Chapter Overview & Weightage
Life Processes is one of the most important chapters in CBSE Class 10 Science. It covers the six fundamental life processes: nutrition, respiration, transportation, excretion, control and coordination, and reproduction.
Weightage: This chapter regularly carries 12-16 marks across questions. Expect 2-3 questions worth 2-3 marks each, plus a 5-mark question on diagrams. Diagrams of the heart, nephron, and cross-section of a leaf are extremely high-priority.
| Year | Marks | Focus Areas |
|---|---|---|
| 2024 | 15 | Nutrition, Respiration, Transportation |
| 2023 | 13 | Excretion, Heart diagram, Stomata |
| 2022 | 14 | Photosynthesis, Blood flow, Nephron |
Key Concepts You Must Know
Nutrition:
- Autotrophic (photosynthesis) vs heterotrophic (ingestion)
- Photosynthesis equation, site, and conditions
- Human digestive system — organs and enzymes
- Role of HCl, pepsin, bile, pancreatic juice
Respiration:
- Aerobic vs anaerobic respiration
- Breathing mechanism (diaphragm, intercostal muscles)
- Alveoli structure and gas exchange
- Energy released: aerobic 38 ATP, anaerobic 2 ATP
Transportation:
- Blood composition: plasma, RBCs, WBCs, platelets
- Heart structure and functioning — 4 chambers, valves
- Blood vessels: arteries, veins, capillaries
- Lymphatic system
- Transport in plants: xylem (water + minerals), phloem (food)
Excretion:
- Nephron structure and functioning
- Filtration → reabsorption → secretion → urine formation
- Plants excrete by diffusion, storing in vacuoles, or shedding leaves
Important Formulas and Equations
Light reactions: occur in thylakoids — split water, produce ATP + NADPH
Dark reactions (Calvin cycle): occur in stroma — fix into glucose
Aerobic: Energy (38 ATP)
Anaerobic (yeast): Energy (2 ATP)
Anaerobic (muscles): (lactic acid) + Energy
Solved Previous Year Questions
PYQ 1 — Diagram Question (5 marks)
Draw a labelled diagram of the human heart and explain the path of blood from the right ventricle to the left atrium.
Path: Right ventricle → Pulmonary artery → Lungs → Pulmonary vein → Left atrium.
This is pulmonary circulation (heart to lungs and back). In the lungs, is released and is absorbed. The blood returning to the left atrium is oxygenated.
Key labels required: right atrium, right ventricle, left atrium, left ventricle, pulmonary artery, pulmonary vein, aorta, valves (tricuspid, bicuspid, semilunar).
PYQ 2 — Excretion (3 marks)
Explain the formation of urine in the nephron.
Blood enters the glomerulus under high pressure. Small molecules — water, urea, glucose, salts — are filtered into the Bowman’s capsule, forming the glomerular filtrate. Blood cells and proteins are too large to pass.
As filtrate moves through the renal tubule, useful substances — glucose, amino acids, most water, essential salts — are reabsorbed back into surrounding capillaries.
Tubule cells actively secrete additional waste products (e.g., H⁺ ions, some drugs) into the filtrate.
What remains — concentrated urea solution — flows into the collecting duct and then the ureter. Normal urine is about 95% water, 2% urea, with uric acid and creatinine.
PYQ 3 — Nutrition (2 marks)
What is the role of bile juice in digestion?
Bile juice, produced by the liver and stored in the gallbladder, is secreted into the duodenum. It does NOT contain enzymes. Its roles: (1) Emulsification of fats — breaks large fat globules into smaller droplets, increasing surface area for lipase action. (2) Alkalinization — neutralizes the acidic chyme from the stomach, making the small intestine’s environment suitable for intestinal enzymes.
Difficulty Distribution
| Level | % | Topics |
|---|---|---|
| Easy | 35% | Define terms, name parts, basic equations |
| Medium | 40% | Short answer explanations, process questions |
| Hard | 25% | Diagram questions, “why” explanations |
Expert Strategy
Strategy 1 — Prioritize diagrams. The heart, nephron, and leaf cross-section (showing stomata, mesophyll) appear almost every year. Practice drawing them from memory with all labels. A well-drawn, fully labelled diagram earns full marks.
Strategy 2 — Learn the “why” not just the “what.” CBSE increasingly asks reasoning questions: “Why does blood not flow backward in the heart?” (valves prevent it). Know the reason behind each feature.
Strategy 3 — Connect structure to function. Alveoli have thin walls and large surface area — why? To maximize gas diffusion rate. Xylem cells are dead and have thick walls — why? To withstand pressure and prevent collapse.
For photosynthesis questions, always mention three conditions: light, , and chlorophyll. Students often forget chlorophyll or write “green parts of leaf” without mentioning chlorophyll as the key pigment.
Common Traps
Trap 1: Writing that “arteries always carry oxygenated blood.” The pulmonary artery carries deoxygenated blood from the heart to the lungs. Always specify: “most arteries carry oxygenated blood, except the pulmonary artery.”
Trap 2: Confusing xylem and phloem direction. Xylem carries water and minerals from root to leaves (upward, unidirectional). Phloem carries food from leaves to all parts (bidirectional).
Trap 3: In excretion, students write “the kidney filters blood” without explaining the glomerular pressure mechanism. CBSE marking scheme typically requires mention of “high pressure” for full marks.
Trap 4: Forgetting that anaerobic respiration in muscles produces lactic acid (not ethanol). Yeast produces ethanol + CO₂. Muscles produce lactic acid. Both produce only 2 ATP.
Trap 5: In photosynthesis, saying light energy is stored “in the chloroplast.” Light energy is converted to chemical energy stored in glucose (food). The chloroplast is only the site — not the storage location.