NCERT Solutions for Class 11 Science Biology Chapter 13 Photosynthesis In Higher Plants are provided here with simple step-by-step explanations. These solutions for Photosynthesis In Higher Plants are extremely popular among Class 11 Science students for Biology Photosynthesis In Higher Plants Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the NCERT Book of Class 11 Science Biology Chapter 13 are provided here for you for free. You will also love the ad-free experience on Meritnation’s NCERT Solutions. All NCERT Solutions for class Class 11 Science Biology are prepared by experts and are 100% accurate.
Page No 68:
Question 1:
Which metal ion is a constituent of chlorophyll?
a. Iron
b. Copper
c. Magnesium
d. Zinc
Answer:
Chlorophyll is a green colour photosynthetic pigment that gives green colour to the plant leaves. It helps in trapping solar energy from the sun during the process of photosynthesis. Magnesium is the constituent of chlorophyll.
Hence, the correct answer is option c.
Page No 68:
Question 2:
Which pigment acts directly to convert light energy to chemical energy?
a. Chlorophyll a
b. Chlorophyll b
c. Xanthophyll
d. Carotenoid
Answer:
Chlorophyll a molecule forms the reaction centre. It is the major pigment associated with photosynthesis which converts light energy into chemical energy.
Hence, the correct answer is option a.
Page No 68:
Question 3:
Which range of wavelength (in nm) is called photosynthetically active radiation (PAR)?
a. 100 – 390
b. 390 – 430
c. 400 – 700
d. 760 – 100,00
Answer:
PAR (Photosynthetically active radiation) is the part of light spectrum used in photosynthesis. It has wave length between 400-700 nm.
Hence, the correct answer is option c.
Page No 68:
Question 4:
Which light range is least effective in photosynthesis?
a. Blue
b. Green
c. Red
d. Violet
Answer:
The efficient wave lengths of visible light for photosynthesis fall within the blue range (425-450 nm) and red range (600-700 nm).
The green light range is the least effective for photosynthesis.
Hence, the correct answer is option b.
Page No 68:
Question 5:
Chemosynthetic bacteria obtain energy from
a. Sun
b. Infra red rays
c. Organic substances
d. Inorganic chemicals
Answer:
Chemosynthetic bacteria obtain energy from inorganic chemicals such as ammonia, molecular hydrogen, sulfur, hydrogen sulfate and ferrous ions. They convert these inorganic chemicals into organic compounds through oxidation of inorganic substances.
Hence, the correct answer is option d.
Page No 69:
Question 6:
Energy required for ATP synthesis in PSII comes from
a. Proton gradient
b. Electron gradient
c. Reduction of glucose
d. Oxidation of glucose
Answer:
The energy required for the synthesis of ATP in PS II comes from proton gradient. It is created across the inner membrane of thylakoid.
Hence, the correct answer is option a.
Page No 69:
Question 7:
During light reaction in photosynthesis the following are formed:
a. ATP and sugar
b. Hydrogen, O2 and sugar
c. ATP, hydrogen and O2
d. ATP, hydrogen and O2 donor
Answer:
The light reaction or photochemical phase of photosynthesis involves absorption of light energy, splitting of water molecule, release of oxygen and the formation of high energy intermediates such as ATP and NADPH.
Hence, the correct answer is option c.
Page No 69:
Question 8:
Dark reaction in photosynthesis is called so because
a. It can occur in dark also
b. It does not depend on light energy
c. It cannot occur during day light
d. It occurs more rapidly at night
Answer:
The dark reaction of photosynthesis is not directly light driven but are dependent on the products of light reactions (ATP and NADPH).
Hence, the correct answer is option b.
Disclaimer-In NCERT the answer given is option a. As dark reaction is independent of light energy it can take place both in the presence of light and dark. So, the correct answer is option b.
Page No 69:
Question 9:
PEP is primary CO2 acceptor in
a. C4 plants
b. C3 plants
c. C2 plants
d. Both C3 and C4 plants
Answer:
PEP (phosphoenolpyruvate) is primary CO2 acceptor present in the mesophyll cells of the C4 plants. In C3 plants RuBisCo acts as a CO2 acceptor.
Hence, the correct answer is option a.
Page No 69:
Question 10:
Splitting of water is associated with
a. Photosystem I
b. Lumen of thylakoid
c. Both Photosystem I and II
d. Inner surface of thylakoid membrane
Answer:
The splitting of water molecule is associated with the PS II. In this, water is split into 2H+. [0] and electrons. Oxygen molecule is released during this process which is the net product of photosynthesis.
2H2O → 4H+ + O2 + 4e–
Page No 69:
Question 11:
The correct sequence of flow of electrons in the light reaction is
a. PSII, plastoquinone, cytochromes, PSI, ferredoxin
b. PSI, plastoquinone, cytochromes, PSII, ferredoxin
c. PSI, ferredoxin, PSII,
d. PSI, plastoquinone, cytochromes, PSII, ferredoxin
Answer:
The correct sequence of flow of electrons in the light reaction is PS II, plastoquinone, cytochromes, PS I, ferredoxin.
Hence, the correct answer is option a.
Disclaimer-In light reaction (non-cyclic photophosphorylation) light energy first excite PS II then PS I. So, option d (given in NCERT Exemplar) is incorrect.
Page No 69:
Question 12:
The enzyme that is not found in a C3 plant is
a. RuBP carboxylase
b. PEP carboxylase
c. NADP reductase
d. ATP synthase
Answer:
PEPcase (phosphoenolpyruvate carboxylase) is present in the mesophyll cells of C4 plants. This enzyme catalyse the conversion of PEP to oxaloacetic acid. Oxaloacetate (OAA) is the first stable product of C4 cycle.
Hence, the correct answer is option b.
Page No 70:
Question 13:
The reaction that is responsible for the primary fixation of CO2 is catalysed by
a. RuBP carboxylase
b. PEP carboxylase
c. RuBP carboxylase and PEP carboxylase
d. PGA synthase
Answer:
Carboxylation reaction is the fixation of CO2 into a stable organic intermediate. This reaction is catalysed by the enzyme RuBP carboxylase and PEP carboxylase in C3 and C4 plants respectively.
Hence, the correct answer is option c.
Page No 70:
Question 14:
When CO2 is added to PEP, the first stable product synthesised is:
a. Pyruvate
b. Glyceraldehyde-3-phosphate
c. Phosphoglycerate
d. Oxaloacetate
Answer:
Phosphoenolpyruvate (PEP) is 3-carbon molecule and the primary CO2 acceptor molecule present in the mesophyll cells of C4 plants. Phosphoenolpyruvate carboxylase (PEP case) is responsible for carboxylation reaction and facilitates the conversion of PEP into oxaloacetic acid (OAA) which is a 4-carbon compound.
Hence, the correct answer is option d.
Page No 70:
Question 1:
Examine the figure
a. Is this structure present in animal cell or plant cell?
b. Can these be passed on to the progeny? How?
c. Name the metabolic processes taking place in the places marked (1) and (2).
Answer:
a. The given figure is the structure of chloroplast present in the leaves of plant cell.
b. Chloroplast have ability to self-replicate and can be passed on to progency.
c. 1- Site for dark reaction
2- Site for replication of chloroplast
Page No 70:
Question 2:
2H2O → 4H+ + O2 + 4e–
Based on the above equation, answer the following questions:
a. Where does this reaction take place in plants?
b. What is the significance of this reaction?
Answer:
a. The splitting of water molecule is associated with the PS II, located in the inner membrane of thylakoid.
b. This reaction continuously provides electrons that are required to replace those electrons removed from photosystem I. They are provided by photosystem II.
Page No 70:
Question 3:
Cyanobacteria and some other photosynthetic bacteria don’t have chloroplasts. How do they conduct photosynthesis?
Answer:
The cyanobacteria and other photosynthetic bacteria are prokaryotes and lack well defined membrane bound cell organelles. But they contains photosynthetic pigments present in a membranous form and are primitive in nature. These pigments trap solar radiation and carry out the process of photosynthesis.
Page No 71:
Question 4:
a. NADP reductase enzyme is located on ___________________.
b. Breakdown of proton gradient leads to release of ___________________.
Answer:
a. NADP reductase enzyme is located on the stroma side of the thylakoid membrane.
b. Breakdown of proton gradient leads to release of ATP.
Page No 71:
Question 5:
Can girdling experiments be done in monocots? If yes, How? If no, why not?
Answer:
No, girdling experiment can not e done in monocotyledons. Girdling is the process of removal of the bark of the tree in the form of ring. This experiment is done in woody plants as their vascular tissues are attached but in monocotyledonous plants, the vascular tissues are scattered.
Page No 71:
Question 6:
Analyze the above reaction and answer the following questions:
a. How many molecules of ATP & NADPH are required to fix one molecule of CO2?
b. Where in the chloroplast does this process occur?
Answer:
a. Three molecules of ATP are required for phosphorylation whereas 2 molecules of NADPH are required for the reduction of carbon dioxide.
b. This process takes place in the stroma of the chloroplast.
Page No 71:
Question 7:
Does moonlight support photosynthesis?
Answer:
No, moonlight can not support the process of photosynthesis because moonlight does not have sufficient energy to excite the chlorophyll molecules.
Page No 71:
Question 8:
Some of these terms/chemicals are associated with the C4 cycle. Explain.
a. Hatch slack pathway
b. Calvin cycle
c. PEP carboxylase
d. Bundle sheath cells
Answer:
(a) Hatch and slack pathway: Hatch and slack pathway was discovered by two scientist MD Hatch and C.R. Slack in 1977. This pathway involves the synthesis of glucose in C4 plants which is different from C3 plant.
(b) Calvin cycle: This pathway is involved in the formation of sugars and is common to both C3 and C4 plants.
(c) PEP carboxylase: It is also called PEPcase and this enzyme is responsible for fixation of carbon dioxide (CO2) molecule and led to the formation of 4-carbon compound called oxaloacetic acid (C4 acid) in the mesophyll cells of C4 plants.
(d) Bundle sheath cells: Bundle sheath cells are the specialised sclerenchymatous cells. They are present around the vascular bundle, i.e., in the veins of monocot leaves. They have large number of chloroplast and thick cell walls that are impervious for gaseous exchange. Calvin cycle occurs in the bundle sheath cells to manufacture glucose in C4 plants.
Page No 71:
Question 9:
Where is NADP reductase enzyme located in the chloroplast? What is the role of this enzyme in proton gradient development?
Answer:
The NADP reductase is located in the stroma side of the thylakoid membrane of the chloroplast.
This enzyme is responsible for the breakdown of proton gradient to release energy (NADPH).
Page No 71:
Question 10:
ATPase enzyme consists of two parts. What are those parts? How are they arranged in the thylakoid membrane? Conformational change occur in which part of the enzyme?
Answer:
ATPase enzyme consists of two parts:- F0 particle and F1 particle. The F0 particle is embeded in the thylakoid membrone while F1 particle is present in the outer side of thylakoid membrane that focus the stroma. The conformational changes occurs in the F1 particle of ATPase enzyme.
Page No 71:
Question 11:
Which products formed during the light reaction of photosynthesis are used to drive the dark reaction?
Answer:
ATP and NADPH are the products formed during light reaction of photosynthesis. They are used in dark reaction for CO2 fixation and for the formation of glucose molecule.
Page No 71:
Question 12:
What is the basis for designating C3 and C4 pathways of photosynthesis?
Answer:
In C3 cycle, a 3-carbon compound called 3-PGA (3-phosphoglycerate) is formed as the first stable intermediate while in C4 cycle, a 4-carbon compound called oxaloacetate is formed as the first stable intermediate by carbon fixation. The number of carbon atoms present in the first stable intermediate is the basis for such designation.
Page No 71:
Question 1:
Succulents are known to keep their stomata closed during the day to check transpiration. How do they meet their photosynthetic CO2 requirements?
Answer:
The succulent plants have enrolled a special method to ensure the daily supply of carbon dioxide during day time. Such plants fix carbon dioxide at night in the form of malic acid.
Page No 71:
Question 2:
Chlorophyll ‘a’ is the primary pigment for light reaction. What are accessory pigments? What is their role in photosynthesis?
Answer:
Thylakoid pigments such as chlorophyll b, xanthophylls and carotenoids. They are called accessory pigments. They absorbs light energy and transfer the energy to chlorophyll a. They also provides protection to the chlorophyll a from photo-oxidation.
Page No 71:
Question 3:
Do reactions of photosynthesis called, as ‘Dark Reaction’ need light? Explain.
Answer:
Dark reaction includes the biosynthetic phase of photosynthesis. In this phase, the synthesis of carbohydrates takes place. This phase is not directly dependent on the light but use the products of light phase of photosynthesis.
Dark reaction does not mean that this reaction occurs in darkness while this continues even in day time. Hence, dark reaction also requires light but does not directly dependent on light.
Page No 71:
Question 4:
How are photosynthesis and respiration related to each other?
Answer:
During photosynthesis, the plants obtain energy from solar radiation. While during respiration the glucose molecule is breakdown to obtain energy in the form of ATP.
Both the processes are related to each other as they are dependent on each other.
The products of photosynthesis (glucose) is utilised during the process of respiration to obtain energy. Carbon dioxide and water is released during respiration and utilised during photosynthesis to produce carbohydrates.
Page No 72:
Question 5:
If a green plant is kept in dark with proper ventilation, can this plant carry out photosynthesis? Can anything be given as supplement to maintain its growth or survival?
Answer:
If a plant is kept in dark with proper ventilation then that plant will get carbon dioxide but does not get enough sunlight. Hence, photosynthesis is not possible in this plant. For the survival of plant, proper supply of water is required. Due to insufficient supply of nutrient, the plant will die.
Page No 72:
Question 6:
Photosynthetic organisms occur at different depths in the ocean. Do they receive qualitatively and quantitatively the same light? How do they adapt to carry out photosynthesis under these conditions?
Answer:
Algae are some plants present in the depth of ocean. They show variations in photosynthetic pigments. They can absorb different wavelengths of light and carryout the process of photosynthesis.
For example:-
Green algae:- chlorophyll a
(absorbed light)
Brown algae:- chlorophyll b
(absorbs violet light)
Brown algae: chlorophyll-a, c and fucoxanthin
(absorb yellow light)
Red algae:- chlorophyll-d and phycoerythrin.
Page No 72:
Question 7:
In tropical rain forests, the canopy is thick and plants growing below receive filtered light. How are they able to carry out photosynthesis?
Answer:
The process of photosynthesis in plants occurs in the presence of light. The rate of photosynthesis is affected by the quality and intensity of light. Plants growing in different canopies will carryout photosynthesis but the rate of photosynthesis could be different and depends upon the intensity and quantity of light received by the plants.
Page No 72:
Question 8:
What conditions enable Rubirco to function as an oxygenase? Explain the ensuing process.
Answer:
RuBisCO has binding affinity for both carbon dioxide and oxygen. The binding of this enzyme with CO2 or oxygen is competitive. If the concentration of carbon dioxide is higher, then this would act as carboxylase but if the concentration of oxygen is higher, then this enzyme would act as oxygenase and it results in photorespiration in C3 plants.
Page No 72:
Question 9:
Why does the rate of photosynthesis decrease at higher temperatures?
Answer:
As we know that, all enzymes acts at an optimum temperature and photosynthesis is an enzyme mediated process. The activity of an enzyme is affected below or above its optimum temperature. The rate of photosynthesis decreases at higher-temperature because the enzyme gets denatured.
Page No 72:
Question 10:
Explain how during light reaction of photosynthesis, ATP synthesis is a chemiosmotic phenomenon.
Answer:
Chemiosmotic movement is the movement of ions across a semi-permeable membrane and down an electron gradient.
The ATP synthesis is occurs during the light reaction of photosynthesis in the thylakoid membrane. This involves the movement of ions across the membrane and these ions are pumped by the proton pump by using a proton gradient. Due to this, ATP synthesis is a chemiosmotic phenomenon.
Page No 72:
Question 11:
Find out how Melvin Calvin worked out the complete biosynthetic pathway for synthesis of sugar.
Answer:
Melvin Calvin used chlorella (algae) for experimental material and they discovered the first stable compound of photosynthesis called 3-PGA (3-phosphoglycerate). They trace the path way of carbon by using a radioactive isotope of carbon labelled 14C and an autoradiography technique.
Then, he compared the radioactive compounds on the chromatogram. He concluded that the PGA (phosphoglyceric acid) is the first stable product of photosynthesis and then the other sugars such as hexoses, pentoses and so on.
Page No 72:
Question 12:
Six turns of Calvin cycle are required to generate one mole of glucose. Explain.
Answer:
In Calvin cycle, for reduction of one molecule of carbon dioxide, two molecules of ATP and two molecules of NADPH are required.
Glucose is 6-carbon compound, thus six molecules of carbon dioxide and six turns of calvin cycle is required to produce one mole of glucose.
Page No 72:
Question 13:
Complete the flow chart for cyclic photo-phosphorylation of the photosystem-I
Answer:
Page No 72:
Question 14:
In what kind of plants do you come across ‘Kranz’ anatomy? To which conditions are those plants better adapted? How are these plants better adapted than the plants which lack this anatomy?
Answer:
C4 Plants such as Maize, sugarcane, sorghum etc have kranz anatomy. C4 plants have large cells around the vascular bundles and are called bundle sheath cells.
The leaves that have such anatomy is called 'kranz' anatomy and 'kranz' means 'Wreath'.
C4 plants are special and are better than C3 plants as they have a special kind of leaf anatomy and can tolerate higher temperature.
Such plant also show responses to high light intensities and lack the process of photorespiration.
∘ They have greater productivity of biomass.
Page No 73:
Question 15:
In a way green plants and cyanobacteria have synthesized all the food on the earth. Comment.
Answer:
Cynobacteria are unicellular and prokaryotic organisms. They contain photosynthetic pigments such as chlorophyll a, c, phyoerythrin and phycocyanin. These photosynthetic pigments helps cynobacteria in manufacturing of food. Whereas green plants are multicellular and eukaryotic organisms that use carbon dioxide, water and light energy for synthesis of their food in the form of sugar (glucose). Hence, cynobacteria and green plants synthesize their food for living organism on the earth.
Page No 73:
Question 16:
Tomatoes, carrots and chillies are red in colour due to the presence of one pigment. Name the pigment. Is it a photosynthetic pigment?
Answer:
Tomatoes, carrot and chilies are red in colour because of the presence of lycopene pigment. Lycopene is not a photosynthetic pigment and is present in the plastid called chromoplast.
Page No 73:
Question 17:
Why do we believe chloroplast and mitochondria to be semi-autonomous organelle?
Answer:
Chloroplast and mitochondria are called semi-autonomous organelles because they contain a circular DNA and 70s ribosomes. These organelles synthesize their own DNA and proteins.
Page No 73:
Question 18:
Observe the diagram and answer the following.
a. Which group of plants exibits these two types of cells?
b. What is the first product of C4 cycle?
c. Which enzyme is there in bundle sheath cells and mesophyll cells?
Answer:
a. Monocot plants (maize, sorghum) have two types of cells - bundle sheet and mesophyll cells.
b. Oxaloacetic acid (OAA) is a C4 acid.
c. PEP carboxylase
Page No 74:
Question 19:
A cyclic process is occurring in C3 plant, which is light dependent, and needs O2. This process doesn’t produce energy rather it consumes energy.
a. Can you name the given process?
b. Is it essential for survival?
c. What are the end products of this process?
d. Where does it occur?
Answer:
a. Photorespiration
b. No, this process is not essential for survival of plant.
c. Hydrogen peroxide is the end product of photorespiration.
d. This process takes place in chloroplast, mitochondria and peroxisomes.
Page No 74:
Question 1:
Is it correct to say that photosynthesis occurs only in leaves of a plant? Besides leaves, what are the other parts that may be capable of carrying out photosynthesis? Justify.
Answer:
Ans
Page No 74:
Question 2:
The entire process of photosynthesis consists of a number of reactions. Where in the cell do each of these take place?
| a. Synthesis of ATP & NADPH | _______________________________ |
| b. Photolysis of water | _______________________________ |
| c. Fixation of CO2 | _______________________________ |
| d. Synthesis of sugar molecule | _______________________________ |
| e. Synthesis of starch | _______________________________ |
Answer:
| a. Synthesis of ATP & NADPH | outerside of thylakoid membrane |
| b. Photolysis of water | Inner of thylakoid membrane |
| c. Fixation of CO2 | stoma of chloroplast |
| d. Synthesis of sugar molecule | chloroplast |
| e. Synthesis of starch | chloroplast |
Page No 74:
Question 3:
Which property of the pigment is responsible for its ability to initiate the process of photosynthesis? Why is the rate of photosynthesis higher in the red and blue regions of the spectrum of light?
Answer:
Ans
Page No 74:
Question 4:
What can we conclude from the statement that the action and absorption spectrum of photosynthesis overlap? At which wavelength do they show peaks?
Answer:
Ans
Page No 74:
Question 5:
Under what conditions are C4 plants superior to C3?
Answer:
Ans
Page No 74:
Question 6:
In the figure given below, the black line (upper) indicates action spectrum for photosynthesis and the lighter line (lower) indicates the absorption spectrum of chlorophyll a. Answer the following:
a. What does the action spectrum indicate? How can we plot an action spectrum?
b. How can we derive an absorption spectrum for any substance?
Answer:
Ans
Page No 75:
Question 7:
List the important events and end products of the light reaction?
Answer:
Ans
Page No 75:
Question 8:
In the diagram given below what is label A, B and C. What type of phosphorylation is possible in this?
Answer:
In this, cyclic photophosphorylation is possible. This process involves the synthesis of ATP from ADP and inorganic phosphate in the presence of light.
Page No 76:
Question 9:
Why is the RuBisCo enzyme more appropriately called RUBP Carboxylase-Oxygenase and what important role does it play in photosynthesis?
Answer:
Ans
Page No 76:
Question 10:
What special anatomical features are displayed by leaves of C4 plants? How do they provide advantage over the structure of C3 plants?
Answer:
Ans
Page No 76:
Question 11:
Name the two important enzymes of C4 pathway, and explain their role in fixing CO2?
Answer:
Ans
Page No 76:
Question 12:
Why is RuBisCo enzyme the most abundant enzyme in the world?
Answer:
Ans
Page No 76:
Question 13:
Why photorespiration does not take place in C4 plants?
Answer:
The process of photorespiration does not occur in C4 plants because these plants have a mechanism to increase the concentration of carbon dioxide at the site of an enzyme.
It occurs when the C4 acid from the mesophyll cell is broken down in the bundle sheath cells to release carbon dioxide and it results in the increase in interacellular concentration of carbon dioxide. In these plants, the RuBisCO functions as a carboxylase and minimise the activity of oxygenase.
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