Class 10 Science · Chapter 5

Life Processes

266 Class 10 Science questions on Life Processes from the NCERT textbook, NCERT Exemplar and CBSE board papers 2024–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 4 of 14

1. Q61 Exemplar · Multiple Choice Questions
   Which of ​the ​following ​equations ​is ​the ​summary of photosynthesis?

   1. (a)$6{\text{CO}}_2+12{\text{H}}_2\text{O}\to {\text{C}}_6{\text{H}}_{12}{\text{O}}_6+6{\text{O}}_2+6{\text{H}}_2\text{O}$
   2. (b)$6{\text{CO}}_2+{\text{H}}_2\text{O}+\text{Sunlight}\to {\text{C}}_6{\text{H}}_{12}{\text{O}}_6+{\text{O}}_2+6{\text{H}}_2\text{O}$
   3. (c)$6{\text{CO}}_2+12{\text{H}}_2\text{O}+\text{Chlorophyll}+\text{Sunlight}\to {\text{C}}_6{\text{H}}_{12}{\text{O}}_6+6{\text{O}}_2+6{\text{H}}_2\text{O}$
   4. (d)$6{\text{CO}}_2+12{\text{H}}_2\text{O}+\text{Chlorophyll}+\text{Sunlight}\to {\text{C}}_6{\text{H}}_{12}{\text{O}}_6+6{\text{CO}}_2+6{\text{H}}_2\text{O}$
   Show answer

   (c) $6{\text{CO}}_2+12{\text{H}}_2\text{O}+\text{Chlorophyll}+\text{Sunlight}\to {\text{C}}_6{\text{H}}_{12}{\text{O}}_6+6{\text{O}}_2+6{\text{H}}_2\text{O}$

   Step-by-step solution →
2. Q62 Exemplar · Multiple Choice Questions
   Choose ​the ​event ​that does ​not ​occur ​in photosynthesis

   1. (a)Absorption of light energy by chlorophyll
   2. (b)Reduction of carbon dioxide to carbohydrates
   3. (c)Oxidation of carbon to carbon dioxide
   4. (d)Conversion of light energy to chemical energy
   Show answer

   (c) Oxidation of carbon to carbon dioxide

   Step-by-step solution →
3. Q63 Exemplar · Multiple Choice Questions
   The ​opening and closing of ​the ​stomatal pore ​depends ​upon

   1. (a)oxygen
   2. (b)temperature
   3. (c)water in guard cells
   4. (d)concentration of ${\text{CO}}_2$ in stomata
   Show answer

   (c) water in guard cells

   Step-by-step solution →
4. Q64 Exemplar · Multiple Choice Questions
   Choose the ​forms ​in which ​most plants absorb nitrogen

   1. (i)Proteins
   2. (ii)​Nitrates ​and ​Nitrites
   3. (iii)Urea
   4. (iv)Atmospheric nitrogen

   1. (a)(i) and (ii)
   2. (b)(ii) and (iii)
   3. (c)(iii) and (iv)
   4. (d)(i) and (iv)
   Show answer

   (b) (ii) and (iii)

   Step-by-step solution →
5. Q65 Exemplar · Multiple Choice Questions
   Which ​is the first ​enzyme to ​mix ​with food ​in the ​digestive tract?

   1. (a)Pepsin
   2. (b)Cellulase
   3. (c)Amylase
   4. (d)Trypsin
   Show answer

   (c) Amylase

   Step-by-step solution →
6. Q66 Exemplar · Multiple Choice Questions
   Which of the following statement(s) is (are) correct?

   1. (i)Pyruvate can be converted into ethanol and ​carbon dioxide ​by ​yeast
   2. (ii)Fermentation ​takes place ​in ​aerobic bacteria
   3. (iii)Fermentation takes place in ​mitochondria
   4. (iv)Fermentation ​is a form of anaerobic respiration

   1. (a)(i) and (iii)
   2. (b)(ii) and (iv)
   3. (c)(i) and (iv)
   4. (d)(ii) and (iii)
   Show answer

   (c) (i) and (iv)

   Step-by-step solution →
7. Q67 Exemplar · Multiple Choice Questions
   Lack ​of oxygen in ​muscles often leads to cramps ​among cricketers. ​This ​results due to

   1. (a)conversion of pyruvate to ethanol
   2. (b)conversion of pyruvate to glucose
   3. (c)non conversion of glucose to pyruvate
   4. (d)conversion of pyruvate to lactic acid
   Show answer

   (d) conversion of pyruvate to lactic acid

   Step-by-step solution →
8. Q68 Exemplar · Multiple Choice Questions
   Choose ​the ​correct ​path ​of urine in our body

   1. (a)kidney $\to$ ureter $\to$ urethra $\to$ urinary bladder
   2. (b)kidney $\to$ urinary bladder $\to$ urethra $\to$ ureter
   3. (c)kidney $\to$ ureters $\to$ urinary bladder $\to$ urethra
   4. (d)urinary bladder $\to$ kidney $\to$ ureter $\to$ urethra
   Show answer

   (c) kidney $\to$ ureters $\to$ urinary bladder $\to$ urethra

   Step-by-step solution →
9. Q69 Exemplar · Multiple Choice Questions
   During deficiency ​of ​oxygen in tissues ​of human ​beings, pyruvic ​acid ​is converted into lactic acid in ​the

   1. (a)cytoplasm
   2. (b)chloroplast
   3. (c)mitochondria
   4. (d)golgi body
   Show answer

   (a) cytoplasm

   Step-by-step solution →
10. Q70 Exemplar · Short Answer Questions
    Name the following

    1. (a)The process in plants that links light energy ​with chemical energy
    2. (b)Organisms that can prepare their own ​food
    3. (c)The cell organelle where ​photosynthesis occurs
    4. (d)Cells that surround a stomatal pore
    5. (e)Organisms that cannot prepare their ​own ​food
    6. (f)An enzyme secreted ​from gastric glands in stomach that ​acts on proteins.
    Show answer

    The answers are photosynthesis, autotrophs, chloroplast, guard cells, heterotrophs and pepsin.

    (a) Photosynthesis; (b) Autotrophs; (c) Chloroplast; (d) Guard cells; (e) Heterotrophs; (f) Pepsin.

    Step-by-step solution →
11. Q71 Exemplar · Short Answer Questions
    “All plants give out oxygen during ​day ​and carbon ​dioxide ​during night”. Do ​you agree with ​this statement? Give ​reason.
    Show answer

    No; respiration goes on day and night, so the statement holds only for the net exchange of a green plant in good light.

    No, not as it stands. Respiration goes on in a plant day and night, using oxygen and releasing carbon dioxide. During the day photosynthesis also takes place, and in good light it is much faster than respiration, so all the carbon dioxide of respiration is used up inside the leaf and the surplus oxygen diffuses out. At night photosynthesis stops while respiration continues, so carbon dioxide is released. The statement therefore describes only the net exchange of a green plant in good light, not the processes themselves, and it fails altogether for non-green plants such as Cuscuta and for green plants in very dim light, where photosynthesis is no faster than respiration.

    Step-by-step solution →
12. Q72 Exemplar · Short Answer Questions
    How ​do the ​guard cells regulate ​opening and ​closing ​of ​stomatal pores?
    Show answer

    Guard cells take in water and become turgid, bowing apart to open the pore; they lose water and become flaccid, closing it.

    Each stomatal pore is bounded by a pair of bean-shaped guard cells whose inner wall, facing the pore, is thick and inelastic while the outer wall is thin and elastic. When the pore is to open, the guard cells take up solutes such as potassium ions, so water enters them from the neighbouring cells by osmosis and they become turgid. Turgor stretches the thin outer wall much more than the thick inner one, so each guard cell bows outward and the pore between the two widens. When the solutes leave, water follows them out, the guard cells become flaccid, the walls straighten, the two cells come together and the pore closes. In this way the guard cells open the pore for the intake of carbon dioxide and close it to check the loss of water vapour.

    Step-by-step solution →
13. Q73 Exemplar · Short Answer Questions
    Two green ​plants are ​kept separately in ​oxygen free containers, one in ​the dark ​and the other ​in continuous light. ​Which one will live ​longer? Give reasons.
    Show answer

    The plant in continuous light lives longer because photosynthesis supplies food and oxygen; the dark plant must respire anaerobically and dies sooner.

    The plant kept in continuous light will live longer. Being in the light it can photosynthesise, so it makes its own food and, more importantly here, releases oxygen inside the sealed container; that oxygen is then used for its own aerobic respiration, and the carbon dioxide respiration returns is used again in photosynthesis. The plant kept in the dark cannot photosynthesise, so it gets neither food nor oxygen. It is forced to respire anaerobically, which yields very little energy per glucose molecule and leaves toxic ethanol behind, so its reserves are exhausted quickly and it dies much sooner.

    Step-by-step solution →
14. Q74 Exemplar · Short Answer Questions
    If ​a plant ​is releasing ​carbon dioxide and taking in oxygen ​during the day, does it mean ​that there is no photosynthesis occurring? ​Justify your ​answer.
    Show answer

    No; both processes run together, and the net exchange of oxygen in and carbon dioxide out only shows that respiration is faster than photosynthesis.

    No, it does not. Respiration and photosynthesis go on together in a green plant during the day, and the gases exchanged with the air are only the difference between the two. Taking in oxygen and giving out carbon dioxide therefore means that the rate of respiration is greater than the rate of photosynthesis at that moment, not that photosynthesis has stopped. This happens when photosynthesis is slowed, for example in very dim light at dawn, dusk or on a heavily overcast day, when the stomata are closed because the plant is short of water so that carbon dioxide cannot enter, or when the leaves are old, dusty or damaged. Photosynthesis would be truly absent only in the dark or in a plant with no chlorophyll, such as Cuscuta.

    Step-by-step solution →
15. Q75 Exemplar · Short Answer Questions
    Why ​do fishes ​die ​when taken ​out ​of water?
    Show answer

    Out of water the gill filaments collapse and dry, so the fish cannot absorb oxygen and dies of asphyxiation.

    A fish breathes by gills, which absorb the oxygen dissolved in water. The gills are made of very fine filaments that are held apart and kept moist by the water flowing over them. When the fish is taken out of water, the filaments are no longer supported, so they collapse and stick together under their own weight and their surface dries. The large, thin, moist surface that gaseous exchange needs is therefore lost, and the fish cannot absorb oxygen even though air is much richer in oxygen than water is. Respiration in its tissues stops for want of oxygen and the fish dies of asphyxiation.

    Step-by-step solution →
16. Q76 Exemplar · Short Answer Questions
    Differentiate ​between ​an autotroph ​and ​a heterotroph.
    Show answer

    An autotroph makes its own food from carbon dioxide and water; a heterotroph depends on other organisms for ready-made food.

    An autotroph prepares its own food from simple inorganic substances, carbon dioxide and water, using an external source of energy, sunlight trapped by the chlorophyll it contains; the food it makes is already simple, so it needs no digestion, and it occupies the first trophic level of a food chain as a producer. Examples are green plants and blue-green algae. A heterotroph cannot prepare its own food and depends on other organisms for ready-made organic food; it has no chlorophyll and gets its energy from the chemical bonds of that food, which must first be digested into simple absorbable molecules, and it occupies a later trophic level as a consumer or a decomposer. Examples are human beings, a deer, fungi and the parasitic plant Cuscuta.

    Step-by-step solution →
17. Q77 Exemplar · Short Answer Questions
    Is ​‘nutrition’ ​a necessity ​for ​an organism? Discuss.
    Show answer

    Yes, nutrition is necessary because food is the only source of energy and of materials for growth and repair.

    Yes, nutrition is a necessity for every organism. Nutrition is the taking in of food and its use, and food is the only source of two things an organism cannot do without. First, it is the source of energy: respiration releases energy from food, and that energy pays for every other life process, transport, excretion, movement, growth and reproduction included, so without food there is nothing to respire. Second, it is the source of materials: growth, the replacement of worn-out cells and the repair of injuries all need proteins, carbohydrates and fats as raw material. In addition, vitamins and minerals, which supply almost no energy, are needed in small amounts for enzymes and hormones to work and for resistance to disease, which is why their absence causes deficiency diseases. An organism deprived of nutrition survives only as long as its stored food lasts and then dies.

    Step-by-step solution →
18. Q78 Exemplar · Short Answer Questions
    What ​would ​happen ​if green plants ​disappear ​from earth?
    Show answer

    Life would end: food chains would collapse, oxygen would fall, carbon dioxide would rise and the earth would become hotter.

    Life on earth would come to an end. Green plants are the producers, the point at which energy from the sun and oxygen enter the living world. With them gone, every food chain would collapse from its base: herbivores would starve first, then the carnivores that feed on them, and finally every heterotroph including human beings, since the stored food already on earth would not be replaced. At the same time respiration, decay and the burning of fuels would go on removing oxygen from the air and adding carbon dioxide, with nothing to reverse them, so the oxygen of the atmosphere would fall steadily and the carbon dioxide would rise. The rising carbon dioxide would strengthen the greenhouse effect and the earth would become hotter, the carbon and other nutrient cycles would break down, transpiration and hence rainfall would fall, and the soil, no longer held by roots, would be eroded.

    Step-by-step solution →
19. Q79 Exemplar · Short Answer Questions
    Leaves of a ​healthy potted ​plant ​were coated ​with ​vaseline. Will ​this plant remain healthy for long? ​Give reasons for your ​answer.
    Show answer

    No; vaseline blocks the stomata, stopping photosynthesis, gaseous exchange and transpiration, so the plant will wilt and die.

    No, the plant will not remain healthy for long. Vaseline is an oily film that seals the stomata, the pores through which a leaf exchanges gases and loses water vapour. Carbon dioxide can no longer enter, so photosynthesis slows and stops and the plant makes no food; oxygen for respiration cannot enter and the carbon dioxide produced cannot leave, so gaseous exchange in the leaf is hampered as well. Transpiration also stops, and with it the transpiration pull that draws water and dissolved minerals up the xylem from the roots, so the ascent of sap and the mineral supply fail; the evaporative cooling that transpiration gave the leaf is lost too, so the leaves overheat in the sun. Deprived of food, of gaseous exchange and of its water and mineral supply, the plant will yellow, wilt and die. The effect is greatest when the lower surface is coated, since most stomata are there.

    Step-by-step solution →
20. Q80 Exemplar · Short Answer Questions
    How does ​aerobic respiration ​differ ​from anaerobic ​respiration?
    Show answer

    Aerobic respiration uses oxygen and fully breaks down glucose in the mitochondria, releasing much energy; anaerobic respiration needs no oxygen and releases little.

    Aerobic respiration takes place in the presence of oxygen and is completed in the mitochondria, where glucose is completely oxidised to carbon dioxide and water, releasing a large amount of energy, about thirty molecules of ATP per molecule of glucose; it is the usual mode of respiration in most organisms. Anaerobic respiration takes place in the absence of oxygen and is completed in the cytoplasm, where glucose is only partly broken down, to ethanol and carbon dioxide in yeast or to lactic acid in our muscle cells, and it releases only a small amount of energy, two molecules of ATP per molecule of glucose; it occurs in yeast and many bacteria and temporarily in our muscles during vigorous exercise. Both begin alike, with glucose broken down to pyruvate in the cytoplasm, and they differ only in what becomes of that pyruvate.

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