Life Processes

Revision Summary: Life Processes (NCERT Class 10)

Chapter at a glance

• Maintenance functions (nutrition, respiration, transportation and excretion) must continue even when an organism is not performing any visible activity; these together are called life processes.
• Autotrophs (green plants, some bacteria) fulfil carbon and energy needs by photosynthesis; heterotrophs depend directly or indirectly on autotrophs.
• Photosynthesis converts CO₂ and H₂O into carbohydrates using sunlight and chlorophyll; unused carbohydrates are stored as starch.
• Respiration breaks down glucose: first step (pyruvate formation) occurs in cytoplasm; aerobic respiration in mitochondria yields more energy than anaerobic (fermentation or lactic acid) pathways.
• In humans, a four-chambered heart ensures separation of oxygenated and deoxygenated blood (double circulation); respiratory pigment haemoglobin carries oxygen.
• Xylem transports water and minerals from roots upwards; phloem translocates products of photosynthesis (mainly sucrose) to storage/growing organs using energy from ATP.
• Excretion removes nitrogenous wastes; in humans, nephrons in kidneys filter blood; plants store wastes in vacuoles, resins/gums or lose them in falling leaves.
• ATP is the energy currency of the cell; terminal phosphate bond hydrolysis releases 30.5 kJ/mol.

Definitions and laws (exact NCERT framing) - Life processes: “The processes which together perform this maintenance job are life processes.” - Excretion: “The biological process involved in the removal of these harmful metabolic wastes from the body is called excretion.” - Transpiration: “The loss of water in the form of vapour from the aerial parts of the plant is known as transpiration.” - Translocation: “This transport of soluble products of photosynthesis is called translocation and it occurs in the part of the vascular tissue known as phloem.” - ATP (energy currency): “ATP is the energy currency for most cellular processes.” “When the terminal phosphate linkage in ATP is broken using water, the energy equivalent to 30.5 kJ/mol is released.” - Blood pressure: “The force that blood exerts against the wall of a vessel is called blood pressure.” “The pressure of blood inside the artery during ventricular systole (contraction) is called systolic pressure and pressure in artery during ventricular diastole (relaxation) is called diastolic pressure. The normal systolic pressure is about 120 mm of Hg and diastolic pressure is 80 mm of Hg.” - Double circulation (implied): blood passes through the heart twice during each cycle in mammals/birds.

Important diagrams and activities

• Fig. 5.1 – Cross-section of leaf (shows chloroplasts).
• Fig. 5.2 – Variegated leaf before/after starch test (demonstrates chlorophyll is necessary for starch formation).
• Fig. 5.3 – Open and closed stomatal pore (guard-cell mechanism).
• Fig. 5.4 – Bell-jar experiment with/without KOH (CO₂ is necessary for photosynthesis).
• Fig. 5.5 – Nutrition in Amoeba (food-vacuole formation and digestion).
• Fig. 5.6 – Human alimentary canal (regions and associated glands).
• Fig. 5.8 – Breakdown of glucose by various pathways (aerobic vs anaerobic routes).
• Fig. 5.9 – Human respiratory system (nostrils → alveoli).
• Fig. 5.10 – Schematic sectional view of human heart (four chambers, valves).
• Fig. 5.11 – Double circulation and gas exchange.
• Fig. 5.12 – Transpiration pull in a tree (xylem water column).
• Fig. 5.13 – Human excretory system (kidneys, ureters, bladder, urethra).
• Fig. 5.14 – Structure of a nephron (Bowman’s capsule, glomerulus, tubule).
• Activities 5.1–5.2, 5.4–5.6, 5.8 – starch test, CO₂ necessity, lime-water test for exhaled CO₂, yeast fermentation, fish gill movement, transpiration demonstration.

Common misconceptions and exam pitfalls

• Using “visible movement” as the sole criterion for life (text explicitly states molecular movement is essential).
• Assuming stomata are only for CO₂ intake (they also allow O₂/CO₂ exchange and water loss; guard cells control opening).
• Confusing fermentation (ethanol + CO₂ in yeast) with lactic-acid pathway in muscle cramps.
• Thinking xylem and phloem both carry food (xylem = water/minerals; phloem = translocation of sucrose etc.).
• Believing plants do not respire during day (they do; CO₂ produced is used in photosynthesis).
• Mixing up re-absorption in nephron with filtration (initial filtrate is modified by selective re-absorption).
• Forgetting that ventricles have thicker walls than atria because they pump blood to lungs/body.

Formula sheet

No other numerical formulas appear in the chapter.