.
Orchid
Scotoactive mechanism of opening of stomata is seen in fleshy xerophytes like opuntia, cactus, etc. They keep their stomata open at night and closed during daytimes.
In which one of the following, the male and female gametophytes don’t have free-living independent existence?
Pteris
Funaria
Polytrichum
Cedrus
A.
Pteris
In Pteris (also Dryopteris), the spore germinates to produce the prothallus. The prothallus is a small, green, flat, surface loving, thallus-like object. It is monoecious and bears sex organs on the ventral side. The antheridia (male sex organs) arise among the rhizoids towards the posterior side of the prothallus and are emergent. The archegonia develop in central cushion behind the apical notch. In these plants, o male and female gametophytes do not have free-living independent existence.
All species of Polytrichum are dioecious. The antheridia and archegonia are borne on different gametophore. The plant body is an erect leafy shoot but is not the entire gametophyte.
The leafy shoot arises from protonema (the juvenile stage). The leafy gametophore of Funaria reproduces sexually by the formation of antheridia and archegonia. The antheridia are formed at the summit of a relatively small, thin, leafy shoot, which develops first. The female branch arises later as a lateral outgrowth from the base of parent male shoot.
Quantasome are present in
Chloroplast
Mitochondria
Golgi body
Lysosome
A.
Chloroplast
Quantasomes are the photosynthetic units present in the thylakoids of the chloroplast. Each of the quantasomes contains about 250-300 chlorophyll molecules.
Which of the following cell organelles is associated with photorespiration?
Mitochondria
Peroxysome
Chloroplast
All of these
B.
Peroxysome
Photorespiration (C2-cycle) is a special type of respiration shown by many green plants (C3-plants) when they are exposed to light. It is a light-dependent process during, which O2 is used and CO2 is released. The process of photorespiration takes place only in chlorophyllous tissues of plants. Therefore, the main site for photorespiration is chloroplast. But mitochondria and peroxysomes are also required to complete the process.
The net requirement of assimilatory power for the formation of 6 hexose molecules in maize plant is
72 ATP, 48 NADPH
90 ATP, 60 NADPH
108 ATP, 72 NADPH
180 ATP, 72 NADPH
D.
180 ATP, 72 NADPH
C4 plants (maize) require 30 ATP and 12 NADPH fpr synthesis of one hexose molecule. Therefore synthesis of six hexose molecules requires 180 ATP and 72 NADPH.
Which one of the following elements is an activator for both ribulose biphosphate, carboxylase oxygenase and phosphoenol-pyruvate carboxylase in photosynthetic carbon fixation?
Mg2+
Zn2+
Mn2+
Cl− and K+
A.
Mg2+
In photosynthetic carbon fixation magnesium ion (Mg) is an activator for both ribulose bisphosphate carboxylase oxygenase and phosphoenol-pyruvate carboxylase enzymes.
Vegetative propagation of Bryophyllus takes place through
Bulbil
Corms
Leaf buds
Eyes
C.
Leaf buds
Vegetative reproduction in Bryophyllum takes place through leaf buds.
Which of the following characteristics out of I, II and III are exhibited by C4 plants?
I. Kranz anatomy.
II. The product of photosynthesis is oxalo acetic acid.
III. Both PEP carboxylase and ribulose-bis phosphate carboxylase act as carboxylating enzyme.
Choose the correct option.
I and II, but not III
II and III, but not I
I and III, but not II
All of these
D.
All of these
C4 plants have an alternative CO2 fixation pathway called Hatch and Slack cycle where QAA, a 4C compound is the first stable product. These plants have Kranz anatomy in leaf.
Light reaction in stroma lamellae of the chloroplast results in the formation of
NADPH
ATP + NADPH
ATP K
O2
C.
ATP K
Photosystem-I is located in a non-appressed part of grana and stroma lamellae. It is involved both in cyclic and non-cyclic photophosphorylation Interrelationship of PS-I and PS-Il produces ATP and NADPH.
In leaves of Ce plants, malic acid synthesis during CO2 fixation occurs in
Bundle sheath
Mesophyll
Epidermis
Guard cells
B.
Mesophyll
In C4- plants CO2 combines with phosphoenol pyruvic acid to form oxalacetic acid in mesophyll chloroplasts. It is further reduced to malic acid which is transferred to chloroplast in bundle sheath cells.
Solarisation is
formation of chlorophyll
destruction of chlorophyll
utilisation of sunlight
effects of solar light
B.
destruction of chlorophyll
Photosynthesis starts at very low intensity of light. High intensity of the same causes oxidation and destruction of pigments, enzymes and intermediates and this destruction is termed as solarisation. Therefore, it causes reduction in photosynthesis yield.
In callus culture, roots can be induced by the supply of
auxin
cytokinin
gibberelin
ethylene
A.
auxin
Callus is a irregular, unorganised and undifferentiated mass of actively dividing cells. It's differentiation is under the control of two hormones: auxin and cytokinin.
| Development of | Condition |
| Root | |
| Shoot | |
| Both root and shoot |
In which form does the food transported in plants?
Sucrose
Fructose
Glucose
Lactose
A.
Sucrose
In palnts, food is produced by a a process known as photosynthesis. It is transported in the form of sucrose through phloem. It is thought that 90% of the total solutecarried in the phloem is the carbohydrate sucrose.
In CAM plants, CO2 acceptor is
RuBP
PEP
OAA
PGA
B.
PEP
The process of photosynthesis in C4 plants and CAM (Crassulacean Acid Metabolism) is same. Instead of spatial separation of initial PEP, case fixation and final Rubisco fixation of CO2. Both the steps occur in same cell but at different times, night and day.
Eg, Opuntia, pinapple, Vanilla. PEP (Phosphoenol Pyruvate) is the first acceptor of CO2 in CAM plants.
DCMU
inhibits PS- I
inhibits PS- II
destroy chloroplast
inhibits oxidative phosphorylation
B.
inhibits PS- II
DCMU (Dichlorophenyl Dimethyl Urea) is a herbicide, used for inhibiting O2 evolution and non- cyclic photophosphorylation. Therefore, both are involved in PS-II.
What happened when we inoculated Rhizobium in wheat field?
No increase in production (nitrogen content of soil remains same)
A lot of increase in production (nitrogen content of soil increases)
Fertility of soil decreases
Fertility of soil increases
A.
No increase in production (nitrogen content of soil remains same)
Rhizobium species is symbiotic nitrogen- fixing bacteria, which occurs in root nodules of legumes. When we inoculated Rhizobium in wheat field, there is no increase in production. Because wheat has no root nodules for fixing nitrogen content. Therefore, nitrogen content of soil will remain same.
The law of limiting factors for photosynthesis was enunciated by
R. Hill
Calvin
Krebs
Blackman
D.
Blackman
Blackman (1905) proposed the law of limiting factor according to which, 'when a biological process is controlled as to its rapidity by a number of separate factors, the rate of the process is limited by the pace of the slowest factor.
Photosynthesis in C4 plants is relatively less limited by atmospheric CO2 levels because
four carbon acids are the primary initial CO2 fixation products
the primary fixation of CO2 is mediated via PEP carboxylase
effective pumping of CO2 into bundle sheath cells
RUBISCO in CO4 plants has higher affinity for CO2
B.
the primary fixation of CO2 is mediated via PEP carboxylase
The fixation of CO2 in C4 plants takes place in two places and by two different organic
compounds. Phosphoenol pyruvate (PEP) is found in mesophyll cells which primarily fixes atmospheric CO2 into oxaloaceticacid (4C).
RUBISCO is present in bundlesheath cells where final fixation of CO2 in hexose sugars takes place. CO2 is primarily fixed by PEP carboxylase because this enzyme has greater affinity to CO2 than RUBISCO.
Chlorophyll in chloroplasts is located in
grana
pyrenoid
stroma
both (a) and (c)
A.
grana
Chloroplast, which is a cytoplasmic cell organelle found only in eukaryotic plant cells. It helps in the production of food through, photosynthesis.
Chlorophyll is a specialized light absorbing pigment which is found in the inner wall of granum. Each granum is a flat, sac like structure in which light reaction of photosynthesis takes place.
Pigment anthocyanin is located in
chloroplast
chromoplast
cytoplasm
vacuole
D.
vacuole
Vacuoles are the storage depots of cells, surrounded by a single membrane. They contain excess water, waste products, mineral elements, cell sap and sometimes a soluble pigment anthocyanin also. Anthocyanin are water-soluble vacuolar pigments that, depending on their pH, may appear red, purple, or blue.
In photosythesis action and absorption spectrum were related by
Von Helmont
Engelmann
Emerson
Lavosier
B.
Engelmann
Engelmann studied the effect of different region of the visible spectrum on the rate of photosynthesis of different algae. The amount of oxygen (O2 ) released was found to be maximum in blue and red absorption bands of chlorophyll.
Stomatal opening in plants occurs due to influx of
Na
K
ABA
Auxins
B.
K
Opening of stomata is an energy consuming process whereas closing of stomata is not. The turgidity of guard cells is usually controlled by K+, Cl- and H+. The opening of stomata is initiated by excretion of H+ by guard cells, intake of K+ and Cl- and closing is controlled by abscisic acid.
Energy transfer in photosynthesis occurs as
Phycoerythrin Phycocyanin Carotenoid Chlorophyll a
Chlorophyll b Carotenoid Phycoerythrin Chlorophyll a
Phycocyanin Phycoerythrin Carotenoid Chlorophyll a
Chlorophyll b Carotenoid Phycocyanin Chlorophyll a
A.
Phycoerythrin Phycocyanin Carotenoid Chlorophyll a
Chlorophyll is the principal pigment involved in photosynthesis. Chlorophyll a is the major pigment involved in trapping light energy and converting it into electrical and chemical energy. Chlorophyll b molecules also acts as accessory pigment.
Other accessory pigments are phycoerythrin, phycocyanin, carotenoids etc. The accessory pigment and reaction centre together form photo-system.
In photosynthesis what occurs in PS-II?
It takes longer wavelength of light and e- from H2O
It takes shorter wavelength of light and e- from H2O
It takes longer wavelength of light and e- from NADP
It takes shorter wavelength of light and e- from NADP
B.
It takes shorter wavelength of light and e- from H2O
Green plants and algae use two type of photo-system called Photosystem- I (PS-I) and Photosystem- II (PS -II).
In PS-I, chlorophyll absorb maximum at 700 nm wavelength of light thus reaction centre is P700 and PS-II absorb maximum at 680 nm wavelength of light thus reaction centre is P680. P680 (PS-II) extracts an electron from water, returning to its unexcited state because hydrolysis of H2O occurs in PS-II. So, O2 evolved in PS-II come from water.
The thylakoid in chloroplast are arranged as
interconnected disc
interconnected sacs
stacked discs
none of the above
C.
stacked discs
Most of the lamellae (folding forms a series of parallel membranous sheets) in the chloroplasts are organised to form sac like structures called thylakoids. These thylakoids may be stacked like a pile of coins, this formation has been termed as grana. Chlorophyll is found in grana and light reaction of photosynthesis occur in grana.
The form of pigment which inhibits germination is
P760
P730
P650
All of these
C.
P650
The seed germination is promoted by red wavelength (650 nm) and inhibited by far red (730 nm). This is due to the pigment phytochrome behaving in the following manner.
Germination P730 P650 No germination
In Hatch and Slack pathway
chloroplast are of same type
occurs in Kranz anatomy where mesophyll have small chloroplast whereas bundle sheath have granal chloroplast
occurs in Kranz anatomy when mesophyll have small chloroplast where as bundle sheath have larger, agranal chloroplast
Kranz anatomy where mesophyll cells are diffused
C.
occurs in Kranz anatomy when mesophyll have small chloroplast where as bundle sheath have larger, agranal chloroplast
C4 plants have Kranz type anatomy. Vascular bundles are surrounded by bundle sheath cells. The chloroplasts are dimorphic. The cells of bundle sheath have very large chloroplasts. They lack grana and contain starch grains. They are centripetally arranged and mesophyll cells have small and granal chloroplast.
In Hatch and Slack type plants CO2 acceptor is
malate
pyruvate
phosphoenol pyruvate
aspartate
B.
pyruvate
In Hatch and Slack cycle CO, acceptor is phosphoenol pyruvic acid and first product is oxaloacetic acid, (a 4-C compound). Therefore it is popularly termed as C4 cycle.
In CAM plants
stomata open in day and close at night
stomata remain open in day and night both
stomata remain closed in day and night both
stomata open at night and close in day
D.
stomata open at night and close in day
CAM is found in members of the family Crassulaceae (e.g., Kalanchoe), family Cactaceae (e.g., Opuntia, Cereus), and some members of Liliaceae, Orchidaceae, Bromeliaceae, Euphorbia sp. All CAM plants are not succulent and stomata open at night.
In C4 plants, CO2 combines with
phosphoglyceric acid
ribulose diphosphate
phosphoenol pyruvate
phosphoglyceraldehyde
C.
phosphoenol pyruvate
In C4 plants, CO2 is picked up by a 3-carbon compound Phosphoenol pyruvate (PEP) to form 4-carbon compound Oxaloacetic acid. This reaction is catalysed by PEP carboxylase and it takes place in the cytoplasm of mesophyll cells.
Photorespiration is favoured by
high O2 and low CO2
high CO2 and low O2
high temperature and low O2
high humidity and temperature
A.
high O2 and low CO2
Photorespiration is a respiratory process in many higher plants by which they take up oxygen in the light and give out some carbon- dioxide.
Oxygen is a competitive inhibitor of CO2 fixation. Increase in O2 concentration would favour the uptake of oxygen by Rubisco leading to increase in photorespiration.
The true statement about 'green-house effect' is that it is
caused only by CO2
caused by CO2, CFCs, CH4 and NO2 gases
caused by combination of many gases
none of the above
B.
caused by CO2, CFCs, CH4 and NO2 gases
A Greenhouse gas is a gas that absorbs and emits radiant energy within the thermal infrared range. It causes the greenhouse effect. Green-house effect is caused by CO2, CFCs, CH4 and NO2.
In C4 plants, CO, fixation is done by
mesophyll cells
guard cells
sclerenchyma
chlorenchyma and hypodermis
A.
mesophyll cells
In C4 plants, CO2 is picked up by phosphoenol pyruvate (PEP) in the cytoplasm of mesophyll cells.
C4 plants have better productivity because
C4 plants absorb more light
C4 plants absorb more CO2
C4 plants lack photorespiration
all of these
C.
C4 plants lack photorespiration
Presence of photorespiration is considered as a wasteful and energy consuming process in crop plants which ultimately leads to reduction in final yield of crops. It is estimated that during C4 photosynthesis, upto 50% of the CO2 fixed may have to pass through photorespiratory process, thereby resulting in considerable decrease in photosynthetic productivity. In C4 plants, there is some loss of photosynthetic activity on account of photorespiration which is absent in C4 plants and hence they have better productivity.
Assertion: Photorespiration is a wasteful process where there is no synthesis of ATP energy.
Reason: RuBisCO is present in mesophyll cells of C4 plants hence they show more productivity.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
C.
If assertion is true but reason is false.
Photorespiration does not produce energy or reducing power. Rather it consumes energy.
In C4 plants, photorespiration, does not occur. Here, RuBisCO is located only in bundle sheath cells where photosynthetic release of oxygen does not occur. Bundle sheath cells have a high intracellular concentration of CO2 due to flow of C4 acids and their decarboxylation to release CO2.
Therefore, RuBisCO functions purely as carboxylase in C4 plants. They show high productivity and hence higher yield.
The 1st CO2 fixation product of C4 plant is
Oxaloacetic acid
ribulose biphosphate
phosphoenolpyruvate
phosphoglyceric acid.
A.
Oxaloacetic acid
In C4 Plants, initial fixation of carbon dioxide occurs in mesophyll cells. The primary acceptor of CO2 i.e. phosphoenol pyruvate (PEP) combines with CO2 in the presence of PEP carboxylase or PEPcase to form oxaloacetic acid, which is the first stable carbon dioxide fixation product in C4 pathway.
Photosynthesis in C4 plants is relatively less limited by atmospheric CO2 levels because
there is effective pumping of CO2 into bundle sheath cells
RuBisCO in C4 plants has higher affinity for CO2
six carbon acids are the primary initial CO2 fixation products
the primary fixation of CO2 is mediated via PEP carboxylase.
D.
the primary fixation of CO2 is mediated via PEP carboxylase.
CO2 acceptor molecule in C4 plants is phosphoenol pyruvate (PEP). C4 plants are more efficient in picking up CO2 even when it is found in low concentration because of high affinity of PEP. PEP carboxylase (PEPcase) is the key enzyme which catalyses the primary fixation of CO2.
The chemiosmotic coupling hypothesis of oxidative phosphorylation proposes that adenosine triphosphate (ATP) is formed because
a proton gradient forms across the inner mitochondrial membrane
there is a change in the permeability of the inner mitochondrial membrane towards adenosine diphosphate (ADP).
high energy bonds are formed in mitochondrial proteins
ADP is pumped out of the matrix into the intermembrane space
A.
a proton gradient forms across the inner mitochondrial membrane
The chemiosmotic hypothesis was given by Mitchell. It explains the process of ATP formation and states that it is linked to development of proton gradient across the mitochondrial membrane. ATP synthase is required for ATP synthesis is located in F1 particles. It becomes active only when there is high concentration of proton on F0 side as compared to F1 side.
Carbon dioxide is necessary for photosynthesis. The chemical used to remove this gas most effectively from entering a control apparatus is
calcium oxide
distilled water
potassium hydroxide solution
sodium carbonate.
C.
potassium hydroxide solution
Like other alkali metals, potassium hydroxide combines with CO2 as such:
2KOH+CO2 K2CO2 +H2O
Assertion: In light reaction of photosynthesis, light is required for the functioning of PS I and PS II, and production of NADPH and ATP.
Reason: Dark reaction does not occur in light.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
C.
If assertion is true but reason is false.
Light reactions of photosynthesis take place in the presence of light. These involve photolysis of water and production of assimilatory power (NADPH + ATP) through PS I and PS II.
Dark reactions of photosynthesis catalyse assimilation of CO2 to carbohydrates. Dark reactions are light independent reactions, hence can take place both in the light as well as in the dark
Assertion : CAM plants lack structural compartmentation of leaf as found in C4 plants.
Reason : Stomata of CAM plants are open during the day.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
C.
If assertion is true but reason is false
CAM plants do not exhibit the structural compartmental as shown by C4 plants which exhibit kranz anatomy. CAM plants fix CO2 at night because their stomata are open at night and remain closed during the day.
Assertion: Photorespiration interferes with the successful functioning of Calvin cycle.
Reason: Photorespiration oxidises ribulose1,5 biphosphate which is an acceptor of CO2 in Calvin cycle.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
A.
If both assertion and reason are true and reason is the correct explanation of assertion.
In the 1920s, the German biochemist Otto Warburg (1883-1970) discovered that plants consumed oxygen at a higher rate when they were illuminated. He also found that this increased rate of oxygen consumption inhibited photosynthesis. Stimulation of oxygen consumption by light is now referred to as photorespiration. Biochemical studies indicate that photorespiration consumes ATP and NADPH, the high-energy molecules made by the light reactions. Thus, photorespiration is a wasteful process because it prevents plants from using their ATP and NADPH to synthesize carbohydrates.
RuBISCO, the enzyme which fixes carbon dioxide during the Calvin cycle, is also responsible for oxygen fixation during photorespiration. In particular, carbon dioxide and oxygen compete for access to RuBISCO. RuBISCO's affinity for carbon dioxide is much higher than its affinity for oxygen. Thus, fixation of carbon dioxide typically exceeds fixation of oxygen, even though atmospheric carbon dioxide levels are about 0.035% whereas oxygen is about 21%.
Which of the following is the characteristic of PS-I?
It is active only upto 680 nm of light.
The reaction centre of PS- I is P680.
PS- I is reduced by the electrons released in photolysis of water.
PS-I is involved in non-cyclic photophosphorylation.
D.
PS-I is involved in non-cyclic photophosphorylation.
Photosystem- I is found in the non appressed part of grana thylakoids as well as stroma thylakoids. Chlorophyll : carotenoid content is high. Its photocenter is P700. This photosystem receives electrons from Photosystem II. It is involved in both cyclic and non- cyclic photophosphorylation.
Assertion : Dark reaction occurs only at night in the stroma of chloroplast.
Reason : CO2 fixation occurs only during C3 cycle.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
D.
If both assertion and reason are false
Dark reaction is also known as light independent phase. Unlike, light reaction, it does not require light as an essential factor. Thus can take place both in the presence or absence of light.
The term dark reaction does not mean that it takes place only in dark period or at night. CO2 fixation occurs in both C3 and C4 cycle. In C3 cycle, CO2 is added by the enzyme, RuBisco to a 5 carbon compound RuBP that is ccnverted to 2 molecules of 3-carbon PGA. In C4 cycle the first product of CO2 fixation (takes place in mesophyll) is a 4-carbon compound, oxaloacetic acid. It is seen in some tropical plants.
In succulent plants the stomata open in night and close in day. Which among the following would be best hypothesis to explain the mechanism of stomatal action in night only.
CO2 accumulates, reduces pH, stimulate enzymes resulting in accumulation of sugars.
Increase in CO2 concentration, conversion of organic acids into starch resulting in the increased conversion into sugars resulting in K+ transport.
Low CO2 concentration accumulates organic acids resulting in the increased concentration of cell sap.
CO2 used up, increase pH results in accumulation of sugars.
B.
Increase in CO2 concentration, conversion of organic acids into starch resulting in the increased conversion into sugars resulting in K+ transport.
In CAM plants stomata open at night. In these plants night acidification occurs. i.e., malic acid is
synthesised during night due to incomplete oxidation of carbohydrates.
In night. 2 C 6H12O6+ 3 O2 3 C 4H6O5+ 3H2O
(malic acid)
leads to opening of stomata
At night malic acid formed in guard cells dissociates into H and malate ions. K ion exchange from subsidiary cells with H ions. Thus due to accumulation of K ions osmotic pressure of guard cells increases, endosmosis occurs and guard cells become turgid due to which stomata opens. The malic acid at clay time breaks into CO2 and pyruvic acid thus increasing the concentration of CO2 in mesophyll cells. This is utilised in Calvin cycle to form sugar which is finally converted into starch.
Chlorenchyma is known to develop in the
cytoplasm of Chlorella
mycelium of a green mould such as Aspergillus
spore capsule of a moss
pollen tube of Pinus
C.
spore capsule of a moss
Chlorenchyma or assimilatory parenchyma are parenchymatous cells that possess abundant chloroplasts in them. They are capable of photosynthesis. A spore capsule of moss can perform photosynthesis because of the presence of chlorenchyma cells in them.
Velamen present in orchids helps in
absorption of nutrients from host plant
respiration
absorption of moisture from air
synthesising food
C.
absorption of moisture from air
Some epiphytes eg., orchids have aerial roots. In these roots the outer covering is made up of a spongy tissue called velamen which absorbs moisture from the air. Thus, the aerial plant can prepare food by photosynthesis.
Assertion: The higher concentration of O2 in the atmosphere is inhibitory to photosynthesis.
Reason: CO2 is the main substrate of photosynthesis.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false.
B.
If both assertion and reason are true but reason is not the correct explanation of assertion
Oxygen accumulation causes substantial inhibition of photosynthesis. Both oxygen evolution and CO2 assimilation were reduced in the presence of atmospheric oxygen. Oxygen causes a direct and indeed competitive inhibition of Ribulose diphosphate carboxylase. As a result glycolate synthesis is enhanced and leads to begin photorespiration. Carbon dioxide being one of the raw materials for photosynthesis, its concentration affects the rate of photosynthesis markedly. Because of its very low concentration in atmosphere (0.03 per cent only) it acts as a limiting factor in natural photosynthesis.
Assertion : Dark reaction is purely enzymatic reaction.
Reason : It occurs only in absence of light.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
C.
If assertion is true but reason is false
Photosynthesis is actually oxidation reduction process in which water is oxidised and CO2 is reduced to carbohydrates.
Both ATP and NADPH2 are required for reduction of CO2. But this reduction is independent of light, ie, it occurs in presence or absence of light. Hence, it is known as light reaction and light independent part is known as dark reaction. It occurs in stroma of chloroplast. Also known as Blackman's reaction.
What is common between chloroplasts, chromoplasts and leucoplasts
Presence of pigments
Possession of thylakoids and grana
Storage of starch, proteins and lipids
Ability to multiply by a fission-like process
D.
Ability to multiply by a fission-like process
Chloroplast, chromoplast and leucoplast are all types of plastids which are classified on the basis of pigments they contain. Plastids are semiautonomous cell organelles bounded by two membranes and arc found in only plant cells & some unicellular organisms (Euglena) of uncertain affinity. The common among all the three organelles are that they have ability to multiply by a fission like process because these organelles contain there own genetic material and protein synthesizing machinery, i.e.. DNA, RNA and ribosomes.
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 light energy for carboxylation to proceed, the excess energy may not cause damage to plants.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false.
C.
If assertion is true but reason is false
Photorespiration protects the plants from photoxidative damage by dissipating excess of excitation energy. When the CO2 supply is limited and under high light intensity photorespiration takes place thus protecting the plants. If enough CO2 is not available to utilize light energy for carboxylation to proceed, the excess energy will cause photoxidative damage to the plants. The energy liberated should be used in photophosphorylation in presence of CO2. If CO2 is less then in C3 plants O2 combines with RuBP to form phosphoglycollatc thus utilizing the excess energy.
Assertion: Photosynthetically C4 plants are less efficient than C3 plants.
Reason: The operation of C4 pathway requires the involvement of only bundle-sheath cells.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is falsen
If both assertion and reason are false.
D.
If both assertion and reason are false.
C4 plants are those plants that produce C4 compound like malic acid or aspartic acid as the first stable compound of CO, fixation cycle, eg. maize. sugar cane etc. These plants can grow in dense tropical, forests where there is poor supply of CO2 because there is internal supply of CO2 Also photorespiration is negligible or absent in these plants. So, they are photosynthetically more efficient than C3 plants. These plants show a special type of leaf anatomy called Kranz anatomy. C4 plants uses mesophyll cells and bundle sheath cells in the outer part of their leaves. The C4 pathway shows 2 carboxylation reactions one in mesophyll chloroplast and the other in bundle sheath. Chloroplasts- CO2 acceptor is PEP and not RuBP and PEP carboxylase is the key enzyme.
The sugarcane plant has
dumb-bell shaped guard cells
pentamerous flowers
reticulate venation
capsular fruits.
A.
dumb-bell shaped guard cells
Guard cells are semilunar or kidney shaped cells which surrounds the minute apertures of epidermis called stomata. Guard cells are living and have chloroplast. In sugarcane and in some other monocots like doob, maize guard cells are dumb bell shaped.
Assertion : C4 photosynthetic pathway is more efficient than the C3 pathway.
Reason : Photorespiration is suppressed in C4 plants.
If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion
If both Assertion and Reason are true but the Reason is not the correct explanation of the assertion
If Assertion is true but Reason is false
If both Assertion and Reason are false
A.
If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion
C4 photosynthetic pathway is more efficient than C3 pathway as C4 plants can pick up CO2 even when it is found in low concentration. PEP enzymes shows high affinity for CO2. C4 plants contain two types of chloroplast : bundle sheath chloroplast and mesophyll chloroplast. Bundle sheath cells contain Calvin cycle enzymes. Due to high concentration of CO2 in bundle sheath cells, RuBP carboxylase works only for Calvin cycle and not for photorespiration.
Photorespiration works to undo the act of photosynthesis in C3 plants. No energy rich compound is produced in this process. When temperature increase more and more photosynthetically fixed carbon is lost by photorespiration, thus reducing the efficiency of C3 plants.
Assertion : The atmospheric concentration of CO2 at which photosynthesis just compensates for respiration is referred to as CO2 compensation point.
Reason : The CO2 compensation point is reached when the amount of CO2 uptake is less than that generated through respiration because the level of CO, in the atmosphere is more than that required for achieving CO2 compensation point.
If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion
If both Assertion and Reason are true but the Reason is not the correct explanation of the assertion
If Assertion is true but Reason is false
If both Assertion and Reason are false
C.
If Assertion is true but Reason is false
A very low CO2 concentration photosynthesis is strongly limited by the low CO2 while respiratory rates are unaffected. As a result, there is a negative balance between CO2 fixed by photosynthesis and CO2 produced by respiration and a net efflux of CO2 from the plant. By increasing the atmospheric concentration of CO2 at which photosynthesis just compensate for respiration is referred to as CO2 compensation point.
Photorespiration in C3 plants starts from:
phosphoglycerate
phosphoglycolate
glycerate
glycine
B.
phosphoglycolate
In the process of photorespiration oxygen combines with RuBP (Ribulose- biphosphate) in chloroplast as following
O2 + RuBP 3- Phosphoglycerate +
2- Phosphoglycerate CO2
Phosphoglycolate enters in peroxisomes and is finally converted to CO2.
Hill reaction occurs in:
high altitude plants
total darkness
absence of water
presence of ferricyanide
D.
presence of ferricyanide
Hill reaction is the light phase or photochemical phase of photosynthesis which consists of light driven splitting of water or photolysis, evolution of oxygen and synthesis of assimilatry power (ATP and NADPH). An enzyme complex, Mn, Cl and ferricyanides are required for this reaction. An overview of hill reaction is as
Which one of the following pairs is correctly matched?
Rhizobium - Parasite in the roots of leguminous plants
Mycorrhizae - Mineral uptake from soil
Yeast - Production of biogas
Myxomycetes - The disease ring worm
B.
Mycorrhizae - Mineral uptake from soil
Mycorrhiza is an example of mutualism. Mutualism is an interaction between two or more species where fitness is increased through direct interaction. It is an association between a fungus and the root of a higher plant. eg. Pine, Birch.
The fungus obtains shelter and food from root and helps the root in absorption of water, dissolution and absorption of inorganic nutrients locked in organic matter (especially nitrogen and phosphorus) and protection from other fungi.
Assertion : Rhoeo leaves contain anthocyanin pigments in epidermal cells.
Reason : Anthocyanins photosynthetic pigments.
If both Assertion and Reason are true and the reason is the correct explanation of the assertion
If both Assertion and Reason are true but the reason is not the correct explanation of the assertion
If Assertion is true statement but Reason is false
If both Assertion and Reason are false statements
C.
If Assertion is true statement but Reason is false
Anthocyanin is a colouring pigment of certain higher plants that imparts a bluish or reddish colour.
Rhoeo leaves contain anthocyanin pigments in epdiermal cells. They are present in lower epidermis. Anthocyanins belong to the group of flavonoid pigments. They are water soluble and able to change color with change of pH.
Stomata open at night and closes during day in
xerophytes
gametophytes
mesophytes
mesophytes
A.
xerophytes
Crassulacean acid metabolism, also known as CAMphotosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. In a plant using full CAM, the stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide (CO2).
During photosynthesis
both CO2 and water get oxidized
both CO2 and water get reduced
water is reduced and CO2 is oxidized
CO2 gets reduced and water gets oxidized
D.
CO2 gets reduced and water gets oxidized
Photosynthesis is an oxidation reduction process where H2O is oxidised by photolysis into O and CO2 is reduced to carbohydrate.
The order of occurrence of the cytochromes in the F1 particle is
cyt-b, cyt-c, cyt-a-cyt a3
cyt-c, cyt-b, cyt-a-cyt a3
cyt-a, cyt-b, cyt-c-cyt a3
cyt-a3, cyt-a, cyt-c-cyt b
A.
cyt-b, cyt-c, cyt-a-cyt a3
The order of occurrence of the cytochromes in the F1 particle present in mitochondrial cristae is cyt-b, cyt-c, cyt-a, cyta3. They accept electron and pass on to the other cytochrome.
Chemiosmotic theory of ATP synthesis, in the chloroplast and mitochondria, is based on :
proton gradient
membrane potential
accumulation of K ions
accumulation of Na ions
A.
proton gradient
The chemiosmotic theory of ATP synthesis, in the chloroplast and mitochondria is based on proton gradient. This proton gradient across the membranes represents the potential for ATP formation.
Photorespiration in C3 -plants starts from :
glycine
glycerate
phosphoglycolate
phosphoglycerate
C.
phosphoglycolate
Photorespiration in C3 -plants starts from phosphoglycolate. Phosphoglycolate is formed in chloroplast which represents the source of carbon dioxide released in photorespiration. Its phosphate group is first hydrolyzed away by a specific phosphatase found in chloroplasts of C3 -plants releasing Pi and glycolic acid. The glycolate then moves out of chloroplasts into the adjacent peroxisomes.
Which of the following is photophosphorylation?
Production of ATP from ADP
Production of NADP
Synthesis of ADP from ATP
Production of PGA
A.
Production of ATP from ADP
Photophosphorylation is the synthesis of ATP from ADP during light reaction of photosynthesis. It was discovered by Amon et al, in 1954.
From which of the following, photosynthetic autotrophs receive their energy?
Heat
Inorganic chemicals
Organic chemicals
Light
D.
Light
Photosynthesis is the synthesis of organic compounds (primarily sugars) from carbon dioxide (CO2) and water using light energy. The green cells of the plant convert the solar energy into chemical energy through this process. It's importance lies in the transformation of low energy compounds ie, CO2 and H2O into high energy compounds such as carbohydrates.
Plants purify air by which process?
Photorespiration
Photosynthesis
Photophosphorylation
Transpiration
B.
Photosynthesis
During photosynthesis, carbon dioxide is reduced into carbohydrates and oxygen is liberated, ie, plants purify air by process of photosynthesis.
Photorespiration is a respiratory process by which they take up oxygen in the light and give out some carbon dioxide, contrary to the general pattern of photosynthesis. It takes place in higher plants.
Photophosphorylation is the synthesis of ATP from ADP and phosphate that occurs in a plant using radiant energy absorbed during photosynthesis.
Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. It is the evaporation of water from plant leaves.
Sunken stomata occur in
xerophytes
hydrophytes
mesophytes
opsanophytes
A.
xerophytes
A sunken stomata is a stomata in a small pit, which protects the escaping water vapor from air currents, decreasing water loss from the leaf. Sunken stomata are commonly found in plants in arid environments as one of their adaptations to preserve water.
Dimorphism of chloroplast is found in
C3 - plants
C4 - plants
CAM plants
Both (b) and (c)
B.
C4 - plants
C4 plants have Kranz anatomy. The chloroplasts of the mesophyll cells are smaller and have well developed grana, while the chloroplasts of bundle sheath cells are agranal, ie, dimorphic chloroplasts are found in C4 plants.
The first carbon dioxide fixation in C4 pathway occurs in chloroplasts of
guard cells
mesophyll cells
bundle sheath cells
epidermal cells
B.
mesophyll cells
Tips: -
In C4 plants, initial CO2 fixation occurs in mesophyll cells. The primary acceptor of CO2 is phosphoenol pyruvate (PEP). It combines with carbon dioxide in presence of PEP carboxylase to form oxaloacetic acid.
CO2 acceptor in C3 cycle is
OAA
RuBP
PEP
Malic acid
B.
RuBP
Primary carbon dioxide acceptor in C4 plant is phosphoenol pyruvic acid,it contains 3 carbon atoms. in C3 plants ribulose 1,5 bisphosphate (RUBP) is the primary CO2 acceptor. It is a 5 carbon compound. In C4 plants phospho enol pyruvate (PEP) is primary CO2 acceptor.
In a CAM plant, the concentration of organic acid
increases during the day
decreases or increases during the day
increases during night
decreases during any time
C.
increases during night
Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. In a plant using full CAM, the stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide (CO2).
Chloroplast dimorphism is a characteristic feature of
plants with Calvin cycle
C4 -plants
all plants
only in algae
B.
C4 -plants
Chloroplast dimorphism means there are two different types of chloroplasts. It is mainly observed in C4 plants and is characteristic feature of these plants. Two types of chloroplasts are:
In which type of reactions related to plant photosynthesis peroxisomes are involved?
Glycolate cycle
Calvin cycle
Bacterial photosynthesis
Glyoxylate cycle
A.
Glycolate cycle
Peroxisome is a small organelle that is bounded by a single membrane. Peroxisome detoxify certain by-products of photosynthesis and oxidise glycolate (produced by photorespiration) to glyoxylate which can then be salvaged by a series of reactions involving mitochondria and chloroplasts as well as peroxisomes.
Example of water soluble plant pigment is
chlorophyll- a
chlorophyll- b
anthocyanin
xanthophyll
C.
anthocyanin
Anthocyanin is a water-soluble pigment. It constitute a class of natural phenolic product. These provide colour to petals and fruits.
Chlorophyll is a green pigment in all green plants and in cyanobacteria, which is responsible for the absorption of light to provide energy for photosynthesis.
Chlorophyll- a is the primary photosynthetic pigment and chlorophyll- b is the accessory pigment that collects energy and passes it on to chl- a.
Xanthophyll is a yellow or brown carotenoid plant pigment which causes the autumn colours of leaves.
Identify the membrane across which the proton (H+) gradient facilitates ATP synthesis in a typical eukaryotic cell
plasma membrane
mitochondrial inner membrane
mitochondrial outer membrane
nuclear membrane
B.
mitochondrial inner membrane
According to chemiosmotic hypothesis, put forward by Mitchell, the electron transfer chain present on the inner mitochondrial membrane generates an electrochemical proton concentration gradient across the membrane. This gradient works as the driving force for ATP synthesis.
Chlorophyll molecules are located in the
thylakoid membrane
thylakoid lumen
stroma
inner chloroplast membrane
A.
thylakoid membrane
The green pigment chlorophyll is located within the thylakoid membrane, and the space between the thylakoid and the chloroplast membranes is called the stroma.
Chlorophyll is specifically arranged in and around photosystems that are embedded in thylakoid membranes of chloroplasts. It also acts as a site of light dependent reactions of photosynthesis, while thylakoid lumen has vital role in photophosphorylation during photosynthesis, stroma is a colourless fluid has surrounding the grana within the chloroplast.
The correct sequence of organelles in which glycolate and glyoxylate are produced sequentially in photorespiration is
chloroplast and mitochondria
chloroplast and peroxisome
peroxisome and mitochondria
peroxisome and chloroplast
B.
chloroplast and peroxisome
Photorespiration is a light dependent phenomenon of oxygenation of RuBP and release of CO2 by the photosynthetic organs of a plant. The site of photorespiration is chloroplast.
Phosphoglycolate produced by RuBP oxygenase activity is converted to glycolate by phosphoglycolate phosphatase in the chloroplast. Glycolate then enters the peroxisomes and is converted to glyoxylate by glycolate oxidase.
Apart from chloroplast and peroxisomes, mitochondria is also involved in the photorespiratory process.
Identify the correct statements in relation to C4 photosynthesis.
Kranz anatomy is an essential feature for C4 plants
C4 plants have higher water use efficiency than C3 plants
Photorespiration can be minimised when C3 pathway is in operation
Conversion of oxaloacetate to malate occurs in the bundle sheath cells
A.
Kranz anatomy is an essential feature for C4 plants
B.
C4 plants have higher water use efficiency than C3 plants
C.
Photorespiration can be minimised when C3 pathway is in operation
C4 photosynthesis is the type of biochemical mechanisms (along with C3 and CAM) of photosynthesis used in carbon fixation. The leaves of C4 plants contains two types of chloroplasts, i.e., mesophyll chloroplast and bundle sheath chloroplast. This is known as Kranz anatomy. C4 plants also have higher water use efficiency than C3 plants. Also, if the C4 pathway is in operation in plants, the photorespiratory pathway tend to get minimised.
C4 pathway is advantageous over C3 pathway in plants as it
occurs in relatively low CO2 concentration
uses more amount of water
occurs in relatively low O2 concentration
is less efficient in energy utilisation
A.
occurs in relatively low CO2 concentration
Plants with the C4 pathway has many advantages over a plant with a C3 pathway. When the weather is hot, acid, dry, the leaves close their stomata to eliminate water less whereas in C3 plants this closure results in low carbon dioxide concentrations and ultimately both loss of RuBP and inhibition of the Calvin-Benson cycle by photorespiration.
There are no such disadvantages in a C4 plant during hot, dry weather. Even with its stomata are closed, carbon dioxide is fixed because of the efficiency of REP carboxylase in trapping and concentrating carbon dioxide. Consequently, the Calvin-Benson cycle continues to produce glucose and there is no loss of chemical energy through photorespiration.
Opening and closing of stomata is controlled by
abscisic acid
CO2 concentration
O2 concentration
light intensity
A.
abscisic acid
B.
CO2 concentration
D.
light intensity
Opening and closing of stomata depends upon the turgidity of guard cells. When the plant has excessive water, the guard cells are turgid and stomata opens. It also depends on CO2 concentration. When CO2 concentration is low is photosynthetic parenchyma, stomata open to absorb more gas. Also as the luminosity increases, the rate of photosynthesis also increases leading to stomatal opening.
ABA or Abscisic Acid is a stress hormone that during water stress conditions induces stomatal closing.
As compared to sun plants, the plants, which are adopted to low light intensity possess
more extended root system
very high rate of CO2 fixation
larger photosynthetic units
more extended shoot system
C.
larger photosynthetic units
As compare to sun plants the plants, which are adapted to low light intensity possess larger photosynthetic units.
How many pigment molecules constitute a single photosystem?
2500
250-400
2000
2
B.
250-400
Photosystem I and Photosystem II consists of 250 - 400 pigment molecules each.
Photosystems are functional and structural units of protein complexes involved in photosynthesis that together carry out the primary photochemistry of photosynthesis, i.e. the absorption of light and transfer of energy and electrons.
Oxygen released in photosynthesis comes outby
photophosphorylation
photolysis of water
photorespiration
Kelvin cycle
B.
photolysis of water
Oxygen released in process of photosynthesis, comes out by photolysis of water in non- cyclic photophosphorylation. The photolysis of water occurs in presence of manganese (Mn). After the photolysis, the released electron is received by Photosystem-ll and then through electron carriers it moves to Photosystem-I.
Glycolate accumulates in chloroplast there is
low CO2
high CO2
bright light
low temperature
A.
low CO2
Glycolate is a respiratory substrate in photo respiration, which is formed in high concent ration of O2 but low concentration of CO2 under the influence of RuBP oxygenase in chloroplast. When temperature and CO2 content are high the affinity of RuBP carboxylase increases for O2 but decreases for carbondioxids. Glycolate is produced as intermediate in C3 cycle.
Which of the following inhibits O2 release in light phase?
Zeatin
PMA
DCMU
None of these
C.
DCMU
DCMU is a very specific and sensitive inhibitor of photosynthesis (photosynthetic inhibitors). It blocks the plastoquinone binding site of photosystem II, disallowing the electron flow from photosystem II to plastoquinone. Thus, it inhibits Hill reaction, by inhibiting release of O2.
First transistory chemical formed by reaction between CO2 and RUBP is
PGA
PGAL/ GAP
dihydroxy acetone phosphate
2 carboxy, 3-keto, 1-5 biphosphoribotol
D.
2 carboxy, 3-keto, 1-5 biphosphoribotol
During first phase, also known as carboxylation, of Calvin cycle RUBP or Ribulose-1, 5-biphosphate combine with CO2 in the presence of RUBP carboxylase or rubisco. It produces a transient intermediate compound 2 carboxy, 3-keto, 1-5 biphosphoribotol.
The carboxylating enzyme present in bundle sheath cells of maize leaves is
RUBP carboxylase
hexokinase
carbonic anhydrase
PEP-carboxylase
A.
RUBP carboxylase
Maize is a C4 -plant having distinct Kranz anatomy and two carboxylation enzymes. One is present in the mesophyll cells of chloroplasts and the other in the bundle sheath cells.
PEP- Carboxylase is present in the mesophyll cell and RUBP carboxylase is present in the bundle sheath cells.
The maximum elements found in cytoplasm is
C
He
H
N
C.
H
Hydrogen (H) is the main constituent of water carbohydrates, proteins and fats and many other constituents of protoplasm.
Calvin cycle takes place in
grana
stroma
intra thylakoid
matrix
B.
stroma
Calvin cycle (dark reaction) takes place in stroma of the chloroplast.
Which of the following is formed in light reaction of photosynthesis?
ATP
NADPH2
O2
All of the above
D.
All of the above
The assimilatory power (ATP and NADPH2) and oxygen forms in the light reaction of photosynthesis.
The plant group in which stomata opens in night is
mesophytes
succulents
hydrophytes
None of the above
B.
succulents
To control loss ofwaterthrough transpiration in succulent plants stomata opens in night. These plants also called as CAM plants.
Chlorophyll- a is characterized by the side group
methyl
aldehyde
phytol
ketone
A.
methyl
Chlorophyll- a has R CH, (methyl group) and chlorophyll- b has R CHO (aldehyde group).
Photorespiration takes place in plants where carbon fixation occurs through
Calvin cycle
Hatch and Slack cycle
Glycolysis
Krebs' cycle
A.
Calvin cycle
Photorespiration or (C2-cycle) occurs only in C3 plants.
Blackman's law of limiting factor is applied to
respiration
transpiration
photorespiration
photosynthesis
D.
photosynthesis
Blackman's law of limiting factors states that when a process is conditioned as to its rapidity by a number of separated factors, the rate of the process is limited by the pace of slowest factor, i.e., factor present in minimum amount.
In sugarcane plant, 14CO2 is fixed in a malic acid, in which the enzyme that fixes CO2 is
ribulose phosphate kinase
fructose phosphatase
ribulose biphosphate carboxylase
phosphoenol pyruvic acid carboxylase
D.
phosphoenol pyruvic acid carboxylase
In C4 -plants, CO2 is picked up by phosphoenol pyruvate (PEP) and the reaction being catalysed by PEP carboxylase.
Which one of the following is wrong in relation to photorespiration?
It is a characteristic of C4 -plants
It is a characteristic of C3 -plants
It occurs in chloroplasts
It occurs in daytime only
A.
It is a characteristic of C4 -plants
Dicker and Tio (1959) discovered photorespiration in tobacco plant. It is a light dependent process of oxygenation of ribulose bis phosphate (RuBP). During this process, carbon dioxide is liberated and oxygen is consumed. C4 -plants avoid photorespiration by following Hatch Slack Pathway.
Stomata of CAM plants
open during the night and close during the day
never open
are always open
open during the day and close at night
A.
open during the night and close during the day
CAM (Crassulacean Acid Metabolism) plants open stomata only at night (when temperature is low and humidity is high) to cause lesser loss of water (eg, Agave, Opuntia, etc).
Boron in green plants assists in
photosynthesis
sugar transport
activation of enzymes
acting as enzyme cofactor
B.
sugar transport
Boron is required by plants for the following reasons:
(i) uptake and utilisation of C2+
(ii) pollen germination arid cell differentiation
(iii) carbohydrate translocation.
Who proved that oxygen evolved in photosynthesis comes from water?
Mayer
Calvin
Ruben, Hassid and Kamen
Blackman
C.
Ruben, Hassid and Kamen
Ruben, Hassid and Kamen (1941) using heavy isotope of oxygen, 18O in water, found that oxygen evolved in photosynthesis comes from water.
Stomata open or close due to the ion
Ca2+
Na+
K+
Cu+
C.
K+
Opening and closing of stomata takes place due to the presence of K+ ion. When guard cellspossess more K+, endosmosis takes place, guard cells become turgid and stomata opening takes place.
The specific character of C4 plants is
bulliform cells
Kranz anatomy
parallel venation
isobilateral leaf
B.
Kranz anatomy
The C4 plants have Kranz anatomy. The vascular bundle of the leaf is surrounded by one or more layer of chloroplast, containing cells (bundle sheath cells). The bundle sheath cells lack grana in their chloroplast while mesophyll cells have well developed grana. The mesophyll cells are specialized for light reaction and initial CO2 fixation during photosynthesis. The CO2 is finally fixed inside bundle sheath cell through Calvin cycle.
In CAM plants, CO2 acceptor is
RuBP
PEP
OAA
PGA
B.
PEP
In CAM or Crassulacean Acid Metabolism plants, spatial separation of initial PEP carboxylase fixation and final Rubisco fixation of CO2, occur in the same cell, but at different times i.e. night and day, eg, Opuntia, pineapple, Vanilla.
PEP (Phosphoenol Pyruvic Acid) is the first acceptor of CO2 in CAM plants like C4 plants.
Law of limiting factor was given by
Leibig
Blackman
Calvin
Arnon
B.
Blackman
Law of minimum was given by Liebig. It states that when a process, such as growth, is governed by a number of separate factors, the rate of the process is limited by pace of slowest factor.
Blackman' (1905) extended the law of minimum to formulate the law of limiting factors which in his own words is when a process is conditioned as to its rapidity by a
number of separate factors, the rate of the process is limited by the pace of slowest factor.
Calvin (1954) (Nobel Prize winner) traced the path of carbon in photosynthesis.
Amon (1960) demonstrated cychic and non-cyclic photophosphorylation.
Which one of the following contain agranal chloroplasts?
C3 plants
Succulants
C4 plants
Hydrophytes
C.
C4 plants
Mesophyll cells of C4 plants consists of granular chloroplast whereas bundle sheath cells consists of agranular chloroplast. They are deficient in PS- II or Photosystem- II activity.
For synthesis of one hexose sugar, how many times Calvin cycle is turned ?
12
2
6
3
C.
6
Each Calvin cycle consume one carbon from CO2. Therefore, to generate one hexose sugar the Calvin cycle turns 6 times.
The number of chlorophyll molecules in a quantasome is
50- 100
200- 250
300- 400
500- 600
B.
200- 250
The quantasome is the smallest group of photosynthetic pigment molecules. It has 200-250 chlorophyll molecules.
Active K+ exchange mechanism for opening and closing of stomata was given by
Darwin
Levit
Scarth
Khorana
B.
Levit
The modern theory or K+ pump hypothesis for opening and closing of stomata was given by Levit, 1964.
Photosynthetic bacteria have :
pigment system I (only one pigment system)
pigment system II
both (a) and (b)
some other type
A.
pigment system I (only one pigment system)
PS I or photosystem I is present in photosynthetic bacteria. The photosynthetic pigments are located in the lamallae of thylacoid called chromatophores. The oxygen is not evolved in bacterial photosynthesis.
Most effective wavelength of light photosynthesis is :
green
violet
red
yellow
C.
red
The Photosynthetically Active Radiation (PAR) has a wavelength between 400-700 nm. But the most effective wavelength of light for photosynthesis is red (660-760 nm).
C4 plants, synthesis of sugars/final CO2 fixation occurs in:
palisade cells
spongy cells
undifferentiated mesophyll cells
bundle sheath cells
D.
bundle sheath cells
In C4 plants, CO2 fixation occurs inside the bundle sheath cell through calvin cycle. RuBP of calvin cycle is called secondary or final acceptor of CO2 in C4 plants.
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