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.

NCERT exercises

Exercises (13) Intext Questions (Page 81) (4) Intext Questions (Page 87) (5) Intext Questions (Page 91) (4) Intext Questions (Page 96) (5) Intext Questions (Page 98) (3)

NCERT Exemplar exercises

Multiple Choice Questions (35) Short Answer Questions (37) Long Answer Questions (10)

CBSE Class 10 Science previous year papers, with answers →

Questions · page 15 of 22

Q281 CBSE 2024

We water the soil but it reaches the topmost leaves of the plants. Explain in brief the process involved.

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Roots absorb water, root pressure pushes it up the xylem, and transpiration pull from the leaves draws it to the topmost leaves.
Water is absorbed from the soil by the roots: root cells in contact with the soil actively take up ions, and the resulting difference in concentration makes water move from the soil into the root and its xylem. The vessels and tracheids of the root, stem and leaves are interconnected and form a continuous channel. Water entering the root pushes the water column upwards (root pressure, more important at night). At the leaves, water evaporates and escapes as vapour through the stomata (transpiration); this creates a suction, the transpiration pull, which draws water up through the xylem to the topmost leaves and is the main driving force during the day.

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Q282 CBSE 2024
Give reasons for the following :
1. (i)Alveoli in lungs are richly supplied with blood capillaries.
2. (ii)Respiratory pigment in the blood takes up oxygen and not carbon dioxide.
3. (iii)During anaerobic respiration, a 3-carbon molecule is formed as an end product instead of $CO_{2}$ in human beings.
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Capillaries give alveoli a large exchange surface; haemoglobin binds oxygen strongly; without oxygen, pyruvate becomes lactic acid, not carbon dioxide.
(i) Alveoli are the sites where gases are exchanged: oxygen from the alveolar air passes into the blood and carbon dioxide from the blood passes into the alveoli. The rich network of blood capillaries in their thin walls provides a large surface for this exchange, making it quick and efficient. (ii) The respiratory pigment, haemoglobin, has a very high affinity for oxygen, so it takes up oxygen in the lungs and carries it to the tissues; carbon dioxide is more soluble in water than oxygen and is mostly transported in the dissolved form in the blood. (iii) In human muscle cells, when there is a lack of oxygen, the pyruvate (a 3-carbon molecule) formed from glucose is converted into lactic acid, which is also a 3-carbon molecule, instead of being broken down into carbon dioxide and water; that complete break-down needs oxygen and takes place in the mitochondria.

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Q283 CBSE 2024
(i) List any two characteristics of lungs which make them an efficient respiratory system. (ii) Name the part of human respiratory system :
1. (1)where air is filtered by fine hair and mucus lining.
2. (2)which separates chest cavity from abdominal cavity.
3. (3)which has balloon like structures where exchange of gases takes place.
4. (4)two large air passages which connect trachea to lungs.
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Lungs are efficient because of many thin-walled alveoli with capillaries; the parts are nasal passage, diaphragm, lungs (alveoli) and bronchi.
(i) Any two of these: the lungs contain a very large number of alveoli, which give a very large surface for the exchange of gases; the walls of the alveoli are very thin and have an extensive network of blood capillaries, so gases diffuse quickly between the air and the blood; the lungs always hold a residual volume of air, so there is sufficient time for oxygen to be absorbed and carbon dioxide to be released. (ii) (1) Nasal passage (entered through the nostrils); (2) Diaphragm; (3) Lungs: their balloon-like air sacs, the alveoli, are where the exchange of gases takes place; (4) Bronchi.

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Q284 CBSE 2024
1. (i)Name the movements that occur all along the gut in human digestive system. How do they help in digestion ?
2. (ii)Where is bile juice stored in human body ? List two roles of bile juice.
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Peristalsis pushes food along the gut; bile, stored in the gall bladder, makes food alkaline and emulsifies fats.
(i) The movements are peristaltic movements (peristalsis): rhythmic contractions of the muscles lining the alimentary canal, occurring all along the gut. They push the food forward in a regulated manner, so that it is processed properly in each part of the canal, and they help to mix the food with the digestive juices. (ii) Bile juice is made in the liver and stored in the gall bladder. Two roles of bile: (1) it makes the acidic food coming from the stomach alkaline, so that the pancreatic enzymes can act on it; (2) its bile salts break large fat globules into smaller globules (emulsification), increasing the efficiency of the enzymes that digest fats.

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Q285 CBSE 2024
(i) In the human excretory system name the following parts :
1. (1)in which urine is produced
2. (2)where urine is stored
3. (3)which connects (1) and (2) mentioned above (4) which provides passage for urine to pass (ii) List two factors on which the amount of water reabsorbed along the tubular part of nephron depends.
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Kidneys, urinary bladder, ureters and urethra; water reabsorbed depends on excess water in the body and dissolved waste to be excreted.
(i) (1) Kidneys; (2) Urinary bladder; (3) Ureters (one from each kidney to the bladder); (4) Urethra. (ii) The amount of water reabsorbed along the tubule depends on (1) how much excess water there is in the body, and (2) how much dissolved waste there is to be excreted.

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Q286 CBSE 2024
In the context of the statement “chlorophyll is necessary for photosynthesis” answer the following questions :
1. (i)What are variegated leaves? Give an example.
2. (ii)When leaf is boiled in alcohol, what happens to the colour of the leaf and the colour of the solution ?
3. (iii)In what form is the carbohydrate produced, stored in the plant? Why is chlorophyll necessary for photosynthesis ?
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Variegated leaves have green and non-green patches; boiling in alcohol pales the leaf and greens the solution; starch is stored, and chlorophyll absorbs light.
(i) Variegated leaves have both green patches (with chlorophyll) and non-green patches, white or yellow (without chlorophyll); example: croton or money plant. (ii) On boiling in alcohol the leaf loses its green colour and becomes pale or colourless, while the alcohol (solution) turns green, because chlorophyll dissolves in it. (iii) The carbohydrate is stored in the form of starch. Chlorophyll is necessary because it absorbs the light energy that drives photosynthesis; in the activity only the green parts of a variegated leaf give the blue-black starch test.

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Q287 CBSE 2024

Write the main difference between aerobic and anaerobic respiration. State the pathway which is common for both. Write the overall chemical equation of aerobic respiration and mention the site where this process occurs inside the cells.

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Aerobic respiration needs oxygen and releases much more energy; glycolysis is common to both; aerobic respiration occurs in the mitochondria.
Main difference: aerobic respiration takes place in the presence of oxygen and breaks glucose down completely into carbon dioxide and water, releasing a large amount of energy; anaerobic respiration takes place without oxygen, breaks glucose down only partly (into ethanol and carbon dioxide in yeast, or lactic acid in muscle cells) and releases much less energy. Common pathway: glycolysis, the break-down of glucose (6-carbon) into pyruvate (3-carbon) in the cytoplasm. Overall equation: $C_{6} H_{12} O_{6} + 6 O_{2} ⟶ 6 CO_{2} + 6 H_{2} O + energy$ . Site: mitochondria (the first step, glycolysis, takes place in the cytoplasm).

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Q288 CBSE 2024
1. (i)Which organisms have a three-chambered heart ? Why do they have three-chambered hearts ?
2. (ii)List two functions of lymph.
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Amphibians and many reptiles have three-chambered hearts because their energy needs are low; lymph carries absorbed fat and returns excess fluid to blood.
(i) Amphibians, such as frogs, and many reptiles, such as lizards, have three-chambered hearts (two atria and one ventricle). They do not use energy to maintain their body temperature, which depends on the temperature of the surroundings, so their energy needs are lower than those of birds and mammals. They can therefore tolerate some mixing of oxygenated and deoxygenated blood in the single ventricle and do not need the complete separation a four-chambered heart gives. (ii) Two functions of lymph: (1) it carries digested and absorbed fat from the intestine; (2) it drains excess fluid from the intercellular spaces back into the blood.

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Q289 CBSE 2024

Design an experiment to demonstrate that carbon dioxide is essential for photosynthesis. Write the observation and conclusion of the experiment.

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The leaf from the jar with potassium hydroxide shows no starch while the other leaf does, so carbon dioxide is essential for photosynthesis.
Experiment: Keep two healthy potted plants of nearly the same size in a dark room for three days to destarch them. Place each on a separate glass plate; beside one (A) put a watch-glass containing potassium hydroxide, which absorbs carbon dioxide, and nothing beside the other (B). Cover each with a bell jar and seal the jars to the plates with vaseline to make them air-tight. Keep both in sunlight for about two hours. Then pluck a leaf from each, dip it in boiling water, heat it in alcohol on a water bath to remove the chlorophyll, and test it with dilute iodine solution. Observation: The leaf from B turns blue-black (starch present); the leaf from A does not turn blue-black (no starch). Conclusion: Without carbon dioxide the plant could not make starch, so carbon dioxide is essential for photosynthesis.

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Q290 CBSE 2024
1. (i)Study the diagram below of alimentary canal of man and name the parts marked as A, B and C. Write the name of the enzyme present in each labelled part.
2. (ii)Explain how digested food reaches each and every cell of the body and is utilised.
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A, B and C are the mouth (salivary amylase), stomach (pepsin) and pancreas (trypsin, lipase); villi absorb food and blood carries it to all cells.
(i) A is the mouth (buccal cavity); the enzyme present is salivary amylase, in saliva, which breaks down starch into sugar. B is the stomach; the enzyme present is pepsin, which digests proteins in the acidic medium created by hydrochloric acid. C is the pancreas; its pancreatic juice contains trypsin, which digests proteins, and lipase, which breaks down emulsified fats. (ii) The digested food is absorbed in the small intestine through the villi — finger-like projections of its inner lining that increase the surface area for absorption and are richly supplied with blood vessels. The blood carries the absorbed food to each and every cell of the body, where it is utilised for obtaining energy, for building up new tissues and for the repair of old tissues.

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Q291 CBSE 2024
Study the following flow chart showing the breakdown of glucose by various pathways. In this flow chart, in four blocks some blanks are given as Ⓐ, Ⓑ, Ⓒ and Ⓓ.
1. (i)Write the names of Ⓐ, Ⓑ, Ⓒ and Ⓓ.
2. (ii)Write the source of glucose molecule involved in cellular respiration in (I) plants, and (II) animals.
3. (iii)Why do athletes sometimes suffer from muscle cramps during running ?
4. (iv)Give reason why the rate of breathing in aquatic organisms is faster than in terrestrial organisms.
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The blanks are pyruvate, ethanol, lack of oxygen and mitochondria; lactic acid causes cramps; water holds little oxygen, so aquatic organisms breathe faster.
(i) Ⓐ Pyruvate, a three-carbon molecule (with energy released); Ⓑ Ethanol; Ⓒ Lack of oxygen, in our muscle cells; Ⓓ Mitochondria. (ii) (I) In plants, glucose is made by photosynthesis in the green parts, mainly the leaves (and starch stored in the plant is broken down to glucose when needed). (II) In animals, glucose comes from food: carbohydrates such as starch are digested to glucose in the alimentary canal and absorbed into the blood. (iii) During vigorous running the muscle cells need energy faster than the oxygen supply can support. With a lack of oxygen, pyruvate is converted into lactic acid in the muscle cells, and this build-up of lactic acid in the muscles causes cramps. (iv) The amount of oxygen dissolved in water is fairly low compared with the amount of oxygen in air, so aquatic organisms have to breathe much faster than terrestrial organisms to obtain enough oxygen.

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Q292 CBSE 2024
1. (i)In the experimental set-up shown above in diagram (I) atmospheric air is being passed into lime water with a syringe while in diagram (II) air is being exhaled into lime water. The time taken for the lime water to turn milky in both the test tubes is different. Give reason.
2. (ii)Draw the diagram of an open stomatal pore and label (I) Guard cells, and (II) Chloroplast on it. Mention two functions performed by stomata.
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Exhaled air has much more carbon dioxide, so its lime water turns milky faster; stomata exchange gases and lose water vapour.
(i) Exhaled air (II) contains much more carbon dioxide than atmospheric air (I), because the cells of the body release carbon dioxide during respiration and it is breathed out. Carbon dioxide turns lime water milky, $Ca(OH)_{2} + CO_{2} \to CaCO_{3} + H_{2} O$ , so the lime water in (II) turns milky much faster than the lime water in (I). (ii) Diagram: two bean-shaped guard cells around an open stomatal pore, each with a nucleus and chloroplasts, labelled (I) Guard cells and (II) Chloroplast. Two functions of stomata: exchange of gases (carbon dioxide in for photosynthesis, oxygen out), and loss of water as water vapour (transpiration).

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Q293 CBSE 2024
1. (i)Study the diagram below showing schematic representation of transport and exchange of gases in human heart and name the parts labelled as A, B and C. Mention the function of each part.
2. (ii)Explain how separation of right and left side of the heart is useful for birds.
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A is the pulmonary artery, B the aorta, C the body capillaries; separate sides prevent blood mixing, giving birds an efficient oxygen supply.
(i) A is the pulmonary artery: it carries deoxygenated blood from the right ventricle to the lungs, where the blood takes in oxygen. B is the aorta: it carries oxygenated blood from the left ventricle to all parts of the body. C is the capillaries in the body organs: across their one-cell-thick walls, oxygen passes from the blood to the body cells and carbon dioxide passes from the cells into the blood, after which the deoxygenated blood returns to the heart. (ii) The separation of the right and left sides of the heart keeps oxygenated and deoxygenated blood from mixing, so the body receives a highly efficient supply of oxygen. Birds have high energy needs because they constantly use energy to maintain their body temperature, so this efficient supply of oxygen is useful to them.

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Q294 CBSE 2024
1. (i)Given below is a diagram showing cross-section of a leaf. Name the parts marked as A and B and write one specific function of each.
2. (ii)Name the two tissues present in a vascular bundle. In what way does each of them help a plant ?
3. (iii)In the experiment “Light is essential for photosynthesis”, why does the uncovered part of the leaf turned blue-black after putting iodine solution on it ?
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A is a chloroplast (makes food), B a stoma (gas exchange); xylem carries water, phloem carries food; only the lit part makes starch.
(i) A is a chloroplast: it contains chlorophyll, which absorbs light energy, and food (glucose) is made here by photosynthesis. B is a stoma, the pore between two guard cells: it allows the exchange of gases, carbon dioxide entering for photosynthesis and oxygen passing out (water vapour is also lost through it in transpiration). (ii) The two tissues are xylem and phloem. Xylem carries water and minerals from the roots to the leaves and other parts of the plant; phloem carries the food made in the leaves (the products of photosynthesis) to the other parts of the plant. (iii) The uncovered part of the leaf received light, so it carried out photosynthesis; the glucose made there was stored as starch, and iodine solution turns starch blue-black. The covered part received no light, so no starch was made in it (the plant had been destarched beforehand), and it did not turn blue-black. This shows that light is essential for photosynthesis.

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Q295 CBSE 2024
Human digestive system is a tube running from mouth to anus. Its main function is to breakdown complex molecules present in the food which cannot be absorbed as such into smaller molecules. These molecules are absorbed across the walls of the tube and the absorbed food reaches each and every cell of the body where it is utilised for obtaining energy.
1. (a)Name the glands present in the buccal cavity and write the components of food on which the secretion of these glands act upon.[1]
2. (b)Two organs have a sphincter muscle at their exit. Name them.[1]
3. (c)What will happen if : (i) mucus is not secreted by the gastric glands. (ii) Villi are absent in the small intestine.[2]
4. (c)OR : “Bile juice does not contain any enzyme, yet it has important roles in digestion.” Justify the statement.[2]
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Salivary glands act on starch; stomach and large intestine have sphincters; mucus protects the stomach; villi aid absorption; bile emulsifies fats.
(a) The salivary glands. Their secretion, saliva, contains the enzyme salivary amylase, which acts on starch (a carbohydrate) and breaks it down into simple sugar. (b) The stomach, whose sphincter releases food into the small intestine in small amounts, and the large intestine (rectum), whose exit, the anus, is regulated by the anal sphincter. (c)(i) If mucus is not secreted: mucus protects the inner lining of the stomach from hydrochloric acid, so without it the acid would damage the lining, which can cause ulcers. (c)(ii) If villi are absent: villi increase the surface area for absorption, so without them far less digested food would be absorbed into the blood, the body would not get enough nutrients, and much digested food would pass on unabsorbed. OR (c) Bile has no enzyme, but (1) it makes the acidic food coming from the stomach alkaline, so that the pancreatic enzymes can act on it; and (2) bile salts break large fat globules into smaller globules (emulsification), which increases the efficiency of the fat-digesting enzyme lipase.

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Q296 CBSE 2024
Kidneys are vital organs for survival. Several factors like infections, injury or restricted blood flow to kidneys reduce the activity of kidneys. This leads to accumulation of poisonous wastes in the body, which can even lead to death. In case of kidney failure, an artificial kidney can be used. An artificial kidney is a device to remove waste products from the blood through dialysis.
1. (a)(i) Name the artery that brings oxygenated blood to the kidney. (ii) Name the cluster the thin-walled blood capillaries present in the Bowman's capsule.[1]
2. (b)In human excretory system name the organ which stores urine. Is this organ under hormonal control or nervous control?[1]
3. (c)(i)List two major steps involved in the formation of urine and state in brief their functions.[2]
4. (c)(ii)OR : In which part of the nephron does selective reabsorption take place? List the factors which the amount of water reabsorbed depends on.[2]
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Renal artery; glomerulus; urinary bladder under nervous control; filtration then selective reabsorption; reabsorption occurs in the tubule.
(a) (i) Renal artery. (ii) Glomerulus. (b) The urinary bladder stores urine. It is muscular and is under nervous control. (c)(i) Filtration: in the glomerulus, blood is filtered into Bowman's capsule, so water, glucose, amino acids, salts and nitrogenous wastes such as urea pass into the capsule while blood cells stay in the blood; its function is to separate the wastes from the blood. Selective reabsorption: as the filtrate flows along the tubule, useful substances such as glucose, amino acids, salts and a major amount of water are reabsorbed into the surrounding capillaries; its function is to return useful substances to the blood, leaving the wastes as urine. (c)(ii) In the tubular part of the nephron (the renal tubule). The amount of water reabsorbed depends on how much excess water there is in the body and on how much dissolved waste there is to be excreted.

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Q297 CBSE 2024
The maintenance functions of every living organism on the earth keeps going on even when they are not doing anything particular. The processes which together perform the job of maintenance of life are known as life processes. These processes are nutrition, respiration, transportation and excretion.
1. (i)List two types of nutrition.[1]
2. (ii)We eat food. What happens to this food during aerobic respiration in our body ?[1]
3. (iii)(a)What is transpiration ? How is it useful to plants ?[2]
4. (iii)(b)OR : Mention the pathway of urine starting from the organ of its formation. Name any two substances which are reabsorbed from the initial filtrate in the tubular part of the nephron.[2]
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Autotrophic and heterotrophic nutrition; glucose breaks down to release energy; transpiration moves water up the plant; urine passes kidneys, ureters, bladder, urethra.
(i) Autotrophic nutrition and heterotrophic nutrition. (ii) The food is digested to glucose, which is broken down in our cells: first in the cytoplasm into pyruvate (a three-carbon molecule), then in the mitochondria, using oxygen, into carbon dioxide and water, releasing a large amount of energy that is used to make ATP. (iii)(a) Transpiration is the loss of water as vapour from the aerial parts of a plant, mainly through the stomata of the leaves. It helps in the absorption and upward movement of water and dissolved minerals from the roots to the leaves, and it helps in temperature regulation. (iii)(b) Kidneys (urine formed) $\to$ ureters $\to$ urinary bladder (urine stored) $\to$ urethra (urine released). Reabsorbed in the tubule: any two of glucose, amino acids, salts and water.

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Q298 CBSE 2023
In the given diagram of a closed stomata : (1), (2), (3) and (4) respectively are
1. (a)nucleus, chloroplast, guard cell, vacuole
2. (b)nucleus, chloroplast, vacuole, guard cell
3. (c)chloroplast, nucleus, vacuole, guard cell
4. (d)vacuole, guard cell, nucleus, chloroplast
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(b) nucleus, chloroplast, vacuole, guard cell

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Q299 CBSE 2023
Given below are two columns, Column I shows enzymes secreted by the glands in the alimentary canal of human beings and Column II indicates the components of food on which enzymes act. Choose the options showing correct matching :
Enzymes and food components offered as pairings
Option Column I (Enzymes) Column II (Component)
(a) Pepsin Starch
(b) Trypsin Proteins
(c) Lipase Proteins
(d) Amylase Emulsified fat
1. (a)Pepsin — Starch
2. (b)Trypsin — Proteins
3. (c)Lipase — Proteins
4. (d)Amylase — Emulsified fat
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(b) Trypsin — Proteins

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Q300 CBSE 2023
An organism which breaks down the food material outside the body and then absorbs it is
1. (a)a plant parasite, Cuscuta
2. (b)an animal parasite, Tapeworm
3. (c)a bacteria, Rhizobium
4. (d)a fungi, Rhizopus
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(d) a fungi, Rhizopus

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Option	Column I (Enzymes)	Column II (Component)
(a)	Pepsin	Starch
(b)	Trypsin	Proteins
(c)	Lipase	Proteins
(d)	Amylase	Emulsified fat