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ICSE Class X Question Bank 2022 : Art

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8B 35 Shaurya Shah
Pawar Public School (PPS), Bhandup, Mumbai

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Question Bank Photosynthesis 1. Name the following : (i) The first stable product of CO2 fixation in plants. (ii) The CO2-acceptor molecule in plants. (iii) The part of chloroplast where Calvin cycle operates. (iv) The source of oxygen during photosynthesis. (v) The final products of light reaction. (vi) In which form are the carbohydrates translocated in plants? (vii) The plant tissue which takes part in translocation of food material within the plant body. (viii) The universal hydrogen acceptor in plants. (xi) A plant which does not perform photosynthesis. Ans.(i) Phosphoglyceric acid (ii) Ribulose biphosphate (iii) Stroma (iv) Water (v) ATP and NADPH+ (vi) Sucrose (vii) Phloem (viii) NADP (ix) Fungus Class-X 1 Question Bank 2. Complete the following statements by choosing the correct alternative out of those given in brackets. (i) Carbon dioxide is necessary for _________. [Respiration / Photorespiration / Photosynthesis] (ii) Animal nutrition is mostly __________. [Autotrophic / Heterotrophic/ Parasitic] (iii) Chlorophyll molecule has a _________ in the middle of the ring structure. [Nitrogen, Manganese, Magnesium] (iv) Splitting of water results in the release of __________ . [Oxygen / Water / Oxygen and water] (v) Presence of starch can be tested by ___________. [Iodine / Hydrochloric acid / Alcohol] Ans.(i) Photosynthesis (iii) Magnesium (ii) Heterotrophic (iv) Oxygen (v) Iodine. 3. Mention if the following statements are true or false. If false, rewrite the wrong ones by changing only the words printed in bold face. (i) Light reaction is called thermo-chemical reaction. (ii) Oxygen evolved during light reaction is from carbon dioxide. (iii) A plant can be destarched by keeping it in dark for 48 hours. (iv) Stroma is the site of light reaction. (v) Potassium hydroxide absorbs oxygen. Class-X 2 Question Bank Ans.(i) False (Photochemical) (ii) False (Water) (iii) True (iv) False (Thylakoid) (v) False (Carbon dioxide). 4. Give the overall chemical equation of photosynthesis. Ans. 6CO 2 + 12H 2 O Sunlight 6O 2 + (CH 2 O)6 + 6H 2 O Chlorophyll 5. What will be the effect of excess oxygen on the process of photosynthesis? Ans. Photosynthesis will be inhibited. 6. Why is Calvin cycle called C3 cycle? Ans. Calvin cycle is called C3 cycle because the first stable compound formed is phosphoglyceric acid (PGA) which has three carbon atoms. 7. Name the main steps of dark reaction. Ans. Carboxylation, glycolytic reversal and regeneration of RuBP. 8. Give the full form of NADP. Ans. Nicotinamide adenine dinucleotide phosphate. Class-X 3 Question Bank 9. (a) What is photolysis of water? (b) What is the function of chlorophyll pigment? Ans. (a) Light induced splitting of water molecule into its two component ions, H+ and OH , is called photolysis of water. (b) During light reaction of photosynthesis solar energy is trapped by chlorophyll which is used for the photolysis of water and ATP formation. 10. (a) What is photosynthesis? (b) What is the role of light in photosynthesis? Ans. (a) Photosynthesis is a physiological process by which green parts of the plant, in the presence of sunlight, prepare food in the form of carbohydrates and release oxygen as a by-product. (b) Light energy is absorbed by chlorophyll and transformed into chemical energy which causes splitting of the water molecule, formation of NADPH2 and ATP which is used for the reduction of carbon dioxide to glucose. 11. (a) All life would come to an end if there were no green plants. Comment. (b) How is the light reaction linked to the dark reaction? Ans. (a) Green plants are the primary producers on the earth. That is, they fix up atmospheric CO2, utilising light, chlorophyll and water, and synthesise food material. This food is utilised by different heterotrophs in the ecosystem. In addition, the plants release oxygen during the photosynthetic process and thus maintain the balance of oxygen in the atmosphere. Oxygen is used by all organism for their respiratory activity. Class-X 4 Question Bank (b) During light reaction, ATP and NADPH are generated. These two compounds are used in the dark reactions during the reduction of 3 PGA to phosphoglyceraldehyde. 12. (i) Describe the structure of chloroplast through a well-labelled diagram. (ii) Suggest some habitats or natural circumstances in which (a) light intensity, (b) carbon dioxide concentration, (c) temperature will be limiting factors in photosynthesis. Ans. (i) Chloroplasts measure about 4-10 m in diameter and 1-3 m in thickness. Each chloroplast is bound by a double membrane. Inside the membranes is the ground substance, the stroma, in which lie a system of chlorophyllbearing double-membraned sacs stacked one above the other to form grana. Individual sacs in each lamellae are known as thylakoids. (ii) Some likely situations would be (a) In a shaded community; dawn and twilight in a warm climate. (b) CO2 is normally limiting, but it would be more so in a place cluttered with plants under sunny warm conditions. (c) A bright winter day. Class-X 5 Question Bank 13. (a) How would you demonstrate that green plants release oxygen when exposed to light? (b) In most of the experiments on photosynthesis one uses destarched leaf or plant. What is the purpose of destarching in these experiments? Ans. (a) Place Hydrilla, a water plant, in a beaker containing pond water and cover it with a short-stemmed funnel. Invert a test tube full of water over the stem of the funnel. Place the apparatus in the sun for a few hours. Bubbles of a gas will collect in the test tube. Test the gas in the test tube. A glowing splinter when introduced on the top of the tube, it bursts into flame which confirms the presence of oxygen. (b) During the destarching period, all the stored starch from the leaves is used up and only that starch is detected which is formed under the experimental conditions. Class-X 6 Question Bank 14. State any five differences between photosynthesis and respiration. Ans. Difference between respiration and photosynthesis : Respiration Photosynthesis 1. It is a catabolic process in which food It is an anabolic process in which substances are broken down. food substances are synthesised. 2. It uses oxygen to oxidise the food It uses carbon dioxide to synthesise substances and releases carbon food and release oxygen. dioxide and energy. 3. It occurs at all times of day and night. It occurs only in the presence of light. 4. It occurs in all living cells. It occurs only in cells containing chlorophyll. 5. It results in the loss of dry weight of It results in a gain in the dry weight the plant due to the break down of of the plant due to the formation of food materials and the formation of carbohydrates which accumulate in carbon dioxide and water which the plant body. escape into the atmosphere. 15. A green leaf is compared to a factory as it manufactures food for the plant. On the basis of this name the following: (i) Power (ii) Raw material, (iii) Machinery (iv) End products, (v) Workrooms, (vi) By-products. Ans.(i) Sunlight (iii) Chloroplast (ii) CO2 and water (iv) Glucose (sugar) (v) Cells in the leaf (vi) Oxygen and water. Class-X 7 Question Bank 16. (i) Water and oxygen are waste products of photosynthesis. But are they really wastes? (ii) How is the leaf adapted for photosynthesis? Ans.(i) There are three end-products of photosynthesis. (a) Sugar, which is immediately utilised by the cells or is stored in the form of insoluble starch. (b) Water, which may be reutilised in the further continuance of photosynthesis. (c) Oxygen, some of it is used in respiration in the leaf cells but the major portion of it is not required and diffuses out into the atmosphere through the leaf surfaces. Though considered a waste product for the plant, all organisms require it for respiration. (ii) The adaptations of leaf for photosynthesis are as follows : (a) Large surface area for maximum light absorption. (b) Leaf arrangement at right angles to the light source to obtain maximum light. (c) Rapid transport to and from mesophyll cells by extensive vein system. (d) Numerous stomata allow rapid exchange of gases (O2 and CO2). (e) Thinness of leaf reduces distance between cells facilitating rapid transport. (f) Chloroplasts are concentrated in upper layers of the leaf to obtain light energy quickly. Class-X 8 Question Bank 17. What do you understand by the law of limiting factors? Explain its significance in photosynthesis. Ans. When a process like photosynthesis depends on more than one variable external factor, the rate of the process will depend on the factor which is in the shortest supply. To understand it, suppose that there is a lot of CO2 in the air and the temperature is just below the optimum temperature but the light intensity is very low, the rate of photosynthesis will be low. Similarly, if light intensity is high but carbon dioxide concentration is low, again the photosynthesis rate will be low. Class-X 9 Question Bank 18. Describe the different factors which influence the rate of photosynthesis. Ans. (i) The size and distribution of intercellular spaces. (ii) Relative proportion and distribution of chloroplast in the mesophyll. (iii) Size, position and structure of stomata. (iv) Thickness of cuticular and epidermal layer. (v) Efficiency of vascular bundles in the midrib. (vi) Rate of entrance of carbon dioxide. (vii) Intensity and nature of light that penetrates the mesophyll cells. (viii) Maintenance of the turgidity of the leaf cells. (ix) The rate of translocation of soluble carbohydrates out of the photosynthesising cells. (x) Age of the leaf. 19. Two healthy green plants were placed in the dark for 24 hours. They were then set up as shown in figure and left for four hours. Then a leaf was taken from each plant and the chlorophyll was removed from the leaves. (i) How is chlorophyll removed? (ii) What would be the next and final step in this experiment? Class-X 10 Question Bank (iii) What would be the result of the final step? (iv) Which of the two plants would serve as a control? Ans. (i) The leaf is boiled in methylated spirit over a water bath. Methylated spirit is used as a solvent to extract the chlorophyll from the leaf. (ii) The next and final step in this experiment is to treat the discoloured leaf with iodine to test for the presence of starch. (iii) Leaf from set-up A stains brown by iodine, indicating the absence of starch, while the leaf from set-up B turns blue-black, indicating the presence of starch. (iv) Set-up B serves as a control. Class-X 11 Question Bank 20. (i) A healthy potted geranium plant with variegated leaves was watered and left in the sunlight for several hours. A leaf was then plucked and tested for starch. It was found that a part of the leaf had starch, but the other had no starch. (a) What is the experiment designed to show? (b) How would you account for the presence of starch in some parts of the plant, but absence in other parts? (c) What experimental details have been omitted while performing the experiment? (ii) Given below is an experimental set-up. Study it and answer the questions given below. (a) What does the set-up show? (b) Where should the set-up be kept? (c) Name the gas that is bubbling out. (d) How do you prove which gas is evolved? Class-X 12 Question Bank Ans. (i) (a) This experiment shows that chlorophyll is necessary for photosynthesis. (b) The part having chlorophyll showed the presence of starch. Whereas, the part without chlorophyll could not synthesize starch. (c) The plant was not destarched before starting the experiment. (ii) (a) It proves that oxygen is released during photosynthesis. (b) The experiment should be set-up in light, preferably sunlight. (c) Oxygen. (d) Introduce a burning splinter inside the accumulated gas after removing the water. It bursts into flames. This proves that the released gas is oxygen. 21. Enumerate the steps involved in testing a green leaf for the presence of starch. Ans. Steps involved in testing the presence of starch. Procedure : 1. Detach a leaf from the plant and dip in boiling water for a minute. This process destroys the enzymes in the leaf and suspends all the chemical changes taking place in it. 2. Boil the leaf in methylated spirit over a water bath. The leaf becomes colourless as it loses its chlorophyll content. The leaf also becomes hard and brittle. 3. Dip the leaf in hot water to soften it. Class-X 13 Question Bank 4. Place the leaf in a petridish and pour a few drops of iodine solution over it. Observation : The leaf turns blue-black in colour. Inference : The appearance of blue-black colouration indicates the presence of starch. (Absence of starch is indicated by appearance of brown colour). 22. Mention one point of difference between the following on the basis of what is given in the brackets. (a) Respiration and photosynthesis (gas released) (b) Light reaction and dark reaction (products formed) (c) Producers and consumers (mode of nutrition) Ans. (a) Respiration Gas released is carbon dioxide. Photosynthesis Gas released is oxygen. (b) Light reaction Product formed is NADPH. Dark reaction Product formed is glucose. (c) Producers Make their own food e.g. green plants Consumers Obtain food directly or indirectly from autotrophs. Can t make their own food e.g. tiger. 23. Given below are sets of five terms. Rewrite the terms in the correct order so as to be in logical sequence with regard to photosynthesis : water molecules, oxygen, grana, hydrogen and hydroxyl ions, photons. Ans. Grana, photons, water molecules, hydrogen and hydroxyl ions, oxygen. The reaction is known as photolysis, which means splitting of water by light (photon). Class-X 14 Question Bank 24. Why is it not possible to demonstrate respiration in a green plant kept in sunlight? Ans. In every period of twenty-four hours, plants are subjected to a regular cycle of changes in light intensity, and the rate of photosynthesis increases from dawn to mid-day and declines as dusk approaches. Plants, like other organisms, respire taking in oxygen and giving out carbon dioxide. In light, the effects of this respiratory activity are marked by those of photosynthesis and there is a net output of oxygen. Thus, in this time, demonstration of respiration is not possible. 25. What is the difference between an autotroph and heterotroph? Give one example of each. Ans. Autotrophs are those organisms which can make their own food. Mainly green plants are autotrophs which can make their own food with the help of chlorophyll. Whereas, heterotrophs are those organisms which can t make their own food. They are dependent directly or indirectly on green plants for the preparation of food. Eg. tiger, lion, human being etc. 26. Most leaves have the upper surface more green and shiny. Why? Ans. This is mainly due to chlorophyll. Chlorophyll is highly sensitive to light. The formation of chlorophyll itself depends on the exposure of the plant to light. As the upper surface of leaves get more sunlight than others, it looks more green and shiny. Class-X 15 Question Bank 27. Oxygen is a waste product of photosynthesis. Comment. Ans. The life supporting gas, oxygen present in the atmosphere in a free state, is released by photosynthesis only. Scientists strongly believe that about 2 billion years ago, when there was no life on the earth in any form, there was no free oxygen in the atmosphere. This oxygen is released as the waste product of photosynthesis in this way light energy C6 H12 O 6 + 6H 2 O + 6O 2 chlorophyll 28. Why is it necessary to place a plant in the dark before starting an experiment 6CO 2 + 12H 2 O on photosynthesis? Ans. A plant used for experiments in photosynthesis should initially be placed in the dark for 24 to 48 hours to destarch the leaves. During this period, all the starch will be removed from the leaves and they will not show the presence of starch. 29. What is the difference between chlorophyll and chloroplast? Ans. Chlorophyll is the green coloured matter found in plants. It is contained in microscopic cell organelles called chloroplasts. It is contained in the walls of thylakoids. It is a highly complex substance, composed of carbon, hydrogen, oxygen, nitrogen and magnesium. Whereas, chloroplasts are minute oval bodies bounded by a double membrane, and their interior contains closely packed flattened sacs (thylakoids) arranged in piles (grana) lying in a colourless ground substance called stroma. Class-X 16 Question Bank

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