Life processes are the essential biological activities that organisms carry out to sustain life. In Class 10’s Chapter 5 (Life Processes), focus is on four major processes — nutrition, respiration, transport, and excretion — and how they operate in plants and animals. Understanding the steps, organ systems involved, and the underlying chemical equations is crucial for board exams.

Why this chapter matters for exams

• Direct questions on definitions and differences (autotrophic vs heterotrophic, aerobic vs anaerobic).
• Diagram‑based marks — labelled leaf sections, chloroplast, human kidney, heart and circulatory diagrams.
• Application and case‑based questions testing real-life meaning of processes (e.g., how exercise affects breathing).

Autotrophic Nutrition (Photosynthesis)

In autotrophic organisms (mainly green plants), food is synthesised from carbon dioxide and water using sunlight. The overall equation:

6 CO₂ + 6 H₂O —(light, chlorophyll)→ C₆H₁₂O₆ + 6 O₂

Key points:

• Occurs mainly in leaf chloroplasts — palisade mesophyll cells are primary sites.
• Two stages: Light reactions (photolysis of water, ATP, NADPH formation) and Dark reactions/Calvin cycle (CO₂ fixation to carbohydrates).
• Factors affecting photosynthesis: light intensity, CO₂ concentration, temperature, chlorophyll amount.

Heterotrophic Nutrition

Heterotrophs (animals, fungi some bacteria) obtain food by consuming other organisms. Types include holozoic (ingestion & digestion), saprophytic (decomposers) and parasitic nutrition.

• Holozoic: ingestion → digestion → absorption → assimilation → egestion. (Example: human digestion)
• Saprophytic: digestion externally by enzymes (fungi, some bacteria).
• Parasitic: organism lives on/in host and derives nutrition, often causing harm.

Respiration is the process where food is oxidised to release energy for cellular activities. Distinguish clearly between breathing (mechanical intake and expulsion of air) and cellular respiration (biochemical breakdown of food).

Aerobic respiration (complete oxidation)

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + energy (≈ 38 ATP in prokaryotes/eukaryote variations)

• Occurs in presence of oxygen — site: mitochondria (matrix and inner membrane)
• Stages: Glycolysis (cytosol), Krebs cycle (mitochondrial matrix), Electron Transport Chain (inner membrane)

Anaerobic respiration (partial oxidation)

• Occurs without oxygen — yields less energy.
• Examples: In yeast → fermentation → ethanol + CO₂; In animals (muscle) → lactic acid production.
• Equation (muscle): Glucose → lactic acid + small ATP; (yeast) Glucose → ethanol + CO₂ + ATP.

Transport in Plants

• Xylem: transports water and minerals upward from roots to shoots — transpiration pull, cohesion, adhesion mechanisms.
• Phloem: transports organic food (sugars) from leaves to storage organs — translocation via pressure flow hypothesis.
• Root pressure: some upward push from roots during night/low transpiration.

Transport in Animals

• Human circulatory system: closed double circulation — pulmonary (to/from lungs) and systemic (to/from body).
• Heart: atria receive blood, ventricles pump; valves prevent backflow. Right side: deoxygenated blood to lungs; left side: oxygenated blood to body.
• Blood composition: plasma (liquid), RBCs (carry O₂ via haemoglobin), WBCs (immune), platelets (clotting).
• Important terms: blood pressure, pulse, lymphatic system role in tissue fluid return.

Excretion removes metabolic waste from the body. In humans, primary excretory organs are the kidneys.

Kidney Structure & Function

• Nephron: functional unit (glomerulus + Bowman's capsule, proximal tubule, loop of Henle, distal tubule, collecting duct).
• Filtration: blood is filtered at glomerulus producing filtrate (water, salts, urea, glucose — proteins and cells largely retained).
• Reabsorption: useful substances (glucose, amino acids, most water, ions) reabsorbed in tubules.
• Secretion: additional waste ions secreted into tubule from blood.
• Urine: concentrated waste (mainly urea, excess salts, water) collected in collecting ducts and passed to ureter → bladder.

Breathing (ventilation) is the mechanical process; exchange of gases occurs at alveoli by diffusion.

• Inhalation: diaphragm contracts and flattens, external intercostals raise ribs increasing thoracic volume; air flows in.
• Exhalation: diaphragm relaxes, intercostal muscles relax reducing volume; air expelled.
• Alveoli: thin-walled, numerous capillaries — large surface area for diffusion of O₂ into blood and CO₂ out of blood.

Breathing rate and exercise

During exercise oxygen demand rises: breathing rate and depth increase, heart pumps faster — describe this chain in causa-effect terms in answers.

Very Short (1 mark)

1. Define photosynthesis. Ans: Process by which green plants synthesize food from CO₂ and H₂O using sunlight and chlorophyll producing glucose and O₂.
2. What is transpiration? Ans: Loss of water vapour from plant surfaces, mainly leaves, through stomata.

Short Answer (3–4 marks)

1. Explain the role of stomata in plants. Ans:
   • Stomata are pores on leaf surface for gas exchange (CO₂ in for photosynthesis, O₂ out), and transpiration regulates water loss and cooling.
   • Guard cells control opening/closing based on turgor pressure.
2. Describe the structure of a nephron. Ans:
   • Bowman’s capsule with glomerulus (filtration). Proximal tubule (reabsorption), loop of Henle (concentrates urine), distal tubule (selective reabsorption/secretion), collecting duct (collects urine).

Long Answer (5 marks)

1. Explain aerobic respiration with stages and site. Ans:
   • Glycolysis (cytosol) — glucose → pyruvate + 2 ATP. Pyruvate enters mitochondria.
   • Krebs cycle (matrix) — acetyl-CoA oxidised producing NADH, FADH₂ and CO₂.
   • Electron Transport Chain (inner membrane) — oxidative phosphorylation yields large ATP and water (O₂ final electron acceptor).

Life Processes — Quick Revision Sheet (Class 10, Chapter 5)

Nutrition:
• Autotrophic: Photosynthesis: 6CO2 + 6H2O —(light, chlorophyll)→ C6H12O6 + 6O2
• Heterotrophic: ingestion → digestion → absorption → assimilation → egestion

Respiration:
• Aerobic: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (mitochondria)
• Anaerobic: Glucose → ethanol + CO2 (yeast) or → lactic acid (muscle)

Transport:
• Plants: Xylem (water up), Phloem (translocation of sugars)
• Animals: Heart (4 chambers), double circulation, blood components (RBC/WBC/platelets/plasma)

Excretion:
• Kidney → nephron (filtration at glomerulus, reabsorption, secretion), urine formation

Breathing:
• Inhalation: diaphragm contracts, chest volume increases
• Exhalation: diaphragm relaxes, chest volume decreases

Exam tips: Draw diagrams; write definitions first; use labelled steps; practice previous year questions.
        

• Start answers with a definition or direct statement to earn the first mark quickly.
• For process‑based questions (photosynthesis, respiration, excretion), write steps in bullet points and include where the process occurs.
• Labelled diagrams earn marks — practise neat, labelled drawings for leaf (stomata), heart, nephron and chloroplast basics.
• Memorise key equations and differences (aerobic vs anaerobic, autotroph vs heterotroph).
• Time management: allocate answer time by marks — 5 marks ≈ 8–10 minutes in practice tests.