NCERT Solution for Class 11 Biology Chapter 13 Photosynthesis of Higher Plants

Welcome to Swastik Classes, your go-to destination for comprehensive NCERT solutions for Class 11 Biology Chapter 13: Photosynthesis of Higher Plants. In this chapter, we delve into the fascinating world of photosynthesis – the process that sustains life on our planet by converting sunlight into chemical energy.

Our meticulously crafted NCERT solutions aim to provide you with a clear understanding of the concepts discussed in this chapter. We have taken great care to present the solutions in a concise yet informative manner, ensuring that you grasp the core principles of photosynthesis with ease.

From the fundamental concepts of chloroplast structure and pigments to the intricate mechanisms of light and dark reactions, our solutions cover every aspect of photosynthesis. We have also included detailed explanations of crucial topics such as the Calvin cycle, C4 and CAM pathways, and the factors affecting photosynthesis.

At Swastik Classes, we understand the importance of a strong foundation in Biology for your academic success. That’s why our solutions not only provide step-by-step answers to the textbook questions but also offer additional insights and explanations to enhance your learning experience.

We believe that learning should be an enjoyable journey, and our NCERT solutions are designed to make studying biology an engaging and enriching experience. So, get ready to unlock the mysteries of photosynthesis and discover the wonders of plant life through our comprehensive NCERT solutions for Class 11 Biology Chapter 13.

Swastik Classes is committed to your success, and we are confident that our NCERT solutions will help you ace your biology exams with flying colors. Let’s embark on this exciting journey of learning and unravel the secrets of photosynthesis together!

NCERT Solution for Class 11 Biology Chapter 13 Photosynthesis of Higher Plants – Exercises

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

Sol. It is not possible to distinguish externally between a C3 and C4 plant, but generally tropical plants are adapted for C4  cycle.

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

Sol. C4  plants live in hot moist or arid and nonsaline or saline habitats. Internally the leaves show kranz anatomy. In kranz anatomy, the mesophyll is undifferentiated and its cells occur in concentric layers around vascular bundles. Vascular bundles are surrounded by large sized bundle sheath cells which are arranged in a wreath-like manner (kranz – wreath). The mesophyll and bundle sheath cells are connected by plasmodesmata or cytoplasmic bridges. The chloroplasts of the mesophyll cells are smaller. They have well developed grana and a peripheral reticulum but no starch. Mesophyll cells are specialised to perform light reaction, evolve 02 and produce assimilatory power (ATP and NADPH). They also possess enzyme PEPcase for initial fixation of COThe chloroplasts of the bundle sheath cells are agranal.

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

Sol. Since, through C cycle, a plant can photosynthesise even in presence of very low concentration of CO2 (upto 10 parts per million), the partial closure of stomata due to xeric conditions would not bring much

effect. Therefore, the plants can adapt to grow at low water content, high temperature and bright light intensities. This cycle is specially suited to such plants which grow in dry climates of tropics and subtropics. Besides, the photosynthetic rate remains higher due to absence of photorespiration in these plants. It can be visualised that both C cycle and photorespiration are the result of evolution or might have been one of the reasons of evolution for the adaptation of plants to different environments. C plants are about twice to efficient as C3 plants in converting solar energy into production of dry matter.

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?

Sol. RuBisCO is an enzyme which acts both as carboxylase (carboxylation during photosynthesis) and oxygenase (during photorespiration). But RuBisCO carries out more carboxylation in C4 plants. In C4  plants, initial fixation of carbon dioxide occurs in mesophyll cells. The primary acceptor of C02 is phosphoenol pyruvate or PER It combines with carbon dioxide in the presence of PEP carboxylase or PEPcase to form oxaloacetic acid or oxaloacetate. Malic acid or aspartic acid is translocated to bundle sheath cells through plasmodesmata. Inside the bundle sheath cells they are decarboxylated (and deaminated in case of aspartic acid) to form pyruvate and CO2 . CO2 is again fixed inside the bundle sheath Cells through Calvin cycle. RuBP of Calvin cycle is called secondary or final acceptor of CO2 in C4  plants. Pyruvate is sent back to mesophyll cells.

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

Sol. Plants that do not possess chlorophyll a will not carry out photosynthesis because it is the primary pigment and act as the reaction centre. It performs the primary reactions of photosynthesis or conversion of light into chemical or electrical energy. Other photosynthetic pigments are called accessory pigments. They absorb light energy of different wavelengths and hence broaden the spectrum of light absorbed by photosynthetic pigments. These pigments hand over the absorbed energy to chlorophylla.

6. Give comparison between the following:

(a) CandC4  pathways

(b) Cyclic and non-cydic photophosphorylation

(c) Anatomy of leaf in C3 and C4  plants.

Sol. (a) The differences between C3 and C

(b) The differences between cyclic and non- cyclic photophosphorylation are as follows :


(c) Differences between the leaf anatomy of C3 and C4plants are as follows :

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

Sol. The leaves of the shaded side are darker green than those kept in sunlight due to two reasons:

(i) The chloroplasts occur mostly in the mesophyll cells along their walls for receiving optimum quantity of incident light.

(ii)The chloroplasts align themselves in vertical position along the lateral walls of high light intensity and along tangential wails in moderate light.

8. The given 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 limiting factor?

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

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

Sol. (a) At regions A and B light is the limiting factor.

(b) In the region A’, light can be a limiting factor.

(c) C is the region where the rate of photosynthesis is not increased when light intensity is increased. D is the point where some other factors become limiting.

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

Sol. Carotenoid pigments are found in all photosynthetic cells. They are accessory pigments also found in roots, petals etc. These pigments do not breakdown easily thus temporarily reveal their colour due to unmasking, following breakdown of chlorophylls. Thus the colour of leaf kept in dark is yellow or pale green.

Conclusions for NCERT Solution for Class 11 Biology Chapter 13 Photosynthesis of Higher Plants

Swastik Classes is proud to provide you with top-notch NCERT solutions for Class 11 Biology Chapter 13: Photosynthesis of Higher Plants. Throughout this chapter, we have explored the intricate processes and mechanisms involved in photosynthesis, shedding light on how plants convert sunlight into vital energy.

Our comprehensive solutions have aimed to simplify the complex concepts of photosynthesis, ensuring a thorough understanding of topics such as chloroplast structure, pigments, light and dark reactions, the Calvin cycle, C4 and CAM pathways, and the factors influencing photosynthesis. We have strived to present the solutions in a concise and informative manner, making it easier for you to grasp the fundamental principles.

At Swastik Classes, we believe that education should be an enjoyable experience, and our NCERT solutions reflect this philosophy. By providing step-by-step answers to textbook questions and offering additional insights and explanations, we have sought to make your learning journey engaging and enriching.

We understand the importance of building a strong foundation in biology, and our NCERT solutions for Class 11 Biology Chapter 13 are designed to support your academic success. Whether you are preparing for exams or simply striving to deepen your knowledge, our solutions are tailored to meet your needs and help you excel in the subject.

Swastik Classes is committed to your growth and success. We are confident that our NCERT solutions will not only equip you with the necessary knowledge but also instill a passion for biology. Let us continue to explore the wonders of the natural world together, one chapter at a time.

What is the primary function of chlorophyll in photosynthesis? A1: The primary function of chlorophyll is to absorb light energy from the sun. It plays a crucial role in capturing photons and initiating the process of photosynthesis. Chlorophyll molecules are responsible for absorbing light in the blue and red regions of the electromagnetic spectrum.

Q2: What are the two stages of photosynthesis? A2: Photosynthesis occurs in two stages: the light-dependent reactions and the light-independent reactions (Calvin cycle). In the light-dependent reactions, light energy is converted into chemical energy in the form of ATP and NADPH. These energy-rich molecules are then utilized in the light-independent reactions to fix carbon dioxide and synthesize glucose.

Q3: What is the Calvin cycle? A3: The Calvin cycle, also known as the light-independent reactions or the dark reactions, is the second stage of photosynthesis. It takes place in the stroma of chloroplasts. In this cycle, carbon dioxide is fixed and converted into glucose with the help of ATP and NADPH generated during the light-dependent reactions.

Q4: What are C4 and CAM pathways of photosynthesis? A4: C4 and CAM pathways are alternative photosynthetic pathways employed by certain plants in response to environmental conditions. In the C4 pathway, carbon dioxide is initially fixed into a four-carbon compound, which is then transported to specialized cells where the Calvin cycle occurs. CAM (Crassulacean Acid Metabolism) plants open their stomata at night to minimize water loss and fix carbon dioxide into organic acids, which are later utilized in the Calvin cycle during the day.

Q5: What factors can affect the rate of photosynthesis? A5: Several factors can influence the rate of photosynthesis, including light intensity, carbon dioxide concentration, temperature, and the availability of water. Optimal conditions for photosynthesis include moderate light intensity, sufficient carbon dioxide levels, suitable temperatures, and an adequate water supply. Any deviations from these optimal conditions can impact the rate of photosynthesis.

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