Class 10 Science · Chapter 5

Life Processes

431 Class 10 Science questions on Life Processes from the NCERT textbook, NCERT Exemplar and CBSE board papers 2018–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 10 of 22

1. Q181 CBSE 2026
   In human ​beings, ​digestion in the ​stomach is taken care of by the gastric glands present ​in the walls of the ​stomach. Briefly describe ​the function of ​gastric glands.
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   Gastric glands secrete hydrochloric acid, pepsin and mucus: the acid helps pepsin digest proteins and kills germs, and mucus protects the lining.

   The gastric glands in the wall of the stomach release gastric juice, which contains: (1) Hydrochloric acid, which makes the medium in the stomach acidic so that the enzyme pepsin can act; it also kills germs that enter with the food. (2) Pepsin, a protein-digesting enzyme, which begins the digestion of proteins, breaking them into smaller peptides. (3) Mucus, which protects the inner lining of the stomach from the action of the acid under normal conditions.

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2. Q182 CBSE 2026
   Briefly describe the ​role of ​saliva and pancreas ​in the digestion ​of food. ​Also, explain ​the peristaltic movement ​in the gut.
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   Saliva's amylase digests starch; the pancreas adds trypsin, lipase and amylase; peristalsis is a muscle wave that pushes food along the gut.

   Saliva: secreted by the salivary glands into the mouth, it moistens the food so that it can be chewed and swallowed easily, and its enzyme salivary amylase breaks down starch into simple sugar (maltose). Pancreas: it secretes pancreatic juice into the small intestine; the juice contains trypsin, which digests proteins, lipase, which breaks down emulsified fats into fatty acids and glycerol, and amylase, which digests the remaining starch. Peristaltic movement: the muscles in the wall of the gut contract and relax rhythmically in a wave that travels along the tube; the muscle behind the food contracts while the muscle ahead of it relaxes, so the food is pushed forward. These movements occur all along the gut and carry the food from the mouth towards the anus.

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3. Q183 CBSE 2026
   Kidneys ​help ​to ​regulate the ​volume of fluid and various ​metabolites waste products in the body. Normally, kidney filter about 180 L of fluid ​daily but the volume actually excreted out is ​only a litre or two a day. Patients with kidney failures can be saved by ​dialysis and kidney transplant.

   1. (a)Write the structure and function of Bowman’s capsule.[1]
   2. (b)Although kidneys filter a large amount (about 180 L daily) of fluids, still the excretion from the body is only about a litre or two. Why ?[1]
   3. (c)What is excretion ? Why is it necessary for any living organism ?[2]
   4. (c)OR : State two similarities between lungs and kidneys.[2]
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   Bowman's capsule is a cup-shaped part holding the glomerulus that collects filtrate; about $99\%$ of filtrate is reabsorbed; excretion removes metabolic wastes.

   (a) Bowman’s capsule is the thin-walled, cup-shaped beginning of a nephron; it encloses the glomerulus, a cluster of very fine blood capillaries, and opens into the coiled tubule. Function: it collects the filtrate (water, glucose, amino acids, salts and urea) filtered out of the blood in the glomerulus and passes it into the tubule. (b) Because almost all of the filtrate is taken back. As it flows along the tubule, glucose, amino acids, salts and most of the water are selectively reabsorbed into the surrounding blood capillaries, about $178$ to $179$ L of the $180$ L, that is roughly $99\%$, so only $1$ to $2$ L is left to be excreted as urine. (c) Excretion is the biological process by which the harmful waste products of metabolism are removed from the body. It is necessary because wastes such as urea and uric acid are made continuously in the cells and are poisonous if they collect in the body; removing them also keeps the water and salt content of the body fluids in balance. OR (c) Two similarities: (i) both are excretory organs that remove metabolic wastes from the blood, the lungs removing carbon dioxide and the kidneys nitrogenous wastes such as urea; (ii) in both, the exchange happens across a cluster of very thin-walled blood capillaries offering a large surface, around the alveoli in the lungs and in the glomerulus of each nephron. (Both are also paired organs with a rich blood supply.)

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4. Q184 CBSE 2026
   The given ​diagram shows ​the human kidney and its ​associated ​structures. Study the Table I and Table ​II ​that shows the concentration of certain substances found ​within the structure P and Q.

   Table I (structure P) and Table II (structure Q) - concentration of components, in per cent

   Components	Table I - Structure P, concentration %	Table II - Structure Q, concentration %
   Urea	0.05	1.00
   Amino acids	0.06	0.00
   Salts	1.72	1.60
   Glucose	0.10	0.00

   1. (A)Where are kidneys located in the human body ? Name the filtration unit of them.[1]
   2. (B)List two factors on which reabsorption of water from the filtrate depends.[1]
   3. (C)Why is there variation in the concentration of given substance in structure P and Q listed in table I and II respectively ?[2]
   4. (C)OR : If a person is suffering from diabetes, concentration of which substance present in structure Q (listed in table II) will be modified and why ?[2]
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   Kidneys lie in the abdomen beside the backbone, with the nephron as filtration unit; filtration then selective reabsorption changes blood into urine.

   (A) The kidneys are a pair of bean-shaped organs lying in the abdomen, one on either side of the backbone, towards the back of the abdominal cavity. Their filtration unit is the nephron. (B) The amount of water reabsorbed from the filtrate depends on (i) how much excess water there is in the body, and (ii) how much dissolved waste there is to be excreted. (C) P is the blood vessel carrying blood into the kidney, so Table I is the composition of blood, and Q is the ureter carrying urine away, so Table II is the composition of urine. In the nephron the blood is first filtered at the glomerulus, so water and all the small dissolved substances enter the tubule, and the filtrate is then selectively reabsorbed as it flows along the tubule. All the glucose and all the amino acids are useful and are taken back completely, so they fall from 0.10% and 0.06% in P to 0.00% in Q. Most of the salts are taken back along with most of the water, so their concentration hardly changes, 1.72% to 1.60%. Urea is a nitrogenous waste and is not reabsorbed, while the water around it is, so it is left behind and becomes concentrated, rising from 0.05% in P to 1.00% in Q. OR (C) The concentration of glucose in structure Q will be modified: there will be more glucose in Q. In a healthy person it is 0.00% because all the filtered glucose is reabsorbed by the tubule. A person suffering from diabetes does not have sufficient insulin, so the glucose level of the blood rises; more glucose is then filtered than the tubule is able to reabsorb, the excess is not taken back and passes out in the urine, so glucose now appears in structure Q at a value above 0.00%.

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5. Q185 CBSE 2026
   Read the following ​passage and answer the ​questions ​that follow : Metabolic activities produce metabolic waste, which refers ​to by-products from the body’s energy-producing processes that are ​unusable and ​potentially toxic. These wastes need removal from the body to maintain health. The wastes like urea, water, salts, ​ammonia, etc. are excreted via kidneys, sweat or ​urine. ${\text{CO}}_2$ is eliminated through the lungs.

   1. (i)What is the purpose of making urine in the human body ?[1]
   2. (ii)Name two main toxic wastes that kidneys filter from the blood.[1]
   3. (iii)(a)A major amount of water is selectively reabsorbed by the tubular part of the nephron. On what factors does the amount of water reabsorbed depend ?[2]
   4. (iii)(b)OR : Quantity of, or the frequency of passing urine is less in summer. Why ?[2]
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   Urine removes wastes such as urea and uric acid; water reabsorption depends on body water and dissolved waste; summer sweating reduces urine.

   (i) Urine is made to filter the waste products, mainly nitrogenous wastes such as urea and uric acid, out of the blood and remove them from the body; this also removes excess water and salts, keeping their amounts in the body steady. (ii) Urea and uric acid. (iii)(a) The amount of water reabsorbed depends on (1) how much excess water there is in the body, and (2) how much dissolved waste there is to be excreted. OR (iii)(b) In summer a large amount of water is lost from the body as sweat, so there is less excess water in the body. The tubules of the nephrons therefore reabsorb more water, and the urine formed is less in quantity and more concentrated, so it is passed less often.

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6. Q186 CBSE 2026
   Read the ​following passage and ​answer the questions that ​follow : Not all plants carry out photosynthesis by the same mechanism. In most plants, it depends directly on gaseous carbon ​dioxide that ​diffuses into the leaf. However, some plants can store carbon dioxide in the ​vacuole of the leaf cells ​as part of a complex carbon compound. This compound is transported to the chloroplast and releases carbon dioxide when required for photosynthesis. This special mechanism is believed to have evolved as an adaptation in such ​plants which do not open stomata during the daytime to conserve water for survival in dry conditions (desert conditions).

   1. (i)Which process in these plants is minimised to help the plants survive in dry conditions ?
   2. (ii)Which part of the leaf is responsible for exchange of gases during photosynthesis ?
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   Transpiration is minimised because the stomata stay closed by day; gas exchange in photosynthesis takes place through the stomata.

   (i) Transpiration, the loss of water as vapour through the stomata: by keeping their stomata closed during the day, these plants minimise it and conserve water. (ii) The stomata, tiny pores in the epidermis of the leaf, each surrounded by two guard cells: carbon dioxide enters and oxygen leaves through them during photosynthesis.

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7. Q187 CBSE 2026
   Read the following passage and answer the questions that follow : Not all ​plants carry out photosynthesis by the same ​mechanism. In most plants, it depends directly on ​gaseous carbon dioxide that diffuses into the leaf. However, some plants can store carbon dioxide in the vacuole of the leaf cells as part of ​a complex carbon compound. This compound is transported to ​the chloroplast and releases carbon dioxide when required for photosynthesis. This special mechanism is believed to ​have evolved ​as an adaptation in such plants which do not open stomata during the daytime to conserve water for survival in dry conditions (desert conditions).

   1. (i)List the events that occur during the process of photosynthesis.
   2. (ii)When are such desert plants likely to take in carbon dioxide from the environment, unlike other plants ?
   3. (iii)Draw a labelled diagram of stomata with open stomatal pore.
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   Photosynthesis: light absorbed, water split, carbon dioxide reduced; desert plants take in carbon dioxide at night; stomata have guard cells around the pore.

   (i) The events are: (1) absorption of light energy by chlorophyll; (2) conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen; (3) reduction of carbon dioxide to carbohydrates. (ii) At night: these plants keep their stomata closed during the day, so they open them at night, take in carbon dioxide and store it as an intermediate compound, which is used for photosynthesis during the day. (iii) The diagram shows two bean-shaped guard cells, each with a nucleus, chloroplasts and a thick inner wall, around an open stomatal pore, with epidermal cells around them (see the labelled diagram).

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8. Q188 CBSE 2026
   1. (a)Draw a ​labelled diagram showing open and ​closed stomatal ​pore.
   2. (b)List the main events that occur during the process of photo-synthesis.
   3. (c)​Write a balanced chemical equation ​showing photo-synthesis ​in ​plants.
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   Turgid guard cells open the pore and flaccid ones close it; photosynthesis absorbs light, splits water and reduces carbon dioxide to carbohydrate.

   (a) Two guard cells face each other around the pore. In the open stoma they are turgid and bow apart, leaving a wide pore between them; in the closed stoma they are flaccid and their inner walls press together, so the pore is shut. Label the guard cells, the chloroplasts in them and the stomatal pore. (b) The main events are: (i) Absorption of light energy by chlorophyll; (ii) Conversion of light energy into chemical energy and splitting of water molecules into hydrogen and oxygen; (iii) Reduction of carbon dioxide to carbohydrates. These events need not follow one another immediately. (c) $6\mathrm{C}{\mathrm{O}}_2+12{\mathrm{H}}_2\mathrm{O}\underset{\text{Sunlight}}{\overset{\text{Chlorophyll}}{\to }}{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6+6{\mathrm{O}}_2+6{\mathrm{H}}_2\mathrm{O}$, where ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$ is glucose. Cancelling the six molecules of water that appear on both sides gives the equivalent net equation $6\mathrm{C}{\mathrm{O}}_2+6{\mathrm{H}}_2\mathrm{O}\to {\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6+6{\mathrm{O}}_2$, which is also balanced.

   Step-by-step solution →
9. Q189 CBSE 2026
   1. (a)​Draw a ​well-labelled diagram of ​nephron and label atleast 4 of ​its parts.
   2. (b)Write the role of ​capillary cluster inside Bowman's capsule.
   3. (c)What is meant by selective ​reabsorption ?
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   The glomerulus filters blood under high pressure into Bowman's capsule; the tubule then selectively reabsorbs useful substances, leaving wastes to form urine.

   (a) The nephron runs from Bowman's capsule, which cups the glomerulus, into the proximal convoluted tubule, then down and up the loop of Henle, into the distal convoluted tubule and finally into the collecting duct; blood enters the glomerulus by the afferent arteriole and leaves by the narrower efferent arteriole. Any four of these parts satisfy the question, and the diagram labels eight. (b) The capillary cluster is the glomerulus. Because the afferent arteriole bringing blood in is wider than the efferent arteriole taking it away, the blood pressure inside the tuft is high, and under that pressure the glomerulus filters the blood: water, glucose, amino acids, salts, urea and other small molecules are forced through the thin capillary walls into Bowman's capsule, while blood cells and large plasma proteins are too big to pass and remain in the blood. The fluid collected is the glomerular filtrate, and the process is ultrafiltration. (c) Selective reabsorption is the taking back into the blood, from the filtrate flowing along the tubule, of the substances the body still needs, while the wastes are left behind. Glucose, amino acids, most salts and a major part of the water are reabsorbed, chiefly in the proximal convoluted tubule, whereas the wastes such as urea, together with the excess salts and the remaining water, pass on to form urine. It is selective because the useful substances are recovered in preference to the wastes, and the amount of water taken back depends on how much excess water the body has and how much dissolved waste it must excrete.

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10. Q190 CBSE 2025
    The essential ​element taken up from ​the soil ​by ​the plants ​to synthesize proteins ​is ​:

    1. (a)Phosphorus
    2. (b)Nitrogen
    3. (c)Iron
    4. (d)Magnesium
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    (b) Nitrogen

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11. Q191 CBSE 2025
    The opening ​and closing ​of stomata is ​regulated ​by ​:

    1. (a)${\text{CO}}_2$ concentration in stomata
    2. (b)Temperature in guard cells
    3. (c)${\text{O}}_2$ concentration in stomata
    4. (d)Amount of water in guard cells
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    (d) Amount of water in guard cells

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12. Q192 CBSE 2025
    The valves in the human heart ensure that :

    1. (i)​Oxygen-rich blood flows ​from left atrium to left ventricle only.
    2. (ii)Deoxygenated ​blood flows from left atrium to left ventricle only.
    3. (iii)​Oxygen-rich blood flows from right atrium to right ventricle only.
    4. (iv)​Deoxygenated blood ​flows from ​right atrium to right ventricle ​only.

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

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13. Q193 CBSE 2025
    Select ​TRUE statements about lymph ​from the ​following ​: A. Lymph vessels carry lymph through the body and finally open into larger arteries. B. Lymph ​contains some amount of plasma, proteins ​and blood cells. C. Lymph contains some amount of plasma, proteins and red blood cells. D. Lymph vessels ​carry lymph through the body and finally open into larger veins. The true statements are :

    1. (a)A and B
    2. (b)B and D
    3. (c)A and C
    4. (d)C and D
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    (b) B and D

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14. Q194 CBSE 2025
    The ​essential element ​used ​in ​the synthesis ​of ​proteins is :

    1. (a)Nitrogen
    2. (b)Phosphorus
    3. (c)Iron
    4. (d)Magnesium
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    (a) Nitrogen

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15. Q195 CBSE 2025
    Select the ​correct option from ​the following statements about ​the functioning ​of the human ​heart.

    1. (a)Right atrium receives deoxygenated blood from different parts of the body and sends it to pulmonary veins.
    2. (b)Left atrium sends oxygenated blood to right ventricle which pumps it to different parts of the body.
    3. (c)Right atrium receives deoxygenated blood from the body and sends it to the right ventricle.
    4. (d)Left atrium receives oxygenated blood from the pulmonary arteries and sends it to the left ventricle.
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    (c) Right atrium receives deoxygenated blood from the body and sends it to the right ventricle.

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16. Q196 CBSE 2025
    Breakdown ​of proteins in ​the ​stomach takes ​place by the ​enzyme ​:

    1. (a)Trypsin
    2. (b)Lipase
    3. (c)Salivary Amylase
    4. (d)Pepsin
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    (d) Pepsin

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17. Q197 CBSE 2025
    One-cell ​thick blood vessels ​are known ​as ​:

    1. (a)Alveoli
    2. (b)Capillaries
    3. (c)Arteries
    4. (d)Veins
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    (b) Capillaries

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18. Q198 CBSE 2025
    Movement of soluble product of photosynthesis ​in ​plants ​from ​leaves ​to other parts ​of the plant ​takes place mainly through

    1. (a)Tracheids
    2. (b)Sieve tubes
    3. (c)Vessels
    4. (d)Companion cells
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    (b) Sieve tubes

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19. Q199 CBSE 2025
    Secretion of less ​saliva ​in ​mouth will ​effect the conversion ​of ​:

    1. (a)proteins into amino acids
    2. (b)fats into fatty acids and glycerol
    3. (c)starch into simple sugars
    4. (d)sugars into alcohol
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    (c) starch into simple sugars

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20. Q200 CBSE 2025
    Select the correct ​statements from the following about the human heart ​:

    1. (i)Right atrium receives oxygenated blood from lungs through pulmonary artery.
    2. (ii)Right atrium receives deoxygenated blood through vena cava from upper and ​lower body.
    3. (iii)Left atrium transfers oxygenated ​blood ​to left ventricle which sends it to various ​parts of ​the body.
    4. (iv)Left atrium transfers oxygenated blood to aorta which sends it to various parts of the body.

    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)

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