NCERT Exemplar Class 11 Biology Solutions Chapter 13 Photosynthesis in Higher Plants

Photosynthesis in Higher Plants provides students with a detailed explanation of how the essential process of photosynthesis takes place in higher plants. NCERT Exemplar Class 11 Biology Solutions Chapter 13 also explores the adaptations present in the plants that live in unusual environmental conditions. All the cycles that occur in the plants during the day and night have been broken down into simpler steps by our subject experts. Students can rely on the NCERT Exemplar to get a clear vision of the concepts and deepen their knowledge.

This Story also Contains

1. NCERT Exemplar for Class 11 Science Chapter 13 Photosynthesis in Higher Plants(MCQs)
2. Discover the NCERT Exemplar Class 11th Biology Solution Chapter 13- Short Answer Type Questions
3. Detailed NCERT Exemplar Class 11th Biology Solutions Photosynthesis in Higher Plants
4. Approach to Solve Questions of Class 11 Biology Chapter 13
5. Main topics of NCERT Exemplar Class 11 Biology Chapter 13
6. Important Question from NCERT Exemplar Class 11 Biology Chapter 13
7. NCERT Exemplar Class 11 Biology Solutions Chapter Wise

To understand how photosynthesis takes place at different wavelengths, along with their graphs, students can go through these resources. The exemplar solutions include various types of questions that allow students to easily solve the questions present in the NCERT Class 11 Biology Book. Regular practice of these will help them to grasp every topic clearly, by which they can score much better marks in the exams, and also in their competitive exams.

NCERT Exemplar for Class 11 Science Chapter 13 Photosynthesis in Higher Plants(MCQs)

A variety of questions like MCQs, Short answers, and long answers, along with the required diagrams and graphs, are provided below to help you understand these complex topics easily and effectively and gain more clarity on your doubts and solve them with ease.

Question:1

Which metal ion is a constituent of chlorophyll?
a. Copper
b. Magnesium
c. Iron
d. Zinc

Answer:

The correct answer is option(b), Magnesium

Explanation- A chlorophyll molecule has a cyclic structure with a ring, and it contains a magnesium atom in the center.

Question:2

Which pigment acts directly to convert light energy to chemical energy?

a. Carotenoid
b. Chlorophyll B
c. Chlorophyll A
d. Xanthophyll

Answer:

The correct answer is the option (c), Chlorophyll A

Explanation – Chlorophyll A absorbs the maximum light and therefore directly converts light energy to chemical energy.

Question:3

Which range of wavelength (in nm) is called photosynthetically active radiation (PAR)? a. 760 -10,000
b. 400 -700
c. 390 -430
d. 100 -390

Answer:

The correct answer is option(b), 400-700nm

Question:4

Which light range is least effective in photosynthesis?

a. Red
b. Blue
c. Green
d. Violet

Answer:

The correct answer is option (c). Green

Explanation - The least effective light in photosynthesis is green light. As chlorophyll is present in leaves, the pigment responsible for photosynthesis reflects the green light rather than absorbing it.

Question:5

Chemosynthetic bacteria obtain energy from
a. Organic substances
b. Inorganic chemical
c. Sun
d. Infrared rays

Answer:

The correct answer is option (b). Inorganic chemical

Explanation - These bacteria obtain energy from the oxidation of inorganic chemicals to produce food.

Question:6

Energy required for ATP synthesis in PS II comes from
a. Electron gradient
b. Reduction of glucose
c. Oxidation of glucose
d. Proton gradient

Answer:

The correct answer is option (d), the Proton gradient

Question:7

During light reaction in photosynthesis, the following are formed.
a. ATP, hydrogen donor and O2
b. ATP and sugar
c. ATP, hydrogen, and O2 donor
d. Hydrogen, O2, and sugar

Answer:

The correct answer is option (c), ATP, Hydrogen, and O2 donor.

Explanation - During the light reaction of photosynthesis, ATP, hydrogen, and oxygen are formed. Hydrogen and oxygen are by-products of water splitting.

Question:8

Dark reaction in photosynthesis is called so because
a. It does not depend on light energy
b. It cannot occur during daylight
c. It occurs during daylight
d. It can occur in the dark also

Answer:

The correct answer is option (a). It does not depend on light energy

Explanation - The "dark reaction" in photosynthesis is called so because it does not directly require light energy to occur, but instead, it uses the energy stored in ATP and NADPH produced during the light-dependent reactions.

Question:9

PEP is the primary CO2 acceptor in
a. C3 plants
b. C4 plants
c. C2 plants
d. Both C3 and C4 plants

Answer:

The correct answer is option (b). C4 plants

Explanation - (PEP is the primary CO2 acceptor in C4 plants because it allows for carbon fixation, majorly in environments with low CO2 concentrations.

Question:10

The splitting of water is associated with
a. Lumen of thylakoid
b. Photosystem I
c. Both photosystem I and II
d. Inner surface of thylakoid membrane

Answer:

The correct answer is option (d). Inner surface of thylakoid membrane

Explanation- The splitting of water is associated with the inner thylakoid membrane because the water-splitting complex, part of Photosystem II (PSII), is located on that side, allowing the release of protons and electrons.

Question:11

The correct sequence of flow of electrons in the light reaction is
a. PSI, ferredoxin, PSII
b. PSI, plastoquinone, cytochromes, PS II, ferredoxin
c. PS II, plastoquinone, cytochromes, PS I, ferredoxin
d. PS I, plastoquinone, cytochromes, PS I, ferredoxin

Answer:

The correct answer is option( c). PS II, plastoquinone, cytochromes, PS I, ferredoxin

Question:12

The enzyme that is found in a C3 plant is
a. ATP synthase
b. NADP reductase
c. PEP carboxylase
d. RuBP carboxylase

Answer:

The correct answer is option(d). RuBP carboxylase

Explanation - It is the main enzyme that catalyzes the first step of carbon fixation in the C3 plants.

Question:13

The reaction that is responsible for the primary fixation of CO2 is catalysed by
a. PGA synthase
b. RuBP carboxylase and PEP carboxylase
c. RuBP carboxylase
d. PEP carboxylase

Answer:

The correct answer is option (b). RuBP carboxylase and PEP carboxylase

Explanation - PEP carboxylase catalyzes the reaction in C4 plants and RuBP carboxylase in C3 plants.

Question:14

When CO2 is added to PEP, the first stable product synthesised is
a. Oxaloacetate
b. Pyruvate
c. Glyceraldehyde -3 -phosphate
d. Phosphoglycerate

Answer:

The correct answer is option(a). Oxaloacetate

Explanation- Oxaloacetate is the first stable product, and it's a four-carbon compound.

Access the NCERT Exemplar Class 11th Biology Solution Chapter 13- Very Short Answer Type Questions:

Question:1

a. Is this structure present in animal cells or plant cells?

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:

1. This structure is only found in plant cells

2. Yes, chloroplasts, along with their DNA, can be passed on to progeny because chloroplasts have an ability to self-replicate, and this inheritance is generally maternal in most flowering plants.

3. (i) This is the site for the occurrence of the dark reaction.

(ii) Replication of chloroplast occurs in the location mentioned as (ii).

Question:2

2H₂O → O₂ + 4H⁺ + 4e⁻

Based on the above equation, answer the following question:
a. Where does this reaction take place in plants?
b. What is the significance of this reaction?

Answer:

(a) It occurs in the thylakoid membrane of chloroplasts, mainly within the Photosystem II (PSII) complex.

(b) This reaction, also known as water splitting or photolysis, is the important step in the light-dependent reactions of photosynthesis because oxygen is released in this reaction as a byproduct of photosynthesis and is essential for respiration, and the electrons released from water are used to give energy to the electron transport chain.

Question:3

Cyanobacteria and some other photosynthesis bacteria don’t have chloroplasts. How do they conduct photosynthesis?

Answer:

Cyanobacteria and other photosynthetic bacteria, which do not have chloroplasts, conduct photosynthesis using photosynthetic pigments present in their cell membranes, specifically in internal membranes called thylakoids.

Question:4

A. Breakdown of proton gradient leads to release of ___________

B. NADP reductase enzyme is located on _______

Answer:

A. ATP molecules

B. The outer side of the thylakoid membrane

Question:5

Can girdling experiments be done in monocots? If yes, how? If no, why not?

Answer:

No girdling experiments can be performed on monocots because their vascular bundles are present throughout the stem, making it impossible to remove a continuous ring of bark (phloem) without disturbing the complete vascular system.

Question:6

3CO2 + 9ATP + 6NADPH + water → Glyceraldehyde 3-phosphate + 9ADP + 6NADP++8Pi

Analyse the above reaction and answer the following question
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) 3 molecules of ATP and 2 molecules of NADPH are required to fix one molecule of carbon dioxide.

(b) This reaction occurs in the stroma of the chloroplast.

Question:7

Does moonlight support photosynthesis? Find out.

Answer:

No, moonlight does not support photosynthesis because it does not have the required energy to excite chlorophyll molecules, which is important for the light-dependent reactions of photosynthesis.

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) The process of formation of glucose that occurs in different ways in C3 and C4 plants. This was explained by two scientists, M.D. Hatch and C.R. Slack. So it is called the Hatch-Slack pathway.

(b) When the process of photosynthesis occurs, the water molecule gets split into hydrogen and oxygen that result in the formation of carbohydrates, and this cycle is called the Calvin cycle.

(c) This is the enzyme located in mesophyll cells of C4 plants that fixes and forms oxaloacetic acid, which is a 4-carbon compound.

(d) These are special types of vascular bundles and these are located in veins of monocots. They contain chloroplasts, and synthesis of glucose takes place here.

Question:9

Where is NADP reductase enzyme located in the chloroplast? What is the role of this enzyme in proton gradient development?

Answer:

NADP reductase enzyme is located on the outer side of the thylakoid membrane in chloroplasts. It plays an important role in maintaining the proton gradient by reducing NADP+ to NADPH, which takes protons from the stroma, thus contributing to the proton gradient.

Question:10

ATPase enzyme consists of two parts. What are those parts? What are those parts? How are they arranged in the thylakoid membrane? Conformational change occurs in which part of the enzyme?

Answer:

The ATPase enzyme consists of two parts: F0 (integral membrane protein) and F1 (peripheral membrane protein). F0 is present in the inner region of the thylakoid membrane, while F1 lies in the outer region of the thylakoid, and conformational changes occur in the F1 portion. All the conformational changes occur in the F1 portion.

Question:11

Which products formed during the light reaction of photosynthesis are used to drive the dark reaction?

Answer:

The products ATP and NADPH formed during the light reaction of photosynthesis drive the dark reaction. These products are used in the formation of glucose, a sugar that provides energy for the cell.

Question:12

What is the basis for designating C3 and C4 pathways of photosynthesis?

Answer:

The basis for the designations of C3 and C4 pathways in photosynthesis are based on the number of carbon atoms present in the first stable product. C3 pathways form a 3-carbon compound (3-PGA), while C4 pathways form a 4-carbon compound, which is oxaloacetate.

Discover the NCERT Exemplar Class 11th Biology Solution Chapter 13- Short Answer Type Questions

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:

Succulent plants grow in dry conditions. To these plants, they have to close down their stomata during the time to prevent water loss through transpiration, and also, the exchange of gases does not take place.

Thus, plants have developed the mechanism to fix C02 during the night in the form of malic acid and release it during the day inside the photosynthetic cells.

Question:2

Chlorophyll ‘a’ is the primary pigment for light reaction. What are the accessory pigments? What is their role in photosynthesis?

Answer:

Chlorophyll 'a' is the primary pigment for the light reaction, and the accessory pigments like chlorophyll b, carotenoids, and xanthophylls also help in photosynthesis by absorbing light of different wavelengths and transferring the energy to chlorophyll 'a' and can carry out the supporting process.

Question:3

Does the reaction of photosynthesis, called the ‘dark reaction,’ need light? Explain.

Answer:

Dark reactions of photosynthesis do not directly require light to occur. The dark reactions occur in the day. As a dark reaction does not require light, it doesn't mean it occurs at night; it only requires products of light reaction like ATP and NADPH. So, dark reactions indirectly need sunlight but can work without it as well.

Question:4

How are photosynthesis and respiration related to each other?

Answer:

Photosynthesis and respiration are interconnected as photosynthesis uses carbon dioxide and water to produce glucose and oxygen, while respiration uses glucose and oxygen, which is released as a by-product of photosynthesis, to produce carbon dioxide and water. It means both act as the reverse of each other.

Question:5

If a green plant is kept in the dark with proper ventilation, can this plant carry out photosynthesis? Can anything be given as a supplement to maintain its growth or survival?

Answer:

A green plant kept in darkness, even with proper ventilation, cannot perform photosynthesis because sunlight is essential to carry out the process of photosynthesis. To maintain its growth or survival, the plant needs to be watered and supplemented with nutrients.

Question:6

Photosynthesis 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:

No, photosynthetic organisms that occur at different ocean depths do not receive the same light, either qualitatively or quantitatively.

But deeper organisms also perform the process of photosynthesis very effectively as these organisms are adapted to low-light conditions due to the presence of different pigments. These pigments absorb the light at available and different wavelengths.

Question:7

In tropical rain forests, the canopy is thick, and shorter plants growing below it receive filtered light. How are they able to carry out photosynthesis?

Answer:

Plants present in tropical rainforests where the canopy is thick, despite receiving less amount of light, are able to carry out photosynthesis because they have adapted themselves to survive in low-light conditions, with changes like large leaves and high chlorophyll units. However, the process slowed down a little bit.

Question:8

What conditions enable RuBisCO to function as an oxygenase? Explain the ensuing process.

Answer:

RuBisCo is an enzyme that has a dual nature. It acts as carboxylase when CO2 concentration is good enough in the atmosphere. But if O2 concentration increases, its nature changes and it binds with oxygen and acts as oxygenase enzymes.

Question:9

Why does the rate of photosynthesis decrease at higher temperatures?

Answer:

The rate of photosynthesis decreases at higher temperatures because the enzymes involved in this process require the optimum conditions of temperature to work effectively but as these conditions change, the rate of photosynthesis also gets affected.

Question:10

Explain how the light reaction of photosynthesis, ATP synthesis is a chemiosmotic phenomenon.

Answer:

Chemiosmosis is the movement of ions across a semipermeable membrane, down their electrochemical gradient, to produce energy. During the light reaction of photosynthesis, ATP is synthesised, which is a chemiosmotic phenomenon because it involves the movement of protons across the thylakoid membrane, which creates a proton gradient that drives ATP synthesis by ATP synthase.

Question:11

Find out how Melvin Calvin worked out the complete biosynthetic pathway for the synthesis of sugar.

Answer:

Melvin Calvin and his associates discovered the Calvin cycle, which consists of various steps:-

• They used C14 as a radioactive label to follow the path of photosynthetic carbon fixation. The labelled CO2 was fed to the algae for short periods.

• The algal cells were killed immediately in boiling alcohol, and radioactivity in various compounds was separated by paper chromatography.

• When alga were exposed to radioactive CO2 for less than five seconds, the first product that became radioactive was the phosphoglyceric acid.

This is how the Calvin cycle was discovered.

Question:12

Six turns of the Calvin cycle are required to generate one mole of glucose. Explain.

Answer:

Six turns of the Calvin cycle are needed to produce one molecule of glucose because each turn reduces one carbon dioxide molecule, two molecules of NADPH, and 2 molecules of ATP. Glucose is a six-carbon molecule, and thus, six CO2 molecules are required for the making of one mole of glucose.

Question:13

Answer:

The complete flow chart for cyclic photophosphorylation is given below:

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 that lack this anatomy?

Answer:

Kranz anatomy, a unique leaf structure, is found in C4 plants like maize and sugarcane. These plants are better adapted to dry, tropical conditions, where temperature and light intensities are very high. These plants are better adapted because Kranz anatomy helps them to minimize the process of photorespiration and maximize carbon fixation, which also leads to the easy manufacturing of glucose.

Question:15

A process is occurring throughout the day, in ’X’ organism. Cells participate in this process. During this process, ATP, CO2, and water are evolved. It is not a light-dependent process.
a. Name the process
b. Is it a catabolic or an anabolic process?
c. What could be the raw material of this process?

Answer:

a. The name of the process is respiration

b. The respiration process is a catabolic process.

c. The raw material used in this process is carbohydrates.

Question:16

Tomatoes, carrots, and chilies are red in color due to the presence of one pigment. Name the pigment. Is it a photosynthetic pigment?

Answer:

Tomatoes, Chillies, and Carrots are red due to the presence of a pigment called Lycopene. Lycopene is not a photosynthetic pigment; it's a carotenoid.

Question:17

Why do we believe chloroplasts and mitochondria to be semi-autonomous organelles?

Answer:

Mitochondria and chloroplasts are considered semi-autonomous organelles because they have their own DNA, ribosomes, and protein-synthesizing parts, allowing them to replicate independently and produce some of their own proteins, though they still depend on the cell for other functions.

Question 18:

Observe

a. Which group of plants exhibits these two types of cells?

b. What is the first product of the C4 cycle?

c. Which enzyme is there in bundle sheath cells and mesophyll cells?

Answer:

a. Bundle sheath cells and mesophyll cells are found in monocot plants

b. Oxaloacetic acid, which is a 4-carbon compound, is the first stable product.

c. PEP carboxylase or PEPcase are the enzymes present in bundle sheath cells and mesophyll cells

Question:19

A cyclic process occurs in a C3 plant, which is light-dependent and needs O2. This process does not 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. The name of the process is called photorespiration.

b. No, it is not important for survival.

c. The end product of this process is hydrogen peroxide.

d. It occurs in chloroplasts, mitochondria, and peroxisomes.

Question:20

Suppose euphorbia and maize are grown in tropical areas.

a. Which one of them do you think will be able to survive under such conditions?
b. Which one of them is more efficient in terms of photosynthetic activity?
c. What differences do you think are there in their leaf anatomy?

Answer:

a. Euphorbia is a CAM plant. Therefore, it will be able to survive under such conditions.

b. Maise will be more efficient in the photosynthesis activity because it is a C4 plant.

c. Kranz leaf anatomy is found in maize plants as they are C4 plants. In contrast, it is absent in euphorbia.

Detailed NCERT Exemplar Class 11th Biology Solutions Photosynthesis in Higher Plants

Question:1

Is it correct to say that photosynthesis occurs only in the leaves of a plant? Besides leaves, what are the other parts that may be capable of carrying out photosynthesis? Justify.

Answer:

No, it's not correct to say that photosynthesis occurs only in the leaves of a plant; while leaves are the main sites to carry out the process, any green part of a plant containing chlorophyll can also photosynthesise, including green stems, branches, and even some roots. For example:

• Green Stems: Plants like cacti have thick and fleshy stems that function as leaves because they contain chlorophyll and chloroplasts for photosynthesis.

• Green Branches: Just like stems, green branches can also do photosynthesis, especially in plants with limited leaf development.

• In some plants, the sepals can also photosynthesise.

Question:2

The entire process of photosynthesis consists of a number of reactions. Where in the cell does each of these take place?
a. Synthesis of ATP and NADPH_____
b. Photolysis of water_______
c. Fixation of CO2 _______
d. Synthesis of sugar molecule________
e. Synthesis of starch________

Answer:

a. Outer region of the thylakoid membrane

b. Inner region of the thylakoid membrane

c. Stroma region of chloroplast

d. Chloroplast of plants

e. Cytoplasm of plant cells

Question:3

What 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:

The property of pigments, specifically chlorophyll, that initiates the process of photosynthesis is their ability to absorb photons of light and become excited, which allows them to transfer the energy, which is utilized to start the process.

The process of photosynthesis is more efficient in red and blue light because these wavelengths are mostly absorbed by chlorophyll, thus increasing the rate of photosynthesis.

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:

Action spectrum - It is the graph that shows the rate of photosynthesis at different wavelengths of light.

Absorption spectrum - A graph that shows the amount of light absorbed at different wavelengths of light.

When both the action and absorption spectra overlap, it indicates that the light which is absorbed is utilized for the process of photosynthesis. The peaks of these spectra indicate that chlorophyll a and b are the main photosynthetic pigments.

By looking at the above graph, it is very clear that the action spectrum shows maximum peaks at 430-470 nm of the blue light, and later in the graph, there is another peak at wavelengths (red light) of 660-670 nm, at 430-470 nm of the blue light.

Looking at the graph, it is very clear that the action spectrum shows maximum peaks at 430-470 nm of the blue light, and later in the graph, there is another peak at wavelengths (red light) of 660-670 nm, at 430-470 nm of the blue light

Question:5

Under what conditions are C4 plants superior to C3?

Answer:

C4 plants are considered to be superior to C3 plants. There are several reasons for this, which are provided below:

C4 plants can respond to higher temperatures and show a higher rate of photosynthesis, while C3 plants respond to a much lesser value of optimum temperature ranges.

The C3 and C3 plants respond differently to Co2 concentrations. At low concentrations, C4 plants can carry out the process of photosynthesis but C3 plants cannot do so.

C4 plants can perform photosynthesis even when their stomata are almost closed, but C3 plants can perform photosynthesis only when their stomata are open.

Question:6

a. What does the action spectrum indicate? How can we plot an action spectrum? Explain with an example.
b. How can we derive an absorption spectrum for any substance?
c. If chlorophyll-a is responsible for the light reaction of photosynthesis, why do the action spectrum and absorption spectrum not overlap?

Answer:

(a) An action spectrum indicates the effectiveness of different wavelengths of light in the process, such as photosynthesis, by plotting the graph of the rate of photosynthesis against the wavelength of light.

To plot an action spectrum, firstly, we need to measure the amount of oxygen released during the process of photosynthesis on the y-axis under different wavelengths of light and then plot these rates against the corresponding wavelengths, which are present on the x-axis.

(b) An absorption spectrum can be plotted by passing a beam of light through a sample and measuring the amount of light that is absorbed at each wavelength. The obtained data is then plotted on a graph, with the given wavelength on the x-axis and how much light is absorbed on the y-axis.

(c) The action spectrum of photosynthesis and the absorption spectrum of chlorophyll-a do not overlap perfectly because, while chlorophyll-a is the primary pigment, other accessory pigments like chlorophyll-b etc., also absorb light and contribute to the photosynthetic process, due to which the spectrum is always at high levels as compared to the absorption spectrum.

Question:7

What are the important events and end products of the light reaction?

Answer:

Light reaction consists of various important events, which are given below:

1- Light Absorption: The pigments present in the leaves, such as chlorophyll and other accessory pigments, absorb the light at different wavelengths and then excite the electrons from lower energy levels to higher energy levels.

2-Water Splitting (Photolysis): Absorbed light energy is utilized to break down the molecule of water into oxygen, hydrogen ions, and electrons.

3- ATP Synthesis (Photophosphorylation): The proton gradient is used in the formation of ATP from ADP through ATP syntase.

4- NADPH formation- Electrons released from the electron transport chain are used to produce NADPH.

The end products of the light reaction are ATP, NADPH, and oxygen molecules.

Question:8

Answer:

The process of cyclic phosphorylation is depicted in this diagram.

Question:9

Why is the RuBisCo enzyme more appropriately called RUBP Carboxylase -Oxygenase, and what important role does it play in photosynthesis?

Answer:

RuBisCo enzyme shows a dual nature as

Carboxylation: When there is a large concentration of carbon dioxide, RuBisCo binds with that and acts as a carboxylase.

Oxygenation: RuBisCo possesses an affinity for oxygen, depending on the concentration and can work accordingly.

Therefore, it is often called RUBP Carboxylase-Oxygenase compound.

Importance of Photosynthesis:

• Carbon Fixation: RuBisCO is the enzyme that fixes atmospheric CO2 into organic molecules, due to which it initiates the entire food chain.

• Calvin Cycle: RuBisCO's carboxylation activity is the first step in the Calvin cycle, where CO2 is converted into sugar.

• Photorespiration: This enzyme also plays a role in protecting plants from stress and in the recycling of carbon.

Question:10

What special autonomous features are displayed by leaves of C4 plants? How do they provide an advantage over the structure of C3 plants?

Answer:

C4 plants show a different type of leaf structure where the vascular bundles are surrounded by cells with large chloroplasts, which helps to concentrate CO2, known as Kranz anatomy, which is not present in the C3 plants.

Advantages over C3 Plants:

• Higher Photosynthetic Rates: C4 plants can maintain higher photosynthetic rates, especially in hot and dry conditions, due to their ability to avoid photorespiration, which C3 plants fail to do.

• Water Conservation: By minimizing photorespiration, C4 plants can conserve water more effectively where less water is present, as they can close their stomata, reducing photosynthetic efficiency.

• Adaptation to Hot Environments: The Kranz anatomy and the C4 pathway allow C4 plants to survive in environments where C3 plants struggle in hot, arid regions.

Question:11

Name the two important enzymes of the C3 and C4 pathway, respectively. What important role do they play in fixing CO2?

Answer:

In the C3 pathway, the key enzyme for CO2 fixation is RuBisCO, which is known as RUBP Carboxylase Oxygenase, while in the C4 pathway, it's PEP carboxylase. RuBisCO fixes CO2 to RuBP, and PEP carboxylase fixes CO2 to PEP.

In C3 plants, RuBisCO (Ribulose-1,5-bisphosphate carboxylase-oxygenase) is the main enzyme that is responsible for carbon fixation.

PEP carboxylase is the key enzyme in the C4 pathway. It combines with carbon dioxide to result in the formation of a 4-carbon compound called OAA or oxaloacetic acid. This is further converted into carbon dioxide.

Question:12

Why is RuBisCo enzyme the most abundant enzyme in the world?

Answer:

Rubisco is the most abundant enzyme on Earth because it's the main enzyme responsible for carbon fixation during photosynthesis. The enzyme is present in all the plants performing photosynthesis, which is an important process essential for plant growth.

Also, Check NCERT Books and NCERT Syllabus here

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