BharatNotes Life processes — nutrition, respiration, transportation, and excretion — are the fundamental biological activities that keep organisms alive. For UPSC, this chapter bridges biology and health policy: understanding how the heart works underpins cardiovascular disease (India's leading cause of death), how kidneys function is essential for understanding dialysis access (a major health equity issue), and how the digestive system works explains malabsorption and malnutrition. GS2 (Health) and GS3 (Science & Tech) questions on NCDs, PMJAY, and healthcare infrastructure all connect back to the physiology in this chapter.
PART 1 — Quick Reference Tables
Nutrition: Autotrophic vs Heterotrophic
| Type | Definition | Mode | Examples |
|---|---|---|---|
| Autotrophic | Makes own food from inorganic sources | Photosynthesis (mainly), Chemosynthesis | Green plants, Algae, Cyanobacteria, Nitrifying bacteria |
| Holozoic | Ingests solid food; internal digestion | Ingestion → Digestion → Absorption → Assimilation → Egestion | Humans, Most animals |
| Saprophytic | Absorbs nutrients from dead organic matter | Secretes enzymes externally; absorbs products | Fungi, some bacteria |
| Parasitic | Obtains nutrition from living host | Attachment to host | Tapeworm, Plasmodium, Mistletoe |
Photosynthesis — Simplified Overview
| Stage | Location | Inputs | Outputs |
|---|---|---|---|
| Light reactions (photolysis) | Thylakoid membranes | Light, H2O, ADP, NADP+ | ATP, NADPH, O2 (released), electrons |
| Dark reactions (Calvin cycle) | Stroma | CO2, ATP, NADPH | Glucose (C6H12O6), ADP, NADP+ |
Overall equation: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2
Human Digestive System — Organs, Secretions, Functions
| Organ | Secretion/Enzyme | Action |
|---|---|---|
| Mouth | Salivary amylase (ptyalin) | Breaks starch → maltose |
| Stomach | HCl, pepsin, mucus | HCl kills bacteria, activates pepsin; pepsin digests proteins → peptides; mucus protects stomach wall |
| Small intestine — duodenum | Bile (from liver), pancreatic juice (amylase, trypsin, lipase) | Bile emulsifies fats; pancreatic enzymes digest carbs, proteins, fats |
| Small intestine — ileum | Intestinal juice (maltase, sucrase, lactase, peptidase) | Final digestion; villi absorb nutrients |
| Large intestine | Mucus, water absorption | Absorbs water; forms faeces; houses gut bacteria |
Aerobic vs Anaerobic Respiration
| Feature | Aerobic | Anaerobic |
|---|---|---|
| Oxygen required | Yes | No |
| Location | Cytoplasm (glycolysis) + Mitochondria | Cytoplasm only |
| End products | CO2 + H2O | Lactic acid (animals/muscle) OR Ethanol + CO2 (yeast) |
| ATP yield | 36–38 ATP per glucose | 2 ATP per glucose |
| Duration | Sustained | Short bursts only |
| Example | Normal cellular respiration | Muscle during intense exercise; fermentation |
Human Heart — Chambers and Blood Flow
| Structure | Side | Function |
|---|---|---|
| Right atrium | Right | Receives deoxygenated blood from body (via superior/inferior vena cava) |
| Right ventricle | Right | Pumps deoxygenated blood to lungs (via pulmonary artery) |
| Left atrium | Left | Receives oxygenated blood from lungs (via pulmonary veins) |
| Left ventricle | Left | Pumps oxygenated blood to body (via aorta) — thickest walls |
| Tricuspid valve | Between right atrium & right ventricle | Prevents backflow |
| Bicuspid (mitral) valve | Between left atrium & left ventricle | Prevents backflow |
| Pulmonary semilunar valve | Right ventricle outlet | Prevents backflow into right ventricle |
| Aortic semilunar valve | Left ventricle outlet | Prevents backflow into left ventricle |
PART 2 — Detailed Notes
1. Nutrition — Getting Energy and Raw Materials
Photosynthesis is the process by which chlorophyll-containing organisms convert light energy to chemical energy (glucose):
The process occurs in two stages:
- Light-dependent reactions: In the thylakoid membranes. Light energy splits water molecules (photolysis) → releases oxygen, generates ATP and NADPH. Photosystems I and II capture light.
- Light-independent reactions (Calvin cycle): In the stroma. ATP and NADPH are used to fix CO2 into glucose. Key enzyme: RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) — the most abundant enzyme on Earth.
Factors affecting photosynthesis: light intensity, CO2 concentration, temperature, water availability, chlorophyll content.
[Additional] C3 vs C4 Plants — Climate Change and Food Security (GS3):
The standard Calvin cycle (C3 pathway) fixes CO2 into a 3-carbon compound (3-phosphoglycerate). A problem: RuBisCO can also bind O2 instead of CO2 (photorespiration) — wasting energy, especially in hot conditions.
C4 pathway (evolved independently in ~60 plant lineages): CO2 is first fixed into a 4-carbon compound (oxaloacetate) in mesophyll cells, then concentrated and released around RuBisCO in bundle sheath cells. This concentrating mechanism suppresses photorespiration.
| Feature | C3 Plants | C4 Plants |
|---|---|---|
| First product of CO2 fixation | 3-phosphoglycerate (3C) | Oxaloacetate (4C) |
| Key enzyme | RuBisCO (in mesophyll) | PEP carboxylase (+ RuBisCO in bundle sheath) |
| Water use efficiency | Lower | ~40% higher |
| Temperature optimum | Cooler (15–25°C) | Warmer (30–40°C) |
| Photorespiration | Significant (reduces yield up to 40%) | Negligible |
| Crop examples | Wheat, rice, potato, soybean, most vegetables | Maize (corn), sugarcane, sorghum, millets (bajra, jowar), amaranth |
UPSC GS3 relevance:
- Climate change impact on agriculture: Rising temperatures favour C4 crops (maize, millets, sugarcane) but disadvantage C3 crops (wheat, rice) — a key concern for India's food security since wheat and rice are the staple crops (PDS, MSP system)
- Millets promotion (Shree Anna): India declared 2023 the International Year of Millets (with UN support); millets are C4 crops — drought-tolerant, heat-tolerant, less water-intensive — promoted as climate-smart crops
- Genetic engineering: Attempts to introduce C4 pathway into rice (C4 Rice Project, IRRI) to increase yield and water use efficiency — one of the most ambitious crop biotechnology projects
- CAM plants (a third pathway: Crassulacean Acid Metabolism): Open stomata at night, fix CO2 at night, photosynthesize in daytime — maximally water-efficient; cacti, succulents, agave (used for ethanol). Relevant to arid zone agriculture.
Photorespiration and its agricultural cost: In C3 crops (wheat, rice), photorespiration under warm conditions can reduce potential yield by 20–40%. This is why wheat production declines in India during unusually hot Rabi seasons (as observed in 2022 when a March heatwave cut wheat output, triggering an export ban).
Human Digestion:
The digestive system converts complex food molecules into absorbable nutrients. The alimentary canal runs from mouth to anus (~9 metres in adults).
Absorption in the small intestine: The inner surface of the small intestine is folded into finger-like projections called villi (singular: villus). Each villus is covered with microvilli (brush border), enormously increasing surface area. Inside each villus is a capillary network (absorbs glucose and amino acids → bloodstream) and a lacteal (lymph vessel — absorbs fatty acids and glycerol as chylomicrons).
Digestion summary:
- Carbohydrates → glucose, fructose, galactose (monosaccharides)
- Proteins → amino acids
- Fats → fatty acids + glycerol
- Nucleic acids → nucleotides
2. Respiration — Releasing Energy
Glycolysis (occurs in cytoplasm, common to both aerobic and anaerobic): Glucose (6C) → 2 Pyruvate (3C) → net gain of 2 ATP, 2 NADH
Aerobic continuation (in mitochondria):
- Pyruvate → Acetyl CoA (link reaction)
- Krebs cycle (citric acid cycle) — 8 steps in mitochondrial matrix; produces CO2, NADH, FADH2
- Oxidative phosphorylation (electron transport chain in inner mitochondrial membrane) — uses NADH and FADH2 to drive ATP synthase; produces ~34 ATP and water
Anaerobic pathways:
- In yeast (fermentation): Pyruvate → Ethanol + CO2 (basis of brewing, bread-making)
- In human muscle during intense exercise: Pyruvate → Lactic acid (causes muscle fatigue and burning sensation)
Human Respiratory System:
- Nasal cavity: Filters, warms, and humidifies air; olfactory receptors
- Pharynx → Larynx (voice box) → Trachea → Bronchi → Bronchioles → Alveoli
- Alveoli: Tiny air sacs with extremely thin walls (one cell layer), surrounded by capillaries. Site of gas exchange — O2 diffuses in; CO2 diffuses out. About 700 million alveoli in human lungs — surface area ~70 m2 (half a tennis court).
- Diaphragm and intercostal muscles contract during inhalation (increases thoracic volume, decreases pressure, air rushes in) and relax during exhalation.
Lung volumes:
- Tidal volume: ~500 mL (normal breath)
- Vital capacity: ~4,500 mL (maximum in+out)
- Residual volume: ~1,200 mL (always remains in lungs)
3. Transportation — Moving Substances Around
Human Circulatory System:
The heart is a double pump. The pulmonary circulation (right side) sends deoxygenated blood to lungs; the systemic circulation (left side) sends oxygenated blood to the body — this is double circulation.
Cardiac cycle:
- Diastole: Heart muscle relaxes; ventricles fill with blood from atria
- Atrial systole: Atria contract; blood pushed into ventricles
- Ventricular systole: Ventricles contract; blood pumped to lungs (right) and body (left)
Blood pressure: Force exerted by blood on vessel walls. Normal: 120/80 mmHg (systolic/diastolic). Hypertension (>140/90 mmHg) is a major risk factor for stroke, heart attack, kidney failure. India has an estimated 220 million hypertensives — one of the highest burdens globally.
Blood composition:
- Plasma (55%): Mostly water; carries dissolved proteins (albumin, fibrinogen, immunoglobulins), nutrients, hormones, CO2
- RBCs (erythrocytes): Contain haemoglobin (iron-containing protein); carry O2. No nucleus in mature human RBCs. Life span ~120 days.
- WBCs (leukocytes): Immune cells. Five types: neutrophils, eosinophils, basophils, lymphocytes, monocytes.
- Platelets (thrombocytes): Cell fragments; involved in blood clotting (coagulation cascade)
Lymphatic system: Network of vessels carrying lymph (tissue fluid that has entered lymph vessels). Lymph nodes filter pathogens. Lymph eventually returns to blood circulation via the thoracic duct.
Plant Transport:
- Xylem transports water and minerals upward. Driving force: transpiration pull — water evaporates from leaf stomata, creating tension that pulls water up.
- Phloem transports food (mainly sucrose) from leaves to other parts. Process: translocation driven by active loading of sugar at source (leaves) and unloading at sink (roots, fruits, seeds). Requires ATP.
4. Excretion — Removing Waste
Excretion is the removal of metabolic waste products. In humans, the main excretory organs are:
- Kidneys — excrete nitrogenous waste (urea), regulate water and salt balance
- Lungs — excrete CO2 and water vapour
- Skin — excretes small amounts of salts, urea, and water via sweat
- Liver — converts amino acids to urea (urea cycle); excretes bile pigments (bilirubin from broken-down haemoglobin)
Kidney structure and function:
The kidney contains about 1 million nephrons — the functional unit.
Nephron structure:
- Bowman's capsule — cup-shaped structure enclosing the glomerulus (knot of capillaries)
- Glomerulus — filtration under pressure; small molecules (water, glucose, urea, salts) pass through into Bowman's capsule → glomerular filtrate
- Proximal convoluted tubule (PCT) — reabsorbs glucose, amino acids, water, Na+
- Loop of Henle — concentrates the filtrate; descending limb is water-permeable; ascending limb is salt-permeable; creates concentration gradient in medulla
- Distal convoluted tubule (DCT) — further salt and water adjustment; regulated by hormones (ADH, aldosterone)
- Collecting duct — final concentration of urine; ADH (antidiuretic hormone) controls water reabsorption here
The filtrate becomes progressively concentrated as it passes through the nephron. Final urine is about 60 times more concentrated than blood plasma.
Dialysis: When kidneys fail, dialysis removes waste from blood artificially. Haemodialysis: Blood is pumped out, passed over a dialysis membrane, and returned. Peritoneal dialysis: Uses the peritoneum (abdominal membrane) as a natural filter.
🎯 UPSC Connect: Dialysis and Healthcare Access
India has approximately 220,000 dialysis patients, but only about 35% have access to regular dialysis — due to cost, distance, and infrastructure gaps. One haemodialysis session costs Rs 1,500–3,000; patients typically need 3 sessions per week. PM National Dialysis Programme under NHM provides free dialysis at district hospitals. PMJAY (Ayushman Bharat) covers dialysis-related costs.
Kidney transplantation (preferred over dialysis — better quality of life, less costly long-term) is governed by THOTA 1994. India has a severe shortage of donor kidneys. NOTTO (National Organ and Tissue Transplant Organisation) manages the national organ donation registry.
[Additional] India's Organ Donation Crisis — NOTTO and the Cadaveric Donor Gap (GS2 — Health / GS3 — Science & Tech):
The scale of the gap — 2024 NOTTO data:
- Total organ transplants in India (2024): 18,911 — a record high; fourfold increase from ~4,990 in 2013
- Deceased-donor transplants: Only 3,236 out of 18,911 (17%) came from deceased donors
- Deceased donors in 2024: 1,128 — India crossed 1,000 deceased donors in a single year for the first time only in 2023
- India's donation rate: ~0.81 per million population (pmp) — one of the lowest in the world
- Global benchmark: Spain leads at ~48 pmp; US ~36 pmp; India is 15–60 times lower
Why the gap is catastrophic for kidney patients:
- Patients waiting for a kidney transplant (registered with NOTTO): ~60,590 (as of 2024-25 data; some estimates cite 150,000 total)
- India's chronic dialysis patients: ~175,000–220,000
- Only ~1 in 30 people waiting for a kidney receives one — the rest remain on dialysis indefinitely or die waiting
- One haemodialysis session costs Rs 1,500–3,000; three sessions per week = Rs 18,000–36,000/month — catastrophic out-of-pocket expenditure
State-level exceptions — what works:
- Tamil Nadu: 1.8 pmp — highest in India; 268 deceased donors in 2024 (highest among all states); 96 heart transplants
- Kerala: 1.03 pmp — four times the national average; strong KNOS (Kerala Network for Organ Sharing) infrastructure
- Reason for southern success: proactive state policies, dedicated transplant coordinators in hospitals, public awareness campaigns, and efficient hospital-based donation systems
Legal framework — THOTA 1994 and key reforms:
- Transplantation of Human Organs and Tissues Act (THOTA), 1994: Central law governing removal, storage, and transplantation of human organs; prohibits commercial dealing in organs
- 2023 amendments: Upper age limit of 65 years for deceased-donor organ recipients removed; domicile restriction removed — patients can register on NOTTO waiting list from any state, not just their home state
- 2025 amendment rules: Mandatory clinical specular microscope requirement for corneal transplant centres removed — easing access to corneal transplantation in smaller and rural hospitals
- NOTTO (National Organ and Tissue Transplant Organisation): Under MoHFW; manages national registry, allocates organs, coordinates ROTTO (Regional) and SOTTO (State) networks
Campaigns and awareness (2025):
- "Angdaan Jan Jagrukta Abhiyaan": Pan-government awareness campaign organised through all Central Ministries, States, medical colleges, NGOs
- 15th Indian Organ Donation Day (IODD): Held 2 August 2025 by NOTTO — honours donor families, celebrates recipients, promotes awareness
- 2025 milestone: Nearly 20,000 transplants, with over 1,200 deceased-donor families in 2025 — each donor now averages multiple organs (multi-organ donation norm)
UPSC Mains connection — why cadaveric donation is low in India:
- Lack of brain-death certification: Many hospitals lack trained neurologists and ICU infrastructure to certify brain death — prerequisite for deceased donation
- Family consent barriers: Cultural and religious hesitation; grief counselling infrastructure absent
- Transplant coordinator shortage: Tamil Nadu's success attributed to dedicated coordinators; absent in most states
- Geographic concentration: Transplant centres concentrated in metros; organ viability time (kidneys: 24–36 hours; heart: 4–6 hours) makes distribution from distant donors impossible
- Registration gap: Low public awareness of organ pledge/registration — NOTTO ABDM portal exists but uptake is limited
Prelims trap: NOTTO is under Ministry of Health and Family Welfare — not Ministry of Science & Technology. Deceased donation requires brain death certification (not cardiac death) — a specific medical and legal criterion under THOTA.
Excretion in plants:
- CO2 released during respiration, O2 released during photosynthesis — both escape through stomata and lenticels
- Excess water eliminated through transpiration (stomata) and guttation (special pores called hydathodes at leaf margins — occurs when water pressure is high and transpiration is low, typically at night)
- Some plants excrete waste into old leaves that are then shed (autumn leaf fall)
- Others deposit waste in vacuoles, bark, or as plant-insoluble crystals (calcium oxalate in taro leaves)
5. [Additional] Blood Groups and Transfusion — ABO System
Blood groups are determined by antigens (glycoproteins) on the surface of red blood cells and corresponding antibodies in plasma. The ABO system (discovered by Karl Landsteiner, 1901; Nobel Prize 1930):
| Blood Group | Antigen on RBC | Antibody in Plasma | Can donate to | Can receive from |
|---|---|---|---|---|
| A | A antigen | Anti-B antibody | A, AB | A, O |
| B | B antigen | Anti-A antibody | B, AB | B, O |
| AB | A + B antigens | None | AB only | All groups (Universal Recipient) |
| O | None | Anti-A + Anti-B | All groups (Universal Donor) | O only |
Rh factor: A separate antigen (D antigen). Rh+ = present; Rh− = absent. Critical in pregnancy: Rh− mother carrying Rh+ foetus may develop anti-Rh antibodies that attack foetal RBCs in subsequent pregnancies (haemolytic disease of the newborn / erythroblastosis foetalis). Prevented by anti-D immunoglobulin within 72 hours of first delivery.
Blood transfusion compatibility: Mismatched transfusion triggers agglutination (clumping of RBCs by antibodies) — a life-threatening haemolytic reaction; cross-matching before transfusion is mandatory.
[Additional] India's Blood Transfusion System (GS2 — Health):
India's annual blood requirement: ~14.6 million units. Collection in 2024-25: ~14.6 million units (15% rise over previous year). 70% from voluntary, non-remunerated donors — target is 100% voluntary (WHO standard).
National Blood Transfusion Council (NBTC): Constituted 1996 under MoHFW/NACO; apex body for national standards. Blood safety is linked to HIV prevention — HIV transmitted through unscreened blood is a historical crisis that drove blood bank regulation.
Key gaps: A 2024 geospatial analysis found ~60 districts in 8 northern states with no licensed blood bank; 80% of PHCs have no blood storage facility. Rural trauma victims and women with postpartum haemorrhage (PPH — leading cause of maternal death) face critical shortages.
Blood components: Whole blood is separated into packed RBCs, platelets (dengue/chemotherapy), fresh frozen plasma (FFP, clotting disorders), cryoprecipitate (haemophilia A). Component therapy maximises one unit's benefit for multiple patients.
Prelims trap: O negative (O−) is the true universal donor (no ABO or Rh antigen) — used in emergencies before blood type is known. O positive can donate to all Rh+ groups but NOT to Rh− patients.
6. [Additional] Anaemia in India — Iron Deficiency and Haemoglobin
Haemoglobin (Hb) is the iron-containing protein inside red blood cells (RBCs) that binds O2 in the lungs and releases it in tissues. Each haemoglobin molecule contains four haem groups, each with one iron (Fe2+) atom — allowing one RBC to carry ~250 million O2 molecules. When iron availability falls, the body cannot synthesise adequate haemoglobin, RBCs become pale and small (microcytic hypochromic anaemia), and oxygen-carrying capacity of blood collapses — this is iron deficiency anaemia (IDA), the most prevalent nutritional deficiency globally and in India.
WHO diagnosis thresholds for anaemia (haemoglobin below):
| Population group | Hb threshold (g/dL) |
|---|---|
| Children 6–59 months | < 11.0 |
| Children 5–11 years | < 11.5 |
| Children 12–14 years | < 12.0 |
| Non-pregnant women (15–49 years) | < 12.0 |
| Pregnant women | < 11.0 |
| Men (>15 years) | < 13.0 |
[Additional] India's Anaemia Crisis — Scale, Causes, and Policy (GS2 — Health / Nutrition):
NFHS-5 (2019–21) — the alarming picture:
- Children (6–59 months): 67.1% anaemic — up from 59% in NFHS-4 (2015–16); an increase of 8.1 percentage points
- Women of reproductive age (15–49 years): 57% anaemic — up from 53% in NFHS-4
- States worst affected for children: Madhya Pradesh, Rajasthan, Punjab, Haryana, Telangana (all >70% prevalence)
- WHO ranks India 5th highest globally for women's anaemia (53% by WHO dashboard), behind Yemen, Mali, Benin, Nigeria
Why is India's anaemia burden so high — multifactorial causes:
- Dietary iron deficiency: Staple foods (rice, wheat) provide ~70% of daily iron intake but as non-haem iron — poorly absorbed (5–12% absorption vs 25–35% for haem iron from meat)
- Phytates: Found in cereals and legumes; India's predominantly plant-based diet is rich in phytates which chelate non-haem iron and block absorption
- Vitamin C deficiency: Ascorbic acid is the most potent enhancer of non-haem iron absorption — low fruit/vegetable intake limits this
- Infections: Hookworm (intestinal blood loss), malaria (destroys RBCs), and other parasitic infections compound dietary deficiency
- Vitamin B12 and folate deficiency: Needed for RBC maturation; B12 deficiency is common in India's largely vegetarian population
- Haemoglobinopathies: Sickle cell disease and thalassaemia contribute in tribal belts and certain states (relevant to Sickle Cell Anaemia Mission)
Anaemia Mukt Bharat (AMB) Programme — 6x6x6 Strategy (launched 2018, MoHFW/NHM):
The AMB programme targets a 3 percentage point reduction in anaemia per year across six beneficiary groups through six interventions via six institutional mechanisms.
Six target groups: pre-school children (6–59 months), school-age children (5–9 years), adolescents (10–19 years), women of reproductive age (15–49 years), pregnant women, lactating women.
Six interventions: (i) Prophylactic Iron Folic Acid (IFA) supplementation; (ii) periodic deworming (bi-annual); (iii) Behaviour Change Communication (BCC) campaigns; (iv) testing of anaemia using digital haemoglobinometers; (v) mandatory IFA-fortified foods in public health programmes; (vi) addressing non-nutritional causes (malaria, haemoglobinopathies).
Recent progress (FY 2024-25):
- Budget allocation to states/UTs: Rs 805.91 crore for FY 2024-25
- Q2 FY 2024-25: 15.4 crore children and adolescents received IFA supplements
- Rice fortification milestone: By March 2024, all custom-milled rice in every central government food scheme (PDS, MDM, ICDS) replaced with fortified rice — a major delivery vehicle for iron, folic acid, and vitamin B12
ICMR-NIN (2024): Updated Recommended Dietary Allowances for Indians note persistent anaemia despite supplementation programmes — evidence points to multifactorial aetiology beyond simple dietary iron deficiency, necessitating integrated nutrition-infection-WASH approaches.
UPSC GS2 angles:
- NFHS-5 data is the key evidentiary basis for nutrition policy critiques
- AMB's 6x6x6 structure — a favourite Prelims fact
- Rice fortification connects food policy (PDS, NFSA 2013) with health outcomes
- Anaemia worsens maternal mortality (PPH), infant mortality, child cognition, and worker productivity — a systemic equity issue
Prelims trap: Iron deficiency is the cause in approximately 96% of anaemia cases among Indian women of reproductive age — but anaemia itself is multifactorial; haemoglobinopathies and infections are significant co-factors.
7. [Additional] Insulin, Diabetes, and the Pancreas
The pancreas is both an exocrine gland (secretes digestive enzymes into the duodenum — amylase, lipase, trypsinogen) and an endocrine gland (secretes hormones into blood).
Islets of Langerhans — clusters of endocrine cells within the pancreas:
- Beta cells (β-cells): Secrete insulin — the only hormone that lowers blood glucose (promotes glucose uptake by cells; glycogen synthesis in liver/muscle; fat storage)
- Alpha cells (α-cells): Secrete glucagon — raises blood glucose (promotes glycogen breakdown in liver; gluconeogenesis)
- Delta cells: Secrete somatostatin — inhibits both insulin and glucagon (a regulatory brake)
Mechanism of insulin action: Blood glucose rises after a meal → beta cells release insulin → insulin binds receptors on muscle/liver/fat cells → cells take up glucose → blood glucose falls back to ~80–120 mg/dL → liver stores excess as glycogen.
Diabetes mellitus — failure of glucose regulation:
| Type | Mechanism | Onset | Treatment |
|---|---|---|---|
| Type 1 (T1DM) | Autoimmune destruction of beta cells — no insulin produced | Childhood/young adult | Insulin injections (lifelong) |
| Type 2 (T2DM) | Insulin resistance — cells don't respond; beta cells eventually exhaust | Adult (increasingly in youth) | Lifestyle; metformin; insulin (later) |
| Gestational diabetes | Insulin resistance during pregnancy | Pregnancy | Diet; insulin; resolves post-delivery |
[Additional] India's Diabetes Crisis (GS2 — Health):
IDF Diabetes Atlas, 11th Edition (April 2025): India has 89.8 million adults (aged 20–79) with diabetes — 2nd highest globally after China. Prevalence: ~10.5%. Projected: 134 million by 2045. Deaths in 2024: ~3.35 lakh (IDF).
South Asian paradox: Indians develop T2DM at lower BMI and younger ages than Europeans (“thin-fat” phenotype — lower muscle mass, higher visceral fat). ICMR-INDIAB study: Indians derive 65–75% of calories from carbohydrates (polished rice, refined wheat) — driving insulin resistance.
Policy:
- National Programme for Prevention and Control of NCDs (NP-NCD): Covers diabetes, hypertension, CVD, cancer; screening at Ayushman Arogya Mandirs (HWCs)
- Biocon recombinant insulin (Bengaluru): India produces recombinant human insulin domestically — reduces import dependency for this life-saving drug
Prelims trap: Insulin is produced in beta (β) cells of islets of Langerhans — NOT alpha cells, NOT the liver, NOT the entire pancreas. Glucagon (alpha cells) does the opposite of insulin.
PART 3 — Frameworks & Analysis
Framework: Life Processes and Non-Communicable Disease (NCD) Burden
Every life process discussed in this chapter corresponds to a major NCD challenge in India:
| Life Process | Disruption | Disease | India's Burden |
|---|---|---|---|
| Nutrition/Digestion | Malabsorption, overconsumption | Malnutrition vs obesity | 35.5% children under 5 stunted (NFHS-5, 2019-21); rising obesity |
| Respiration | Lung damage | COPD, asthma, lung cancer | 55 million COPD patients; tobacco use |
| Transportation (blood/Hb) | Iron deficiency, haemoglobin failure | Anaemia | 67% children, 57% women anaemic (NFHS-5); Anaemia Mukt Bharat |
| Transportation (heart/vessels) | Blocked arteries, hypertension | CVD (heart disease, stroke) | India's #1 cause of death |
| Excretion (kidneys) | Renal failure | Chronic Kidney Disease | 17% of population has CKD risk; 175,000–220,000 on dialysis |
Framework: Double Circulation and Blood Pressure Policy
Understanding double circulation explains why:
- Blood pressure varies between systemic (higher) and pulmonary circulation (lower)
- Left ventricular hypertrophy occurs in untreated hypertension (heart works harder)
- India's National Programme for Prevention and Control of NCDs targets hypertension, diabetes, and CVD through screening at Health and Wellness Centres
Exam Strategy
Prelims traps:
- Pulmonary artery carries deoxygenated blood (from right ventricle to lungs); pulmonary veins carry oxygenated blood (from lungs to left atrium) — the only vessels where artery/vein labels seem reversed.
- Guttation is NOT the same as transpiration — guttation is liquid water release through hydathodes; transpiration is water vapour loss through stomata.
- The left ventricle has the thickest wall (pumps to entire body; highest pressure).
- RBCs in humans have no nucleus at maturity (but do in birds, reptiles, fish).
- Anaerobic respiration in yeast produces ethanol + CO2; in muscles produces lactic acid (not CO2).
- Anaemia Mukt Bharat targets 3 percentage points per year reduction — NOT 3% total. The 6x6x6 = 6 beneficiary groups × 6 interventions × 6 institutional mechanisms.
- NOTTO is under Ministry of Health and Family Welfare — NOT Ministry of Science & Technology. Deceased donation requires brain death (not cardiac death) certification.
- India’s deceased organ donation rate is ~0.81 per million population — Spain’s is ~48 pmp (60× higher).
Mains frameworks:
- Anaemia: haemoglobin/iron physiology → NFHS-5 (57% women, 67% children anaemic) → dietary iron + phytates + hookworm → Anaemia Mukt Bharat 6x6x6 → rice fortification → SDG 2
- Organ donation crisis: kidney excretion physiology → renal failure → dialysis inadequacy → deceased donation rate 0.81 pmp → THOTA 1994 + 2023/2025 reforms → NOTTO → Tamil Nadu model → equity in access
- Dialysis access: kidney physiology → renal failure → cost burden (Rs 18,000–36,000/month) → PM National Dialysis Programme → PMJAY → equity in healthcare
- NCDs: cardiovascular disease → risk factors (hypertension, diabetes, tobacco) → NCD programme → SDG 3.4
- Nutrition and malnutrition: digestion physiology → nutrient absorption → POSHAN Abhiyaan → SDG 2
Practice Questions
Q1 (Prelims 2022): With reference to the human body, which of the following statements about the lymphatic system is correct? (Tests: lymph composition, immune function, relation to blood circulation)
Q2 (Prelims 2018): With reference to “Pradhan Mantri National Dialysis Programme”, which of the following statements is/are correct? (Direct policy application of kidney excretion physiology)
Q3 (Mains GS2 2021): “Non-communicable diseases are the new challenge facing India’s health system.” Critically examine with specific reference to cardiovascular diseases. Connects heart physiology → hypertension → CVD burden → NCD programme
Q4 (Prelims 2016): Consider the following statements with respect to photosynthesis... (Tests light vs dark reactions, role of chlorophyll, products of each stage)
Q5 (Mains GS2 — thematic): Despite years of government intervention, anaemia prevalence in India increased between NFHS-4 and NFHS-5. Critically examine the reasons and evaluate the Anaemia Mukt Bharat programme’s approach. Connects Hb/iron physiology → NFHS-5 data → dietary + infection causes → AMB 6x6x6 → rice fortification → programme gaps
Q6 (Mains GS2 — thematic): India performs nearly 19,000 organ transplants annually yet its cadaveric donation rate is among the world’s lowest. Examine the structural barriers and suggest policy reforms. Connects kidney/excretion physiology → THOTA → NOTTO → brain-death certification → Tamil Nadu model → ABDM organ pledge
