MP Board Class 11th Biology Important Chapter 13 Photosynthesis in Higher Plants

Photosynthesis in Higher Plants  Class 11 Important Questions Very Short Answer Type

Question 1.
What is Photosynthesis? Explain it with chemical reaction.
Answer:
Photosynthesis: Photosynthesis is a chemical process by which green plants synthesize carbohydrate like simple food materials from carbon dioxide and water in the presence of sunlight. Water molecules are oxidized and CO2 molecules are reduced by this process. Photosynthesis is expressed with the help of following chemical reaction :
MP Board Class 11th Biology Important Questions Chapter

Question 2.
Name the products of light reaction of photosynthesis process.
Answer:
The products of light reaction of photosynthesis process are ATP and NADPH2.

Chapter 16 Digestion and Absorption

Question 3.
What are Hill reagents or Hill’s oxidizing agents?
Answer:
Hill observed that evolution of O2 was possible when chloroplast of Stellaria media suspended in water in absence of CO2 were exposed to light and supplied with salts such as ferricyanides, benzoquinones, dichlorophenol, which served as hydrogen acceptors. These substances are called as Hill reagents.

Question 4.
Name the photosynthetic pigments found in bacteria.
Answer:
Photosynthetic pigments found in the bacteria are :

  • Bacteriochlorophyll,
  • Bacterioviridin
  • Carotenoids etc.

Question 5.
Name any two insectivorous plants.
Answer:

  1. Nepenthes,
  2. Drosera.

Question 6.
Write any two differences between CAM and C4 plants.
Answer:
Differences between CAM and C4 plants

CAM plants C4 plants
1. They are succulent plants of family Crassulaceae. They are monocot plants with Kranz anatomy in their leaves.
2. Two carbon cycles are separate due today and night. Two carbon cycles are separate due to Kranz anatomy of leaves.

Photosynthesis in Higher Plants  Class 11 Important Questions Short Answer Type 

Question 1.
Give one example to prove that oxygen released during photosynthesis pro-cess is oxygen of water, not of CO2.
Answer:
The oxygen liberated during photosynthesis is a part of water molecule. This is proved by Rubem and Camanis experiment. For this process such type of water is taken whose oxygen contains O18 isotopes and after equation the oxygen liberated is also O18.
MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 2
By this experiments it is proved that after photosynthesis the liberated O2 is the part of water molecule.

Question 2.
What is compensation point of Light intensity?
Answer:
Afternoon when intensity of light is high, rate of photosynthesis is high so plants releases O2 whereas at night when there is no sunlight, photosynthesis process does not occur but during morning and evening when there is less intensity of light rate of photosynthesis become very low, equal to rate of photosynthesis.

Therefore, during this time O2 released during photosynthesis process is totally used for respiration process and CO2 produced during respiration is toally used up for photosynthesis process by the plant, thus there is no net release of any gas during this time. This condition is called as compensation point.

Question 3.
Describe Hill Reaction in 50 words and give required chemical reactions.
Answer:
Hill reaction : It is the first step of photosynthesis process, which occurs in the grana part of the chloroplast.
It occurs in the presence of light and it was discovered by scientist Hill. It is completed in following steps:
1. Photophosphorylation :

MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 3

2. Photolysis of water :
12H2O → 12H+ +12OH
12OH -12e →12OH
12OH → 6H2O + 3CO2

3. Hydrogenation :
MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 3

Question 4.
Give significance of Photosynthesis process.
Answer:
Significance of Photosynthesis process :

  • By this process green plants not only produces food for themselves but also for all other organisms. Thus, green plants are also called as producers.
  • Plants uses harmful CO2 from the atmosphere to prepare organic food and releases 02 into the atmosphere, thus help to maintain O2-CO2 balance in the nature.
  • It regulates temperature by absorbing sunlight.
  • By absorbing CO2 from the atmosphere it helps to reduce global warming.

Question 5.
Give affect of Light and CO2 on photosynthesis process.
Answer:

  • Affect of Light: Rate of photosynthesis increases with increase in the intensity of light and decreases in less intensity of light. Colour of light also affect rate of photosynthesis. Rate of photosynthesis is highest in red light, in blue light rate of photosynthesis is second highest. Greenlight is reflected back by chlorophyll molecule, thus rate of photosynthesis is nil in green light.
  • Affect of CO2: Rate of photosynthesis increases with increase in the quantity of CO2 but up to a certain limit (according to law of limiting factor) beyond which there is no effect.

Question 6.
Explain any two internal factors which affect photosynthesis process.
Answer:
Internal factors affecting photosynthesis process :

  1. Chlorophyll: The amount of chlorophyll present in the plant part has a direct relationship with the rate of photosynthesis because it is the pigment which is photoreceptive and is directly involved in trapping the light energy.
  2. Accumulation of end products: The rate of translocation of food manufactured in the leaves decreases in the afternoon and therefore it starts accumulating in the mesophyll cells. The accumulation of the end product decreases the rate of photosynthesis in the afternoon.

Question 7.
If a leaf is kept in a dark room then its colour gradually become yellow and greenish-yellow. Which pigment is more stable according to your view ? (NCERT)
Answer:
Chlorophyll-b is more stable which is yellow-green coloured pigment and Xanthophyll (Yellow pigment) in the leaves are more stable.

Chapter 16 Digestion and Absorption

Question 8.
Two sides of dorsiventral leaves are different in colour, Le., upper part is dark as compared to lower part or compare leaves of the plants kept in the shade with plants kept in light. Which one is dark coloured and why? (NCERT)
Answer:
In dorsiventral leaves upper surface of the leaves contain more chlorophyll-a. Place where chlorophyll-a is found increases rate of absorption of light as compared to lower part. Part of the leaf where more chlorophyll-a is found appears bright green coloured whereas part of the leaves which remain in the shade appears less green due to less quantity of chlorophyll-a.

Question 9.
What is Emmerson effect?
Answer:
Emmerson effect: During working on photosynthesis process Robert Emmerson determined quantum production (number of O2 molecules produced by absorption of one quantum light) of light of various wavelengths and found that quantum production is maximum in red light of680 nm. wavelength but when wavelength of this red light is increased more, then quantum production falls all of a sudden. This is called as Red drop.
Emmerson also observed that when less wavelength light is provided with red light of 680 nm. wavelength then quantum production increases again. This is called as Emmerson enhancement effect.

Question 10.
Can you identify observing external features whether the plant is C3 Or C4 plant?
Answer:
Generally C4 plants grow at high intensity of light at day temperature 30-35°C, i.e, in dry atmosphere whereas C3 plants grows in moderate temperature. C4 plants has special anatomy called as Kranz anatomy. Thus, unless we observe internal anatomy it is not possible to identify a plant whether it is Cor C4 plant.

Question 11.
Can you identify observing internal structure whether the plant is C3 or C4 plant?
Answer:
Anatomy of C4 shows that it has Kranz anatomy, i.e., (a) Presence of a double spiral bundle sheath cells tightly packed around the vascular bundle.
(b) Bundle sheath cells are connected with mesophyll cells by plasmodesmata.
(c) Leaves of C4 plants contain two types of chloroplasts :

  1. Mesophyll chloroplast: It is smaller, grana is present there and starch grains are absent.
  2. Bundle sheath chloroplast: It is larger in size, lacking grana and possessing starch grains.
    In C4 plants, CO2 fixation occurs by C3 and C4 cycle. C3 cycle occurs in the bundle sheath whereas C4 cycle occurs in the mesophyll cells.

Question 12.
RuBisCo is an enzyme which acts as carboxylase and oxygenase enzyme. Why you assume that RuBisCo is found in C4 plants does carboxylation in more quantity?
Answer:
RuBisCo enzyme shows more affinity to CO2 as compared to O2. Both CO2 and O2 may bind to the active site of this enzyme. This binding is competitive type. Binding of O2 or CO2 to the enzyme depends on concentration of these substances.
C4 plants has such a system that increases CO2 concentration in them. Thus, it acts as RuBisCo carboxylase in them and it cannot act like oxygenase.

Question 13.
Assume that here plants having higher concentration of chlorophyll-b were found, whereas chlorophyll-a deficient plants were less in number, were capable to do photosynthesis? Then why chlorophyll-b is found in the plants and what are the role of other minor pigments ? (NCERT)
Answer:
Chromatography of chlorophyll shows that green colour of leaves is due to presence of four pigments:

  1. Chlorophyll-a,
  2. Chlorophyll-b,
  3. Xanthophyll and
  4. Carotene.

Following diagram proof that maximum photosynthesis occurs in the area of blue and red light of the spectrum. Some photosynthesis occurs in other waves of the spectrum. Though chlorophyll-a is the main pigment which absorbs light, then also other pigments found in the thylakoid, such as Chlorophyll-b, Xanthophyll and carotene absorb light and transfer it to the chlorophyll-a. Thus, they are called as accessory pigments.
These pigments increases wave area which also prevent chlorophyll-a from photooxidation.
MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 5

Question 14.
Rate of photosynthesis is affected by light.
MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 6
Answer following questions on the basis of graph:
(a) At which points (A, B, C or D) of the graph light is the limiting factor.
(b) Which limiting factor lies at point A.
(c) What is represented by C and D in the graph.
Answer:
(a) At point B and C light is the limiting factor.
(b) At point A of the graph sunlight, temperature, CO2 concentration, water etc. fac-tors of photosynthesis are present and they altogether affecting photosynthesis at a time. Out of them anyone become main factor affecting photosynthesis process.

(c) C and D of the graph represent that there is linear relationship between low intensity of light and rate of CO2 assimilation.
At high intensity of light there is no increase in this rate but other factors become limiting.
After a limit incident, ray causes decomposition of chlorophyll molecule, due to which rate of photosynthesis decreases.

Chapter 16 Digestion and Absorption

Question 15.
Write differences between following : (NCERT)
(a) C and C4 Pathways.
(b) Cyclic and Non-Cyclic Photophosphorylation.
(c) Morphology of leaves of C and C4 plants.
Answer:
(a) Differences between C and C4 Pathways

C3 Pathway                           C4 Pathway
1. CO2 acceptor is RuDP [a 5 carbon compound] CO2 acceptor is PEP (phosphoenol pyruvate) [a 3 carbon compound].
2. First stable product is PGA (Phospho glyceric acid) First stable product is OAA (oxaloacetic acid.)
3. Excess of atmospheric O2 inhibits photosynthesis process. Excess of atmospheric O2 has no effect on photosynthesis.
4. There is only Calvin-Benson pathway. There is both Calvin-Benson and Hatch- Slack pathway.
5. Assimilation of one molecule of CO2 requires 2NADPFH2 and 3ATP molecules. Assimilation of one molecule of CO2 requires 2NADPH and 5ATP molecules.
6. Optimum temperature for photosynthesis is 10-25°C. The optimum temperature for photosynthesis is 30-45°C.
7. C3 path can be observed in temperate plants like potato, mango etc. C4 path can be observed in tropical grasses like sugar-cane, maize etc.

(b) Differences between Cyclic and Non-Cyclic Photophosphorylation

Cyclic Photophosphorylation Non-Cyclic Photophosphorylation
1. It involves only pigment system-I. It involves both pigment system-I and pigment system-II.
2. Electrons released by the pigment Electrons released by the pigment system- I return back to it. II do not return back to it.
3. It produces only ATP. It produces ATP and NADPH2.
4. Photolysis of water does not occur. Photolysis of water occur.
5. Oxygen is not given off. Oxygen is given off.

(c) Differences between Morphology of leaves of C3 and C4 plants

Morphology of C3 Plants Morphology of C4 Plants
1. They do not have Kranz anatomy. They have Kranz anatomy.
2. Thin layered parenchymatous bundle of sheath is found surrounding vascular bundle. Double spiral bundle sheath cells are found tightly packed around the vascular bundle.
3. Bundle sheath cells are in contact with mesophyll cells. Bundle sheath cells are connected with mesophyll cells by plasmodesmata.
4. Leaves of C3 plants contain similar chloroplasts. Leaves of C4 plants contain two types of chloroplasts :
(a) Mesophyll chloroplasts which are smaller, grana is present there and starch grains are absent.
(b) Bundle sheath chloroplasts, which are larger, lacking grana and possessing starch grains.

Question 16.
Describe Photorespiration in brief.
Answer:
Photorespiration or C2 Cycle: It was normally believed that rate of respiration is equal in day and night. Recently it has been observed that light affects respiration and the rate of respiration in light maybe three to five times higher than the respiration in darkness. Such type of respiration is called photorespiration and is marked as one of the new discoveries of plants physiology. In photorespiration, temperature plays a very vital role, its rate being very high in between 25-35°C. It also depends upon the concentration of oxygen and increases with increasing oxygen concentration even up to 100%. However, the normal respiration is independent of oxygen concentration. In normal respiration the respiratory substrate is glucose while in photorespiration glycolic acid (2-carbon compound) serves as a substrate.

The diagnostic features of photorespiration are as follows :

  • The respiratory substrate is glycolate a 2-carbon compound.
  • The substrate is always recently formed.
  • The entire process of photorespiration occurs in between chloroplast, cytoplasm, peroxisome and mitochondria.
  • It shows positive correlationship with O2 concentration. The ribulose diphosphate reacts with O2 to produce one molecule of 3-carbon, phosphoglyceric acid (PGA) and one molecule of 2-carbon phosphoglycolic acid.

RuDP + O2 → phosphoglyceric acid + phosphoglycolic acid

Phosphoglycolic acid is immediately dephosphorylated into glycolate. The latter en-ters the peroxisome, where glycolate is catalyzed to produce glyoxylate and H2O2.
The glyoxylate is transmitted to glycine which is also obtained from serine.
The glycine molecule enters the mitochondria where they lose CO2 to form serine. Serine diffuses into the peroxisome where it is converted into glycerate which then enters the chloroplast and the Calvin cycle to produce sugars.

  • In this process ATP molecules are not formed.
  • The rate of photorespiration is highly accelerated in between 25° to 35°C.
  • This is found only in presence of light and only in green cells.

Question 17.
What do you mean by Total parasitic? Explain with example.
Answer:
Total Parasitic Nutrition: It is a type of nutrition in which parasitic plant totally depend on the host plant for food as well as shelter. Such plants are non-green e.g., Cuscuta orobanche. The total parasites develop haustoria or sucking roots which go into the vascular bundles of the host plant and absorb prepared food and water from there.

Question 18.
“CO2 is very essential for the production of carbohydrates by the plants.” Prove this statement by describing the experiment with labelled diagram.
Or,
Give one experiment to prove that CO2 is necessary for photosynthesis pro¬cess.
Answer:
Experiment to demonstrate that CO2 is necessary for photosynthesis process: It can be demonstrated by Moll’s experiment:
MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 7

Method: Take a potted plant having long leaves. Keep it in darkness for 24 to 48 hours to make it starch free. In the morning before sunrise, insert the apex of a leaf (through a split cork) in a wide mouthed bottle which has been laid on its side on the table, and in which caustic potash has been introduced.

Now expose the apparatus to sunlight for some-time. Then pluck the leaf and decolourize it with the help of hot alcohol and test with weak iodine solution. It is found that the apical portion of the leaf lying inside the bottle does not give the starch reaction, whereas the portion outside the bottle turns blue. This proves that starch is formed in those parts only which get CO2.

Chapter 16 Digestion and Absorption

Question 19.
Write short note on Facultative or Semi-parasitic nutrition.
Answer:
Facultative or Semi-parasitic nutrition: The type of nutrition in which plant may become parasite under certain conditions is called as facultative nutrition. These parasitic plants have chlorophyll and therefore, synthesize their organic food but they depend on the host plants for their water and mineral requirements.

Question 20.
Write differences between Light reaction and Dark reaction.
Answer:
Differences between Light Reaction and Dark Reaction

Light Reaction Dark Reaction
1. It occurs in presence of light. It occurs in absence of light.
2. It occurs in the grana part of the chloroplast. It occurs in the stroma part of the chloroplast.
3. Fixation of CO2 do not occur. Fixation of CO2 occurs.
4. Photolysis of water occurs and O2 is produced. Photolysis of water do not occurs.
5. Products of light reaction are ATP and NADPH2. Product of dark reaction is glucose.
e.g. Loranthus, Mistletoe etc.

Question 21.
What are CAM plants? Give characteristic features of CAM plants and explain mechanism of CAM cycle.
Answer:
Crassulacean Acid Metabolism or CAM Cycle: Crassulacean acid metabolism occurs in certain succulent plants of the family Crassulaceae. As they exhibit a special type of CO2 assimilation, they are called as CAM plants.
MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 8

1. Dicotyledonous family:

  • Crassulaceae (e.g.,Sedum, Opuntia),
  • Cactaceae,
  • Chenopodiaceae,
  • Compositae,
  • Convolvulaceae,
  • Euphorbiaceae,
  • Caryo- phyllaceae.

2. Monocotyledonous family :

  • Liliaceae,
  • Orchidaceae.

3. Pteridophytic family: Polypodiaceae.
Characteristic features of CAM plants: CAM plants exhibit the following characteristic features:

  • Normally stomata are open during night (dark) and closed during day (light)
  • CO2 fixation takes place during day time and malic acid is formed during night.
  • Malic acid is stored in the large vacuoles, which is the characteristic of the cells of CAM plants.
  • In day light, decarboxylation of malic acid takes place and CO2 is formed which is used in C3 cycle to produce storage glycans.

Malic acid + NADP+ → Pyruvic acid + CO2 + NADPH2

  • In next dark period storage glycans are catabolized through glycolysis and produces PEP as CO2 acceptor molecule.
  • Stomata remain closed during day and open at night.
  • CO2 is fixed via. PEP-carboxylase initially into OAA and then to other 4 carbon acids i.e., malic acid. This is called as dark
  • CO2 fixation and is more efficient at 10-15°C.
  • The larger vacuoles are used for storing malic and other acids in large amount.

Photosynthesis in Higher Plants  Class 11 Important Questions Long Answer Type 

Question 1.
Describe light reaction of photosynthesis process.
Answer:
Light Reaction: In this reaction photolysis of water and production of the reducing power take place.
In this step, which takes place in the presence of sunlight and chlorophyll there is a break down of the water molecules. Oxygen escapes to the air in the molecular form while hydrogen is accepted by Nicotinamide adenine dinucleotide phosphate (NADP). The whole process can be represented by following summary equation.
MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 9
This part of the photosynthetic mechanism which takes place in light is known as the Light Reaction or Hill Reaction, after its discoverer. Not only is the reducing agent produced but some solar energy get stored up as the chemical energy of NADPH2 (about 18 molecules of ATP).

According to Robert Emmersion absorption of water in light reaction occurs through two pigment systems :

(a) Pigment System I: This pigment system absorbs only the light of 680 nm wavelength of sunlight. P700 on absorbing photon of light expels two-electron, P700 becomes oxidized. The expelled electron is picked up by ferredoxin. They transfer the electron to cytochrome b6 which supply it to cytochrome f. They transfer the electron to plastocyanin. From here it is handed over back to P700.

The synthesis of ATP in this cyclic electron transport scheme is possible at two locations. Synthesis of ATP may occur between ferredoxin and cytochromes bg and the other when the electron travels from cytochromes fg to plastocyanin.
In this case the electron expelled out by an excited chlorophyll trap is returned to the oxidized chlorophyll after passing through a series of electrons carriers, therefore this process is also called as Cyclic photophosphorylation.

(b) Pigment System II: This pigment system absorbs only the light of wavelength less than 680 nm of sunlight.
In this process pigment chlorophyll-a673 become excited by absorbing 2 photons of light and emit 2 electrons. It then moves through a series of electron carriers, some of which are plastoquinone, cytochrome bg, cytochrome f and plastocyanin. Most probably energy for ATP synthesis is given out between cytochrome bg and cytochrome f. Plastocyanin hand over the electron to P700.
MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 10
When pigment system II absorbs light then 24 molecules of water dissociates into H+ and OH ions.
24H2O → 24OH + 24H+

OH ion from this goes to pigment system II and oxidized to reduce to produce water and oxygen.

24OH – 24e → 240H
24OH → 12H2O + 6O2

24 H+ produced by photolysis of water obtain electrons from ferredoxin and reacts with NADP to form NADPH2.

24H+ + 24e +12NADP →12NADPH2
In this electron transfer, one ATP is formed when it transfer from Cyt. bg to Cyt.f. It is the normal process of photophosphorylation in higher plants. The electron expelled by the excited chlorophyll trap is never returned to the same chlorophyll. Therefore this process also called as Acyclic phosphorylation.

In this way in six complete cycle of cyclic phosphorylation 12ATP are formed and in six complete acyclic phosphorylation 6ATP and 12NADPH2 are formed. Whereas in one acyclic phosphorylation 2NADPH2 are formed and 24H2O dissociates. Therefore both the systems of light reaction together produces 18ATPand 12NADPH2 molecules.
Both the reactions occurs in light reaction simultaneously. To complete photosynthesis process both the pigment systems are essential.

Chapter 16 Digestion and Absorption

Question 2.
Explain dark reaction of photosynthesis process in brief.
Or,
What is Calvin cycle? Describe it in brief.
Answer:
Dark reaction or Blackman’s reaction or Biosynthesis phase or Calvin’s cycle : The non-photochemical reaction or dark reaction of photosynthesis was first of all established by Blackman (1905). The reactions of dark phase of photosynthesis occur in the stroma of the chloroplast. In this phase the carbon dioxide is converted to carbohydrate through a series of enzyme catalyzed reactions.

The path of carbon in photosynthesis is popularly called Calvin cycle or C3 cycle. For this great piece of work Calvin was awarded Noble prize in 1961. This cycle is also called as Bassham and Calvin cycle, Blackman reaction, Carbon assimilation, Path of carbon in photosynthesis etc.

The process can be represented by following reaction :

6CO2 + 12NADPH2 +18 ATP→ C6H12O6 + 12NADP + 18ADP + 6H2O + 18Pi

Most of the intermediate compounds of Calvin cycle are 3 carbon compounds. Therefore this cycle is also called as C3 cycle.
Calvin cycle may be explained by following two steps :

  1. Synthesis of carbohydrates
  2. Regeneration of ribulose diphosphate.

1. Synthesis of carbohydrates: 6 molecules of CO2 are first accepted by 6 molecules of Ribulose-1, 5-diphosphate and forms an unstable compound which soon breaks into 12 molecules of 3 carbon compound called as Phosphoglyceric acid. The phosphoglyceric acid is then reduced to 12 molecules of phosphoglyceraldehyde by 12 molecules of NADPH2. 5 molecules from 12 molecules of phosphoglyceraldehyde converts into Dihydroxyacetone phosphate.

Now dihydroxyacetone phosphate reacts with 3 molecules of phosphoglyceraldehyde to form Fructose-1, 6-diphosphate. One molecule from it converts into Fructose-6-phosphate which converts into glucose or starch.

2. Regeneration of ribulose diphosphate: The regeneration of ribulose-1, 5- diphosphate is essential to carry on the process of photosynthesis. Fructose 6 phosphate and phosphoglyceraldehyde combine and break into 4-carbon compound erythrose-4-phosphate and 5-carbon compound xylulose-5-phosphate.

The former combines with a molecule of dihydroxyacetone phosphate to form sedoheptulose-1,7-diphosphate from which one phosphate is removed to form sedoheptulose-7- phosphate. The latter and phospho¬glyceraldehyde combine to produce one molecule each of xylulose-5-phosphate and ribulose-5-phosphate. Both of these compounds get converted into ribulose-5-phosphate which ultimately forms ribulose-1,5-diphosphate using ATP which is obtained from the photophosphorylation process.
MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 11

Question 3.
Write a short essay on Bacterial photosynthesis.
Answer:
Bacterial photosynthesis: The anaerobic photosynthetic bacteria may be rods, cocci, or spirilla depending on their colouration. They are known as green or purple bacteria. They use sunlight as source of energy for photosynthesis but like other eukaryotic cells they do not ‘split water’ to transfer the energy or to obtain reducing power. Thus no oxygen is evolved by them. This process is therefore called anoxygenic (without producing oxygen) photosynthesis.

In place of water these bacteria obtain reducing power from hydrogen sulphide, thiosulphate, hydrogen or even some organic compound. They possess a pigment called bacterio-chlorophyll which is different from the chlorophyll pigment found in higher plants. This can be summarized as below :

There are three types of photosynthetic bacteria :

  1. Green sulphur bacteria: They contain bacterial chlorophyll. These bacterias are found in H2S medium. In presence of light they reduces CO2 Reaction is exergonic.
    MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 12
    Example: Chlorobacteria, chlorobium.
  2. Purple sulphur bacteria : Bacteriochlorophyll is found. They can survive as heterotrophs in organic compounds in absence of inorganic sulphur compound.
    MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 13
    Example: Chromacium.
  3. Purple non sulphur bacteria : These bacteria uses simple organic compounds such as alcohol, organic acid etc.
    MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 14
    As these bacterias uses visible light therefore they are also called as photo-autotrophic.

Chapter 16 Digestion and Absorption

Question 4.
Write differences between photorespiration, true respiration and photosynthesis.
Answer:
Differences between Photorespiration, True Respiration and Photosynthesis
MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 15

Question 5.
Explain Blackman’s principle of limiting factor.
Answer:
According to Blackman’s principle of limiting factor: When a physiological process is conditioned by number of factors then the rate of physiological process is limited by the factor found in least quantity.
For example, photosynthesis process is conditioned by many factors such as CO2, water, light etc. If the concentration of CO2 is least, then the rate of photosynthesis increases with increase in the quantity of CO2. As the CO2 supply increases gradually some other factor become limiting factor i.e., in such condition increased quantity of CO2 does not help to increase rate of photosynthesis.

The principle was explained by Blackman as follows :

Suppose a leaf is exposed to such a light intensity which can allow the leaf to utilize 5mg of CO2 per hour in photosynthesis. If 1 mg of CO2 enters the leaf in one hour, the rate of photosynthesis is limited due to CO2 factor. If the concentration of the CO2 is increased from 1 to 5mg per hour, the rate of photosynthesis also increases along the line AC. Thus, the increase in photosynthetic rate will be proportionate with the increase in CO2 concentration up to 5mg. Any further increase in the CO2 concentration will have no effect on the rate of photosynthesis, which has become constant along the line CD. It is because the light factor (low intensity) has now become the limiting factor.

Now the rate of photosynthesis will increase further along the line CE only if the light intensity is also increased from low to a medium. At point E, the medium light intensity again becomes limiting factor and the rate of photosynthesis will again be- Fig Graphical representation of Blackman„’S come constant along the line EF. In the same way, law of limiting factor, when light intensity is increased from medium to higher, an increase in the rate of photosynthesis takes place along the EG by adding CO2. When the rate attains maximum at G, further increase in CO2 will not increase the rate of photosynthesis which become constant along the line GH. Here, higher light intensity again becomes a limiting factor.

Thus, it is quite evident from the above illustration that the rate of photosynthesis cannot be increased by increasing only one factor. The other factor should also be increased in proper proportion for favourable effect. Besides CO2 and light, other factors such as temperature, water, etc. may also become limiting under certain conditions.
MP Board Class 11th Biology Important Questions Chapter 13 Photosynthesis in Higher Plants 16

 

Photosynthesis in Higher Plants Class 11 Important Questions Objective Type

1. Choose the correct answers:

Question 1.
Which method was used by Calvin to explain path of photosynthesis :
(a) Chromatography
(b) Electrophoresis
(c) Spectrophotometry
(d) Histochemistry.
Answer:
(a) Chromatography

Question 2.
Highest effective wavelength of light for photosynthesis is of which colour :
(a) Green
(b) Yellow
(c) Red
(d) Violet.
Answer:
(c) Red

Chapter 16 Digestion and Absorption

Question 3.
Light reaction occurs in :
(a) Stroma
(b) Grana
(c) Membrane of Chloroplast
(d) Endoplasmic reticulum.
Answer:
(b) Grana

Question 4.
After absorption of radiation by pigment system-I electrons are emitted by:
(a) Chlorophyll-683
(b) Chlorophyll-673
(c) Chlorophyll-695
(d) P-700.
Answer:
(d) P-700.

Question 5.
First step of photosynthesis is :
(a) ATP synthesis
(b) Excitement of chlorophyll and emission of electrons
(c) Photolysis of water
(d) Release of oxygen.
Answer:
(b) Excitement of chlorophyll and emission of electrons

Question 6.
Photophosphorylation is the method in which :
(a) Aspartic acid is formed
(b) CO2 and H2O combine
(c) Light energy converts into chemical energy
(d) PGA is formed.
Answer:
(c) Light energy converts into chemical energy

Question 7.
Rate of photosynthesis depends on :
(a) Photoperiod
(b) Intensity of light
(c) Quality of light
(d) Temperature.
Answer:
(a) Photoperiod

Question 8.
CO2 acceptor of C3 cycle is :
(a) Phosphoglyceraldehyde
(b) Ribulose diphosphate
(c) Phosphoglyceric acid
(d) Pyruvic acid.
Answer:
(c) Phosphoglyceric acid

Chapter 16 Digestion and Absorption

Question 9.
C4 cycle of photosynthesis is absent in :
(a) Zea mays
(b) Triticum vulgare
(c) Oryza sativa
(d) Euphorbia.
Answer:
(d) Euphorbia.

Question 10.
During photosynthesis :
(a) Reduction of water and oxidation of CO2
(b) Reduction of CO2 and oxidation of water
(c) Oxidation of both CO2 and H2O
(d) Reduction of both CO2 and H2O.
Answer:
(b) Reduction of CO2 and oxidation of water

Question 11.
Electron acceptor required for photophosphorylation and oxidative phosphorylation is:
(a) O2
(b) CO2
(c) Cytochrome
(d) Water.
Answer:
(c) Cytochrome

Question 12.
First stable compound of C3 plant during photosynthesis is :
(a) PGA
(b) Starch
(c) Pyruvic acid
(d) Ribulose diphosphate.
Answer:
(a) PGA

Question 13.
Product of photophosphorylation is :
(a) NADP
(b) ADP from ATP
(c) ATP from ADP
(d) PGA.
Answer:
(c) ATP from ADP

Question 14.
COz acceptor of C3 cycle is :
(a) RuDP
(b) PGA
(c) OAA
(d) PEPA.
Answer:
(a) RuDP

Question 15.
Kranze anatomy is found in the leaves of:
(a) C2 plants
(b) C3 plants
(c) C4 plants
(d) Fleshy plants.
Answer:
(c) C4 plants

Chapter 16 Digestion and Absorption

Question 16.
CO2 acceptor of C4 cycle is :
(a) PEP
(b) RuDP
(c) PGA
(d) OAA.
Answer:
(a) PEP

Question 17.
Solar energy converts into chemical energy in which process :
(a) Digestion
(b) Respiration
(c) Transpiration
(d) Photosynthesis.
Answer:
(d) Photosynthesis.

Question 18.
NADP is reduced to NADPH2 during :
(a) Cyclic photophosphorylation
(b) Acyclic photophosphorÿlation
(c) Calvin’s cycle
(d) PS – I.
Answer:
(b) Acyclic photophosphorÿlation

Question 19.
In pigment system-il:
(a) Fixation of CO2 occurs
(b) Reduction of CO2 occurs
(c) Decomposition of water occurs
(d) All of these.
Answer:
(c) Decomposition of water occurs

Question 20.
Every green plant which do photosynthesis have:
(a) Chlorophyll-a
(b) Chlorophyl1b
(c) Chlorophyll-c
(d) Chlorophyll-d.
Answer:
(a) Chlorophyll-a

Question 21.
Photorespiration is the special quality of these plants:
(a) C3 plants
(b) C4 plants
(c) CAM plants
(d) None of these.
Answer:
(a) C3 plants

Chapter 16 Digestion and Absorption

Question 22.
in photorespiration the first process is:
(a) Carboxylation
(b) Decarboxylation
(c) Oxygenation
(d) Phosphorylation.
Answer:
(c) Oxygenation

Question23.
In photorespiration glycolate is changed into CO2 and serin amino acid in:
(a) Chioroplast
(b) Peroxisorne
(c) both (a) and (b)
(d) Mitochondria.
Answer:
(d) Mitochondria.

Question 24.
The end product of the photosynthesis is:
(a) CO2 and °2
(b) Carbohydrates
(c) CO2 and carbohydrates
(d) CO2 and starch.
Answer:
(b) Carbohydrates

Question 25.
The principle of limiting factor was proposed by:
(a) Blackman
(b) Arnon
(c) Living
(d) Hatch and Slack.
Answer:
(a) Blackman

2. Fill in the blanks:

1. In photorespiration the formation of glycine from glycolic acid is done in ……………. .
Answer:
Peroxisome,

2. Photorespiration is also called ……………. metabolism.
Answer:
Glycolate

3. The process of intake or synthesis of food material is called ……………. .
Answer:
Nutrition

4. Ribose diphosphate works in high concentration of ……………. as oxygenate.
Answer:
Oxygenase

Chapter 16 Digestion and Absorption

5. Monatropa is a main ……………. plant.
Answer:
Saprophytic

6. In pigment system I ……………. photophosphorylation occurs.
Answer:
Cyclic

7. Products of light reaction are ……………. and ……………. .
Answer:
ATP, NADPH2

8. Chemical formula of chlorophyll-a is ……………. .
Answer:
C55H72O35N4Mg

9. Main pigment required for photosynthesis is ……………. .
Answer:
Chlorophyll

10. ……………. is reduced during photosynthesis.
Answer:
CO2

3. Match the following:

(A)

Column ‘A’ Column ‘B’
1. Glycolate metabolism (a) Green chlorophyll
2. Halophyte (b) C4
3. Chlorophyll (c) Photorespiration
4. Hatch and Slack (d) Plants which need light
5. Photosynthesis (e) Symbiont
6. Lichen (f) Autotroph.

Answer:
1. (c) Photorespiration
2. (d) Plants which need light
3. (a) Green chlorophyll
4. (b) C4
5. (f) Autotroph.
6. (e) Symbiont

(B)

Column ‘A’ Column ‘B’
1. PEP (a) C3 cycle
2. Amon (b) Red drop
3. Blackman (c) C4 cycle
4. Calvin and Benson (d) Photophosphorylation
5. Robert Emerson (e) Principle of limiting factor.

Answer:
1. (c) C4 cycle
2. (d) Photophosphorylation
3. (e) Principle of limiting factor.
4. (a) C3 cycle
5. (b) Red drop

Chapter 16 Digestion and Absorption

4. Answer in one word:

1. Where does light reaction occurs in the chloroplast?
Answer:
Grana

2. What is the main source of oxygen evolved during photosynthesis?
Answer:
Water

3. Write the names of end-products of light reaction.
Answer:
ATP and NADPH2

4. Give chemical formula of chlorophyll.
Answer:
C55H72O35N4Mg

5. Name the element found in the middle of chlorophyll molecule.
Answer:
Magnesium

6. Name the raw materials of photosynthesis process.
Answer:
CO2, water, chlorophyll, light

7. Which colour of light shows highest rate of photosynthesis?
Answer:
Red light

8. Where does photosynthesis process occur.
Answer:
Chloroplast

9. Name first product of the C3 cycle.
Answer:
Phosphoglyceric acid (PGA)

10. Name photosynthetic pigments found in the bacteria.
Answer:
Bacteriochlorophyll, Bacterioviridin, carotenoids

11. Name one enzyme found in the cells of C4 plants.
Answer:
Phosphoenol-pyruvate carboxylase

12. Write full name of CAM.
Answer:
Crassulacean acid metabolism.

MP Board Class 11th Biology Important Questions

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