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Class 10 Life Processes notes: NCERT Science Chapter 5 revision
Life Processes is Chapter 5 of the NCERT Class 10 Science textbook (Reprint 2026-27), printed pages 79 to 99. It asks one big question: what jobs must a body keep doing, even when it is asleep, just to stay alive? The chapter's answer is four jobs: nutrition, respiration, transportation and excretion. These notes put each one on a single screen, with the terms you must be able to define, one diagram to practise and the mistakes that lose marks.
Keep the textbook open next to these notes. The wording here is our own; the textbook is the authority.
How much it counts
In CBSE's Class 10 Science curriculum for 2026-27 this chapter sits in Unit II, World of Living, worth 25 of the 80 theory marks, together with Control and Coordination, How do Organisms Reproduce? and Heredity. CBSE gives marks per unit, not per chapter, so any "chapter weightage" you see elsewhere is a guess. Our Class 10 Science syllabus guide lists the whole unit.
The big idea (section 5.1)
A living body is an ordered structure, and order breaks down unless it is repaired all the time. Repair needs energy, and the energy comes from outside the body as food. So every organism needs:
- Nutrition: bringing food (an energy and carbon source) in from outside.
- Respiration: taking in oxygen and using it to break food down for the cell's energy.
- Transportation: carrying food and oxygen to every cell once the body is too big for diffusion alone.
- Excretion: getting rid of harmful by-products of these reactions.
A one-celled organism can do all of this through its surface. A large, many-celled body cannot, which is why specialised organs and a transport system appear.
Nutrition (section 5.2)
Two modes. Autotrophs (green plants and some bacteria) make food from carbon dioxide and water. Heterotrophs (animals and fungi) use complex food made by others and need enzymes to break it down, so they depend, directly or indirectly, on autotrophs.
Photosynthesis (5.2.1). In the presence of sunlight and chlorophyll:
6CO₂ + 12H₂O → C₆H₁₂O₆ (glucose) + 6O₂ + 6H₂O
It happens in three events, which need not follow one another at once: chlorophyll absorbs light; light energy becomes chemical energy and water is split into hydrogen and oxygen; carbon dioxide is reduced to carbohydrate. Desert plants take in CO₂ at night and finish the job in daylight. Unused carbohydrate is stored as starch (in us, spare energy is stored as glycogen). Chlorophyll sits in chloroplasts.
Stomata. Tiny pores on the leaf surface where most gas exchange for photosynthesis happens. Each pore is opened and closed by two guard cells: they swell with water and the pore opens; they shrink and it closes. The plant closes them when it does not need CO₂, because open pores also lose water.
Other raw materials. Water comes in through the roots. Nitrogen, phosphorus, iron and magnesium come from the soil; nitrogen is taken up as nitrates or nitrites, or as organic compounds made by bacteria from air.
Heterotrophic strategies (5.2.2, 5.2.3). Fungi such as bread mould, yeast and mushrooms digest food outside the body and absorb it. Parasites (cuscuta, ticks, lice, leeches, tapeworms) feed on a host without killing it. Amoeba wraps food in finger-like extensions to form a food vacuole; Paramoecium uses its cilia to sweep food to one fixed spot.
The human gut (5.2.4), in order:
| Part | What happens there |
|---|---|
| Mouth | Teeth crush food; saliva wets it; salivary amylase turns starch into simple sugar |
| Oesophagus | Peristalsis (rhythmic muscle contractions) pushes food along, as it does along the whole gut |
| Stomach | Gastric glands release hydrochloric acid (acidic medium for pepsin), pepsin (digests protein) and mucus (protects the lining from the acid) |
| Small intestine | Longest part; complete digestion of carbohydrates, proteins and fats. Bile from the liver makes the food alkaline and breaks fat into small droplets; pancreatic juice has trypsin (proteins) and lipase (fats); intestinal juice finishes the job: amino acids, glucose, fatty acids and glycerol. Villi absorb the products |
| Large intestine | Absorbs more water; the anal sphincter controls the exit of waste |
A sphincter muscle lets food leave the stomach a little at a time. Grass-eaters have a longer small intestine than meat-eaters, because cellulose takes longer to digest.
Respiration (section 5.3)
Step one is the same in every organism: in the cytoplasm, glucose (6 carbons) is broken into pyruvate (3 carbons), releasing some energy. Then the paths split:
- No oxygen, in yeast: pyruvate → ethanol + carbon dioxide + energy (fermentation, anaerobic).
- Short of oxygen, in our muscle cells: pyruvate → lactic acid + energy. A build-up of lactic acid during sudden hard exercise causes cramps.
- With oxygen, in the mitochondria: pyruvate → carbon dioxide + water + energy (aerobic). This path releases far more energy than the other two.
The energy is used to make ATP from ADP and phosphate. ATP is the cell's energy currency: breaking its last phosphate link releases energy (30.5 kJ/mol) for muscle contraction, protein synthesis, nerve impulses and more.
Gas exchange. Plants exchange gases by diffusion through stomata and air spaces; at night they mainly give out CO₂, by day mainly oxygen. Fish breathe faster than land animals because water holds little dissolved oxygen.
The human path of air: nostrils (hairs and mucus filter it) → throat (rings of cartilage keep it open) → lungs → smaller and smaller tubes → alveoli, thin balloon-like sacs wrapped in blood vessels, where gases are exchanged. Breathing in lifts the ribs and flattens the diaphragm, so the chest gets bigger and air rushes in. The lungs always keep a residual volume of air. Haemoglobin in red blood corpuscles carries oxygen; carbon dioxide travels mostly dissolved in the blood, because it dissolves in water more easily than oxygen does.
Transportation (section 5.4)
Blood: plasma (carries food, CO₂ and nitrogenous wastes in solution), red blood corpuscles (oxygen) and platelets (clot the blood at a cut).
The heart is about the size of a fist and has four chambers: two thin-walled atria on top, two thick-walled ventricles below (ventricles pump to organs, so they need more muscle). Valves stop blood flowing backwards.
Double circulation. In each round trip blood passes through the heart twice: once on the way to the lungs, once on the way to the body. Keeping oxygen-rich and oxygen-poor blood apart suits birds and mammals, which spend energy keeping their body warm. Amphibians and many reptiles have three chambers and allow some mixing; fish have two chambers and blood passes through the heart only once per trip.
Blood vessels:
| Vessel | Direction | Wall |
|---|---|---|
| Artery | Away from the heart | Thick and elastic (high pressure) |
| Vein | Back to the heart | Thinner, with valves for one-way flow |
| Capillary | Between the two, inside organs | One cell thick; exchange happens here |
Normal blood pressure is about 120 (systolic, ventricle contracting) over 80 (diastolic, ventricle relaxing) mm of Hg, measured with a sphygmomanometer.
Lymph is tissue fluid that leaks from capillaries: like plasma but colourless, with less protein. It carries absorbed fat from the intestine and returns extra fluid to the blood.
In plants (5.4.2) there are two separate sets of tubes:
- Xylem carries water and minerals up from the roots. Root cells take in ions, water follows into the root, and this root pressure matters most at night. By day the main driver is transpiration, the loss of water vapour from the leaves, which pulls water up. Transpiration also helps control temperature.
- Phloem carries food (sugars such as sucrose, plus amino acids) up or down to where it is needed: storage organs, fruits, seeds, growing buds. This translocation uses energy from ATP, in sieve tubes helped by companion cells.
Excretion (section 5.5)
In humans: two kidneys → two ureters → urinary bladder → urethra. Each kidney holds many nephrons, the filtration units. About 180 L of filtrate is made each day, but only a litre or two leaves as urine, because most of the water, with glucose, amino acids and salts, is taken back. How much water is taken back depends on how much extra water and dissolved waste the body has. Kidney failure can be treated with an artificial kidney (dialysis), which filters but does not reabsorb.
In plants: extra water leaves by transpiration; other wastes are stored in vacuoles, in leaves that later fall, as resins and gums in old xylem, or released into the soil. Oxygen from photosynthesis can be thought of as a waste too.
Key terms to define in one line
- Autotroph: an organism that makes its food from simple inorganic substances.
- Enzyme: a biological catalyst that breaks complex food into simpler substances.
- Peristalsis: waves of muscle contraction that push food along the gut.
- Villi: finger-like projections of the small intestine lining that increase the area for absorption.
- Alveoli: tiny air sacs in the lungs where oxygen and carbon dioxide are exchanged.
- ATP: the molecule that stores the energy released in respiration and supplies it to the cell's reactions.
- Double circulation: blood passing through the heart twice in one complete trip round the body.
- Transpiration: loss of water as vapour from the parts of a plant above the ground.
- Translocation: movement of the soluble products of photosynthesis through the phloem.
- Nephron: the filtering unit of the kidney.
One diagram to practise: the nephron
The textbook's Figure 5.14 shows one nephron. Practise drawing it from memory like this:
- At the top left, draw a small tangle of blood vessels (the glomerulus) sitting inside a cup (Bowman's capsule). Draw a branch of the renal artery entering the tangle.
- From the cup, draw a long coiled tube going down and back up (the tubular part of the nephron), with a network of capillaries wound around it.
- Join the end of the tube to a straight tube running down the right side (the collecting duct), which leads towards the ureter.
- Draw a branch of the renal vein leaving the capillaries.
Label those seven parts. Then write one line under it: blood is filtered in the capsule, useful substances and much of the water are taken back along the tube, and what is left is urine.
Common mistakes
- "Respiration is breathing." Breathing moves air in and out; respiration is the breakdown of food in cells to release energy. They are linked but not the same.
- Mixing up where each step happens. Glucose to pyruvate: cytoplasm. Pyruvate with oxygen: mitochondria.
- Saying arteries carry oxygen-rich blood, always. Arteries are defined by direction (away from the heart). The pulmonary artery carries oxygen-poor blood to the lungs.
- Mixing up xylem and phloem. Xylem: water and minerals, upwards. Phloem: food, in either direction, using energy.
- Leaving bile out of fat digestion, or calling it an enzyme. Bile breaks fat into small droplets and makes the food alkaline; lipase does the digesting.
- Saying all 180 L of filtrate leaves as urine. Almost all of it is reabsorbed.
Revise with questions
Test yourself next: Class 10 Life Processes, 8 questions with worked answers. For timed practice, the free Class 10 revision papers include a Science paper. Later in the same unit: Class 10 Heredity notes.
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Sources
All checked on 3 November 2026.
- NCERT, Science, Textbook for Class X, Chapter 5 "Life Processes" (Reprint 2026-27): sections 5.1 to 5.5, Figures 5.8, 5.10, 5.11 and 5.14, the "More to Know" boxes on ATP, blood pressure and the artificial kidney. ncert.nic.in/textbook/pdf/jesc105.pdf
- CBSE, Science curriculum, Class X, 2026-27 (course structure, Unit II): cbseacademic.nic.in/web_material/CurriculumMain27/SecPart1/Science_SecP1_2026-27.pdf
The facts, section numbers and figure labels on this page are from the documents above. The notes, tables, diagram steps and mistakes list are written in our own words.
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