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 2 of 14

1. Q21 NCERT · Intext Questions (Page 87)
   What is the ​function ​of ​digestive enzymes?
   Show answer

   Digestive enzymes are biological catalysts that break large, insoluble food molecules into small, soluble ones that can be absorbed into the blood.

   Digestive enzymes are biological catalysts that break down the large, complex, insoluble molecules of the food we eat into small, simple, soluble molecules that can be absorbed through the wall of the alimentary canal into the blood. Each enzyme acts on one class of food: salivary amylase (in saliva) breaks starch into simple sugar; pepsin (in the stomach, in an acidic medium) and trypsin (from the pancreas) break down proteins; lipase (from the pancreas) breaks down emulsified fats; and the enzymes of the intestinal juice complete the process, converting proteins to amino acids, complex carbohydrates to glucose, and fats to fatty acids and glycerol. Without these enzymes the food could not be absorbed or used by the cells for energy, growth and repair.

   Step-by-step solution →
2. Q22 NCERT · Intext Questions (Page 87)
   How is the ​small ​intestine ​designed to ​absorb ​digested ​food?
   Show answer

   The small intestine's length, villi, thin walls and rich blood supply give a large surface, a short path and rapid removal of absorbed food.

   The small intestine is designed for absorption in three ways. (1) It is the longest part of the alimentary canal, fitted into a compact space by extensive coiling, so the digested food stays in contact with a very long absorbing tube (herbivores, which must digest cellulose, have an even longer one). (2) Its inner lining is thrown into numerous finger-like projections called villi, which increase the surface area for absorption enormously; the wall of each villus is thin, so the digested food has only a short distance to cross. (3) The villi are richly supplied with blood vessels, which take up the absorbed food (glucose, amino acids, fatty acids and glycerol) and carry it to each and every cell of the body, where it is used for energy, building new tissues and repairing old ones; this constant removal keeps absorption going.

   Step-by-step solution →
3. Q23 NCERT · Intext Questions (Page 91)
   What ​advantage over an aquatic organism does a terrestrial ​organism ​have ​with regard ​to ​obtaining oxygen for ​respiration?
   Show answer

   Terrestrial organisms use oxygen-rich air, so they get more oxygen per breath and breathe slowly, using less energy than aquatic organisms.

   A terrestrial organism obtains its oxygen from the air, which is rich in oxygen (about one-fifth of it by volume), whereas an aquatic organism has to use the oxygen dissolved in water, and the amount of dissolved oxygen is fairly low: a litre of water holds only a small fraction of the oxygen that a litre of air does. So the terrestrial organism gets far more oxygen from each breath, can breathe much more slowly, and spends much less energy on breathing than an aquatic organism, which must keep forcing a large volume of water past its gills at a much faster rate to obtain the same amount of oxygen.

   Step-by-step solution →
4. Q24 NCERT · Intext Questions (Page 91)
   What ​are the different ​ways ​in ​which glucose is oxidised to provide energy ​in various ​organisms?
   Show answer

   Glucose becomes pyruvate in the cytoplasm; pyruvate then yields carbon dioxide and water with oxygen, or ethanol in yeast, or lactic acid in muscle.

   In all organisms the first step is the same: glucose, a six-carbon molecule, is broken down in the cytoplasm into pyruvate, a three-carbon molecule, with the release of a small amount of energy; this step needs no oxygen. What happens to the pyruvate then depends on the organism and on whether oxygen is available. (1) Aerobic respiration (presence of oxygen): in the mitochondria the pyruvate is broken down completely into carbon dioxide and water, releasing a large amount of energy, ${\text{C}}_6{\text{H}}_{12}{\text{O}}_6+6{\text{O}}_2\to 6{\text{CO}}_2+6{\text{H}}_2\text{O}+\text{energy}$; this is the route in most organisms, including us. (2) Anaerobic respiration in yeast (absence of oxygen): the pyruvate is converted into ethanol (a two-carbon molecule) and carbon dioxide with a little energy; this is fermentation. (3) Anaerobic break-down in our muscle cells (lack of oxygen during sudden activity): the pyruvate is converted into lactic acid (a three-carbon molecule) with a little energy, and its build-up causes cramps. The aerobic route releases far more energy than either anaerobic route, and in every case the energy released is used to make ATP, the energy currency of the cell.

   Step-by-step solution →
5. Q25 NCERT · Intext Questions (Page 91)
   How is oxygen and ​carbon ​dioxide transported ​in ​human beings?
   Show answer

   Oxygen is carried bound to haemoglobin in red blood corpuscles; carbon dioxide is mostly carried dissolved in the plasma.

   Oxygen: in the alveoli of the lungs, oxygen from the air diffuses into the blood in the alveolar capillaries and binds to haemoglobin, the respiratory pigment present in the red blood corpuscles, which has a very high affinity for oxygen. The blood carries this oxygen to all the tissues of the body, and haemoglobin releases it in the tissues that are deficient in oxygen. Carbon dioxide: the carbon dioxide produced in the cells during respiration is more soluble in water than oxygen is, so it is mostly transported in dissolved form in the plasma of the blood. The blood brings it back to the lungs, where it is released into the alveoli and breathed out. Thus oxygen travels bound to haemoglobin in the red blood corpuscles, and carbon dioxide travels mainly dissolved in the plasma.

   Step-by-step solution →
6. Q26 NCERT · Intext Questions (Page 91)
   How ​are ​the lungs designed in human ​beings ​to maximise the ​area for ​exchange of gases?
   Show answer

   Branching air passages end in millions of thin-walled alveoli with a rich blood supply, giving a very large surface for gas exchange.

   The lungs maximise the area for gas exchange in the following ways. (1) Inside each lung the air passage divides again and again: bronchi into bronchioles and then into smaller and smaller tubes. (2) Each of the finest tubes ends in a cluster of balloon-like structures, the alveoli; there are about 300 million of them, and dividing the air space into so many tiny sacs gives a far larger surface than one large sac of the same volume; if spread out, the alveolar surface would cover about 80 square metres. (3) The wall of each alveolus is very thin, so the gases have only a short distance to cross, and it contains an extensive network of blood vessels, so blood is always close to the air, bringing carbon dioxide for release and taking up oxygen. (4) This fine, moist surface is kept protected inside the chest, and the lungs always retain a residual volume of air so that there is enough time for the exchange to take place.

   Step-by-step solution →
7. Q27 NCERT · Intext Questions (Page 96)
   What are ​the components of ​the ​transport system in human beings? What are ​the ​functions of ​these ​components?
   Show answer

   The heart pumps blood, vessels carry it, blood transports materials and clots at injuries, and lymph carries absorbed fat and returns tissue fluid.

   The transport system in human beings has four components. (1) The heart — a muscular organ with four chambers — is the pump: its atria receive blood and its thick-walled ventricles push it out, the right side sending carbon dioxide-rich blood to the lungs and the left side sending oxygen-rich blood to the body, with valves preventing any backward flow. (2) The blood vessels are the network of tubes: arteries carry blood away from the heart under high pressure and so have thick elastic walls; capillaries, one cell thick, are where materials are exchanged between the blood and the cells; veins collect the blood from the organs and bring it back to the heart, with valves to keep the flow one way. (3) The blood is the fluid that is carried: its plasma transports food, carbon dioxide, nitrogenous wastes and salts in dissolved form, its red blood corpuscles carry oxygen, and its platelets clot the blood at an injury to plug the leak and keep up the pressure. (4) Lymph, or tissue fluid, formed from plasma that escapes through the capillary pores, drains through lymphatic capillaries and lymph vessels into the larger veins; it carries the digested and absorbed fat from the intestine and returns excess fluid from the tissues to the blood.

   Step-by-step solution →
8. Q28 NCERT · Intext Questions (Page 96)
   Why is ​it necessary ​to separate oxygenated ​and ​deoxygenated blood in ​mammals ​and ​birds?
   Show answer

   Warm-blooded mammals and birds need much energy, so unmixed oxygen-rich blood must reach the body for an efficient oxygen supply.

   Mammals and birds are warm-blooded: they constantly use energy to maintain their body temperature, so their energy needs are high and continuous. That energy is released by oxidising food with oxygen, so their cells need a highly efficient, uninterrupted supply of oxygen. If oxygenated blood from the lungs mixed with deoxygenated blood from the body in the heart, the blood pumped to the body would carry less oxygen in every round and the supply of energy would fall. Keeping the two kinds of blood separate — the right side of the four-chambered heart handling only carbon dioxide-rich blood bound for the lungs and the left side only oxygen-rich blood bound for the body — ensures that the body always receives fully oxygenated blood, giving the highly efficient oxygen supply these animals need. Animals with lower energy needs, such as amphibians and reptiles, whose body temperature depends on the surroundings, can tolerate some mixing in a three-chambered heart.

   Step-by-step solution →
9. Q29 NCERT · Intext Questions (Page 96)
   What ​are ​the ​components of ​the transport ​system in highly ​organised ​plants?
   Show answer

   Xylem (vessels, tracheids) carries water and minerals upwards; phloem (sieve tubes, companion cells) carries food in both directions.

   The transport system of a highly organised plant consists of two independently organised conducting tissues. (1) Xylem — made of vessels and tracheids, which in the roots, stems and leaves are interconnected into a continuous system of water-conducting channels reaching all parts of the plant; it transports water and the minerals dissolved in it, absorbed from the soil, from the roots upward. (2) Phloem — made of sieve tubes with adjacent companion cells; it transports the soluble products of photosynthesis (food) from the leaves, where they are made, to the storage organs of roots, fruits and seeds and to growing organs, along with amino acids and other substances, in both upward and downward directions.

   Step-by-step solution →
10. Q30 NCERT · Intext Questions (Page 96)
    How are water ​and ​minerals ​transported ​in plants?
    Show answer

    Water and dissolved minerals rise in the xylem, pushed by root pressure and pulled mainly by transpiration pull from the leaves.

    Water and minerals are transported in the xylem, whose vessels and tracheids in the roots, stems and leaves form one continuous system of water-conducting channels. (1) At the roots, the cells in contact with the soil actively take up ions (minerals). This creates a difference in ion concentration between the root and the soil, so water moves from the soil into the root to eliminate the difference. The steady entry of water into the root xylem creates a column of water that is pushed upward — root pressure. (2) Root pressure alone cannot lift water to the heights seen in tall plants. Water evaporates from the cells of the leaves and is lost through the stomata as vapour (transpiration); the water lost is replaced from the xylem vessels in the leaf, and this evaporation creates a suction — the transpiration pull — that pulls water up from the xylem of the roots to the highest parts of the plant. (3) During the day, when the stomata are open, the transpiration pull is the major driving force; root pressure matters more at night. The minerals, taken up as ions at the root, travel dissolved in this rising water. Transpiration thus helps in the absorption and upward movement of water and minerals, and also in temperature regulation.

    Step-by-step solution →
11. Q31 NCERT · Intext Questions (Page 96)
    How ​is food ​transported ​in ​plants?
    Show answer

    Food is translocated in the phloem: sucrose loaded using ATP draws in water, and the pressure moves food to where it is needed.

    Food — the soluble products of photosynthesis, chiefly sucrose, together with amino acids and other substances — is transported in the phloem; this transport is called translocation. It takes place in the sieve tubes with the help of the adjacent companion cells, and it delivers the food from the leaves to the storage organs of roots, fruits and seeds and to growing organs. Unlike transport in the xylem, which can be explained by simple physical forces, translocation uses energy: (1) sucrose is transferred into the phloem tissue using energy from ATP; (2) this increases the osmotic pressure of the phloem, so water moves into it; (3) the pressure so created moves the material in the phloem to tissues which have less pressure. Because the flow goes from the loaded tissue to any tissue of lower pressure, the phloem can move food according to the plant's needs, both upward and downward — for example, in spring the sugar stored in root or stem tissue is transported up to the buds, which need energy to grow.

    Step-by-step solution →
12. Q32 NCERT · Intext Questions (Page 98)
    Describe the ​structure and ​functioning of ​nephrons.
    Show answer

    A nephron filters blood at the glomerulus, re-absorbs the useful substances along the tubule, and passes the remaining urine to the collecting duct.

    Structure: A nephron is the basic filtration unit of the kidney, and each kidney contains a very large number of them packed close together. Each nephron consists of (1) a glomerulus — a cluster of very thin-walled blood capillaries supplied by a branch of the renal artery; (2) Bowman's capsule — the cup-shaped end of a long coiled tube, which encloses the glomerulus and collects the filtrate; (3) the tubular part of the nephron — the long coiled tube that leads on from the capsule, surrounded by a network of capillaries that carry blood on to a branch of the renal vein; and (4) a collecting duct, into which the tubule opens and which carries urine towards the ureter. Functioning: Blood enters the glomerulus under pressure, and water together with the small dissolved substances — glucose, amino acids, salts and the nitrogenous waste urea — is filtered through the thin capillary walls into Bowman's capsule (filtration). As this initial filtrate flows along the tubule, the useful substances — glucose, amino acids, salts and a major amount of water — are selectively re-absorbed into the surrounding capillaries; the amount of water taken back depends on how much excess water there is in the body and on how much dissolved waste has to be excreted (selective reabsorption). The fluid left — urea, excess water and excess salts — is urine; it passes into the collecting duct and then through the ureter to the urinary bladder, where it is stored until it is passed out through the urethra.

    Step-by-step solution →
13. Q33 NCERT · Intext Questions (Page 98)
    What ​are the ​methods ​used ​by ​plants ​to get rid ​of excretory products?
    Show answer

    Plants lose gases through stomata and water by transpiration, store wastes in vacuoles, leaves, resins and gums, and release some into the soil.

    Plants have no excretory organs and use several methods to get rid of their excretory products: (1) Gaseous wastes — oxygen produced in photosynthesis and carbon dioxide produced in respiration — diffuse out through the stomata (and the surfaces of other parts). (2) Excess water is lost as vapour by transpiration. (3) Many waste products are stored in the vacuoles of cells. (4) Wastes may be stored in leaves, which then fall off, taking the wastes with them. (5) Other wastes are stored as resins and gums, especially in old xylem, whose cells are dead. (6) Some waste substances are excreted into the soil around the plant. Plants can use storage in this way because many of their tissues consist of dead cells and because they can lose parts such as leaves.

    Step-by-step solution →
14. Q34 NCERT · Intext Questions (Page 98)
    How ​is ​the ​amount ​of urine produced ​regulated?
    Show answer

    The volume of urine is set by how much water the tubule re-absorbs, which depends on excess body water and dissolved waste.

    The amount of urine produced is regulated by how much water is re-absorbed from the filtrate as it flows along the tubular part of the nephron. About 180 L of initial filtrate is formed a day, but a major amount of its water is selectively re-absorbed and only a litre or two leaves as urine. The amount of water re-absorbed depends on two things: (1) how much excess water there is in the body — when the body has excess water, less is re-absorbed and a large volume of dilute urine is produced; when the body is short of water, more is re-absorbed and only a small volume of concentrated urine is produced; and (2) how much dissolved waste there is to be excreted — more waste needs more water to carry it out, so less water is re-absorbed and more urine is formed.

    Step-by-step solution →
15. Q35 Exemplar · Multiple Choice Questions
    Which of ​the ​following ​statements about ​the ​autotrophs ​is incorrect?

    1. (a)They synthesise carbohydrates from carbon dioxide and water in the presence of sunlight and chlorophyll
    2. (b)They store carbohydrates in the form of starch
    3. (c)They convert carbon dioxide and water into carbohydrates in the absence of sunlight
    4. (d)They constitute the first trophic level in food chains
    Show answer

    (c) They convert carbon dioxide and water into carbohydrates in the absence of sunlight

    Step-by-step solution →
16. Q36 Exemplar · Multiple Choice Questions
    In ​which of the ​following groups of ​organisms, food ​material ​is broken down outside the ​body and absorbed?

    1. (a)Mushroom, green plants, Amoeba
    2. (b)Yeast, mushroom, bread mould
    3. (c)Paramecium, Amoeba, Cuscuta
    4. (d)Cuscuta, lice, tapeworm
    Show answer

    (b) Yeast, mushroom, bread mould

    Step-by-step solution →
17. Q37 Exemplar · Multiple Choice Questions
    Select the correct statement

    1. (a)Heterotrophs do not synthesise their own food
    2. (b)Heterotrophs utilise solar energy for photosynthesis
    3. (c)Heterotrophs synthesise their own food
    4. (d)Heterotrophs are capable of converting carbon dioxide and water into carbohydrates
    Show answer

    (a) Heterotrophs do not synthesise their own food

    Step-by-step solution →
18. Q38 Exemplar · Multiple Choice Questions
    Which ​is ​the ​correct sequence ​of ​parts in human alimentary canal?

    1. (a)$\text{Mouth}\to \text{stomach}\to \text{small intestine}\to \text{oesophagus}\to \text{large intestine}$
    2. (b)$\text{Mouth}\to \text{oesophagus}\to \text{stomach}\to \text{large intestine}\to \text{small intestine}$
    3. (c)$\text{Mouth}\to \text{stomach}\to \text{oesophagus}\to \text{small intestine}\to \text{large intestine}$
    4. (d)$\text{Mouth}\to \text{oesophagus}\to \text{stomach}\to \text{small intestine}\to \text{large intestine}$
    Show answer

    (d) $\text{Mouth}\to \text{oesophagus}\to \text{stomach}\to \text{small intestine}\to \text{large intestine}$

    Step-by-step solution →
19. Q39 Exemplar · Multiple Choice Questions
    If ​salivary amylase ​is lacking in the saliva, ​which of the following events ​in ​the mouth ​cavity ​will be affected?

    1. (a)Proteins breaking down into amino acids
    2. (b)Starch breaking down into sugars
    3. (c)Fats breaking down into fatty acids and glycerol
    4. (d)Absorption of vitamins
    Show answer

    (b) Starch breaking down into sugars

    Step-by-step solution →
20. Q40 Exemplar · Multiple Choice Questions
    The inner lining of stomach ​is ​protected by ​one of ​the following from hydrochloric acid. ​Choose the correct ​one

    1. (a)Pepsin
    2. (b)Mucus
    3. (c)Salivary amylase
    4. (d)Bile
    Show answer

    (b) Mucus

    Step-by-step solution →