NIOS Class 12 Biology Intext Solutions Chapter 11

Class 12 NIOS Biology Intext Solutions Chapter 11

INTEXT QUESTIONS 11.1

1. (i) Define photosynthesis

(ii) Give the overall general chemical equation of photosynthesis.

(i) It is the process by which green plants produce food (carbohydrates) from simple substances like CO2 and water in the presence of sunlight and chlorophyll.

(ii)

2. (i) List the two categories of photosynthetic pigments.

(ii) Which pigments are known as accessory pigments?

(i) Chlorophylls and carotenoids.
(ii) Carotenoids and chlorophyll b

3. (i) What does chlorophyll do to the light falling on it?

(ii) Which pigment system absorbs maximally the red wavelength of light?

(i) Absorb it and then convert it into chemical energy.
(ii) Chlorophyll a and b

4. Answer the following

(i) In which colour of light, rate of photosynthesis is minimum and in which colour of light it is maximum?

(ii) Name the type of energy that is used in the process of photosynthesis. In which form does this energy get stored in plant body?

(i) Minimum in green and yellow light and maximum in blue and red light.
(ii) light energy; chemical energy

5. Which molecule is the source of evolution of oxygen in photosynthesis— CO₂ or H₂O?

From the photolysis of water in PSII.

INTEXT QUESTIONS 11.2

1. What is the role of NADP?

NADP acts as an electron acceptor and H+ acceptor, and finally, it gets reduced to NADPH₂.

2. Why is dark reaction called so?

It is called the dark reaction because it can occur independently of light, i.e., can occur both in light and in the dark.

3. What is the role of the enzymes (i) rubisco and (ii) PEPCo, and where are they present?

(i) Rubisco is a part of the C3 cycle and combines with CO2 to produce a C3 compound called PGA.

Rubisco is present in the mesophyll cells of C3 plants and in the bundle sheath cells of C4 plants.

(ii) PEPCo is a part of the C4 pathway and combines with CO2 to form a C4 compound called OAA.

PEPCo is found only in mesophyll cells of C4 plants.

4. Explain Kranz anatomy.

Kranz anatomy refers to the special type of vascular bundles seen in the leaves of C4 plants. Kranz means wreath. In these plants, the vascular bundles have a sheath of large parenchyma cells around them in the form of a wreath, thus the name Kranz anatomy.

5. Differentiate between the chloroplasts present in the mesophyll cells and in the bundle sheath cells of the leaf of a C4 plant.

These leaves possess two types of chloroplasts (dimorphic chloroplasts).

Chloroplasts in the mesophyll cells are smaller and have well-developed grana (granal chloroplasts) but do not accumulate starch.
Chloroplasts in the bundle sheath cells are larger and lack grana (agranal chloroplasts) but contain numerous starch grains.

6. Why are C4 plants more efficient than C3 plants?

C4 plants have no photorespiration and thus there is no loss of additional carbon dioxide, due to breakdown of RuBP to Glycolate and CO₂.

7. Name the two sets of reactions in photosynthesis in which light energy is required.

(i) Photolysis of water

INTEXT QUESTIONS 11.3

1. List the internal factors that influence the rate of photosynthesis?

leaf age, chlorophyll content, leaf anatomy (size, internal structure, stomatal distribution)

2. State the principle of limiting factor.

According to the principle of limiting factor, when a process is affected by various factors, the rate of the process depends upon the pace of the slowest factor.

3. Give an example of chemosynthetic bacteria.

Nitrosomonas and Nitrobacter.

4. Why are prokaryotes not able to produce ATP by chemiosmosis?

Prokaryotes are not able to produce ATP by chemiosmosis because they are not able to maintain a H+ gradient across a membrane in the absence of membrane-bound organelles in their cytoplasm.

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View Comments

アイムノットヒューマン says:

October 10, 2025 at 2:48 am

This NIOS Biology text is a treasure trove of green-fingered facts! While Kranz anatomy sounds like a fancy party plan and photorespiration seems like a plants bad habit, the sheer detail is impressive. Its like a survival guide for chloroplasts! However, explaining chemiosmosis in prokaryotes without organelles feels a bit like telling a fish it cant swim – necessary, but slightly obvious. Overall, a dense but delightfully botanical read for the dedicated plant detective!