CBSE Class 10 Biology Life Processes: Complete Chapter Notes with Diagrams (2025-2026)
Mastering CBSE Class 10 Biology Life Processes is essential for securing a perfect score in your 2025-2026 board exam 10. Chapter 5 (Life Processes) forms the foundational pillar of Class 10 Science, carrying significant weightage across short-answer, diagram-based, and competency-focused questions. This comprehensive guide delivers curriculum-aligned NCERT revision notes, detailed physiological equations, step-by-step anatomical breakdowns, and official CBSE question bank solutions to streamline your board preparation.
Key Concepts in Life Processes
Life processes are the fundamental biological mechanisms performed by living organisms to maintain cellular organization, repair tissues, and sustain life. The four vital life processes covered in the CBSE Biology syllabus are Nutrition, Respiration, Transportation, and Excretion.
1. Nutrition: Autotrophic and Heterotrophic Systems
Nutrition is the intake and physiological utilization of nutrients required for energy, tissue synthesis, and metabolic regulation.
- Autotrophic Nutrition: Organisms synthesize organic food from inorganic raw materials (CO₂ and H₂O) using sunlight trapped by chlorophyll. This occurs via Photosynthesis.
Balanced Chemical Equation:
6CO₂ + 12H₂O + Sunlight + Chlorophyll → C₆H₁₂O₆ + 6O₂ + 6H₂O
Key Events:- Absorption of light energy by chlorophyll pigments.
- Conversion of light energy into chemical energy and photolysis of water (splitting of H₂O into H⁺, electrons, and O₂).
- Reduction of carbon dioxide into carbohydrates (glucose).
- Heterotrophic Nutrition: Organisms depend on pre-synthesized organic matter. Subtypes include:
- Holozoic: Ingestion of solid food followed by internal digestion and absorption (e.g., Amoeba, humans).
- Saprophytic: Breakdown of dead organic matter externally followed by nutrient absorption (e.g., fungi, yeast, bread mould).
- Parasitic: Deriving nourishment directly from a living host without killing it immediately (e.g., Cuscuta/Amarbel, tapeworm, leeches).
Human Alimentary Canal & Digestive Secretions
Human digestion is extracellular and follows a sequential pathway through specialized organs:
| Organ / Gland | Secretions & Enzymes | pH / Substrate | Enzymatic Action & Product |
|---|---|---|---|
| Mouth (Salivary Glands) | Salivary Amylase (Ptyalin), Mucus | Slightly Alkaline (pH ~6.8) | Starch (complex carbohydrate) → Maltose (simple disaccharide) |
| Stomach (Gastric Glands) | Hydrochloric Acid (HCl), Pepsinogen, Mucus | Highly Acidic (pH ~1.5 - 2.0) | HCl activates Pepsinogen → Pepsin; Pepsin converts Proteins → Peptones & Proteoses. Mucus protects stomach lining. |
| Liver & Gall Bladder | Bile Juice (Bile Salts & Pigments; no enzymes) | Alkaline | Neutralizes acidic chyme; emulsifies large fat globules into micro-droplets. |
| Pancreas | Pancreatic Juice (Trypsin, Pancreatic Amylase, Lipase) | Alkaline | Trypsin: Proteins/Peptones → Peptides; Lipase: Emulsified Fats → Fatty Acids + Glycerol; Amylase: Residual Starch → Maltose. |
| Small Intestine (Ileum) | Intestinal Juice (Succus Entericus) | Alkaline | Final digestion: Peptides → Amino acids; Carbohydrates → Glucose; Lipids → Fatty acids & Glycerol. Absorbed through finger-like villi. |
2. Respiration: Cellular Oxidation and Energy Release
Respiration is the biochemical catabolism of glucose inside cells to liberate metabolic energy in the form of ATP (Adenosine Triphosphate).
Universal First Step (Glycolysis): In the cytoplasm of all living cells, one molecule of 6-carbon glucose is broken down into two molecules of 3-carbon Pyruvate, yielding a net gain of 2 ATP.
Breakdown Pathways of Pyruvate:
- Aerobic Respiration (Mitochondria - Presence of O₂):
Pyruvate + O₂ → 6CO₂ + 6H₂O + 38 ATP (High energy yield) - Anaerobic Respiration / Alcoholic Fermentation (Yeast - Absence of O₂):
Pyruvate → 2C₂H₅OH (Ethanol) + 2CO₂ + 2 ATP - Anaerobic Respiration in Human Muscle Tissues (Lack of O₂ during intense exercise):
Pyruvate → 2C₃H₆O₃ (Lactic Acid) + 2 ATP
Clinical Application: Accumulation of lactic acid in muscle fibers causes localized fatigue, muscle cramps, and soreness.
Human Respiratory Mechanism and Alveolar Gas Exchange
Air enters via the external nostrils → nasal passage (filtered by fine hair and mucus) → pharynx → larynx → trachea (supported by C-shaped cartilaginous rings preventing collapse) → bronchi → bronchioles → Alveoli.
- Inhalation: External intercostal muscles contract, lifting the ribs upwards and outwards, while the diaphragm contracts and flattens downward. This increases thoracic cavity volume, lowering intrapulmonary air pressure below atmospheric pressure; air rushes into the lungs.
- Alveolar Exchange: Alveoli provide an expansive surface area (~80 m²) lined with a one-cell-thick moist epithelium surrounded by dense blood capillaries. O₂ diffuses across the respiratory membrane down its partial pressure gradient into blood, binding with the red pigment Hemoglobin to form Oxyhemoglobin (Hb + 4O₂ → Hb(O₂)₄), while CO₂ dissolved in blood plasma diffuses into the alveolar air for exhalation.
3. Transportation in Living Organisms
Human Circulatory System & Double Circulation
Humans possess a muscular, four-chambered heart that maintains Double Circulation, preventing the mixing of oxygenated and deoxygenated blood and ensuring high metabolic efficiency:
- Pulmonary Circulation: Deoxygenated blood from the body enters the Right Atrium via the Vena Cava → Right Ventricle → Pulmonary Artery → Lungs (oxygenation occurs) → Pulmonary Veins → Left Atrium.
- Systemic Circulation: Oxygenated blood from Left Atrium → Left Ventricle (thick muscular wall) → Aorta → Systemic Arteries → Body Tissues → Systemic Veins → Vena Cava.
Blood vs. Lymph: Blood contains RBCs, WBCs, platelets, and plasma, transporting respiratory gases, nutrients, and waste. Lymph (tissue fluid) is a colorless fluid containing specialized lymphocytes and plasma proteins that drains excess extracellular fluid back into the venous system and transports emulsified fats absorbed by intestinal lacteals.
Transport in Plants: Xylem vs. Phloem
- Xylem (Tracheids & Vessels): Transports water and dissolved minerals unidirectionally from roots to aerial parts driven by root pressure and the negative hydrostatic pressure gradient created by transpiration pull.
- Phloem (Sieve Tubes & Companion Cells): Translocates soluble photosynthetic products (sucrose, amino acids) bidirectionally from source (leaves) to sink (roots, fruits, growing buds). Translocation requires metabolic energy in the form of ATP to generate osmotic pressure.
4. Excretion in Humans and Plants
Excretion is the biological process of eliminating toxic nitrogenous metabolic wastes (primarily urea and uric acid in humans) from the body.
Nephron Structure and Urine Formation
The Nephron is the structural and functional filtration unit of the human kidney (~1 million nephrons per kidney). Urine formation occurs through three precise physiological phases:
- Ultrafiltration (Glomerular Filtration): Blood enters the Glomerulus under high hydrostatic pressure via the wide afferent arteriole. Water, glucose, amino acids, urea, and inorganic salts filter across the glomerular-Bowman's capsule membrane into the renal lumen, forming the initial filtrate (~180 liters/day in adults).
- Selective Reabsorption: As filtrate passes through the Proximal Convoluted Tubule (PCT) and the Loop of Henle, essential substances (100% of glucose and amino acids, major fractions of Na⁺, Cl⁻, and ~99% of water) are reabsorbed back into peritubular capillaries.
- Tubular Secretion: Distal Convoluted Tubule (DCT) cells actively secrete surplus K⁺, H⁺, and ammonia into the tubular lumen to regulate blood pH and ionic equilibrium, producing concentrated final urine (~1.5 liters/day) that drains into the collecting duct → ureter → urinary bladder → urethra.
Important CBSE Class 10 Biology Questions with Answers
The following questions are selected directly from the official CBSE question bank and previous board examination papers. Study the point-wise marking scheme keys carefully:
Q1: Define nutrition. Name the mode of nutrition in Amoeba.
Answer:
- Definition: Nutrition is the physiological process of obtaining, ingesting, digesting, absorbing, and assimilating nutrients by an organism to generate ATP energy, facilitate growth, and perform cellular maintenance.
- Mode in Amoeba: Amoeba exhibits Holozoic nutrition (phagocytosis). It extends finger-like temporary projections called pseudopodia to engulf food particles, enclosing them within an intracellular food vacuole where digestive enzymes break down complex nutrients into simple diffusible substances.
Q2: What is the role of stomata in plants?
Answer:
- Gaseous Exchange: Stomatal apertures allow the diffusion of Carbon Dioxide (CO₂) into the leaf mesophyll for photosynthesis and facilitate the release of byproduct Oxygen (O₂) and respiratory CO₂.
- Transpiration: Stomata regulate the evaporation of surplus water vapor from aerial plant organs. This generates a continuous transpiration pull essential for the upward conduction of water/minerals through xylem vessels and provides evaporative cooling to leaf tissues.
Q3: What is the function of the enzyme pepsin in the human digestive system?
Answer:
- Pepsin is a major proteolytic (protein-digesting) enzyme secreted by the gastric chief cells of the stomach mucosa in its inactive zymogen form, pepsinogen.
- In the presence of Hydrochloric Acid (which creates an optimal acidic environment of pH 1.5 to 2.0), pepsinogen is activated to pepsin.
- Function: Active pepsin hydrolyzes complex dietary proteins into smaller soluble peptide fragments, namely proteoses and peptones.
Q4: What happens to the pH of the mouth after eating? Why does tooth decay occur?
Answer:
- pH Change: After consuming meals, oral bacteria (such as Streptococcus mutans) ferment residual dietary sugars and carbohydrate particles lodged between teeth, releasing organic acids (e.g., lactic acid). Consequently, the pH of the oral cavity drops significantly below the critical threshold of 5.5.
- Mechanism of Tooth Decay (Dental Caries): Tooth enamel is composed of calcium hydroxyapatite (a crystalline form of calcium phosphate), which is the hardest substance in the human body. However, when the oral pH drops below 5.5, the enamel undergoes chemical demineralization and corrosion. Prolonged acid exposure damages enamel and dentin, allowing bacterial invasion and cavity formation.
Q5: How is the amount of urine produced regulated in the human body?
Answer:
The volume and concentration of urine excreted are regulated through homeostatic osmoregulation dependent upon two primary factors:
- Volume of Excess Water in Body Fluids: If an individual is well-hydrated, less water is reabsorbed by the nephron tubules, leading to the excretion of a larger volume of dilute urine. When water intake is low, maximum water is reabsorbed, resulting in concentrated, low-volume urine.
- Quantity of Dissolved Nitrogenous Wastes: A higher concentration of urea and salts in the blood requires a proportionate volume of water for safe excretion.
- Hormonal Feedback (ADH / Vasopressin): Osmoreceptors in the hypothalamus detect hemoconcentration and stimulate the posterior pituitary to release Antidiuretic Hormone (ADH). ADH increases the water permeability of the Distal Convoluted Tubule (DCT) and Collecting Duct, promoting selective reabsorption of water back into the bloodstream.
Q6: Compare aerobic and anaerobic respiration. Write the equations for both.
Answer:
| Parameter | Aerobic Respiration | Anaerobic Respiration |
|---|---|---|
| Oxygen Requirement | Requires molecular oxygen (O₂). | Occurs in the complete absence or deficiency of oxygen. |
| Site of Occurrence | Cytoplasm (Glycolysis) and Mitochondria (Krebs Cycle). | Cytoplasm only. |
| Substrate Breakdown | Complete oxidation of glucose into inorganic products. | Incomplete breakdown of glucose into organic end products. |
| End Products | Carbon dioxide (CO₂) and Water (H₂O). | Ethanol + CO₂ (in Yeast) OR Lactic Acid (in animal muscles). |
| Energy Yield | High energy yield: 38 ATP (or ~36-38 ATP) per glucose. | Low energy yield: 2 ATP per glucose. |
Chemical Equations:
- Aerobic Respiration:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP - Anaerobic Respiration in Yeast (Alcoholic Fermentation):
C₆H₁₂O₆ → 2C₂H₅OH (Ethanol) + 2CO₂ + 2 ATP - Anaerobic Respiration in Skeletal Muscle:
C₆H₁₂O₆ → 2C₃H₆O₃ (Lactic Acid) + 2 ATP
Q7: Describe the mechanism of gas exchange in human beings. How does oxygen reach every cell?
Answer:
- Ventilation / Inhalation: Contraction of the diaphragm and intercostal muscles increases the thoracic cage volume, decreasing intra-alveolar pressure and drawing atmospheric air into millions of thin-walled alveoli.
- Alveolar Diffusion: The partial pressure of oxygen in alveolar air is higher than that in the deoxygenated blood of adjacent pulmonary capillaries. O₂ diffuses passively across the ultra-thin alveolar-capillary membrane into the blood. Simultaneously, CO₂ diffuses from capillary blood into the alveoli down its concentration gradient.
- Systemic Oxygen Delivery via Hemoglobin: Because simple diffusion cannot distribute oxygen through large multicellular human bodies, the respiratory pigment Hemoglobin present inside Red Blood Cells (RBCs) binds with O₂ molecules to form Oxyhemoglobin. The heart pumps this oxygenated blood through the aorta and systemic arterial tree to peripheral tissue capillaries.
- Cellular Uptake: At the tissue level, where cells continuously consume O₂ for aerobic respiration, partial pressure of O₂ is low. Oxyhemoglobin dissociates, and O₂ diffuses into individual cells across capillary walls for cellular oxidation.
Q8: Explain the process of nutrition in humans with a labeled diagram of the alimentary canal.
Answer:
Human nutrition involves five interconnected physiological stages:
- 1. Ingestion: Taking in solid food through the oral cavity using lips, teeth, and tongue.
- 2. Digestion: Mechanical mastication by teeth mixed with salivary amylase initiates carbohydrate breakdown. In the stomach, gastric juices and pepsin digest proteins in an acidic medium. In the duodenum, bile emulsifies fats, and pancreatic enzymes (trypsin, lipase, amylase) digest proteins, lipids, and carbohydrates into simpler monomers.
- 3. Absorption: The inner mucosal lining of the small intestine features millions of vascularized microscopic projections called villi and microvilli, which exponentially amplify surface area for rapid absorption of glucose, amino acids, and fatty acids into blood and lymph vessels (lacteals).
- 4. Assimilation: Absorbed nutrients are transported via the bloodstream to somatic cells to synthesize new protoplasm, repair cellular components, and generate ATP.
- 5. Egestion: Undigested and unabsorbed food residue passes into the large intestine, where excess water is reabsorbed. The remaining solid fecal waste is stored temporarily in the rectum and eliminated through the anus, regulated by the anal sphincter.
Schematic Representation of the Human Alimentary Canal:
[Mouth / Buccal Cavity] <-- Salivary Glands (Salivary Amylase)
|
v
[Pharynx]
|
v
[Oesophagus] <-- Peristaltic Wave Contractions
|
v
[Stomach] <-- Gastric Glands (HCl, Pepsin, Mucus)
|
+-----------------------------+
| |
v v
[Liver & Gall Bladder] [Pancreas]
(Bile: Emulsification) (Trypsin, Lipase, Amylase)
\ /
+------------+--------------+
|
v
[Small Intestine] <-- Villi & Intestinal Enzymes
(Duodenum → Jejunum → Ileum: Final Digestion & Absorption)
|
v
[Large Intestine] <-- Colon (Water & Mineral Reabsorption)
|
v
[Rectum] <-- Temporary Fecal Storage
|
v
[Anus] <-- Anal Sphincter (Egestion)
How to Prepare for This Topic in CBSE Class 10
To maximize your score in the Life Processes unit during your CBSE Class 10 examination, incorporate these targeted revision habits:
- Master High-Yield Diagrams: Regularly practice neat, labeled line diagrams of the Human Alimentary Canal, Schematic Flow of Double Circulation (Heart), Structure of a Nephron, Cross-Section of a Leaf, and Open vs. Closed Stomatal Pore. Ensure labels are aligned horizontally on one side.
- Memorize Biochemical Equations: Write out the balanced equations for Photosynthesis, Aerobic Respiration, and both types of Anaerobic Respiration (Fermentation in Yeast vs. Lactic Acid in Muscle) without omitting catalysts and ATP yields.
- Construct Enzyme-Substrate Flashcards: Differentiate between gastric pepsin and pancreatic trypsin based on site of secretion, optimal pH, and activation mechanisms to avoid confusing them in board questions.
- Solve Case-Based & Assertion-Reason Questions: The 2025-2026 examination pattern allocates substantial marks to competency-based clinical scenarios (e.g., dialysis mechanisms, bile duct blockages, dental plaque formation).
Where to Practice More
Consistently testing your conceptual clarity with real exam-style questions is the single most effective way to secure an A1 grade in Class 10 Science. Access curated CBSE previous years' question papers (PYQs), NCERT exemplar solutions, and customized mock assessments at qptool.theorify.in to test your readiness and master every chapter with ease.