Nutrition, respiration, transportation, excretion in plants and animals
All living beings perform certain basic functions essential for life, called life processes. These include:
Nutrition → Respiration → Transportation → Excretion
Without these, an organism cannot survive. They require energy (obtained from nutrition).
Nutrition is the process by which organisms obtain and use food/energy to sustain life, growth, and repair.
Autotrophs: Make their own food (plants, algae, some bacteria)
Heterotrophs: Cannot make own food; depend on others (animals, fungi, most bacteria)
6CO₂ + 6H₂O + Sunlight → C₆H₁₂O₆ + 6O₂
Carbon dioxide + Water + Light Energy → Glucose + Oxygen
• Sunlight — source of energy
• Chlorophyll — green pigment that absorbs light (found in chloroplasts)
• CO₂ — enters through stomata in leaves
• Water — absorbed through roots, transported to leaves
Think of a leaf as a kitchen. The sun provides energy (like electricity). CO₂ and water are the ingredients. Chlorophyll is the chef who converts these into food (glucose). Oxygen is the "exhaust" let out as a by-product — and we breathe it!
1. Light Reactions (in thylakoids):
• Chlorophyll absorbs light → splits water into H⁺, e⁻, and O₂ (photolysis)
• O₂ is released as by-product
• ATP and NADPH (energy carriers) are produced
2. Dark Reactions / Calvin Cycle (in stroma):
• CO₂ is fixed using ATP and NADPH → Glucose is synthesised
Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus
Aerobic Respiration (with oxygen): C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP (energy)
Anaerobic Respiration (without oxygen):
In yeast: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + 2 ATP (fermentation)
In muscles (during intense exercise): C₆H₁₂O₆ → 2C₃H₆O₃ (lactic acid) + 2 ATP
Lactic acid buildup causes muscle cramps and fatigue
Breathing: Physical process — inhaling/exhaling air (mechanical)
Respiration: Chemical process — oxidation of glucose to release energy (at cellular level)
Breathing brings oxygen needed for cellular respiration. They are NOT the same!
Xylem: Transports water and mineral salts from roots to leaves (upward only)
Mechanism: Transpiration pull (evaporation from leaves creates suction)
Phloem: Transports food (glucose, sucrose) from leaves to other parts (bidirectional)
Mechanism: Translocation — driven by pressure
Human heart has 4 chambers: 2 atria (upper) + 2 ventricles (lower)
Pulmonary circulation: Heart → Lungs → Heart (deoxygenated to oxygenated)
Systemic circulation: Heart → Body → Heart (oxygenated blood to body)
This double circulation ensures oxygenated and deoxygenated blood don't mix → more efficient!
Kidneys filter blood using millions of units called nephrons.
Step 1 — Filtration: Blood enters Bowman's capsule, all small molecules (water, glucose, urea, salts) filtered out
Step 2 — Selective Reabsorption: Useful substances (glucose, amino acids, most water, salts) reabsorbed back into blood
Step 3 — Secretion: Some extra waste substances added from blood to filtrate
Product: Urine = water + urea + salts + excess substances → stored in bladder → eliminated via urethra