Where Mindful Learning Begins
Where Mindful Learning Begins
Class 10 Science NCERT Solutions Chapter 5 (CBSE 2026-27) — every in-text question, every embedded Activity question, and all 13 back-of-chapter Exercises on this one page, solved with the reasoning behind each answer.
Life Processes opens the biology portion of Class 10 Science and asks what it actually means to be alive, before working through the four maintenance functions every living organism depends on: nutrition (autotrophic and heterotrophic, photosynthesis, human digestion), respiration (aerobic and anaerobic, the human respiratory system), transportation (the human heart, blood and blood vessels, plus xylem and phloem in plants), and excretion (the human kidney and nephron, plus how plants get rid of waste). These NCERT solutions work through every Activity-based question — the starch tests, the fermentation and breathing experiments — and the full 13-question Exercise set in detail, making this one of the most diagram-rich chapters in the biology portion of the Class 10 Science syllabus.
Life Processes is the opening chapter of the biology unit, and it starts with a genuinely interesting question: what actually makes something alive? The chapter's answer — that living structures constantly need molecular-level repair and maintenance — sets up everything that follows. It moves through nutrition (how autotrophs make their own food by photosynthesis, and how heterotrophs like us digest complex food along the alimentary canal), respiration (the aerobic and anaerobic pathways that release usable energy from glucose, and how humans and other organisms take in oxygen), transportation (the human heart's four chambers and double circulation, blood vessels, and the very differently-driven xylem and phloem systems in plants), and excretion (how the nephron filters blood into urine, and how plants get rid of waste without a dedicated excretory organ at all). Every question woven through the chapter is solved here, section by section, in the order the textbook presents it: the five "QUESTIONS" boxes after Sections 5.1 through 5.5, the questions embedded directly inside Activities, and the full 13-question Exercise set at the end.
Photosynthesis and autotrophic nutrition, heterotrophic strategies, and the full journey of food through the human digestive system.
Aerobic vs anaerobic respiration and ATP, the human respiratory system and alveoli, the heart's double circulation, and xylem/phloem in plants.
How the nephron filters blood into urine in the human kidney, and the very different waste-disposal strategies plants use.
Diffusion is a slow process that only works effectively across short distances and when the entire surface of an organism is in contact with the environment. In multi-cellular organisms like humans, most cells lie deep inside the body and are not directly exposed to the environment, so oxygen cannot reach them fast enough or in sufficient quantity by diffusion alone — the surface area available relative to the number of cells needing oxygen is far too small. This is why specialised respiratory and circulatory systems are needed to actively transport oxygen to every cell.
The presence of molecular movement within an organism is used as the underlying criterion. Since living structures are constantly being broken down by the effects of the environment, they must be continuously repaired and maintained through the movement of molecules — this invisible molecular-level activity, rather than visible movement alone, is taken as the defining basis of life.
Outside raw materials provide energy (through nutrition and respiration) for maintaining the body's structures, and supply the material needed for growth, development, and repair — such as building new cells and tissues and synthesising substances like proteins.
Nutrition, respiration, transportation (of materials within the body), and excretion (removal of waste products) are the essential life processes needed to maintain the body's organisation and function.
Autotrophic nutrition: organisms (e.g., green plants and some bacteria) prepare their own food from simple inorganic substances — carbon dioxide and water — using an external energy source (sunlight) and chlorophyll, through photosynthesis.
Heterotrophic nutrition: organisms (e.g., animals and fungi) cannot make their own food, and instead obtain complex organic substances by consuming other organisms (directly or indirectly depending on autotrophs), which are then broken down using enzymes.
The hydrochloric acid secreted by the gastric glands (i) creates an acidic medium that activates and facilitates the action of the enzyme pepsin (which digests proteins), and (ii) kills harmful bacteria that may enter the stomach along with food.
Digestive enzymes are biological catalysts that break down complex food molecules (starch, proteins, fats) into simpler molecules (simple sugars, amino acids, fatty acids and glycerol) that the body can absorb and use for energy, growth and repair.
The inner lining of the small intestine has numerous finger-like projections called villi, which greatly increase the surface area available for absorption. The villi are richly supplied with blood vessels, which take up the absorbed food and carry it to every cell of the body for energy, tissue-building, and repair.
The amount of oxygen dissolved in water is fairly low compared to the amount present in the atmosphere. Terrestrial organisms, breathing atmospheric oxygen directly, have access to a much higher and more readily available concentration of oxygen than aquatic organisms, which must extract the relatively scarce dissolved oxygen from water — this is why aquatic organisms need a much faster rate of breathing.
(i) Anaerobic, in yeast (fermentation): glucose → pyruvate → ethanol + carbon dioxide + energy.
(ii) Anaerobic, in our muscle cells (during vigorous exercise, lack of oxygen): glucose → pyruvate → lactic acid + energy.
(iii) Aerobic, in the mitochondria: glucose → pyruvate → carbon dioxide + water + a much larger amount of energy.
Oxygen is transported mainly bound to haemoglobin, a respiratory pigment in the red blood corpuscles with a very high affinity for oxygen. Carbon dioxide, being more soluble in water than oxygen, is mostly transported in the dissolved form in blood plasma.
Within the lungs, the air passage divides into smaller and smaller tubes, finally terminating in millions of tiny balloon-like structures called alveoli. The alveoli provide an enormous surface area (about 80 m² if spread out) for gas exchange, and their walls contain an extensive network of blood vessels, allowing efficient diffusion of oxygen into the blood and carbon dioxide out of it.
Mammals and birds are warm-blooded animals with high, constant energy needs (to maintain body temperature independent of the environment). Separating oxygenated and deoxygenated blood, via a four-chambered heart, ensures a highly efficient supply of oxygen to the body — oxygen-rich blood reaching the tissues isn't diluted by mixing with deoxygenated blood, and this efficiency is necessary to sustain their high energy demands.
Xylem (transports water and minerals from the roots to the rest of the plant) and Phloem (transports the products of photosynthesis and other substances, such as amino acids, from the leaves to other parts of the plant).
Through the xylem. Roots actively take up ions from the soil, creating a concentration difference that draws water into the root by osmosis, generating root pressure that pushes a column of water upward. Since this alone can't move water to great heights, transpiration — water vapour loss through stomata — creates a suction (transpiration pull) that pulls water upward through the xylem from roots to leaves, especially during the day.
Food is transported through the phloem, in a process called translocation. Using energy from ATP, material such as sucrose is actively transferred into the phloem, which increases the tissue's osmotic pressure and draws water into it. This builds up pressure that pushes material through the phloem to tissues where the pressure is lower — both upward and downward, according to the plant's needs.
Structure: a nephron consists of a cluster of thin-walled blood capillaries called the glomerulus, enclosed in a cup-shaped structure called Bowman's capsule that collects the filtrate, leading into a long, coiled tubular part.
Functioning: blood entering the glomerulus under pressure is filtered — small molecules like glucose, amino acids, salts and water pass into Bowman's capsule as filtrate, while larger molecules (proteins, blood cells) stay in the blood. As this filtrate flows along the tubule, useful substances (glucose, amino acids, the necessary amount of salts and water) are selectively reabsorbed back into the blood, while the remaining filtrate (nitrogenous wastes like urea, excess salts and water) becomes urine, sent via the ureter to the urinary bladder.
By how much water is reabsorbed as filtrate flows along the tubular part of the nephron. This depends on (i) how much excess water there is in the body, and (ii) how much dissolved waste needs to be excreted. Excess body water means less is reabsorbed and more (dilute) urine is produced; needing to conserve water means more is reabsorbed and less (more concentrated) urine is produced.
After boiling the leaf in alcohol, the leaf's green colour is removed (it turns pale/white as chlorophyll dissolves out), and the alcohol turns green as the pigment dissolves into it. When the decolourised leaf is then dipped in iodine, only the areas that were originally green (contained chlorophyll) turn blue-black, showing starch was made there — the parts that lacked chlorophyll show no colour change. This demonstrates that chlorophyll is essential for photosynthesis.
No — the leaf from the plant kept with potassium hydroxide (which absorbed the CO2 inside the sealed jar) shows no starch, while the leaf from the plant without potassium hydroxide (with normal CO2 available) shows the presence of starch. This shows that carbon dioxide is essential for photosynthesis.
Yes. Take a potted plant and cover part of one leaf on both sides with black paper (or foil), keeping part of the leaf in the dark while the rest stays exposed to sunlight, and leave the set-up in sunlight for a few hours. Testing the leaf for starch afterwards, only the part exposed to sunlight turns blue-black with iodine, while the covered (dark) part does not — demonstrating that sunlight is essential for photosynthesis.
A blue-black colour change (with iodine) is observed in test tube B (no saliva added), showing starch is still present. Test tube A (with saliva) shows no colour change, indicating the absence of starch. This tells us that saliva contains an enzyme (salivary amylase) that breaks down starch into simpler sugars, so no starch remains in test tube A to react with iodine.
Besides activating pepsin, the hydrochloric acid in the stomach also kills harmful bacteria that may have entered the body along with food, protecting against infection.
Yes. "Acidity" refers to the excessive production of hydrochloric acid by the gastric glands (often due to overeating, stress, or irregular eating), which can irritate the stomach lining or move up into the oesophagus, causing a burning sensation and discomfort — directly related to the acid-secreting function of the stomach discussed above.
The lime water into which breath is blown directly turns milky much faster than lime water through which ordinary air is passed with a syringe/pichkari. This tells us that exhaled air contains a much higher concentration of carbon dioxide than atmospheric air, confirming CO2 as a waste product removed during respiration.
The lime water connected to the fermenting yeast-sugar mixture turns milky, showing that carbon dioxide gas is being released. This tells us that carbon dioxide is one of the products of fermentation (anaerobic respiration in yeast), along with ethanol.
Yes — the opening and closing of the fish's mouth and its gill-slits (operculum) are coordinated, working together in rhythm as water is taken in through the mouth and pushed out past the gills. The fish opens and closes its mouth at a much faster rate per minute than a human's breathing rate, because the oxygen dissolved in water is far lower than in air, so aquatic animals must process a much larger volume of the oxygen-poor medium more rapidly to get enough oxygen.
Answer: (c) excretion
Answer: (a) transport of water (along with minerals dissolved in it)
Answer: (d) all of the above
Answer: (b) mitochondria (this is aerobic respiration)
Fats enter the small intestine as large globules, making it hard for enzymes to act efficiently. Bile juice (from the liver, stored in the gall bladder) emulsifies these globules into smaller ones, increasing the surface area for enzyme action. The pancreas then secretes lipase, which breaks down the emulsified fats into fatty acids and glycerol. This entire process takes place in the small intestine.
Saliva moistens and softens the food to make its passage through the alimentary canal smooth, and contains the enzyme salivary amylase, which begins the digestion of starch by breaking it down into simpler sugars.
Necessary conditions: carbon dioxide, water, sunlight, and chlorophyll.
By-products: oxygen (released when water molecules split) and water.
Aerobic: requires oxygen, occurs in the mitochondria; glucose is completely broken down into CO2 and water; releases much more energy.
Anaerobic: occurs without oxygen, in the cytoplasm; glucose is incompletely broken down (into ethanol + CO2, or into lactic acid); releases much less energy.
Organisms using anaerobic respiration: yeast (during fermentation), some bacteria, and human muscle cells during vigorous exercise (when oxygen supply is insufficient).
Millions of tiny, balloon-like alveoli provide an enormous surface area (about 80 m² in total) for gas exchange. Their walls are very thin (one cell thick), allowing easy diffusion, and are richly supplied with blood capillaries, allowing efficient, rapid exchange of oxygen and carbon dioxide.
Haemoglobin is the main oxygen carrier in the blood. A deficiency (anaemia) would significantly reduce blood's oxygen-carrying capacity, leading to insufficient oxygen reaching body tissues — causing symptoms such as fatigue, weakness, breathlessness, and reduced overall energy and body function.
In double circulation, blood passes through the heart twice per complete circuit: (i) Pulmonary circulation — deoxygenated blood from the body enters the right atrium, moves to the right ventricle, and is pumped to the lungs to be oxygenated. (ii) Systemic circulation — oxygenated blood returns from the lungs to the left atrium, moves to the left ventricle, and is pumped to the rest of the body.
It is necessary because it keeps oxygenated and deoxygenated blood completely separate (unlike fish, where blood passes through the heart only once per cycle), ensuring a highly efficient, undiluted supply of oxygen-rich blood — essential for warm-blooded animals like humans with high, constant energy needs.
| Feature | Xylem | Phloem |
|---|---|---|
| Transports | Water and minerals | Food (photosynthesis products) and amino acids |
| Direction | Unidirectional (upward) | Bidirectional (up and down, as needed) |
| Driving force | Root pressure and transpiration pull (physical forces) | Active use of ATP energy (osmotic pressure) |
| Cell type | Dead, hollow cells (vessels, tracheids) | Living cells (sieve tubes with companion cells) |
Similarities: both are the basic functional units of their respective organs, built around a cluster of thin-walled blood capillaries to allow efficient exchange between blood and the surrounding structure; both provide a huge surface area (many units packed together) and rely on diffusion across very thin, delicate walls.
Differences: alveoli are balloon-like air sacs that exchange gases (oxygen and CO2) between air and blood by simple diffusion. Nephrons are coiled tubular structures that filter blood (via the glomerulus and Bowman's capsule) to remove nitrogenous wastes, and selectively reabsorb useful substances (glucose, amino acids, water, salts) back into the blood — a filtration and selective-reabsorption process, not simple gas diffusion.
Next up is Chapter 6 — Control and Coordination. Or explore the full chapter list, browse the Class 10 Science hub, or book a free demo class for personalised coaching.
Expert CBSE Coaching · Class 9–12