Life processes are the basic functions that keep organisms alive. AMU asks 3–4 MCQs — focus on photosynthesis, human digestive system, respiration types, heart & double circulation, and nephron structure.
1) What are life processes?
Six essential life processes: Nutrition, Respiration, Transport (Circulation), Excretion, Growth & Reproduction, Response to stimuli.
• Unicellular organisms rely on diffusion (large SA:V ratio).
• Multicellular organisms need specialized organ systems (small SA:V, cells are far from environment, specialization).
• Unicellular organisms rely on diffusion (large SA:V ratio).
• Multicellular organisms need specialized organ systems (small SA:V, cells are far from environment, specialization).
2) Nutrition
| Mode | Definition | Examples |
|---|---|---|
| Autotrophic | Synthesize own food from CO₂ + H₂O using sunlight (photosynthesis) or chemical energy | Green plants, cyanobacteria |
| Heterotrophic | Cannot synthesize food; depend on other organisms | All animals, fungi, most bacteria |
2.1 Photosynthesis
• Equation: 6CO₂ + 12H₂O →(sunlight, chlorophyll)→ C₆H₁₂O₆ + 6O₂ + 6H₂O
• Site: Chloroplasts (in palisade & spongy mesophyll of leaves).
• Needs: Sunlight, Chlorophyll, CO₂, Water.
• Light reaction (grana): Light energy → ATP + NADPH + O₂ (photolysis of water).
• Dark reaction (Calvin cycle) (stroma): CO₂ fixation → glucose (uses ATP & NADPH from light reaction).
• Stomata — pores in leaf epidermis, surrounded by guard cells (regulate opening/closing). CO₂ enters through open stomata; water loss via transpiration.
• Site: Chloroplasts (in palisade & spongy mesophyll of leaves).
• Needs: Sunlight, Chlorophyll, CO₂, Water.
• Light reaction (grana): Light energy → ATP + NADPH + O₂ (photolysis of water).
• Dark reaction (Calvin cycle) (stroma): CO₂ fixation → glucose (uses ATP & NADPH from light reaction).
• Stomata — pores in leaf epidermis, surrounded by guard cells (regulate opening/closing). CO₂ enters through open stomata; water loss via transpiration.
2.2 Heterotrophic nutrition types
| Type | Definition | Example organisms |
|---|---|---|
| Holozoic (Phagotrophic) | Ingest solid/liquid food, digest internally | Humans, Amoeba, Hydra, most animals |
| Saprophytic (Saprotrophic) | Feed on dead/decaying organic matter (extracellular digestion) | Fungi (mushrooms, yeast), some bacteria |
| Parasitic | Live in/on host, derive nutrition at host's expense | Tapeworm, Roundworm, Cuscuta (dodder — plant parasite), Mosquito, Leeches |
2.3 Human digestive system
Alimentary canal: Mouth → Oesophagus → Stomach → Small intestine → Large intestine → Rectum → Anus.
Accessory organs: Salivary glands, Liver, Gall bladder, Pancreas.
Accessory organs: Salivary glands, Liver, Gall bladder, Pancreas.
| Organ | Secretion | Digests | Product |
|---|---|---|---|
| Mouth (Saliva) | Salivary amylase (ptyalin) | Starch → Maltose | Bolus (chewed + moistened food) |
| Stomach | HCl (acidic pH ~1.5–2), Pepsin (pepsinogen), Mucus | Proteins → Peptides | Chyme (semi-fluid) |
| Small intestine | Bile (liver — emulsifies fats), Pancreatic juice (trypsin, lipase, amylase), Intestinal juice (disaccharidases, peptidases) | Carbs → Glucose; Proteins → Amino acids; Fats → Fatty acids + Glycerol | Absorption via villi & microvilli |
| Large intestine | — | Water & electrolyte absorption | Faeces formation |
🔥 AMU PYQ: Bile is produced by:
(A) Pancreas (B) Liver (C) Gall bladder (D) Stomach Ans: B (stored in gall bladder)
(A) Pancreas (B) Liver (C) Gall bladder (D) Stomach Ans: B (stored in gall bladder)
3) Respiration
• Respiration = oxidation of glucose to release ATP (energy).
• Aerobic respiration (with O₂): Glucose → 38 ATP + CO₂ + H₂O.
• Anaerobic respiration (without O₂): Glucose → 2 ATP + Lactic acid (muscles) or Ethanol + CO₂ (yeast).
• Phases of aerobic respiration: Glycolysis (cytoplasm) → Kreb's cycle (mitochondrial matrix) → Electron Transport Chain (inner mitochondrial membrane).
• Aerobic respiration (with O₂): Glucose → 38 ATP + CO₂ + H₂O.
• Anaerobic respiration (without O₂): Glucose → 2 ATP + Lactic acid (muscles) or Ethanol + CO₂ (yeast).
• Phases of aerobic respiration: Glycolysis (cytoplasm) → Kreb's cycle (mitochondrial matrix) → Electron Transport Chain (inner mitochondrial membrane).
3.1 Human respiratory system
Nostrils → Nasal cavity → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli (air sacs).
• Alveoli — site of gas exchange (thin walls, rich capillary network, large surface area).
• Breathing mechanism: Inhalation (diaphragm contracts, rib cage moves up → air enters) → Exhalation (diaphragm relaxes, rib cage moves down → air exits).
• Gas exchange in tissues: O₂ from blood → cells; CO₂ from cells → blood (carried as bicarbonate in plasma, also as carbaminohemoglobin in RBCs).
• Haemoglobin in RBCs transports O₂ (oxyhaemoglobin). CO₂ is mostly transported as bicarbonate (HCO₃⁻).
• Alveoli — site of gas exchange (thin walls, rich capillary network, large surface area).
• Breathing mechanism: Inhalation (diaphragm contracts, rib cage moves up → air enters) → Exhalation (diaphragm relaxes, rib cage moves down → air exits).
• Gas exchange in tissues: O₂ from blood → cells; CO₂ from cells → blood (carried as bicarbonate in plasma, also as carbaminohemoglobin in RBCs).
• Haemoglobin in RBCs transports O₂ (oxyhaemoglobin). CO₂ is mostly transported as bicarbonate (HCO₃⁻).
4) Transportation
4.1 Human circulatory system
Blood components: Plasma (55% — water + proteins) + RBCs (erythrocytes — O₂ transport) + WBCs (leucocytes — immunity) + Platelets (thrombocytes — clotting).
Heart structure: 4 chambers — Right Atrium (RA), Right Ventricle (RV), Left Atrium (LA), Left Ventricle (LV).
• RA receives deoxygenated blood from body → RV → lungs (pulmonary artery).
• LA receives oxygenated blood from lungs → LV → body (aorta).
• Double circulation: Pulmonary (heart → lungs → heart) + Systemic (heart → body → heart).
• Heartbeat: SA node (pacemaker) → AV node → Purkinje fibres. Normal: 72 bpm.
• BP: 120/80 mm Hg (normal). Systolic = contraction; Diastolic = relaxation.
• Pulse: Expansion & contraction of artery wall with each heartbeat.
• RA receives deoxygenated blood from body → RV → lungs (pulmonary artery).
• LA receives oxygenated blood from lungs → LV → body (aorta).
• Double circulation: Pulmonary (heart → lungs → heart) + Systemic (heart → body → heart).
• Heartbeat: SA node (pacemaker) → AV node → Purkinje fibres. Normal: 72 bpm.
• BP: 120/80 mm Hg (normal). Systolic = contraction; Diastolic = relaxation.
• Pulse: Expansion & contraction of artery wall with each heartbeat.
🔥 AMU PYQ: The chamber of the heart that receives oxygenated blood from the lungs is:
(A) Right atrium (B) Right ventricle (C) Left atrium (D) Left ventricle Ans: C
(A) Right atrium (B) Right ventricle (C) Left atrium (D) Left ventricle Ans: C
4.2 Blood vessels
| Vessel | Direction | Wall thickness | Valves? | Pulse felt? |
|---|---|---|---|---|
| Arteries | Away from heart | Thick, muscular, elastic | No | Yes |
| Veins | Toward heart | Thin, less muscular | Yes (prevent backflow) | No |
| Capillaries | Arteries → Veins | One-cell thick | No | No |
4.3 Plant transport
• Xylem — transports water & minerals (root → shoot). Mechanism: Transpiration pull (evaporation from leaves creates suction) + Root pressure (pushes water upward).
• Phloem — transports food (source → sink). Mechanism: Translocation (pressure flow hypothesis — sucrose loaded into sieve tubes at source, water follows → pressure pushes sap to sink).
• Phloem — transports food (source → sink). Mechanism: Translocation (pressure flow hypothesis — sucrose loaded into sieve tubes at source, water follows → pressure pushes sap to sink).
5) Excretion
5.1 Human excretory system
Organs: Kidneys (2) → Ureters (2) → Urinary bladder → Urethra.
• Each kidney has ~1 million nephrons (functional units).
• Nephron structure: Bowman's capsule + Glomerulus (together = Malpighian body) → Proximal Convoluted Tubule (PCT) → Loop of Henle → Distal Convoluted Tubule (DCT) → Collecting Duct.
• Each kidney has ~1 million nephrons (functional units).
• Nephron structure: Bowman's capsule + Glomerulus (together = Malpighian body) → Proximal Convoluted Tubule (PCT) → Loop of Henle → Distal Convoluted Tubule (DCT) → Collecting Duct.
Urine formation (3 steps):
1. Glomerular filtration — Blood filtered in glomerulus (water, glucose, salts, urea pass into Bowman's capsule; proteins & RBCs retained). Filtration pressure = ~60 mm Hg.
2. Reabsorption — Useful substances reabsorbed: glucose (all), amino acids, most water, Na⁺, HCO₃⁻, Cl⁻. PCT reabsorbs ~65% of filtrate. Loop of Henle concentrates urine.
3. Secretion — H⁺, K⁺, NH₃, drugs secreted into tubule (DCT, collecting duct) — helps maintain pH & ion balance.
• ADH (Vasopressin) — increases water reabsorption in collecting duct → concentrated urine. Alcohol inhibits ADH → more dilute urine.
• Dialysis — artificial kidney used when kidneys fail (hemodialysis — blood filtered through machine).
1. Glomerular filtration — Blood filtered in glomerulus (water, glucose, salts, urea pass into Bowman's capsule; proteins & RBCs retained). Filtration pressure = ~60 mm Hg.
2. Reabsorption — Useful substances reabsorbed: glucose (all), amino acids, most water, Na⁺, HCO₃⁻, Cl⁻. PCT reabsorbs ~65% of filtrate. Loop of Henle concentrates urine.
3. Secretion — H⁺, K⁺, NH₃, drugs secreted into tubule (DCT, collecting duct) — helps maintain pH & ion balance.
• ADH (Vasopressin) — increases water reabsorption in collecting duct → concentrated urine. Alcohol inhibits ADH → more dilute urine.
• Dialysis — artificial kidney used when kidneys fail (hemodialysis — blood filtered through machine).
🔥 AMU PYQ: The functional unit of the kidney is:
(A) Neuron (B) Nephron (C) Alveolus (D) Villus Ans: B
(A) Neuron (B) Nephron (C) Alveolus (D) Villus Ans: B
5.2 Plant excretion
• Plants produce waste (O₂ from photosynthesis, CO₂ from respiration, excess water, salts, latex, gums).
• No specialized excretory organs.
• Methods: Stomata (gas exchange), Lenticels (gas exchange through bark), Vacuoles (store waste like alkaloids, tannins, latex), Leaf shedding (waste accumulated in old leaves → dropped), Secretion as resins, gums, essential oils.
• No specialized excretory organs.
• Methods: Stomata (gas exchange), Lenticels (gas exchange through bark), Vacuoles (store waste like alkaloids, tannins, latex), Leaf shedding (waste accumulated in old leaves → dropped), Secretion as resins, gums, essential oils.
6) AMU PYQs — quick revision
Q1. The site of photosynthesis in plants is:
(A) Chloroplast (B) Mitochondria (C) Nucleus (D) Ribosome Ans: A
(A) Chloroplast (B) Mitochondria (C) Nucleus (D) Ribosome Ans: A
Q2. The enzyme in saliva that digests starch is:
(A) Pepsin (B) Trypsin (C) Lipase (D) Salivary amylase Ans: D
(A) Pepsin (B) Trypsin (C) Lipase (D) Salivary amylase Ans: D
Q3. In which organ does complete digestion of food occur?
(A) Stomach (B) Mouth (C) Small intestine (D) Large intestine Ans: C
(A) Stomach (B) Mouth (C) Small intestine (D) Large intestine Ans: C
Q4. The respiratory pigment in humans is:
(A) Chlorophyll (B) Haemoglobin (C) Myoglobin (D) Melanin Ans: B
(A) Chlorophyll (B) Haemoglobin (C) Myoglobin (D) Melanin Ans: B
Q5. During inhalation, the diaphragm:
(A) Relaxes (B) Contracts and moves downwards (C) Moves upward (D) Remains flat Ans: B
(A) Relaxes (B) Contracts and moves downwards (C) Moves upward (D) Remains flat Ans: B
Q6. The blood vessel that carries deoxygenated blood from heart to lungs is:
(A) Aorta (B) Pulmonary artery (C) Pulmonary vein (D) Vena cava Ans: B
(A) Aorta (B) Pulmonary artery (C) Pulmonary vein (D) Vena cava Ans: B
Q7. The process by which plants lose water vapour through leaves is called:
(A) Transpiration (B) Translocation (C) Respiration (D) Guttation Ans: A
(A) Transpiration (B) Translocation (C) Respiration (D) Guttation Ans: A
Q8. Which of the following is not a life process?
(A) Nutrition (B) Respiration (C) Transpiration (D) Excretion Ans: C (Transpiration is a plant process, not a fundamental life process)
(A) Nutrition (B) Respiration (C) Transpiration (D) Excretion Ans: C (Transpiration is a plant process, not a fundamental life process)
Q9. The hormone that increases water reabsorption in the kidney is:
(A) ADH (B) Aldosterone (C) Insulin (D) Thyroxine Ans: A
(A) ADH (B) Aldosterone (C) Insulin (D) Thyroxine Ans: A
Q10. The part of the nephron responsible for maximum reabsorption is:
(A) Bowman's capsule (B) PCT (C) Loop of Henle (D) DCT Ans: B (PCT — ~65% of filtrate reabsorbed)
(A) Bowman's capsule (B) PCT (C) Loop of Henle (D) DCT Ans: B (PCT — ~65% of filtrate reabsorbed)
Q11. Which of the following is NOT a component of blood?
(A) Plasma (B) RBC (C) WBC (D) Lymph Ans: D (Lymph is a separate fluid — tissue fluid, not a component of blood)
(A) Plasma (B) RBC (C) WBC (D) Lymph Ans: D (Lymph is a separate fluid — tissue fluid, not a component of blood)
Q12. The normal blood pressure in a healthy adult is:
(A) 80/120 (B) 120/80 (C) 140/90 (D) 90/140 Ans: B
(A) 80/120 (B) 120/80 (C) 140/90 (D) 90/140 Ans: B
Q13. Stomata help in:
(A) Gas exchange only (B) Transpiration only (C) Both gas exchange and transpiration (D) Photosynthesis only Ans: C
(A) Gas exchange only (B) Transpiration only (C) Both gas exchange and transpiration (D) Photosynthesis only Ans: C
Q14. The energy currency of the cell is:
(A) Glucose (B) ATP (C) NADPH (D) FADH₂ Ans: B
(A) Glucose (B) ATP (C) NADPH (D) FADH₂ Ans: B
📝 Pro Tip for AMU: Know the 5 life processes. Photosynthesis — light (grana, ATP/NADPH/O₂) + dark (stroma, Calvin cycle, glucose). Digestive system: Saliva (mouth, starch), HCl/Pepsin (stomach, proteins), Bile (liver, fat emulsification), Trypsin/Lipase/Amylase (pancreas). Respiration: Aerobic (38 ATP) vs Anaerobic (2 ATP). Heart: 4 chambers, double circulation. Nephron: filtration (glomerulus → Bowman's), reabsorption (PCT), concentration (Loop of Henle), ADH (increases water reabsorption).