What keeps a living organism alive? Unlike non-living objects, living organisms continuously perform vital maintenance functions even when resting, sleeping, or sitting idle. Life Processes is Chapter 6 of the CBSE Class 10 Biology curriculum and forms the core foundation of human and plant physiology.
This comprehensive guide details the four fundamental life processes: Nutrition (autotrophic & human digestive system), Respiration (3 pathways of glucose breakdown & gas exchange), Transportation (human heart, double circulation, xylem & phloem), and Excretion (kidney & nephron urine formation).
- 1. Nutrition: Autotrophic (Photosynthesis) & Heterotrophic
- 2. Human Digestive System & Enzymes
- 3. Respiration & 3 Pathways of Glucose Breakdown
- 4. Human Respiratory System & Gas Exchange
- 5. Human Circulatory System & Double Circulation
- 6. Transportation in Plants (Xylem vs Phloem)
- 7. Excretion in Humans (Nephron) & Plants
- 8. Solved Board Exam Questions
- 9. Frequently Asked Questions (FAQ)
1. Nutrition: Autotrophic (Photosynthesis) & Heterotrophic
Nutrition is the process of intake of nutrients (carbohydrates, proteins, fats, minerals, vitamins) and their utilization by an organism to obtain energy, growth, and repair.
• Examples: Green plants, cyanobacteria.
• Site of Photosynthesis: Chloroplasts containing green pigment Chlorophyll.
• Stomata Function: Tiny pores on leaves guarded by kidney-shaped Guard Cells. When guard cells absorb water, they swell and open the stoma; when they lose water, they shrink and close the stoma.
• Saprotrophic: Feed on dead & decaying organic matter (Fungi, Bread mould, Mushrooms).
• Parasitic: Derive nutrition from host body without killing it (Cuscuta/Amarbel, Tapeworms, Ticks, Lice).
• Holozoic: Ingestion of solid food followed by digestion (Humans, Amoeba, Paramecium).
1. Absorption of light energy by chlorophyll.
2. Conversion of light energy to chemical energy and Splitting of water molecules (H₂O) into hydrogen and oxygen.
3. Reduction of Carbon Dioxide (CO₂) to Carbohydrates (Glucose).
2. Human Digestive System & Enzymes
Human digestion is a multi-step holozoic process occurring within the Alimentary Canal (Mouth to Anus):
| Organ / Gland | Secretion / Enzyme Produced | Function & Chemical Action |
|---|---|---|
| Mouth (Salivary Glands) | Salivary Amylase (Ptyalin) | Breaks down complex Starch into simple maltose sugar. |
| Stomach (Gastric Glands) | HCl, Pepsin, Mucus | HCl: Creates acidic medium (pH 1.5-2) and kills bacteria. Pepsin: Digests proteins into peptones. Mucus: Protects stomach wall from HCl acid erosion. |
| Liver (Biliary System) | Bile Juice & Bile Salts | Emulsification: Breaks large fat globules into small emulsified droplets. Makes acidic food alkaline for pancreatic enzymes. |
| Pancreas | Pancreatic Juice (Trypsin, Lipase, Pancreatic Amylase) | Trypsin: Digests proteins to peptides. Lipase: Digests emulsified fats to fatty acids & glycerol. |
| Small Intestine (Ileum) | Intestinal Juice (Succus Entericus) & Villi | Final digestion: Proteins → Amino Acids, Carbohydrates → Glucose, Fats → Fatty acids + Glycerol. Villi (finger-like projections) maximize surface area for nutrient absorption into bloodstream. |
3. Respiration & 3 Pathways of Glucose Breakdown
Respiration is the biochemical process of releasing cellular energy (ATP) by oxidizing digested food molecules (glucose).
Pathway 1: In Absence of Oxygen (Anaerobic in Yeast / Fermentation):
Pyruvate → Ethanol (2-carbon) + Carbon Dioxide (CO₂) + 2 ATP Energy
Pathway 2: In Lack of Oxygen (Anaerobic in Human Muscle Cells):
Pyruvate → Lactic Acid (3-carbon) + 2 ATP Energy
Accumulation of Lactic Acid during sudden heavy exercise causes muscle cramps!
Pathway 3: In Presence of Oxygen (Aerobic in Mitochondria):
Pyruvate → Carbon Dioxide (CO₂) + Water (H₂O) + 38 ATP Energy
4. Human Respiratory System & Gas Exchange
Air enters through nostrils (filtered by fine hair and mucus) → Pharynx → Larynx → Trachea (supported by C-shaped rings of cartilage so it does not collapse) → Bronchi → Bronchioles → Alveoli.
- Alveoli: Balloon-like structures with thin walls surrounded by extensive blood capillaries. Site of actual gas exchange (O₂ diffuses into blood, CO₂ diffuses out into alveoli).
- Respiratory Pigment: Haemoglobin present in Red Blood Cells (RBCs) has high affinity for oxygen and transports O₂ from lungs to tissues. CO₂ is more soluble in water and is mostly transported in dissolved form in blood plasma.
5. Human Circulatory System & Double Circulation
The human heart is a 4-chambered muscular organ: Right Atrium, Right Ventricle, Left Atrium, Left Ventricle. Deoxygenated and oxygenated blood are kept completely separate to ensure high metabolic efficiency.
1. Pulmonary Circulation: Deoxygenated blood from body → Right Atrium → Right Ventricle → Pulmonary Artery → Lungs (oxygenated) → Pulmonary Vein → Left Atrium.
2. Systemic Circulation: Oxygenated blood → Left Ventricle → Aorta → All Body Tissues → Vena Cava → Right Atrium.
• Arteries: Carry blood AWAY from heart (thick elastic walls, high pressure, no valves).
• Veins: Carry blood TOWARDS heart (thin walls, low pressure, contain valves to prevent backflow).
• Capillaries: One-cell thick microscopic vessels where substance exchange occurs.
• Platelets: Blood cells responsible for blood clotting at injury sites.
• Lymph: Extracellular tissue fluid that carries digested fat and returns interstitial fluid to blood.
6. Transportation in Plants (Xylem vs Phloem)
| Feature | Xylem Tissue | Phloem Tissue |
|---|---|---|
| Substances Transported | Water and Dissolved Minerals | Soluble products of photosynthesis (Sucrose, amino acids) |
| Direction of Movement | Unidirectional (Upwards from roots to leaves) | Bidirectional (Upwards and downwards to all plant parts) |
| Driving Force / Mechanism | Transpiration Pull (evaporation of water from stomata creates suction) & Root Pressure | Translocation (requires energy from ATP to create osmotic pressure) |
| Conducting Cells | Tracheids and Vessels (Dead cells at maturity) | Sieve tubes and Companion cells (Living cells) |
7. Excretion in Humans (Nephron) & Plants
Excretion is the biological process of removing toxic nitrogenous metabolic wastes (urea, uric acid) from the body.
Human Excretory System: Pair of Kidneys → Pair of Ureters → Urinary Bladder → Urethra.
1. Ultrafiltration: High-pressure blood enters Glomerulus (capillary cluster) inside Bowman's Capsule. Liquid filtrate (water, glucose, amino acids, salts, urea) passes into nephron tube.
2. Selective Reabsorption: As filtrate moves through tubular part of nephron, useful substances (glucose, amino acids, essential salts, major water) are selectively reabsorbed back into surrounding blood capillaries.
3. Tubular Secretion & Urine Collection: Remaining fluid containing concentrated Urea, extra salts, and water forms Urine, which flows into collecting duct → Ureter → Urinary Bladder.
Excretion in Plants:
• Oxygen released as byproduct of photosynthesis.
• Excess water removed by transpiration.
• Waste substances stored in cellular vacuoles, old dying leaves (which fall off), and as resins/gums in old xylem.
8. Solved Board Exam Questions
(1) Absorption of light energy by chlorophyll.
(2) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
(3) Reduction of carbon dioxide to carbohydrates.
No, it is not necessary that these steps take place immediately one after the other. For example, desert plants (xerophytes) take up CO₂ at night (when stomata are open to prevent water loss) and prepare an intermediate compound, which is acted upon by light energy absorbed by chlorophyll during the daytime.
(1) Aerobic Respiration (In Mitochondria with O₂): Yields CO₂ + H₂O + 38 ATP Energy.
(2) Anaerobic in Yeast (Absence of O₂): Yields Ethanol + CO₂ + 2 ATP Energy (Fermentation).
(3) Anaerobic in Muscle Cells (Lack of O₂): Yields Lactic Acid + 2 ATP Energy (Causes cramps during rigorous exercise).
Why necessary: It completely separates oxygenated blood from deoxygenated blood. This prevents mixing of blood, ensuring a highly efficient supply of oxygen to body cells, which is essential to maintain high metabolic rate and constant body temperature (warm-blooded endothermy).
Four chambers: Right Atrium, Right Ventricle, Left Atrium, Left Ventricle.
(2) Xylem movement is unidirectional (root to leaves); Phloem movement is bidirectional.
(3) Xylem relies on physical forces (transpiration pull & root pressure); Phloem translocation relies on active transport using ATP energy.
(4) Xylem vessels/tracheids are dead cells; Phloem sieve tubes/companion cells are living cells.
Urine formation steps:
1. Glomerular Filtration: Blood filtered under pressure in glomerulus into Bowman's capsule.
2. Selective Reabsorption: Glucose, amino acids, salts, and major water are reabsorbed in renal tubule.
3. Secretion & Collection: Wastes like urea and excess ions remain as urine in collecting duct.
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9. Frequently Asked Questions (FAQ)
Life processes are the basic essential activities performed by living organisms to maintain their life on Earth.
The four basic life processes are: (1) Nutrition, (2) Respiration, (3) Transportation, and (4) Excretion.
During heavy exercise, oxygen supply to muscle cells becomes insufficient for aerobic respiration. Muscle cells switch to anaerobic breakdown of pyruvate, which produces Lactic Acid. The accumulation of lactic acid in muscle tissue causes painful muscle cramps.
Double circulation means blood passes through the human heart twice in one complete circuit (Pulmonary circulation to lungs + Systemic circulation to body). It completely separates oxygenated and deoxygenated blood, ensuring an efficient oxygen supply for high energy needs and body temperature regulation.
Water moves upwards through xylem vessels primarily due to Transpiration Pull. Evaporation of water vapor from leaf stomata creates a continuous suction pressure (transpiration pull) that pulls a continuous column of water upwards from the roots to the highest leaves.
A Nephron is the structural and functional filtering unit of the human kidney. Its main functions are: (1) Ultrafiltration of blood in the Glomerulus, (2) Selective reabsorption of glucose, amino acids, and water in the renal tubule, and (3) Excretion of nitrogenous wastes (urea) as urine.
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