Life Processes — Class 10 Science

What CBSE examines here (2026-27). This chapter is unchanged by rationalisation — nutrition, respiration, transportation and excretion in both humans and plants are all still here, across five in-text question sets (21 questions) and one end-of-chapter Exercise (13 questions, not 20 as some older manifests claim). One thing worth knowing: the current chapter describes the breathing passage and the kidney's filtering tube in functional, generic terms rather than naming every intermediate structure. It never says "trachea," "bronchi" or "bronchioles" — just "the passage divides into smaller and smaller tubes." It never says "loop of Henle," "proximal/distal tubule" or "collecting duct" — just "the tube" that carries filtrate from Bowman's capsule to the ureter. Those names are correct biology and are used in Class 11 and NEET-level material, but this chapter's own answers don't require them.

"What separates a living organism from a stone? Six basic processes: nutrition, respiration, transport, excretion, growth, response."

1. About the Chapter

This is one of the LARGEST chapters in Class 10 Biology. Covers:

• Nutrition (autotrophic, heterotrophic)
• Respiration (aerobic, anaerobic)
• Transportation (blood, lymph in animals; xylem/phloem in plants)
• Excretion (kidneys, sweating)
• Plant systems (photosynthesis, transpiration)

Key Idea

Life processes = essential functions that keep an organism alive.

2. Six Life Processes

1. Nutrition — getting food
2. Respiration — releasing energy from food
3. Transportation — moving materials within body
4. Excretion — removing waste
5. Growth — increasing size/cells
6. Response — reacting to environment (Chapter 6)

This chapter covers 1-4. Chapter 6 covers 5-6.

3. NUTRITION

Modes of Nutrition

Autotrophic (self-made): plants, some bacteria

• Use sunlight + CO₂ + water to make food (photosynthesis)

Heterotrophic (others-made): animals, fungi, most bacteria

• Eat plants/animals/decomposing matter

Heterotrophic Types

• Holozoic: ingest, digest, absorb (humans, lions)
• Saprophytic: feed on dead/decaying matter (fungi)
• Parasitic: live on/inside host (tapeworms, malaria parasite)

Photosynthesis (Plant Nutrition)

Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (Catalysed by CHLOROPHYLL, using SUNLIGHT)

Where: Chloroplasts of leaf cells (chlorophyll in stroma)

Steps:

1. Absorption of LIGHT by chlorophyll
2. Conversion of light energy to chemical energy
3. Splitting of water (H₂O → H⁺ + OH⁻) — releases O₂
4. Carbon dioxide reduction to form glucose

Stomata: tiny pores in leaves for CO₂ in, O₂ out, water vapour transpiration. Guarded by guard cells (open/close based on water).

Human Digestive System

Organs (in order):

1. Mouth: chewing, salivary amylase (breaks starch to maltose)
2. Oesophagus: tube to stomach (peristalsis)
3. Stomach: HCl, pepsin (breaks proteins)
4. Small intestine (main digestion):
   • Bile from liver emulsifies fats
   • Pancreatic juice (trypsin, amylase, lipase)
   • Intestinal juice (final digestion)
   • VILLI absorb nutrients into blood
5. Large intestine: water absorption, waste storage
6. Rectum and anus: excretion

Important Enzymes

• Amylase: starch → maltose (mouth, pancreas)
• Pepsin: proteins → peptides (stomach)
• Trypsin: peptides → amino acids (small intestine)
• Lipase: fats → fatty acids + glycerol (small intestine)

4. RESPIRATION

What is Respiration?

Breakdown of food (mainly glucose) to RELEASE ENERGY for life processes.

Cellular Respiration Equation

Aerobic: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ENERGY (ATP)

Anaerobic (no oxygen): different products

• In muscles: C₆H₁₂O₆ → 2C₃H₆O₃ (lactic acid) + LITTLE energy
• In yeast: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ (ethanol + CO₂) — used in bread, beer

Aerobic vs Anaerobic

• Aerobic: O₂ used. Full breakdown (CO₂ + H₂O). MORE energy.
• Anaerobic: No O₂. Partial breakdown (lactic acid or ethanol). LESS energy.

Human Respiratory System

The chapter describes this passage functionally rather than naming every stop along it:

1. Nostrils: air enters, filtered by fine hairs and mucus
2. Throat: held open by rings of cartilage so it doesn't collapse (commonly called the trachea/windpipe, though the chapter itself doesn't use that word)
3. Passage divides into smaller and smaller tubes inside the lungs (these branches are commonly called bronchi and bronchioles)
4. Alveoli: tiny balloon-like air sacs where gas exchange happens (~80 m² of surface area if spread out)
5. Lungs: contain the alveoli; huge surface area for gas exchange

Gas Exchange

At alveoli:

• O₂ diffuses INTO blood (low concentration in blood, high in alveoli)
• CO₂ diffuses OUT of blood (high in blood, low in alveoli)

Breathing Mechanism

• Inhalation: diaphragm contracts (flattens), ribs move up; chest expands; air in
• Exhalation: diaphragm relaxes (domes up), ribs move down; chest contracts; air out

Respiration in Plants

• Plants RESPIRE 24×7 (like animals)
• Day: photosynthesis dominates (releases O₂)
• Night: respiration only (uses O₂, releases CO₂)
• That's why people advise against sleeping under trees at night.

5. TRANSPORTATION

In Humans (Circulatory System)

Components:

• Heart: pump (4 chambers)
• Blood vessels: arteries (away from heart), veins (toward heart), capillaries (smallest)
• Blood: red cells (oxygen), white cells (immunity), platelets (clotting), plasma

Heart Chambers

• 2 Atria (upper): receive blood
• 2 Ventricles (lower): pump blood

Right side: receives deoxygenated blood from body, sends to lungs Left side: receives oxygenated blood from lungs, sends to body

Double Circulation

Blood passes through heart TWICE in one cycle:

1. Pulmonary circulation: heart → lungs → heart
2. Systemic circulation: heart → body → heart

This ensures EFFICIENT oxygen delivery.

Blood Components

• Plasma (55%): liquid; carries nutrients, hormones, waste
• RBC (Red Blood Cells): contain HAEMOGLOBIN (carries O₂); biconcave; no nucleus
• WBC (White Blood Cells): immunity
• Platelets: clotting (stop bleeding)

Lymph

A clear fluid that drains from tissues back to blood.

• Carries fats (from intestines)
• Cleans tissues
• Part of immune system

Plants: Xylem and Phloem

Xylem:

• Carries WATER + MINERALS from roots to leaves (UPWARD only)
• Tracheids and vessels (dead, hollow tubes)
• Driven by: ROOT PRESSURE + TRANSPIRATION PULL (most important)

Phloem:

• Carries FOOD (mainly sucrose) from leaves to all parts (UP, DOWN, BOTH directions)
• Sieve tubes (alive) and companion cells
• Driven by: TURGOR PRESSURE differences (osmosis)

Transpiration

Loss of water vapour through stomata in leaves.

• Cools the plant
• Creates UPWARD PULL for water in xylem
• Helps mineral transport
• Some water loss is necessary

6. EXCRETION

In Humans

Main organ: KIDNEYS (one pair)

Kidney Structure

• Bean-shaped, fist-sized
• Contains millions of NEPHRONS (functional units)
• Each nephron filters blood

Nephron Function

The chapter describes two main steps, using "the tubule" generically rather than naming its sub-regions (loop of Henle, proximal/distal tubule, collecting duct are standard terms from more detailed treatments, not this chapter's own vocabulary):

1. Filtration: blood capillaries clustered at the cup-shaped Bowman's capsule filter out water, glucose, amino acids, salts and urea
2. Selective reabsorption: as the filtrate flows along the tubule, useful substances (glucose, amino acids, most salts and water) are reabsorbed back into the blood — how much water is reabsorbed depends on the body's excess water and dissolved waste
3. The remaining fluid (urine) passes into the ureter

Urinary System

• 2 kidneys
• 2 ureters (kidney to bladder)
• 1 bladder (storage)
• 1 urethra (out)

Composition of Urine

• 95% water
• 2.5% urea
• 2.5% salts, ions, etc.

Artificial Kidney (Dialysis)

For patients with kidney failure. Machine filters blood like a kidney.

Plant Excretion

• Plants don't have specialised excretory organs
• Excess water via transpiration
• Some waste stored in vacuoles, dropped with leaves (autumn)
• Resins, gums, latex are stored wastes

7. Worked Examples

Example 1: Photosynthesis

Write the equation for photosynthesis.

• 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in presence of sunlight and chlorophyll)

Example 2: Aerobic vs Anaerobic

Compare aerobic and anaerobic respiration.

• Aerobic: O₂ used; CO₂ + H₂O + LOTS energy; e.g., in human cells
• Anaerobic: No O₂; lactic acid (muscles) or ethanol (yeast); LITTLE energy

Example 3: Why Double Circulation?

Why is double circulation important?

• Keeps oxygen-rich and oxygen-poor blood SEPARATE.
• Allows EFFICIENT oxygen delivery throughout body.
• Birds and mammals have it; reptiles/amphibians have partial division.

Example 4: Nephron Steps

What happens in a nephron?

• 1. Filtration (glomerulus)
• 2. Reabsorption (water, glucose)
• 3. Secretion (more waste)
• 4. Excretion (urine)

8. Common Mistakes

1. Confusing inhalation and exhalation

   • INHALE: diaphragm FLATTENS, chest EXPANDS, air IN
   • EXHALE: diaphragm DOMES UP, chest CONTRACTS, air OUT

2. Wrong gas direction

   • O₂ goes INTO blood from alveoli; CO₂ goes OUT of blood.

3. Plants photosynthesise only

   • Plants RESPIRE too (24×7). Photosynthesis only in light.

4. Veins always carry deoxygenated blood

   • GENERALLY YES, EXCEPT pulmonary vein (lungs to heart, oxygenated!).

5. All food gets digested in stomach

   • Most digestion happens in SMALL INTESTINE.

9. Indian Context

Ayurveda

• Ancient Indian medicine emphasises digestion, food
• Charaka Samhita describes anatomy/physiology
• Sushruta Samhita: surgery

Modern Indian Medicine

• AIIMS (multiple centres) world-class
• Indian Heart Hospital network
• Manipal, Fortis, Apollo hospitals
• Indian doctors lead globally

Health Challenges in India

• Heart disease (#1 killer)
• Diabetes (~80 million Indians)
• Kidney disease
• Respiratory issues (air pollution)

10. Conclusion

Life Processes is the HEART of Class 10 Biology:

• Nutrition (autotrophic photosynthesis, holozoic digestion)
• Respiration (aerobic for energy)
• Transportation (heart, blood, xylem, phloem)
• Excretion (kidneys, nephrons)

Master:

• Photosynthesis equation
• Respiratory and circulatory systems
• Kidney structure and function
• Differences in plants vs animals

Practice 20+ problems. This is HIGH-MARK chapter (~10-12 marks).

Every breath, every heartbeat, every digestion — life processes in action.