NCERT-Based Quick Revision

NEET Chapter Notes 2026

Concise bullet-point notes for every high-yield NEET chapter. Colour-coded by exam weightage to focus your revision time.

Very High WeightageHigh WeightageMedium WeightageBased on NEET 2021–2024 PYQ frequency
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Botany

Class 11 & 12 · ~90 questions in NEET

Cell: The Unit of Life

High Weightage
  • Prokaryotes: no membrane-bound nucleus, 70S ribosomes (50S + 30S subunits)
  • Eukaryotes: 80S ribosomes (60S + 40S); plant cells have cell wall, plastids, central vacuole
  • Plasma membrane: fluid mosaic model (Singer & Nicolson, 1972) — phospholipid bilayer + proteins
  • Endoplasmic reticulum: RER (ribosomes, protein synthesis) vs SER (lipid synthesis, detox)
  • Golgi: secretory organelle — forms lysosomes; cis face (receiving) → trans face (shipping)
  • Mitochondria: double membrane; 70S ribosomes; cristae = inner membrane folds = ATP synthesis site
  • Chloroplast: double membrane; thylakoids stacked into grana; stroma = Calvin cycle site
  • Centrosome: absent in plant cells; centriole = 9+0 triplet microtubule arrangement
  • Nucleus: nuclear envelope (2 membranes) + nuclear pores; nucleolus makes rRNA
  • Cell wall: primary (cellulose, growing) → secondary (lignin/suberin in non-growing); middle lamella = pectin

Cell Cycle & Cell Division

High Weightage
  • Cell cycle phases: G1 (growth) → S (DNA replication) → G2 (prep) → M (mitosis)
  • Mitosis: Prophase → Metaphase → Anaphase → Telophase → Cytokinesis
  • Metaphase: chromosomes most condensed; chromosomes align at metaphase plate — best for karyotyping
  • Anaphase: centromeres split; sister chromatids pulled to poles by spindle fibres
  • Meiosis I: reductional division — bivalent formation, crossing over in prophase I
  • Prophase I stages (ZPLDD): Leptotene → Zygotene → Pachytene (crossing over) → Diplotene → Diakinesis
  • Meiosis II: equational division — identical to mitosis but no DNA replication between
  • Result: Mitosis → 2 diploid cells; Meiosis → 4 haploid cells
  • Significance of crossing over: genetic variation, new combinations

Photosynthesis in Higher Plants

Very High Weightage
  • Overall equation: 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O (in presence of light + chlorophyll)
  • Light reactions (thylakoid membrane): PS II → ETC → PS I → NADPH; water splitting releases O₂
  • Z-scheme: non-cyclic photophosphorylation → 3ATP + 2NADPH per 3CO₂ fixed
  • Calvin cycle (stroma): CO₂ fixation by RuBisCO → 3-PGA → G3P → RuBP regeneration
  • C3 plants: CO₂ fixed directly by RuBisCO into 3-carbon compound (3-PGA) — wheat, rice, soybean
  • C4 plants: CO₂ fixed by PEP carboxylase in mesophyll → OAA (4C) → bundle sheath for Calvin cycle
  • C4 examples: maize, sugarcane, sorghum; better in high temperature, light, low CO₂
  • CAM plants: stomata open at night (CO₂ stored as malic acid), Calvin in day — cacti, pineapple
  • Emerson effect: two wavelengths (680nm + 700nm) give more photosynthesis than either alone
  • Photorespiration: RuBisCO adds O₂ to RuBP → wastes energy; absent in C4 plants

Respiration in Plants

High Weightage
  • Glycolysis (cytoplasm): Glucose → 2 Pyruvate; Net: 2ATP + 2NADH
  • Aerobic respiration: Pyruvate → Acetyl-CoA (mitochondria matrix) → Krebs cycle → ETC
  • Krebs cycle: 1 Acetyl-CoA → 3NADH + 1FADH₂ + 1GTP + 2CO₂ (per turn, 2 turns per glucose)
  • ETC (inner mitochondrial membrane): NADH → 2.5ATP; FADH₂ → 1.5ATP
  • Total ATP per glucose (aerobic): ~36-38 ATP
  • Fermentation (anaerobic): Pyruvate → Ethanol + CO₂ (yeast) OR Lactic acid (muscle, bacteria)
  • RQ (respiratory quotient) = CO₂ released / O₂ consumed
  • RQ = 1 (carbohydrates), < 1 (fats = 0.7), > 1 (organic acids), 0 (anaerobic)
  • Amphibolic pathway: intermediates used in both catabolism and anabolism

Plant Growth & Development

Medium Weightage
  • Growth: irreversible increase in size; measured by fresh/dry weight, length, or cell number
  • Meristems: apical (primary growth), lateral (secondary growth), intercalary (grasses)
  • Differentiation → Dedifferentiation → Redifferentiation
  • Auxin (IAA): cell elongation; apical dominance; produced in shoot tip; synthetic = NAA, 2,4-D
  • Gibberellin (GA): stem elongation, seed germination, breaks dormancy, parthenocarpy
  • Cytokinin: cell division, delays senescence (Richmond-Lang effect), promotes lateral bud growth
  • ABA: 'stress hormone'; stomatal closure; inhibits growth; promotes seed dormancy
  • Ethylene: fruit ripening, horizontal growth, epinasty, produced from methionine
  • Photoperiodism: SDP (chrysanthemum, tobacco), LDP (wheat, barley), Day-neutral (tomato)
  • Vernalisation: cold temperature induces early flowering — wheat, barley

Mineral Nutrition

Medium Weightage
  • Essential elements: C, H, O (non-mineral); 17 total essential elements
  • Macronutrients (>10 mmol/kg): N, P, K, Ca, Mg, S
  • Micronutrients (<10 mmol/kg): Fe, Mn, Zn, Cu, Mo, B, Cl, Ni
  • N deficiency: chlorosis (yellowing), stunted growth
  • Mg deficiency: interveinal chlorosis (Mg is central atom in chlorophyll)
  • Fe deficiency: interveinal chlorosis (young leaves first)
  • Nitrogen fixation: Rhizobium (symbiotic with legumes), Azotobacter, Clostridium (free-living)
  • Nitrogenase enzyme: fixes N₂ → NH₃; requires anaerobic conditions and ATP
  • Nitrogen cycle: fixation → nitrification → assimilation → ammonification → denitrification
  • Mycorrhiza: fungal symbiosis with roots; increases phosphorus absorption

Molecular Basis of Inheritance (Bio section)

Very High Weightage
  • DNA double helix: Watson & Crick (1953); antiparallel strands; B-DNA most common
  • Base pairing: A=T (2H bonds), G≡C (3H bonds); Chargaff: A=T, G=C
  • DNA replication: semiconservative (Meselson-Stahl 1958); origin of replication
  • Enzymes: Helicase (unwind) → Primase (RNA primer) → DNA Pol III (synthesis) → DNA Pol I (primer removal) → Ligase
  • Leading strand: continuous synthesis; Lagging strand: Okazaki fragments (discontinuous)
  • Transcription: DNA → mRNA; Template (antisense) strand read 3'→5'; mRNA synthesized 5'→3'
  • RNA Pol I: rRNA; RNA Pol II: mRNA (hnRNA); RNA Pol III: tRNA
  • Post-transcription: 5'-capping, poly-A tail, splicing (introns removed)
  • Translation: mRNA → protein; ribosome moves 5'→3'; tRNA brings amino acids
  • Start codon: AUG (Met); Stop codons: UAA, UAG, UGA (nonsense, non-sense)
  • Genetic code: triplet, degenerate, universal, unambiguous, non-overlapping
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Zoology

Class 11 & 12 · ~90 questions in NEET

Human Digestion & Absorption

High Weightage
  • GI tract: Mouth → Pharynx → Esophagus → Stomach → SI (duodenum, jejunum, ileum) → LI → Rectum → Anus
  • Saliva: salivary amylase (ptyalin) — starch → maltose; pH 6.8; lysozyme antibacterial
  • Stomach: HCl (kills bacteria, denatures protein, activates pepsinogen); pepsin (protein → peptides)
  • Gastric glands: Chief cells (pepsinogen), Parietal/Oxyntic cells (HCl), Goblet cells (mucus)
  • Small intestine: bile (emulsification, no enzymes); pancreatic enzymes (amylase, lipase, trypsin, chymotrypsin)
  • Intestinal enzymes: maltase, lactase, sucrase (sugars); enterokinase (activates trypsinogen)
  • Absorption: mainly in jejunum; villi + microvilli increase surface area; lacteals absorb fat
  • Sugars and amino acids → blood (portal vein); fats → lymph (chylomicrons via lacteals)
  • Large intestine: water absorption, bacterial action, formation of feces
  • BMR: Basal Metabolic Rate; RQ varies with substrate (1 for carbs, 0.7 for fat)

Breathing & Gas Exchange

High Weightage
  • Respiratory volumes: TV=500mL, IRV=3000mL, ERV=1000mL, RV=1500mL
  • Capacities: IC=TV+IRV=3500, FRC=ERV+RV=2500, VC=IRV+TV+ERV=4500, TLC=6000mL
  • Tidal volume: air moved in one normal breath (500 mL)
  • Ventilation: inspiration (diaphragm contracts, ribs up → negative pressure); expiration (passive, elastic recoil)
  • O₂ transport: 98% as oxyhaemoglobin (HbO₂); 2% dissolved in plasma
  • CO₂ transport: 70% as bicarbonate (HCO₃⁻ in plasma), 20-25% as carbaminohaemoglobin, 7% dissolved
  • Chloride shift: HCO₃⁻ moves out of RBC in exchange for Cl⁻ (maintains electroneural balance)
  • Bohr effect: increased CO₂/decreased pH → decreased O₂ affinity of Hb (sigmoidal curve shifts right)
  • Disorders: Asthma (bronchospasm), Emphysema (alveolar damage, loss of elastic recoil), Pneumonia, Occupational diseases
  • Alveolar PO₂ ≈ 104 mmHg; venous blood PO₂ ≈ 40 mmHg → O₂ moves into blood by diffusion

Body Fluids & Circulation

Very High Weightage
  • Blood components: plasma (55%), formed elements (45%); plasma = 91-92% water
  • RBC: biconcave, no nucleus, 120-day lifespan, contain Hb, 5 million/mm³
  • WBC: leucocytes; neutrophils (most common, 60-65%), eosinophils, basophils, lymphocytes, monocytes
  • Platelets: thrombocytes; 1.5-3.5 lakh/mm³; involved in clotting
  • Blood groups: ABO (antigen A, B on RBC; antibody in plasma); Rh factor
  • Erythroblastosis foetalis: Rh+ fetus, Rh- mother → antibodies attack fetal RBC in 2nd pregnancy
  • Cardiac cycle: 0.8 sec (72 beats/min); Systole 0.3s + Diastole 0.5s
  • Cardiac output = Heart Rate × Stroke Volume = 72 × 70 = ~5040 mL/min ≈ 5L/min
  • ECG: P wave (atrial depolarization), QRS (ventricular depolarization), T (ventricular repolarization)
  • Lymph: plasma without large proteins + lymphocytes; lacteals carry fat; empties into subclavian veins
  • Double circulation: pulmonary (right heart → lungs → left heart) + systemic (left heart → body → right heart)

Excretory Products & Elimination

High Weightage
  • Ammonotelism (fish, aquatic): excrete ammonia; Ureotelism (mammals, frogs): urea; Uricotelism (birds, reptiles, insects): uric acid
  • Nephron: Bowman's capsule → PCT → Loop of Henle → DCT → Collecting duct
  • Glomerular filtration: 180L/day filtered; creates ultrafiltrate (blood – proteins)
  • GFR (Glomerular Filtration Rate): ~125 mL/min in humans
  • PCT: reabsorption of Na⁺, K⁺, glucose (100%), amino acids, 70% water; active transport
  • Loop of Henle: descending (water permeable, solute impermeable), ascending (impermeable to water, Na⁺/Cl⁻ reabsorbed)
  • Countercurrent mechanism (medullary gradient): facilitates water reabsorption from collecting duct
  • DCT & CD: ADH (vasopressin) promotes water reabsorption; aldosterone promotes Na⁺ reabsorption
  • Juxtaglomerular apparatus (JGA): macula densa + JG cells; secretes renin → angiotensin → aldosterone
  • Final urine: 1.5L/day; urea 2%, creatinine, uric acid, Na⁺, K⁺; pH 6

Neural Control & Coordination

High Weightage
  • Neuron: dendrites → cell body → axon → synaptic knob; myelinated (fast conduction)
  • Resting potential: -70mV (more K⁺ inside, more Na⁺ outside)
  • Action potential: Na⁺ rush in → depolarization (+40mV) → K⁺ rush out → repolarization
  • Synapse: electrical or chemical; neurotransmitters released from presynaptic vesicles
  • Neurotransmitters: Acetylcholine (nicotinic & muscarinic), noradrenaline, dopamine, serotonin, GABA
  • Reflex arc: Receptor → Afferent nerve → Spinal cord → Efferent nerve → Effector
  • Cerebrum: largest, voluntary actions, intelligence, memory, reasoning
  • Cerebellum: balance, coordination of voluntary movements, posture
  • Medulla oblongata: respiratory centre, cardiac centre, reflex actions (coughing, sneezing)
  • Thalamus: relay station; Hypothalamus: thermoregulation, hunger, circadian rhythm, links NS & endocrine

Chemical Coordination & Integration

High Weightage
  • Pituitary (master gland): Anterior (adenohypophysis) + Posterior (neurohypophysis)
  • Anterior pituitary: GH, TSH, ACTH, FSH, LH, Prolactin (FLAT PIG mnemonic)
  • Posterior pituitary: ADH (vasopressin) and Oxytocin — made in hypothalamus, stored in posterior pituitary
  • Thyroid: T3 (triiodothyronine) & T4 (thyroxine); calcitonin (reduces blood Ca²⁺)
  • Hypothyroidism: cretinism (children), myxoedema (adults); Hyperthyroidism: Graves' disease (exophthalmos)
  • Parathyroid: PTH (parathormone) — increases blood Ca²⁺ (antagonist to calcitonin)
  • Adrenal cortex: glucocorticoids (cortisol — stress, anti-inflammatory), mineralocorticoids (aldosterone — Na⁺/K⁺)
  • Adrenal medulla: adrenaline & noradrenaline — 'fight or flight'; increase BP, heart rate, glucose
  • Pancreas: alpha cells (glucagon — raises blood glucose), beta cells (insulin — lowers blood glucose)
  • Gonads: testosterone (Leydig cells), estrogen & progesterone (ovaries), inhibin (Sertoli cells)

Principles of Inheritance & Variation

Very High Weightage
  • Mendel's laws: Law of Dominance, Law of Segregation, Law of Independent Assortment
  • Monohybrid ratio: 3:1 (phenotype) = 1:2:1 (genotype); Dihybrid: 9:3:3:1
  • Incomplete dominance: F₂ ratio 1:2:1 (phenotype); e.g. snapdragon, four o'clock flower
  • Codominance: both alleles expressed simultaneously; e.g. ABO blood groups (IA, IB codominant; i recessive)
  • Lethal alleles: yellow coat in mice (AY/AY lethal) → 2:1 ratio instead of 3:1
  • Linkage: genes on same chromosome; reduces recombination frequency
  • Sex-linked inheritance: X-linked recessive — haemophilia, colour blindness (carrier female, affected male)
  • Mutation: chromosomal (structural/numerical) or gene (point mutation)
  • Down syndrome: trisomy 21 (2n=47); Turner's (45,X); Klinefelter's (47,XXY)
  • Pedigree analysis: square=male, circle=female, filled=affected; autosomal/sex-linked determination

Evolution

High Weightage
  • Origin of life: Oparin & Haldane (chemical evolution), Miller & Urey experiment (amino acids from NH₃, CH₄, H₂, H₂O)
  • Lamarck: use & disuse of organs; inheritance of acquired characters (incorrect)
  • Darwin: natural selection + survival of fittest + variation → evolution
  • Hardy-Weinberg principle: allele frequencies constant in ideal population (no evolution)
  • H-W equilibrium disturbed by: mutation, gene flow, genetic drift, natural selection, non-random mating
  • Types of evolution: divergent (adaptive radiation), convergent (analogous structures), parallel
  • Analogous structures: similar function, different origin (butterfly wing & bird wing = convergent)
  • Homologous structures: same origin, different function (human arm & whale flipper = divergent)
  • Industrial melanism: Biston betularia (peppered moth) — selection pressure
  • Human evolution: Ramapithecus → Australopithecus → H. habilis → H. erectus → H. sapiens

Human Reproduction

Very High Weightage
  • Male: testis (sperm + testosterone), epididymis (storage/maturation), vas deferens → ejaculatory duct → urethra
  • Accessory glands: seminal vesicle (fructose, prostaglandins), prostate (citric acid, enzymes), Cowper's (lubrication)
  • Spermatogenesis: Spermatogonia (2n) → Primary spermatocyte → Secondary spermatocyte → Spermatids → Spermatozoa
  • Sperm: head (acrosome + nucleus), middle piece (mitochondria = energy), tail (motility)
  • Female: ovaries (oogenesis + hormones), fallopian tubes (site of fertilisation), uterus (implantation), vagina
  • Oogenesis: Oogonia → Primary oocyte (arrested prophase I) → Secondary oocyte (after puberty, arrested metaphase II) → Ovum at fertilisation
  • Menstrual cycle: 28 days; Follicular (day 1-13) → Ovulation (day 14, LH surge) → Luteal (day 15-28)
  • Fertilisation: acrosomal reaction → sperm penetrates zona pellucida → cortical reaction (prevents polyspermy)
  • Implantation: blastocyst implants in endometrium (day 7 after fertilisation)
  • Placenta: exchange of nutrients, O₂, CO₂; secretes hCG, oestrogen, progesterone

Human Health & Disease

High Weightage
  • Innate immunity: non-specific (skin, mucus, phagocytes, NK cells, complement)
  • Adaptive immunity: specific; B-cells (humoral, antibodies) + T-cells (cell-mediated)
  • Memory cells: responsible for faster secondary immune response (basis of vaccination)
  • Antibody structure: Y-shaped; 2 heavy + 2 light chains; variable region = antigen binding
  • Immunoglobulin classes: IgG (most abundant, crosses placenta), IgE (allergy), IgA (secretions), IgM (primary response)
  • AIDS: HIV (retrovirus) attacks CD4+ T helper cells; spreads via blood, sexual contact, mother to child
  • Cancer: uncontrolled cell division; proto-oncogenes → oncogenes; carcinogens, viruses, radiation
  • Drugs of abuse: opioids (morphine, heroin), cannabinoids (marijuana), cocaine (coca plant), LSD
  • Common diseases: typhoid (Salmonella typhi), pneumonia (Streptococcus), malaria (Plasmodium falciparum — most lethal)
  • Malaria life cycle: mosquito (Anopheles female) → sporozoites in blood → liver → RBC → merozoites → gametocytes
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