NCERT Solutions for Class 10 Science Chapter 5: Life Processes (NCERT 2026–27)
These Class 10 Science Chapter 5 solutions cover Life Processes — the basic functions of nutrition, respiration, transportation and excretion that keep an organism alive. Every in-text question and all 13 end-of-chapter exercises are reproduced from the NCERT textbook and answered in clear, exam-ready language for the 2026–27 session.
Class: 10Subject: ScienceChapter: 5Title: Life ProcessesType: Biology (conceptual)Session: 2026–27
Living organisms must constantly repair and maintain their highly ordered structures, and the processes that carry out this maintenance are called life processes. Chapter 5 studies four of them in detail. Nutrition brings in food (energy and raw materials) — autotrophs make their own food by photosynthesis, while heterotrophs depend on others; in humans, food is processed along the alimentary canal. Respiration breaks down glucose to release energy as ATP, either aerobically (in mitochondria, more energy) or anaerobically. Transportation moves materials around the body — the heart, blood and blood vessels in humans, and xylem and phloem in plants. Excretion removes harmful nitrogenous wastes, mainly through the kidneys (nephrons) in humans. Together these processes keep the organism alive and growing.
Key Concepts & Definitions
Life processes: the basic functions (nutrition, respiration, transportation, excretion) performed by an organism to maintain and repair its body.
Autotrophic nutrition: making food from simple inorganic substances (CO2 and water) using sunlight and chlorophyll — photosynthesis.
Heterotrophic nutrition: taking in complex food made by other organisms and breaking it down using enzymes.
Respiration: the breakdown of food (glucose) in cells to release energy that is stored as ATP.
Transpiration: loss of water as vapour from the aerial parts of a plant; it creates the suction (transpiration pull) that lifts water in the xylem.
Translocation: transport of soluble products of photosynthesis (e.g. sucrose) in the phloem, using energy from ATP.
Double circulation: blood passes through the heart twice in one complete cycle, keeping oxygenated and deoxygenated blood separate.
Excretion: the removal of harmful nitrogenous metabolic wastes from the body (by nephrons in human kidneys).
Anaerobic (yeast): Glucose → Pyruvate → Ethanol + CO2 + little energy.
Anaerobic (muscle): Glucose → Pyruvate → Lactic acid + little energy (causes cramps).
ATP: ADP + inorganic phosphate + energy → ATP; breaking ATP releases ~30.5 kJ/mol.
Normal blood pressure: systolic ~120 mm Hg, diastolic ~80 mm Hg.
In-text Questions — Answers
These are the “Questions” boxes that appear within the chapter, reproduced verbatim and answered in order.
Page 80
Q1. Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
ANSWERIn multi-cellular organisms such as humans, all the body cells are not in direct contact with the surrounding environment, and the body is large and three-dimensional.Diffusion is a very slow process and can supply oxygen only over very short distances. It cannot move enough oxygen quickly to the deeper cells. Hence a special respiratory surface (lungs) and a transport system (blood with haemoglobin) are needed to meet the oxygen demand of all cells.
Q2. What criteria do we use to decide whether something is alive?
ANSWERVisible movement (growth-related or locomotory) is one common sign, but it is not enough — a plant that is not visibly growing is still alive, and some animals breathe without visible movement.The more reliable criterion is molecular movement: living things constantly move molecules to repair and maintain their ordered structures and to carry out life processes such as nutrition and respiration. The presence of these life processes tells us something is alive.
Q3. What are outside raw materials used for by an organism?
ANSWEROutside raw materials (food, water, oxygen and minerals) provide the energy needed to maintain order in the body and to drive molecular movements.They also supply the building materials needed for growth, for repair of damaged tissues and structures, and for the synthesis of proteins and other substances the body requires.
Q4. What processes would you consider essential for maintaining life?
ANSWERThe processes essential for maintaining life are nutrition (intake of food for energy and raw materials), respiration (release of energy from food), transportation (carrying materials to and from cells) and excretion (removal of harmful wastes).
Page 87
Q1. What are the differences between autotrophic nutrition and heterotrophic nutrition?
ANSWER
Autotrophic nutrition
Heterotrophic nutrition
Food is synthesised by the organism itself.
Food is taken from other organisms (made by others).
Uses simple inorganic raw materials (CO2 and water).
Uses complex organic substances that must be broken down.
Requires sunlight and chlorophyll.
Does not require sunlight or chlorophyll.
Occurs in green plants and some bacteria.
Occurs in animals and fungi.
Q2. Where do plants get each of the raw materials required for photosynthesis?
ANSWERCarbon dioxide — from the air, entering through the stomata on leaves (and through stems and roots).Water — absorbed from the soil by the roots and carried up through the xylem.Sunlight — from the Sun, absorbed by chlorophyll in the chloroplasts.Minerals (nitrogen, phosphorus, iron, magnesium) — taken up from the soil as inorganic salts (e.g. nitrates).
Q3. What is the role of the acid in our stomach?
ANSWERThe hydrochloric acid secreted by the gastric glands creates an acidic medium in the stomach that is necessary for the protein-digesting enzyme pepsin to act.It also kills harmful germs that enter with the food and softens the food.
Q4. What is the function of digestive enzymes?
ANSWERDigestive enzymes are biological catalysts that break down complex food molecules into simpler, absorbable molecules — carbohydrates into glucose, proteins into amino acids, and fats into fatty acids and glycerol — so that the food can be absorbed by the body.
Q5. How is the small intestine designed to absorb digested food?
ANSWERThe inner lining of the small intestine has numerous finger-like projections called villi that greatly increase the surface area for absorption.The villi are richly supplied with blood vessels, which carry the absorbed food to every cell of the body. The small intestine is also very long and highly coiled, adding to the absorptive area.
Page 91
Q1. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
ANSWERA terrestrial organism uses oxygen from the atmosphere, where oxygen is plentiful (about 21%). An aquatic organism must use the oxygen dissolved in water, which is far less.Because air contains much more oxygen, terrestrial animals can obtain it more easily and can breathe at a slower rate than aquatic animals, which must breathe much faster to get enough oxygen.
Q2. What are the different ways in which glucose is oxidised to provide energy in various organisms?
ANSWERIn all organisms, glucose (6-carbon) is first broken down in the cytoplasm into pyruvate (3-carbon). The fate of pyruvate then differs:Aerobic respiration (presence of oxygen, in mitochondria): pyruvate → CO2 + water + a large amount of energy.Anaerobic respiration / fermentation (absence of oxygen, e.g. in yeast): pyruvate → ethanol + CO2 + little energy.Lack of oxygen in muscles: pyruvate → lactic acid + little energy (this build-up causes muscle cramps).
Q3. How is oxygen and carbon dioxide transported in human beings?
ANSWEROxygen is carried by the respiratory pigment haemoglobin present in the red blood corpuscles, which has a high affinity for oxygen.Carbon dioxide is more soluble in water than oxygen, so it is mostly transported in the dissolved form in the blood plasma.
Q4. How are the lungs designed in human beings to maximise the area for exchange of gases?
ANSWERWithin the lungs the air passage divides into smaller and smaller tubes that end in tiny balloon-like structures called alveoli.The very large number of alveoli provides an enormous surface area (about 80 m2 if spread out). Their walls are thin and contain a dense network of blood vessels, so gases can be exchanged efficiently by diffusion.
Page 95
Q1. What are the components of the transport system in human beings? What are the functions of these components?
ANSWERThe main components are the heart, blood and blood vessels (arteries, veins, capillaries); lymph is also involved.Heart: a muscular pump that pushes blood around the body. Blood: carries oxygen, food, CO2 and nitrogenous wastes. Arteries: carry blood away from the heart at high pressure. Veins: bring blood back to the heart, with valves to prevent backflow. Capillaries: thin-walled vessels where exchange of materials with cells takes place. Lymph: carries digested fat and drains excess fluid back into the blood.
Q2. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
ANSWERSeparating the two prevents oxygenated and deoxygenated blood from mixing, which ensures a highly efficient supply of oxygen to the body.Mammals and birds have high energy needs because they constantly use energy to maintain a warm, constant body temperature; this efficient oxygen supply is essential to meet that demand.
Q3. What are the components of the transport system in highly organised plants?
ANSWERThe transport system in plants is the vascular tissue, which consists of xylem (transports water and minerals from the roots) and phloem (transports the products of photosynthesis from the leaves to other parts).
Q4. How are water and minerals transported in plants?
ANSWERWater and minerals are transported through the xylem, whose vessels and tracheids form continuous tubes from roots to leaves.Root cells actively take up ions, so water moves into the root by osmosis, creating root pressure that pushes water up (more important at night).During the day, evaporation of water from the leaves (transpiration) creates a suction called the transpiration pull, which is the main force that draws water up the xylem to the top of the plant.
Q5. How is food transported in plants?
ANSWERFood (soluble products of photosynthesis, e.g. sucrose) is transported through the phloem by a process called translocation, in both upward and downward directions.Sucrose is loaded into the phloem using energy from ATP. This raises the osmotic pressure, so water enters and the increased pressure moves the food to regions of lower pressure (such as storage organs and growing parts), according to the plant’s needs.
Page 98
Q1. Describe the structure and functioning of nephrons.
ANSWERStructure: The nephron is the basic filtration unit of the kidney. Each nephron has a cluster of thin-walled blood capillaries (glomerulus) enclosed by the cup-shaped Bowman’s capsule, which leads into a long, coiled tube.Functioning: Blood is filtered in the glomerulus, and the filtrate (containing glucose, amino acids, salts, urea and water) is collected by Bowman’s capsule. As the filtrate flows along the tube, useful substances such as glucose, amino acids, salts and most of the water are selectively reabsorbed into the blood. The remaining waste forms urine, which passes through the ureter to the urinary bladder.
Q2. What are the methods used by plants to get rid of excretory products?
ANSWERPlants get rid of gaseous wastes (O2, CO2) and excess water through stomata and transpiration.Many waste products are stored in cellular vacuoles, or as resins and gums (especially in old xylem). Some wastes are stored in leaves that later fall off, and others are excreted into the surrounding soil.
Q3. How is the amount of urine produced regulated?
ANSWERThe amount of urine depends on how much water is reabsorbed in the kidney tubules, which in turn depends on how much excess water there is in the body and how much dissolved waste has to be excreted.When the body has excess water, less is reabsorbed and more, dilute urine is produced; when the body needs to conserve water, more is reabsorbed and less, concentrated urine is produced.
End-of-Chapter Exercises — Answers
All 13 exercise questions are reproduced verbatim from the NCERT textbook and solved below.
1. The kidneys in human beings are a part of the system for
(a) nutrition. (b) respiration. (c) excretion. (d) transportation.
ANSWER(c) excretion. The kidneys filter nitrogenous wastes such as urea from the blood and form urine, so they belong to the excretory system.
2. The xylem in plants are responsible for
(a) transport of water. (b) transport of food. (c) transport of amino acids. (d) transport of oxygen.
ANSWER(a) transport of water. Xylem conducts water and dissolved minerals upward from the roots; food is transported by the phloem.
3. The autotrophic mode of nutrition requires
(a) carbon dioxide and water. (b) chlorophyll. (c) sunlight. (d) all of the above.
ANSWER(d) all of the above. Photosynthesis needs carbon dioxide and water as raw materials, chlorophyll to trap light, and sunlight as the energy source.
4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm. (b) mitochondria. (c) chloroplast. (d) nucleus.
ANSWER(b) mitochondria. The aerobic breakdown of pyruvate into CO2, water and energy occurs in the mitochondria (which is why they are called the powerhouse of the cell).
5. How are fats digested in our bodies? Where does this process take place?
ANSWERFats are digested mainly in the small intestine.Fats reach the small intestine as large globules. Bile salts from the liver emulsify them, breaking them into smaller globules and increasing the surface area for enzyme action. The enzyme lipase (from the pancreas and intestinal juice) then breaks down the emulsified fats into fatty acids and glycerol.
6. What is the role of saliva in the digestion of food?
ANSWERSaliva, secreted by the salivary glands, moistens the food so it can be swallowed easily, and helps the tongue mix and move the food while chewing.It contains the enzyme salivary amylase (ptyalin), which begins the chemical digestion of food by breaking down starch into simple sugar (maltose).
7. What are the necessary conditions for autotrophic nutrition and what are its by-products?
ANSWERNecessary conditions: carbon dioxide, water, sunlight and chlorophyll.By-products:oxygen (released during photosynthesis) and, when carbohydrates are not used immediately, starch is stored. Water vapour may also be released.
8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
ANSWER
Aerobic respiration
Anaerobic respiration
Takes place in the presence of oxygen.
Takes place in the absence of oxygen.
Occurs in the mitochondria (after cytoplasm).
Occurs only in the cytoplasm.
End products are CO2 and water.
End products are ethanol + CO2 (yeast) or lactic acid (muscles).
Releases a large amount of energy.
Releases a much smaller amount of energy.
Organisms that respire anaerobically: yeast and some bacteria; muscle cells of humans respire anaerobically temporarily during vigorous exercise.
9. How are the alveoli designed to maximise the exchange of gases?
ANSWERThe alveoli are present in very large numbers, giving a huge total surface area (about 80 m2) for the exchange of gases.Their walls are extremely thin and are surrounded by a dense network of blood capillaries. This thin, moist, well-supplied surface allows oxygen and carbon dioxide to diffuse rapidly and efficiently between the air and the blood.
10. What would be the consequences of a deficiency of haemoglobin in our bodies?
ANSWERHaemoglobin carries oxygen in the blood. A deficiency reduces the blood’s oxygen-carrying capacity, so the tissues receive less oxygen.This leads to a condition called anaemia, with symptoms such as tiredness, weakness, breathlessness and pale skin, because cells cannot release enough energy through respiration.
11. Describe double circulation of blood in human beings. Why is it necessary?
ANSWERIn double circulation, blood passes through the heart twice in one complete cycle. In pulmonary circulation, deoxygenated blood from the right side of the heart goes to the lungs, gets oxygenated, and returns to the left side. In systemic circulation, this oxygenated blood is pumped from the left side to the body, and deoxygenated blood returns to the right side.Why necessary: it keeps oxygenated and deoxygenated blood completely separate, ensuring an efficient supply of oxygen to the body. This is essential for warm-blooded animals (mammals and birds) that need a lot of energy to maintain their body temperature.
12. What are the differences between the transport of materials in xylem and phloem?
ANSWER
Transport in xylem
Transport in phloem
Transports water and minerals.
Transports food (soluble products of photosynthesis).
Movement is mainly upward (roots to leaves).
Movement is in both directions (up and down).
Driven by physical forces (root pressure and transpiration pull); no energy used.
Driven by active process (translocation) using energy from ATP.
Conducted through vessels and tracheids (dead cells).
Conducted through sieve tubes with companion cells (living).
13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
ANSWER
Alveoli (lungs)
Nephrons (kidneys)
Tiny balloon-like sacs with very thin walls, surrounded by a network of blood capillaries.
Filtration units with a glomerulus (capillary cluster) inside a cup-shaped Bowman’s capsule, leading to a coiled tubule.
Carry out exchange of gases — oxygen enters the blood and carbon dioxide leaves it by diffusion.
Carry out filtration of blood — nitrogenous wastes such as urea are removed to form urine.
Both are richly supplied with blood capillaries to make exchange efficient.
Useful substances (glucose, amino acids, salts, water) are selectively reabsorbed into the blood.
Similarity: both are tiny, thin-walled units with a large blood supply, designed to remove unwanted substances (CO2 in alveoli, nitrogenous waste in nephrons) from the blood.
Extra Practice Questions
Short Answer Type Questions
Q1. Why do herbivores have a longer small intestine than carnivores?
ANSWERHerbivores eat grass, which is rich in cellulose and difficult to digest, so they need a longer small intestine to allow time for cellulose to be broken down. Meat is easier to digest, so carnivores have a shorter small intestine.
Q2. What is the role of bile in digestion?
ANSWERBile from the liver makes the acidic food coming from the stomach alkaline so that pancreatic enzymes can act. Bile salts also emulsify large fat globules into smaller ones, increasing the efficiency of fat-digesting enzymes (lipase).
Q3. Why does a build-up of lactic acid in muscles cause cramps?
ANSWERDuring sudden, vigorous activity the muscles do not get enough oxygen, so pyruvate is converted into lactic acid by anaerobic respiration. The accumulation of lactic acid in the muscle cells causes painful cramps.
Q4. State two functions of transpiration in plants.
ANSWER(i) It creates the transpiration pull that helps in the absorption and upward movement of water and dissolved minerals from the roots to the leaves. (ii) It helps in regulating the temperature of the plant by cooling it.
Q5. Why are the walls of the ventricles thicker than those of the atria?
ANSWERThe ventricles have to pump blood out of the heart to distant organs (and to the lungs) under high pressure, so they need thicker, more muscular walls. The atria only push blood to the nearby ventricles, so their walls are thinner.
Long Answer Type Questions
Q1. Describe the journey of food through the human alimentary canal, naming the digestive juices and end products.
ANSWERIn the mouth, teeth crush the food and salivary amylase begins digesting starch into sugar. The food is pushed down the oesophagus by peristalsis into the stomach, where gastric juice (hydrochloric acid, pepsin and mucus) creates an acidic medium and digests proteins. A sphincter releases the food in small amounts into the small intestine, where bile from the liver makes it alkaline and emulsifies fats, and pancreatic juice (trypsin, lipase) and intestinal juice complete digestion — carbohydrates to glucose, proteins to amino acids, and fats to fatty acids and glycerol. The digested food is absorbed by the villi and carried to all cells. Undigested food passes into the large intestine, where water is absorbed, and the waste is removed through the anus.
Q2. Explain how the human heart works as a double pump, tracing the path of blood through its four chambers.
ANSWEROxygen-rich blood from the lungs enters the left atrium, which relaxes to collect it and then contracts, transferring blood to the left ventricle. The muscular left ventricle contracts and pumps this oxygenated blood to the whole body. Deoxygenated blood returns from the body to the right atrium, which contracts and passes blood to the right ventricle. The right ventricle then pumps it to the lungs for oxygenation. Valves prevent backflow of blood. Because blood passes through the heart twice in one cycle (once to the lungs, once to the body), this is called double circulation, and the heart acts as a double pump that keeps oxygenated and deoxygenated blood separate.
Q3. Explain the process of photosynthesis, listing the events that occur during it and the role of each raw material.
ANSWERPhotosynthesis is the process by which autotrophs convert carbon dioxide and water into carbohydrates using sunlight and chlorophyll. The main events are: (i) absorption of light energy by chlorophyll; (ii) conversion of light energy into chemical energy and the splitting of water into hydrogen and oxygen; and (iii) reduction of carbon dioxide to carbohydrates. Carbon dioxide enters through the stomata and provides carbon; water, absorbed by the roots and carried by the xylem, is split to provide hydrogen and release oxygen; sunlight supplies energy; and chlorophyll traps that light energy. The carbohydrate made is used for energy, and the excess is stored as starch. Oxygen is released as a by-product.
MCQs & Assertion–Reason
1. The process of loss of water as vapour from the aerial parts of a plant is called:
For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.
A-R 1. Assertion: Aerobic respiration releases more energy than anaerobic respiration.
Reason: In aerobic respiration, glucose is completely broken down into carbon dioxide and water.
A-R 2. Assertion: The small intestine has numerous villi.
Reason: Villi increase the surface area for the absorption of digested food.
A-R 3. Assertion: Diffusion alone can meet the oxygen needs of large multi-cellular animals.
Reason: All the cells of a large animal are in direct contact with the environment.
A-R 4. Assertion: Arteries have thick, elastic walls.
Reason: Blood flows through arteries under high pressure as it leaves the heart.
A-R 5. Assertion: Transport of food in the phloem requires energy.
Reason: Sucrose is loaded into the phloem using energy from ATP, which increases osmotic pressure.
Answer key: 1-(A), 2-(A), 3-(D), 4-(A), 5-(A).
Common Mistakes to Avoid
Watch out for these
Confusing xylem (water and minerals, upward) with phloem (food, both directions) — and forgetting that phloem transport needs energy.
Writing that pyruvate is formed in the mitochondria — glucose is broken into pyruvate in the cytoplasm; only the aerobic breakdown of pyruvate occurs in the mitochondria.
Mixing up nephron (kidney unit) with neuron (nerve cell).
Saying oxygen is carried in plasma — oxygen is carried by haemoglobin; mostly carbon dioxide is carried dissolved in plasma.
Forgetting that fishes have a two-chambered heart and blood passes through the heart only once per cycle (single circulation).
Confusing emulsification (done by bile salts) with digestion of fat (done by the enzyme lipase).
How to score full marks in this chapter
Draw and label the diagrams asked frequently — the human alimentary canal, respiratory system, heart, nephron and a cross-section of the leaf — as labelled diagrams carry marks. Learn the four life processes as a framework and answer comparison questions (aerobic vs anaerobic, xylem vs phloem, autotrophic vs heterotrophic, alveoli vs nephrons) in a clear two-column table. Always use the correct terms (haemoglobin, alveoli, nephron, villi, translocation, transpiration) and link structure to function, e.g. “thin walls and rich blood supply → efficient exchange”.
Frequently Asked Questions
What are the four life processes in Class 10 Science Chapter 5?
The four life processes are nutrition (taking in food for energy and raw materials), respiration (releasing energy from food as ATP), transportation (carrying materials around the body) and excretion (removing harmful wastes). Together they keep an organism alive and able to repair itself.
What is the difference between aerobic and anaerobic respiration?
Aerobic respiration takes place in the presence of oxygen, occurs in the mitochondria, fully breaks glucose into carbon dioxide and water, and releases a lot of energy. Anaerobic respiration occurs without oxygen, in the cytoplasm, gives ethanol and carbon dioxide (in yeast) or lactic acid (in muscles), and releases much less energy.
Why is double circulation necessary in humans?
Double circulation keeps oxygenated and deoxygenated blood completely separate, ensuring an efficient supply of oxygen to the body. This is essential for warm-blooded animals like humans and birds, which need a lot of energy to maintain a constant body temperature.
Are these Class 10 Science Chapter 5 solutions free?
Yes. All solutions are free and follow the official NCERT Science textbook for the 2026-27 session, with every in-text question and exercise solved.
