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

*According to the CBSE Syllabus 2023-24, this chapter has been renumbered as Chapter 11.

NCERT Solutions for Class 11 Biology Chapter 13 Photosynthesis in Higher Plants aid students in understanding complex topics and in preparation for the final examination as well as entrance examinations. Studying answers from NCERT Solutions helps students to check their own understanding of a specific topic and assess their analysing capabilities, which will help them chalk out their strengths and weaknesses.

NCERT Solutions for Class 11 have been formulated by subject experts having vast knowledge, which benefits students in a way that they understand the topics covered in the latest CBSE Syllabus 2023-24 effectively. This not only helps students to perceive a concept completely but is also crucial for the examination, as a better understanding lays a strong foundation for higher studies. Students can download Chapter 13 NCERT Solutions for Class 11 here.

NCERT Solutions for Class 11 Biology Chapter 13 – Photosynthesis in Higher Plants

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Access Answers to NCERT Class 11 Biology Chapter 13 – Photosynthesis in Higher Plants

1. By looking at a plant externally, can you tell whether a plant is C3 or C4? Why and how?

Solution:

Though plants which are adapted to dry tropical climates have the C4 pathway, they do not show any external morphologic characteristics. Hence, it is not possible to say whether the plant is C3 or C4 by looking at its external appearance.

2. By looking at which internal structure of a plant can you tell whether a plant is C3 or C4? Explain.

Solution:

Leaves of C4 plants have kranz anatomy, which makes them different from C3 plants. C4 plants also have specialised cells called bundle sheath cells which surround the vascular bundles. Every cell of the bundle sheath has chloroplasts. The mesophyll cells of leaves do not differentiate into the spongy and palisade parenchyma possessing fewer intercellular spaces, while there is a normal occurrence of chloroplasts in the mesophyll cells. But in C3 plants, the bundle sheath does not exhibit chloroplast, and the mesophyll cells of the leaves are differentiated into the spongy and palisade parenchyma. Hence, by examining the internal structure, we can tell whether the plant is C3 or C4.

3. Even though very few cells in a C4 plant carry out the biosynthetic – Calvin pathway, yet they are highly productive. Can you discuss why?

Solution:

Plant productivity can be estimated by the rate at which photosynthesis takes place. The amount of carbon dioxide in a plant is directly proportional to the rate of photosynthesis. In C4 plants, very few of the cells carry out the biosynthetic pathway, yet they are highly productive for the following reasons:

  • They have a mechanism that increases the CO2 concentration at the site of the enzyme.
  • Mesophyll cells are broken down in the bundle sheath cells, resulting in CO2 release, which, in turn, increases the intracellular CO2 concentration.
  • Rubisco functions as a carboxylase, minimising oxygenase activity.
  • An increase in photosynthesis makes C4 plants more productive.

4. RuBisCO is an enzyme that acts both as a carboxylase and oxygenase. Why do you think RuBisCO carries out more carboxylation in C4 plants?

Solution:

The affinity of RUBISCO is much higher than its affinity for Oxygen. It is the concentration of Oxygen and CO2 that determines the binding of the enzyme. Mesophyll cells of C4 plants lack this enzyme but are found in the bundle sheath cells that girdle the vascular bundles where the Calvin cycle occurs.

RuBisco functions as oxygenase when the concentration of Oxygen is higher, and it acts as carboxylase when the concentration of CO2 is high. In the mesophyll cells, the primary carbon dioxide acceptor is a three-carbon compound – phosphoenol pyruvate, which is converted into a four-carbon compound, oxaloacetic acid or OAA. This is converted further into malic acid, which is transported to the bundle-sheath cells where it undergoes decarboxylation, and carbon fixation takes place through the Calvin cycle, which prevents RuBisCo from serving as an oxygenase.

5. Suppose there were plants that had a high concentration of Chlorophyll b but lacked chlorophyll a. Would they carry out photosynthesis? Then, why do plants have chlorophyll b and other accessory pigments?

Solution:

In the absence of chlorophyll-a, photosynthesis will not take place because chlorophyll-a is a reaction centre responsible for the conversion of solar energy into chemical energy. Although chlorophyll is the primary pigment that traps sunlight, accessory pigments like chlorophyll-b, xanthophylls and carotenoids also absorb sunlight and transfer energy to chlorophyll-a.

6. Why is the colour of a leaf kept in the dark, frequently yellow or pale green? Which pigment do you think is more stable?

Solution:

Chlorophyll fails to absorb the energy in the absence of light; hence, it loses stability to give the leaf yellow colouration. This proves that carotenoids, which impart yellow colour, are more stable.

7. Look at the leaves of the same plant on the shady side and compare them with the leaves on the sunny side. Or, compare the potted plants kept in the sunlight with those in the shade. Which of them has leaves that are darker green? Why?

Solution:

Leaves in the shade get less sunlight to carry out photosynthesis than plants kept in sunlight. In leaves that get less sunlight, more chlorophyll is present to carry out photosynthesis efficiently. In the presence of strong light, the orientation of the chloroplasts in the mesophyll cells is irregular and in vertical files along the walls. Also, in bright light, photooxidation of chloroplasts takes place, while non-oxidation takes place in shaded regions. Hence, the plants kept in the shade have dark green leaves due to the high concentration of chlorophyll.

8. Figure shows the effect of light on the rate of photosynthesis. Based on the graph, answer the following questions:

(a) At which point/s (A, B or C) in the curve is light a limiting factor?

(b) What could be the limiting factor/s in region A?

(c) What do C and D represent on the curve?

NCERT Solutions Class 11-chapter-13-1

Solution:

a) Light is a limiting factor at A and 50% of B, which is due to the increase in the photosynthetic rate with an increase in the intensity of light.

b) Light, CO2 and H2O could be the limiting factor/s in region A.

c) C indicates a stage beyond which light is not a limiting factor, and D is the line beyond which the intensity of light does not affect the photosynthetic rate.

9. Give a comparison between the following:

(a) C3 and C4 pathways

(b) Cyclic and non-cyclic photophosphorylation

(c) Anatomy of leaf in C3 and C4 plants

Solution:

a) C3 and C4 pathways

C3 Pathway C4 Pathway
RUBP is the primary acceptor of CO2. PEP is the primary acceptor of CO2
3- Phosphoglycerate is the first stable product. Oxaloacetic acid is the first stable product.
Occurs in the mesophyll cell of the leaves. Occurs in mesophyll cells and bundle sheath.
The process of Carbon fixation is slower. The process of Carbon fixation is faster.

b) Cyclic and non-cyclic photophosphorylation

Cyclic photophosphorylation Non-cyclic photophosphorylation
Occurs only in photosystem-I. Occurs both in Photosystem-I and II.
ATP is produced. ATP and NADPH2 are produced.
Photolysis of water does not occur; hence, Oxygen is not produced. Photolysis of water occurs; hence, Oxygen is produced.
Electrons move in a closed circle. Electrons do not move in a closed circle.

c) Anatomy of leaf in C3 and C4 plants

Anatomy of leaf in C3 Anatomy of leaf in C4
Do not possess Kranz anatomy. They have Kranz anatomy.
Chloroplasts are not dimorphic. Chloroplasts are dimorphic and organised centripetally. The size of bundle sheaths is larger.
Mesophyll cells possess intercellular space. Mesophyll cells do not possess intercellular space.

NCERT Solutions for Class 11 Biology Chapter 13 – Photosynthesis in Higher Plants

NCERT Solutions for Class 11 Biology Chapter 13 – Photosynthesis in Higher Plants is important for the final exam. The chapter Plant Physiology, on the whole, contributes to about 25% of the questions appearing in the final examination. 18 marks of the total 70 marks are known to appear from Unit – 4.

Students are hence required to thoroughly revise and practise answers along with a deep understanding of concepts so that they are able to answer questions that assess their analysing abilities, conceptual knowledge, etc.

Listed below is the typology of questions that students can expect in the board examinations:

  • Knowledge-based
  • Application-based
  • Comprehension-based
  • High-order thinking skills-based questions
  • Evaluation type

List of subtopics covered in Chapter 13 – Photosynthesis in Higher Plants

Number Subtopic
13.1 What Do We Know?
13.2 Early Experiments
13.3 Where Does Photosynthesis Take Place?
13.4 How Many Pigments Are Involved in Photosynthesis?
13.5 What Is Light Reaction?
13.6 The Electron Transport
13.7 Where Are the ATP and NADPH Used?
13.8 The C4 Pathway
13.9 Photorespiration
13.10 Factors Affecting Photosynthesis

NCERT Solutions for Class 11 Biology Chapter 13 – Photosynthesis in Higher Plants

Photosynthesis in Higher plants emphasises the details of one of the most crucial processes that are carried out in plants – photosynthesis. This process is observed only in green plants which possess the pigment chlorophyll. Green plants synthesise their food through this process and hence are termed autotrophs. Photosynthesis is a Physicochemical process wherein light energy is utilised to synthesise organic compounds. Sun is the ultimate source of energy. Therefore, all living forms on Earth depend on sunlight for their energy.

The basis of life on earth is the plant process called photosynthesis. It is important due to the following two reasons: it is the primary source of all food on the earth and is responsible for releasing oxygen into the atmosphere by the green plants.

The chapter discusses the structure of photosynthetic machinery and the different reactions that transform light energy into chemical energy.

Key Features of NCERT Solutions for Class 11 Biology Chapter 13 – Photosynthesis in Higher Plants

  • All exercise questions are answered elaborately.
  • Solving NCERT Solutions will help students easily solve sample papers and previous years’ question papers.
  • Referring to these solutions can boost the confidence of students and help them jot down their weaknesses.
  • Neatly labelled diagrams help to understand the concepts better.
  • Questions are provided along with the answers so that students do not have to go back to the textbook to refer to the correct question number.

Frequently Asked Questions on NCERT Solutions for Class 11 Biology Chapter 13

Q1

Is Chapter 13 of NCERT Solutions for Class 11 Biology important for the board exam?

Yes, Chapter 13 of NCERT Solutions for Class 11 Biology is important for the final exam as it carries 18 marks. This chapter is categorised under Unit 4, which contributes about 25% of the questions which appear in the final exam. So the students should thoroughly practise and revise the concepts on a regular basis to score well in the board exam. These solutions help students to assess their conceptual knowledge and analyse abilities which are important for the exam.
Q2

What topics can I learn from Chapter 13 of NCERT Solutions for Class 11 Biology?

From Chapter 13 of NCERT Solutions for Class 11 Biology, you can learn important topics like
13.1 – What Do We Know?
13.2 – Early Experiments
13.3 – Where Does Photosynthesis Take Place?
13.4 – How Many Pigments Are Involved in Photosynthesis?
13.5 – What Is Light Reaction?
13.6 – The Electron Transport
13.7 – Where Are the ATP and NADPH Used?
13.8 – The C4 Pathway
13.9 – Photorespiration
13.10 – Factors Affecting Photosynthesis
Q3

What are the advantages of referring to the NCERT Solutions for Class 11 Biology Chapter 13?

The advantages of referring to the NCERT Solutions for Class 11 Biology Chapter 13 are
1. All the textbook questions are answered in a descriptive manner.
2. Students will be able to solve complex questions effortlessly using the solutions PDF.
3. By regular practice, students can jot down their areas of weakness and work on them for a better score.
4. Diagrams are present under each concept to help students learn them easily.
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