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NCERT Exemplar · Class 10 Science Life Processes

82 questions · 82 still being checked

Short Answer Questions 46–55 (part 6 of 9)

  1. Exercise 46

    How does aerobic respiration differ from anaerobic respiration?

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    NCERT’s answer
    Aerobic respirationAnaerobic respiration
    1. Oxygen is utilised for the breakdown of respiratory substrate.1. Oxygen is not required.
    2. It takes place in cytoplasm (glycolysis) and inside mitochondria (Krebs cycle)2. It takes place in cytoplasm only.
    3. End products are carbon dioxide and water3. End products are lactic acid or ethanol and carbon dioxide.
    4. More energy is released.4. Less energy is released.
    \[\mathrm{C_6H_{12}O_6} + 6\,\mathrm{O_2} \xrightarrow{\text{aerobic}} 6\,\mathrm{CO_2} + 6\,\mathrm{H_2O} + \text{energy}\ (\approx 38\,\mathrm{ATP}) \] \[\mathrm{C_6H_{12}O_6} \xrightarrow[\text{yeast}]{\text{anaerobic}} 2\,\mathrm{C_2H_5OH} + 2\,\mathrm{CO_2} + \text{energy}\ (2\,\mathrm{ATP}) \] \[\mathrm{C_6H_{12}O_6} \xrightarrow[\text{muscle}]{\text{anaerobic}} 2\,\mathrm{C_3H_6O_3}\ (\text{lactic acid}) + \text{energy}\ (2\,\mathrm{ATP}) \] Glucose is fully oxidised with \(\displaystyle \mathrm{O_2}\) in aerobic respiration, but only partly broken down without \(\displaystyle \mathrm{O_2}\) in anaerobic respiration. Answer: Aerobic: needs \(\displaystyle \mathrm{O_2}\); cytoplasm (glycolysis) and mitochondria (Krebs cycle); complete oxidation; more energy. Anaerobic: no \(\displaystyle \mathrm{O_2}\); cytoplasm only; incomplete breakdown; less energy.

  2. Exercise 47

    Match the words of Column (A) with that of Column (B)
    Column (A)Column (B)
    (a) Phloem(i) Excretion
    (b) Nephron(ii) Translocation of food
    (c) Veins(iii) Clotting of blood
    (d) Platelets(iv) Deoxygenated blood

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    NCERT’s answer
    (a)(ii)
    (b)(i)
    (c)(iv)
    (d)(iii)
    Phloem transports food (translocation); the nephron is the kidney's excretory filtering unit; veins return deoxygenated blood to the heart; platelets trigger clotting at a wound.

  3. Exercise 48

    Differentiate between an artery and a vein.

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    NCERT’s answer
    ArteryVein
    1. Have thick elastic, muscular walls.1. Have thin, non-elastic, walls.
    2. Lumen is narrow.2. Lumen is wide.
    3. Carry blood from heart to all body parts.3. Carry blood from all body parts to heart.
    4. Carry oxygenated blood (except pulmonary artery).4. Carry deoxygenated blood (except pulmonary vein).
    Artery: thick elastic muscular wall, narrow lumen, no valves; carries blood away from the heart at high pressure, oxygenated (except pulmonary artery). Vein: thin wall, wide lumen, valves prevent backflow; carries blood towards the heart at low pressure, deoxygenated (except pulmonary vein). Answer: artery: thick wall, narrow lumen, no valves; vein: thin wall, wide lumen, valves.

  4. Exercise 49

    What are the adaptations of leaf for photosynthesis?

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    NCERT’s answer
    (a)
    Leaves provide large surface area for maximum light absorption.
    (b)
    Leaves are arranged at right angles to the light source in a way that causes overlapping.
    (c)
    The extensive network of veins enables quick transport of substances to and from the mesophyll cells.
    (d)
    Presence of numerous stomata for gaseous exchange.
    (e)
    The chloroplasts are more in number on the upper surface of leaves.
    A broad, thin lamina maximises the light-capturing surface; palisade cells packed with chloroplasts lie just below the upper epidermis; a transparent cuticle admits light while limiting water loss; numerous stomata (mostly on the lower surface) exchange \(\displaystyle CO_2\) and \(\displaystyle O_2\); veins supply water and carry food away.

  5. Exercise 50

    Why is small intestine in herbivores longer than in carnivores?

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    NCERT’s answer
    Digestion of cellulose takes a longer time. Hence, herbivores eating grass need a longer small intestine to allow complete digestion of cellulose. Carnivorous animals cannot digest cellulose, hence they have a shorter intestine.
    Herbivores eat plant matter that is rich in cellulose, which is hard to digest and needs prolonged microbial (bacterial) fermentation and a much larger absorptive surface, so the intestine is long. Carnivores eat protein- and fat-rich meat, which digests easily and quickly, needing a shorter intestine.

  6. Exercise 51

    What will happen if mucus is not secreted by the gastric glands?

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    NCERT’s answer
    Gastric glands in stomach release hydrochloric acid, enzyme pepsin and mucus. Mucus protects the inner lining of stomach from the action of hydrochloric acid and enzyme pepsin. If mucus is not released, it will lead to erosion of inner lining of stomach, leading to acidity and ulcers.
    \[\text{No mucus} \Rightarrow \text{HCl, pepsin act directly on the stomach wall} \Rightarrow \text{self-digestion} \] The mucus that gastric glands secrete normally coats and protects the stomach lining from its own acid and enzyme; without it, hydrochloric acid and pepsin would erode the wall itself.

  7. Exercise 52

    What is the significance of emulsification of fats?

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    NCERT’s answer
    Fats are present in food in the form of large globules which makes it difficult for enzymes to act on them. Bile salts present in bile break them down mechanically into smaller globules which increases the efficiency of fat digesting enzymes.
    Bile salts break large fat globules into many tiny droplets. \[\text{surface area of fat} \uparrow \;\Rightarrow\; \text{lipase action} \uparrow \;\Rightarrow\; \text{rate of fat digestion} \uparrow \] More surface is exposed to lipase, so fats are hydrolysed faster and more completely. Answer: Emulsification increases the exposed surface area of fat, speeding up its digestion by lipase.

  8. Exercise 53

    What causes movement of food inside the alimentary canal?

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    NCERT’s answer
    The wall of alimentary canal contains muscle layers. Rhythmic contraction and relaxation of these muscles pushes the food forward. This is called peristalsis, which occurs all along the gut.
    Alternate contraction and relaxation of the muscular gut wall forms a travelling wave. \[\text{muscle behind bolus contracts, muscle ahead relaxes} \;\Rightarrow\; \text{bolus pushed forward} \] This wave, peristalsis, repeats along the oesophagus, stomach and intestine, driving food onward. Answer: Peristaltic movement -- rhythmic waves of muscular contraction and relaxation in the gut wall -- moves food along the alimentary canal.

  9. Exercise 54

    Why does absorption of digested food occur mainly in the small intestine?

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    NCERT’s answer
    Maximum absorption occurs in small intestine because
    (a)
    digestion is completed in small intestine
    (b)
    inner lining of small intestine is provided with villi which increases the surface area for absorption.
    (c)
    wall of intestine is richly supplied with blood vessels (which take the absorbed food to each and every cell of the body).
    The small intestine's inner wall bears millions of finger-like villi.\[\text{villi} \;\Rightarrow\; \text{surface area} \uparrow \;\Rightarrow\; \text{contact with digested food} \uparrow \;\Rightarrow\; \text{absorption} \uparrow \] Each villus carries a rich network of blood capillaries that carry away absorbed nutrients, and by this point digestion of food is essentially complete. Answer: The small intestine has both fully digested food and a villus-lined wall of huge surface area, so most absorption happens here.

  10. Exercise 55

    Match Group (A) with Group (B)
    Group (A)Group (B)
    (a) Autotrophic nutrition(i) Leech
    (b) Heterotrophic nutrition(ii) Paramecium
    (c) Parasitic nutrition(iii) Deer
    (d) Digestion in food vacuoles(iv) Green plant

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    NCERT’s answer
    (a)
    — (iv)
    (b)
    — (iii)
    (c)
    — (i) (d) — (ii)
    (a)
    Autotrophic nutrition -- self-made food -- matches (iv) Green plant.
    (b)
    Heterotrophic nutrition -- food from other organisms -- matches (iii) Deer.
    (c)
    Parasitic nutrition -- food from a host -- matches (i) Leech.
    (d)
    Digestion in food vacuoles -- intracellular digestion -- matches (ii) Paramecium.
    Answer: (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)