Life Processes – Class 10 Biology Chapter 5

Life Processes

Life processes are the basic functions performed by living organisms to maintain life. The key life processes are nutrition, respiration, transportation, and excretion.

Nutrition

Nutrition is the process of intake and utilisation of food for energy, growth, and repair.

Autotrophic Nutrition (Plants)

Green plants make their own food through photosynthesis:

6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂

Requirements: sunlight, chlorophyll (in chloroplasts), CO₂ (from stomata), and water (from roots). The process occurs mainly in leaves.

Heterotrophic Nutrition (Animals)

Organisms that depend on other organisms for food. In humans, digestion occurs in the alimentary canal:

1. Mouth: Teeth crush food; salivary amylase converts starch → maltose.
2. Stomach: HCl activates pepsin which digests proteins → peptones.
3. Small Intestine: Bile (from liver) emulsifies fats; pancreatic enzymes (trypsin, lipase, amylase) complete digestion. Villi absorb nutrients into blood.
4. Large Intestine: Absorbs water; undigested waste is expelled via anus.

Respiration

Respiration is the breakdown of glucose to release energy (ATP).

Aerobic (with O₂):

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)

Anaerobic (without O₂):

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + Energy (in yeast — fermentation)

C₆H₁₂O₆ → 2C₃H₆O₃ + Energy (in muscles — lactic acid)

Transportation

In Humans

• Heart: 4-chambered (2 atria + 2 ventricles). Double circulation: pulmonary (lungs) + systemic (body).
• Blood: Plasma (55%) + RBCs + WBCs + Platelets. Haemoglobin in RBCs carries O₂.
• Arteries carry oxygenated blood (except pulmonary artery); Veins carry deoxygenated blood (except pulmonary vein). Capillaries enable exchange.

In Plants

• Xylem: Transports water and minerals upward (from roots to leaves) via transpiration pull.
• Phloem: Transports food (sucrose) from leaves to all parts (translocation).

Excretion

Removal of metabolic waste products from the body.

• Kidneys filter blood to form urine. Each kidney contains ~1 million nephrons (the functional unit). Filtration → reabsorption → secretion → urine formation.
• Plants: Store waste in vacuoles, old leaves, bark; remove O₂ and CO₂ through stomata.

Reference: NCERT Science Textbook for Class 10 – Chapter 5; Trueman's Biology; Pradeep's Biology.