NIOS Class 12 Biology Chapter 11 Solution – Photosynthesis
NIOS Class 12 Biology Solution Chapter 11 Photosynthesis . NIOS Class 12 Biology Chapter 11 Question Answers Download PDF. NIOS Class 12 Biology Notes.
Board |
NIOS |
Class |
12th (Higher Secondary) |
Subject |
Biology |
Topic |
Question Answer, Solution, Notes |
INTEXT 11.1
1.) (i) Define photosynthesis
Ans: It is a process by which green plants, algae and chlorophyll containing bacteria utilize the energy of sunlight to synthesize their own food (organic matter) from simple inorganic molecules . It is the most vital process on earth, photosynthesis (photo = light; synthesis = to unite), is essential to human life as well as nearly all other living things.
(ii) Give the overall general chemical equation of photosynthesis.
Ans: 6CO2 + 12H2O Chlorophyll ⎯⎯⎯⎯⎯ Sunlight → C6H12O6 + 6H2O + 6O2
2.(i) List the two categories of photosynthetic pigments.
Ans: Chlorophylls and carotenoids are the photosynthetic pigments
(ii) Which pigments are known as accessory pigments?
Ans: Carotenoids and chlorophyll b are known as accessory pigments
3)… (i) What does chlorophyll do to the light falling on it?
Ans: The photosynthetic pigment chlorophyll is the principle pigment involved in photosynthesis. It is a large molecule and absorbs light maximally and convert it into chemical energy
(ii) Which pigment system absorbs maximally the red wavelength of light?
Ans: Chlorophyll a and b pigment system absorbs maximally the red wavelength of light
4).. Answer the following
(i) In which colour of light, rate of photosynthesis is minimum and in which colour of light it is maximum?
Ans: The rate of photosynthesis is Minimum in green and yellow light and maximum in blue and red light.
(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?
Ans: light energy is used in process of photosynthesis and in form of chemical energy it get stored in plant body.
5).. Which molecule is the source of evolution of oxygen in photosyntheisis— CO2 or H2O?
Ans: the source of oxygen in photosynthesis is from photolysis of water in PSII
INTEXT 11.2
1.) What is the role of NADP?
Ans: NADP acts as an electron acceptor and H+ acceptor and finally, it gets reduced to NADPH
2.) Why is dark reaction called so?
Ans: These reactions are independent of light i.e. light is not necessary but can continue in light as well if products of the light reaciton are available. Thus it is also called dark reaction.
3.) What is the role of the enzymes and where are they present?
(i) rubisco – Rubisco is a part of C3 cycle and combines with CO2 to produce a C3 compound called PGA. It is present in the mesophyll cells of C 3 plants and in the bundle sheath cells of C4 plants
(ii) PEPCo – PEPCo is a part of C4 path way and combines with CO2 to form a C4 compound called OAA, it is found only in mesophyll cells of C4 plants
4.) Explain Kranz anatomy.
Ans: The Kranz anatomy, or dimorphic chloroplasts, are seen in the leaves of C4 plants.
(a) These plants have vascular bundles that are encircled by a wreath-shaped sheath of massive parenchymal cells, giving rise to the term Kranz anatomy.
(b) Chloroplasts in leaves come in two varieties (dimorphic chloroplasts).
(c) Granal chloroplasts, which are smaller and highly developed in the mesophyll cells’ chloroplasts but do not accumulate starch.
(d) Bundle sheath cells have bigger, agranal chloroplasts that lack grana yet are packed with many starch grains.
5.) Differentiate between the chloroplasts present in the mesophyll cells and in the bundle sheath cells of the leaf of a C4 plant.
Ans: Chloroplasts in the mesophyll cells are smaller and have well developed grana , but do not accumulate starch, while in buldle sheath cells chloroplast are larger and lack grana but contain numerous starch grains.
6.Why are C4 plants more efficient than C3 plants?
Ans: C4 plants more efficient than C3 plants due to the breakdown of RuBP into Glycolate and CO2 in C4 plants, there is no photorespiration, and as a result, there is no further carbon dioxide loss
7.) Name the two sets of reactions in photosynthesis in which light energy is required
Ans: Photolysis of water
INTEXT 11.2
1.) List the internal factors that influence the rate of photosynthesis?
Ans: leaf age, chlorophyll content, leaf anatomy are the internal factors that influence the rate of photosynthesis
2.) State the principle of limiting factor.
Ans: It is defined as when a process is conditioned as to its rapidity by a number of separate factors, the rate of the process is limited by the pace of the slowest factor which is known as the limiting factor. It is defined as when a process is conditioned as to its rapidity by a number of separate factors, i.e,the rate of the process is limited by the pace of the slowest factor which is known as the limiting factor
3.) Give an example of chemosynthetic bacteria.
Ans: Nitrosomonass and Nitrobacter are chemosynthetic bacteria
4.) Why are prokaryotes not able to produce ATP by chemiosmosis?
Ans: During photosynthesis, chemiosmosis is used by chloroplasts to produce ATP. The organelles mitochondria and chloroplast, which produce H+ gradients across plasma membranes and can be used for ATP generation, are absent in prokaryotes, therefore prokaryotes are not able to produce ATP by chemiosmosis.
TERMINAL EXERCISE
1.) Describe briefly the process of photosynthesis.
Ans: Green plants use a process called photosynthesis to combine water and carbon dioxide to create carbohydrates when there is light. As a byproduct of photosynthesis, oxygen is released. In photosynthesis, CO2 is fixed (or reduced) to carbohydrates (glucose C6H12O6). Water is split in the presence of light (called photolysis of water) to release O2. Note that O2 released comes from the water molecule and not from CO2
2.) Write short notes on
- i) Ultrastructure of chloroplast : The chloroplast has an empty intermediate area between its inner and outer membranes. The dense fluid known as stroma and stacks of thylakoids known as grana are both found inside the chloroplast. The chlorophyll required for photosynthesis to occur in the plant is present in these thylakoids.
(ii) Pigments involved in photosynthesis : The pigments’ function is to absorb light energy and transform it into chemical energy. These pigments are located on the thylakoid membranes. The primary pigment involved in photosynthesis is the photosynthetic pigment chlorophyll. Carotenoids absorb light in spectral ranges where chlorophylls do not. Chlorophyll is the main pigment that traps solar energy. Since chlorophyll b and carotenoids transfer the absorbed light energy to chlorophyll a, they are referred regarded as accessory pigments.
3.) What are accessory pigments? Why they are called so?
Ans: They are referred to as accessory pigments because chlorophyll b and carotenoids pass the absorbed light energy to chlorophyll a.
4.) Mention path of electrons in the light reaction of photosynthesis.
Ans: The electrons from PSII and PSI are stimulated to a higher energy level upon light absorption.The electron acceptor accepts the electrons as they gain energy, reduces the electron acceptor, and releases the electrons into the PSII and PSI reaction centres. This shows how light energy is transformed into chemical energy. The electrons then go from one electron acceptor to another in a succession of oxidation-reduction reactions, moving downhill in terms of energy.This influx of electrons is ‘coupled’ to the production of ATP.
5.) What do you understand by photophosphorylation.
Ans:It is the process to generate energy rich ATP molecule by transferring one molecule of phosphate to the ADP molecule in presence of light .
6.) Discuss photolysis of water and its significance.
Ans: Breakdown of water in presence of light is called photolysis of water, this process helps in the photosynthesis by donating an electron.
7.) Describe the reactions occurring during dark reaction of photosynthesis.
Ans: Light is not required for these reactions to occur, although they can still do so if the byproducts of the light reaction are present. Therefore, it is also known as a dark reaction.
8). Differentiate between C3 and C4 plants.
Ans: Carbondioxide fixation in C3 plant occurs only once while in C4 plant it occurs twice. C3 plant is less efficient than C4 plants.
9.) Differentiate between PSI and PSII
Ans: PSI have reaction centre of chlorophyll a maximum light absorption at 700 nm while PSII absorbs at 680 mm. In PSI Primary electron acceptor is an iron protein while, in PSII Primary electron acceptor is pheophytin,
10.) What are the products of light reactions. What is the fate of these products?
Ans: The products of lighe reaction are ATP , Oxygen and NADPH further they are used in dark reaction.
11.) Why is cyclic photophosphorylation called so?
Ans: When PS-II is absent, cyclic photophosphorylation only includes PSI and occurs in photosynthetic bacteria. In this procedure, NADP does not get any electrons from PSI. The oxidised P700 molecule receives the same electrons back in its place. ATP is formed as the electrons migrate downward throughout this process. Thus, this process is known as cyclic photophosphorylation.
12.) What is Kranz anatomy?
Ans: The Kranz anatomy, or dimorphic chloroplasts, are seen in the leaves of C4 plants.
(a) These plants have vascular bundles that are encircled by a wreath-shaped sheath of massive parenchymal cells, giving rise to the term Kranz anatomy.
(b) Chloroplasts in leaves come in two varieties (dimorphic chloroplasts).
(c) Granal chloroplasts, which are smaller and highly developed in the mesophyll cells’ chloroplasts but do not accumulate starch.
(d) Bundle sheath cells have bigger, agranal chloroplasts that lack grana yet are packed with many starch grains.
13.) Name the two carboxylase enzymes in C4 cycle.
Ans: PEP carboxylase and RUBP carboxylase are the enzymes used in C4 cycle.
14.) What are chemosynthetic autotrophs?
Ans: Bacteria that can convert the chemical energy released by the biological oxidation of some inorganic materials to carbohydrates. These microorganisms are referred to as chemosynthetic autotrophs.
15.) How does CO2 concentration affect the rate of photosynthesis?
Ans: Because of its extremely low atmospheric concentration (0.03%), it restricts spontaneous photosynthesis. If the carbon dioxide supply is increased at the ideal temperature and light level, photosynthesis accelerates until the CO2 concentration reaches 3.0%. As a result, photosynthesis is always constrained by the amount of CO2 in the atmosphere.
16.) What is the effect of excess of oxyygen on the rate of photosynthesis?
Ans: extra oxygen around a plant slows down photosynthetic rate by speeding up aerobic respiration.
17.) Whether light absorbed by green plants, on global basis is limiting factor for photosynthesis or not! Explain.
Ans: Within physiological bounds, the rate of photosynthesis increases with light intensity, or the rate of photosynthesis is directly proportional to light intensity. Light is never a limiting element in photosynthesis in nature, with the exception of on cloudy days and at night.
Also See: Next Chapter No. 12 Question Answer