Life Processes Class 10 Notes (2026-27) — CBSE
Class 10 Science Chapter 5 revision notes: nutrition, photosynthesis, human digestive and respiratory systems, transportation (heart, xylem, phloem) and excretion.
Life Processes — Class 10 Science Notes
Chapter Snapshot
Life processes are the basic functions that maintain and sustain life: nutrition, respiration, transportation, and excretion. This chapter looks at how these happen in humans and in plants — from photosynthesis and digestion to the beating heart, the flow of sap through xylem and phloem, and the filtering work of the kidneys.
Board relevance: a high-scoring chapter. Expect a labelled diagram (human heart or nephron), the photosynthesis and respiration equations, and 2–3 mark questions on digestion, double circulation, and transport in plants.
Key Concepts & Definitions
Nutrition — the process of taking in and using food for energy, growth, and repair.
- Autotrophic nutrition — organisms make their own food from simple inorganic substances (green plants, some bacteria) by photosynthesis.
- Heterotrophic nutrition — organisms depend on others for food (animals, fungi).
Photosynthesis — autotrophs use chlorophyll to trap sunlight and convert CO₂ and water into glucose:
6CO₂ + 6H₂O →(sunlight, chlorophyll) C₆H₁₂O₆ + 6O₂
Steps: absorption of light by chlorophyll → conversion of light energy to chemical energy and splitting of water into hydrogen and oxygen → reduction of CO₂ to carbohydrate. Stomata (pores mostly on leaf undersides, guarded by guard cells) allow gas exchange; they open and close by the swelling/shrinking of guard cells.
Respiration — the breakdown of glucose to release energy stored as ATP. Glucose is first broken in the cytoplasm into pyruvate (a 3-carbon molecule).
Nutrition in Humans (Digestion)
Food passes through the alimentary canal; enzymes break large molecules into absorbable ones.
Region What happens Key secretions
Mouth Chewing; starch digestion begins Saliva with salivary amylase (ptyalin) → starch to sugar
Stomach Churning; protein digestion begins; kills germs HCl (acidic medium), pepsin (protein enzyme), mucus (protects lining)
Small intestine Complete digestion of carbs, proteins, fats; absorption Bile (from liver — emulsifies fat), pancreatic juice (trypsin, lipase, amylase), intestinal juice
Small intestine wall Absorption of nutrients into blood Villi — increase surface area
Large intestine Absorption of water —
Bile makes the medium alkaline (for pancreatic enzymes) and emulsifies fats into small droplets. Digested food (glucose, amino acids, fatty acids) is absorbed by villi and carried by blood.
Respiration
Feature Aerobic Anaerobic
Oxygen Present Absent
Site Mitochondria Cytoplasm
Energy Large amount Small amount
Products CO₂ + H₂O Ethanol + CO₂ (yeast) or lactic acid (muscles)
- Glucose → pyruvate (cytoplasm, common step).
- Aerobic: pyruvate → CO₂ + H₂O + energy (mitochondria).
- Anaerobic in yeast (fermentation): pyruvate → ethanol + CO₂.
- Anaerobic in our muscles during heavy exercise: pyruvate → lactic acid, causing cramps.
Human respiratory system: air enters through the nostrils → pharynx → larynx → trachea → bronchi → lungs. Inside the lungs, tubes end in balloon-like alveoli, which provide a huge surface for gas exchange. Oxygen diffuses into the blood and is carried by haemoglobin; CO₂ is carried mostly dissolved in plasma and released in the lungs.
Transportation
In humans — the heart: a four-chambered pump (two atria, two ventricles). Double circulation:
- Right atrium → right ventricle → lungs (pick up O₂) → left atrium → left ventricle → body.
- The left ventricle has the thickest wall (pumps oxygenated blood to the whole body at high pressure).
- Arteries carry blood away from the heart (thick walls, no valves); veins carry blood back (thinner walls, valves prevent backflow); capillaries are one-cell-thick for exchange.
- Platelets help clot blood; lymph carries digested fats and drains extra fluid back to blood.
In plants:
- Xylem transports water and minerals upward from roots to leaves; driven mainly by transpiration (evaporation of water from leaves creating a pull).
- Phloem transports food (sucrose) made in leaves to all parts — called translocation; it uses energy (ATP) and can move food in any direction.
Excretion
Removal of harmful nitrogenous wastes (like urea) from the body.
Human excretory system: two kidneys, ureters, urinary bladder, urethra. The nephron is the functional unit — about a million per kidney. In a nephron: blood is filtered in the glomerulus; useful substances (glucose, amino acids, salts, most water) are reabsorbed; the remaining urine passes to the bladder.
Dialysis: an artificial kidney machine filters the blood of patients whose kidneys have failed.
In plants: excretion is simpler — O₂ is a photosynthesis waste, gases leave via stomata, some waste is stored in leaves/bark (shed later) or released into the soil.
Key Facts
Quick facts that boards ask directly:
Topic Fact to remember
Photosynthesis site Chloroplast (contains chlorophyll)
Raw materials CO₂, water, sunlight, chlorophyll
Salivary enzyme Salivary amylase / ptyalin (digests starch)
Stomach acid & enzyme HCl (acidic medium) + pepsin (protein)
Emulsifies fat Bile (from the liver)
Absorption organ Small intestine, via villi
Common respiration step Glucose → pyruvate (in cytoplasm)
Aerobic products CO₂ + water + energy (in mitochondria)
Anaerobic in muscles Lactic acid (causes cramps)
Anaerobic in yeast Ethanol + CO₂
Gas-exchange surface Alveoli (lungs)
O₂ carrier in blood Haemoglobin (in red blood cells)
Heart chambers Four (2 atria, 2 ventricles)
Thickest heart wall Left ventricle
Water transport Xylem (upward, transpiration pull)
Food transport Phloem (translocation, needs ATP)
Kidney's functional unit Nephron (~1 million per kidney)
Kidney-failure treatment Dialysis (artificial kidney)
Two useful definitions: Transpiration is the loss of water vapour from the aerial parts of a plant, mainly through stomata — it creates the pull that lifts water up the xylem. Peristalsis is the wave-like contraction of the muscles of the alimentary canal that pushes food forward through the gut.
Important Question Patterns
1. Photosynthesis (2–3 marks): write and explain the equation; role of chlorophyll, stomata, guard cells; where each step occurs.
2. Digestion (3 marks): trace food through the alimentary canal; match enzymes to their sites and substrates; role of HCl, bile, and villi.
3. Respiration (2–3 marks): aerobic vs anaerobic table; why we get muscle cramps; the common pyruvate step; role of alveoli.
4. Labelled diagram (3–5 marks): human heart or nephron; explain double circulation from the diagram.
5. Transport in plants (2 marks): xylem vs phloem; role of transpiration; meaning of translocation.
⚡ Quick Revision
- Life processes: nutrition, respiration, transportation, excretion.
- Photosynthesis: 6CO₂ + 6H₂O →(sunlight/chlorophyll) C₆H₁₂O₆ + 6O₂. Gas exchange through stomata (guard cells).
- Digestion enzymes: mouth = salivary amylase (starch); stomach = HCl + pepsin (protein); small intestine = bile (emulsifies fat) + pancreatic trypsin/lipase; absorption by villi.
- Respiration: glucose → pyruvate (cytoplasm). Aerobic → CO₂ + H₂O (mitochondria, more energy); anaerobic → ethanol + CO₂ (yeast) or lactic acid (muscles).
- Alveoli = gas-exchange surface; haemoglobin carries O₂.
- Heart: 4 chambers, double circulation, left ventricle wall thickest. Arteries away, veins back (valves).
- Xylem = water up (transpiration pull); phloem = food, translocation (needs ATP).
- Nephron = functional unit of kidney: filtration + reabsorption. Dialysis for kidney failure.
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