NEET 2025 • Class XI Biology

NCERT 2025–26: Class 11 Biology Hub — Notes, Figures, Summaries, Quizzes & Downloads

This hub brings together all five NCERT units — (1) Diversity of Living Organisms, (2) Structural Organisation in Plants & Animals, (3) Cell: Structure & Function, (4) Plant Physiology, and (5) Human Physiology — with chapters 1–19 presented in a consistent, exam-ready format. Every chapter block follows the same layout: Notes → Figures → Quick Summary → 10-MCQ Quiz → Downloads. Use the sticky contents at left to jump between chapters, and the search box to filter chapters live on this page.

Syllabus verified • Updated: 03 Sep 2025

Unit Overview

This page is your master table of contents for NCERT Class XI Biology. Units are ordered as in NCERT, and each chapter block is self-contained for teaching and revision: topic-wise notes with definitions & logic, diagram callouts for labelling practice, a quick summary for last-minute revision, a 10-MCQ quiz for NEET pattern practice, and downloads (revision sheets, tables, diagrams). Progress chips flag weightage (High/Medium), diagram-heavy topics, and PYQ density to help you prioritise.

High-yield PYQs Diagram labelling 10-MCQ quizzes Quick revision sheets

01 The Living World

Summative Weightage: Medium Updated: 01 Sep 2025
Chapter Notes
  • Characteristics of living: growth, reproduction, metabolism, consciousness (note exceptions).
  • Taxonomic hierarchy: species → genus → family → order → class → phylum/division → kingdom.
  • Binomial nomenclature: italics; Genus capitalized, species lowercase.
  • Taxonomical aids: herbarium, botanical gardens, museums, keys.
Important Figures
Taxonomic hierarchy ladder
Taxonomic hierarchy with correct order.
Sample herbarium sheet
Herbarium sheet annotations.
Quick Summary

Core ideas: what defines life, how organisms are classified, and tools used in taxonomy. Expect format-based MCQs on binomial rules and hierarchy order.

Practice Quiz (3 MCQs)
Downloads
Revision Sheet (PDF) Flashcards (Print)

02 Biological Classification

Summative Weightage: High Updated: 02 Sep 2025
Chapter Notes
  • Whittaker’s five-kingdom system uses cell type, body organisation, nutrition, and reproduction as key criteria.
  • Monera: prokaryotic; peptidoglycan cell wall; 70S ribosomes; diverse nutrition (auto/heterotrophic, chemotrophic).
  • Protista: mostly unicellular eukaryotes; locomotion by cilia/flagella/pseudopodia; examples include diatoms, dinoflagellates, protozoans.
  • Fungi: eukaryotic heterotrophs with chitinous cell walls; reproduce via spores; important groups—Ascomycetes, Basidiomycetes.
  • Plantae and Animalia: multicellular eukaryotes; autotrophic vs. heterotrophic nutrition; cell wall presence vs. absence.
  • Viruses are acellular obligate parasites with protein coat (capsid) and nucleic acid (DNA or RNA); viroids are infectious RNA; prions are proteinaceous infectious particles.
  • Slime moulds show characteristics of both fungi and protists; true classification hinges on life cycle and nutrition patterns.
  • Remember exam traps: virus vs. viroid vs. prion; Protista subdivisions; spore types in fungi; Monera cell wall and ribosome details.
Important Figures
Diagram of five-kingdom classification with criteria
Five-kingdom overview and criteria used by Whittaker.
Comparison table of Monera and Protista
Monera vs. Protista: cell type, wall, ribosomes, nutrition, reproduction.
Fungal groups and spore types diagram
Fungal groups: spores and life cycle highlights.
Generalised virus structure with capsid and nucleic acid
Virus structure: capsid, envelope (if present), nucleic acid.
Illustrations of dinoflagellate and diatom forms
Representative Protista: dinoflagellates and diatoms.
Schematic of slime mould life cycle
Slime mould life cycle showing plasmodial stage.
Quick Summary

This chapter builds the logic of classifying life based on structural, nutritional, and reproductive criteria. Master contrasts among Monera, Protista, and Fungi; know hallmark examples and spore types. Be precise on acellular entities (viruses, viroids, prions) and remember typical NEET questions target definitions, exceptions, and example mapping.

Practice Quiz (10 MCQs)
Downloads
Revision Sheet (PDF) Figure Pack (PNG, ZIP) Flashcards (Print PDF)
Cross-links

Related chapters: The Living World · Plant Kingdom

03 Plant Kingdom

Summative Weightage: High Updated: 02 Sep 2025
Chapter Notes
  • Criteria of classification: thallus organisation, vascular tissues, seed/enclosure, and alternation of generations.
  • Algae (primarily aquatic, simple thallus, chlorophyll a): three classes
    • Chlorophyceae (green): pigments chlorophyll a, b; reserve food—starch; wall—cellulose; flagella equal (2–8), apical; mostly freshwater.
    • Phaeophyceae (brown): pigments chlorophyll a, c + fucoxanthin; reserve—laminarin/mannitol; wall—cellulose + algin; flagella unequal (pear-shaped and whiplash); mostly marine.
    • Rhodophyceae (red): pigments chlorophyll a, d + phycoerythrin; reserve—floridean starch; no motile cells; largely marine.
  • Algal life cycles: haplontic (e.g., Volvox), diplontic (rare in algae), haplo-diplontic (e.g., Polysiphonia).
  • Bryophytes (amphibians of plant kingdom): dominant gametophyte, dependent sporophyte; need water for fertilisation.
    • Liverworts (e.g., Riccia, Marchantia): dorsiventral thallus; gemmae in gemma cups.
    • Mosses (e.g., Funaria): protonema (juvenile) → leafy gametophyte; sporophyte with capsule, seta, foot.
  • Pteridophytes: first vascular plants (xylem/phloem), independent sporophyte with true root, stem, leaves; sporangia on sporophylls, grouped in strobili; many are homosporous, some heterosporous (e.g., Selaginella).
  • Heterospory → seed habit: microspores (♂) and megaspores (♀); retention of megaspore within megasporangium and development of endosporic female gametophyte are precursors to seed habit.
  • Gymnosperms: naked seeds (no fruit), usually woody; Pinus, Cycas; wind pollination; haplo-diplontic with dominant sporophyte.
  • Angiosperms: flowers, fruits (seeds enclosed); double fertilisation → zygote + triploid endosperm; monocots vs dicots (cotyledons, leaf venation, vascular bundle arrangement).
  • Economic importance: algae (food, agar, algin), gymnosperms (timber, ephedrine), angiosperms (crops, medicines, fibres).
  • Exam focuses: pigment–reserve–wall–flagella table for algal classes; life cycle types; dominance (gametophyte vs sporophyte); heterospory and examples; double fertilisation and endosperm.
Important Figures
Table comparing Chlorophyceae, Phaeophyceae, Rhodophyceae by pigments, reserves, wall, flagella
Algal classes: pigments, reserve food, wall, flagella, habitat.
Bryophyte life cycle with dominant gametophyte and dependent sporophyte
Bryophyte life cycle and dominance pattern.
Sporangia on sporophylls in a pteridophyte strobilus
Pteridophyte sporangia on sporophylls; strobilus.
Diagram showing heterospory leading to seed habit with Selaginella example
Heterospory (e.g., Selaginella) → seed habit evolution.
Comparison of gymnosperm and angiosperm reproductive structures
Gymnosperm vs. angiosperm reproductive structures.
Double fertilisation and endosperm formation in angiosperms
Double fertilisation and triploid endosperm formation.
Quick Summary

Plant Kingdom surveys evolutionary grades from thalloid algae to seed plants. Memorise the algal class table (pigments–reserve–wall–flagella), life-cycle dominance (gametophyte in bryophytes, sporophyte in pteridophytes upwards), and the logic of heterospory leading to seed habit. For angiosperms, the hallmark is double fertilisation producing a diploid zygote and triploid endosperm.

Practice Quiz (10 MCQs)
Downloads
Revision Sheet (PDF) Figure Pack (PNG, ZIP) Flashcards (Print PDF)
Cross-links

Related chapters: Biological Classification · Animal Kingdom · Photosynthesis in Higher Plants

04 Animal Kingdom

Summative Weightage: High Updated: 03 Sep 2025
Chapter Notes
  • Basis of classification: levels of organisation (cellular → tissue → organ → organ-system), body symmetry (asymmetry, radial, bilateral), germ layers (diploblastic vs. triploblastic), coelom (acoelomate, pseudocoelomate, coelomate), segmentation (metamerism), notochord (chordates vs. non-chordates).
  • Porifera (sponges): cellular level; canal system; choanocytes; spicules/spongin skeleton; asexual bud & sexual reproduction; mostly marine.
  • Cnidaria (Coelenterata): tissue level; radial symmetry; diploblastic; cnidocytes with nematocysts; polyp/medusa forms; gastrovascular cavity; e.g., Hydra, Aurelia.
  • Ctenophora: radially symmetrical, diploblastic, marine; eight comb plates (ctenes) for locomotion; bioluminescence; e.g., Pleurobrachia.
  • Platyhelminthes: dorsoventrally flattened, acoelomate, triploblastic, bilateral; parasitic forms common; flame cells for excretion; e.g., Taenia, Fasciola.
  • Nematoda (Aschelminthes): triploblastic, pseudocoelomate, bilateral; unsegmented; parasitic forms like Ascaris, Wuchereria.
  • Annelida: true coelom (schizocoelom), metameric segmentation, closed circulation; e.g., Nereis, Earthworm, Leeches.
  • Arthropoda: largest phylum; chitinous exoskeleton; jointed appendages; open circulation; Malpighian tubules; tracheal/gills; e.g., insects, prawns, spiders.
  • Mollusca: soft body; mantle & shell; muscular foot; radula (except bivalves); open circulation (closed in cephalopods); e.g., Pila, Sepia.
  • Echinodermata: marine; endoskeleton of calcareous ossicles; water vascular system; adult radial (pentaradial), larvae bilateral; e.g., starfish, sea urchin.
  • Hemichordata: marine, soft-bodied; proboscis-collar-trunk; stomochord; burrowers; e.g., Balanoglossus.
  • Chordata (notochord present at some stage): dorsal hollow nerve cord; pharyngeal gill slits; post-anal tail; closed circulation. Subphyla: Urochordata, Cephalochordata, Vertebrata.
  • Vertebrata classes—key cues:
    • Pisces (fishes): gills; scales; fins; 2-chambered heart; ectothermic.
    • Amphibia: moist skin; cutaneous respiration; 3-chambered heart; aquatic larvae.
    • Reptilia: dry scaly skin; mostly 3-chambered (crocodiles 4); amniotic eggs.
    • Aves: feathers; pneumatic bones; 4-chambered heart; endothermic.
    • Mammalia: hair; mammary glands; diaphragm; 4-chambered; endothermic.
  • High-yield comparisons: acoelomate vs. pseudo- vs. eucoelomate; radial vs. bilateral; open vs. closed circulation; excretory organs (flame cells, nephridia, Malpighian tubules, green glands, kidneys).
Important Figures
Diagrams of asymmetry, radial symmetry, and bilateral symmetry
Body symmetry: asymmetry (sponges), radial (cnidaria/ctenophora adults), bilateral (most others).
Acoelomate, pseudocoelomate, and coelomate body plans
Coelom types with examples.
Arthropod external features showing exoskeleton and jointed appendages
Arthropoda: chitinous exoskeleton & jointed appendages.
Echinoderm water vascular system schematic
Echinodermata: water vascular system (madreporite to tube feet).
Chordate hallmarks including notochord, dorsal nerve cord, pharyngeal slits, post-anal tail
Chordate hallmarks across development.
Key diagnostic features for vertebrate classes
Key cues: Pisces, Amphibia, Reptilia, Aves, Mammalia.
Quick Summary

Animal classification hinges on organisation level, symmetry, germ layers, coelom, segmentation, and presence of notochord. Non-chordates progress from cellular (Porifera) to complex organ-system (Arthropoda/Mollusca/Echinodermata). Chordates share notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail; vertebrate classes are best mastered via hallmark trait tables.

Practice Quiz (10 MCQs)
Downloads
Revision Sheet (PDF) Figure Pack (PNG, ZIP) Flashcards (Print PDF)
Cross-links

Related chapters: Plant Kingdom · Morphology of Flowering Plants · Neural Control & Coordination

05 Morphology of Flowering Plants

Summative Weightage: High Updated: 03 Sep 2025
Chapter Notes
  • Root system: tap (dicots), fibrous (monocots), adventitious (grasses, prop/pneumatophore). Modifications: storage (carrot), prop roots (banyan), pneumatophores (mangroves).
  • Stem: nodes–internodes; buds (terminal/axillary). Modifications: tendrils (passionflower), thorns (Bougainvillea), rhizome (ginger), tuber (potato), stolon/runner (strawberry).
  • Leaf: venation (reticulate vs parallel), phyllotaxy (alternate/opposite/whorled). Modifications: tendril (pea), spines (cactus), phyllode (Acacia).
  • Inflorescence: racemose (indeterminate; main axis grows) vs cymose (determinate; main axis ends in a flower). Special: hypanthodium (Ficus), cyathium (Euphorbia).
  • Flower: complete/incomplete; symmetry (actinomorphic/zygomorphic); ovary position (hypogynous/perigynous/epigynous). Aestivation (valvate, twisted, imbricate, vexillary).
  • Placentation: marginal, axile, parietal, basal, free-central.
  • Fruit types: true vs false; simple/aggregate/multiple; dry (indehiscent/dehiscent) vs fleshy.
  • Seed: monocot (single cotyledon, endosperm present) vs dicot (two cotyledons, often non-endospermic).
  • Family diagnostics: Fabaceae (papilionaceous corolla, diadelphous stamens, legume fruit), Solanaceae (actinomorphic, epipetalous, berry/capsule), Liliaceae (monocot, trimerous flowers, superior ovary, capsule/berry).
  • Exam targets: floral formula/diagram reading, placentation mapping, inflorescence recognition, stem/leaf/root modifications, family trait tables.
Important Figures
Diagrams of tap, fibrous, adventitious roots and modifications like prop roots, pneumatophores
Root systems & key modifications.
Rhizome, tuber, runner, thorn and tendril modifications of stem
Stem modifications with examples.
Leaf phyllotaxy types and venation patterns
Phyllotaxy & venation patterns.
Racemose vs cymose inflorescence comparison
Racemose vs. cymose inflorescence.
Hypogynous, perigynous, epigynous ovary positions and aestivation types
Ovary position & floral aestivation.
Placentation types: marginal, axile, parietal, basal, free-central
Placentation: marginal, axile, parietal, basal, free-central.
Quick Summary

Master recognition tables (root/stem/leaf modifications, inflorescence, placentation) and family diagnostics. Translate floral formulae into diagrams and vice-versa. Typical NEET stems test recognition (e.g., “diadelphous stamens → Fabaceae”) or structural comparisons (racemose vs cymose; ovary position; seed types).

Practice Quiz (10 MCQs)
3) Identify the inflorescence shown.
Schematic inflorescence with continuous axis and lateral flowers
6) Placentation in the figure is:
Transverse section of a multilocular ovary with central placenta
9) Identify the floral symmetry shown.
Flower diagram showing a single plane of symmetry
Downloads
Revision Sheet (PDF) Figure Pack (PNG, ZIP) Floral Formula & Diagram Pack (PDF)
Cross-links

Related chapters: Animal Kingdom · Anatomy of Flowering Plants · Photosynthesis in Higher Plants

06 Anatomy of Flowering Plants

Summative Weightage: High Updated: 03 Sep 2025
Chapter Notes
  • Meristematic tissues: apical (root/shoot tips), intercalary (leaf bases/internodes—grasses), lateral (cambia) → cause growth.
  • Permanent tissues: Simple—parenchyma (living, storage), collenchyma (living, corner thickening, support in young parts), sclerenchyma (dead, lignified, fibres/sclereids). Complex—xylem (tracheids, vessels, xylem fibres, xylem parenchyma), phloem (sieve tube elements, companion cells, phloem fibres, phloem parenchyma).
  • Tissue systems: epidermal (cuticle, stomata, trichomes), ground (cortex, endodermis with Casparian strips, pericycle, pith), vascular (bundles).
  • Root anatomy: radial vascular bundles; xylem is exarch. Dicot root—limited xylem, large pith small; Monocot root—many xylem poles (polyarch), distinct large pith.
  • Stem anatomy: Dicot stem—vascular bundles in a ring (eustele), open collateral with cambium; Monocot stem—bundles scattered (atactostele), closed collateral, no secondary growth.
  • Leaf anatomy: Dicot leaf—dorsiventral (palisade + spongy mesophyll); Monocot leaf—iso(bi)lateral, bulliform cells in upper epidermis for rolling.
  • Secondary growth (dicot stem/roots): intrafascicular + interfascicular cambium → cambial ring → secondary xylem (in) & phloem (out). Annual rings: earlywood vs latewood.
  • Periderm: phellogen (cork cambium) forms phellem (cork) outward & phelloderm inward; lenticels for aeration. Heartwood (non-conducting, dark, impregnated) vs sapwood (functional).
  • Secretory structures: laticifers (latex), resin ducts, oil glands.
  • Exam targets: dicot vs monocot (root/stem/leaf) tables; endarch vs exarch; open vs closed bundles; components of xylem/phloem; cambium/periderm/annual ring logic.
Important Figures
Transverse section of dicot root showing exarch xylem and small pith
Dicot root TS: exarch xylem, endodermis with Casparian strips.
TS of monocot stem with scattered closed vascular bundles
Monocot stem TS: scattered, closed collateral bundles (no cambium).
TS of dicot stem showing ring of open collateral bundles and cambium
Dicot stem TS: ring of open collateral bundles (cambium present).
Mesophyll types in dicot and monocot leaves with bulliform cells
Leaf TS: dorsiventral (dicot) vs isobilateral (monocot, bulliform cells).
Cambial ring formation and earlywood-latewood annual rings
Secondary growth: cambial ring → secondary xylem/phloem; annual rings.
Periderm layers—phellem, phellogen, phelloderm—and a lenticel
Periderm & lenticel structure; heartwood vs sapwood concept.
Quick Summary

Anatomy explains how tissues build organs. Remember the triad—tissue types, organ TS differences (dicot vs monocot), and secondary growth (cambium → rings, periderm). Typical NEET stems ask for endarch vs exarch, closed vs open bundles, presence of cambium, and diagnostic leaf/stem/root features including bulliform cells and Casparian strips.

Practice Quiz (10 MCQs)
Downloads
Revision Sheet (PDF) Figure Pack (PNG, ZIP) TS Diagrams (Print PDF)
Cross-links

Related chapters: Morphology of Flowering Plants · Structural Organisation in Animals · Plant Growth & Development

07 Structural Organisation in Animals

Summative Weightage: Medium–High Updated: 03 Sep 2025
Chapter Notes
  • Levels of organisation: cell → tissue → organ → organ system.
  • Epithelial tissue (lining/covering; minimal intercellular matrix): Simple (squamous, cuboidal, columnar, ciliated, pseudostratified) and Stratified (protective). Specialised: glandular (exocrine/endocrine); junctions—tight, adhering, gap.
  • Connective tissue (abundant matrix): Proper—areolar (packing), adipose (storage/insulation), dense regular (tendons/ligaments); Supporting—cartilage (hyaline, elastic, fibro-), bone (compact/spongy; Haversian systems); Fluid—blood/lymph.
  • Muscle tissue: skeletal (striated, voluntary), smooth (non-striated, involuntary), cardiac (striated, branched, intercalated discs).
  • Nervous tissue: neurons (soma, dendrites, axon) + neuroglia; synapses—chemical > electrical in human body.
  • Earthworm (Pheretima): metameric segmentation; body wall (cuticle–epidermis–circular–longitudinal muscles); coelomate; closed circulation; hemoglobin dissolved in plasma; nephridia for excretion; hermaphrodite; typhlosole increases absorption.
  • Frog (Rana): smooth moist skin; three-chambered heart; double circulation; mesonephric kidneys; cutaneous buccopharyngeal and pulmonary respiration; external fertilisation; metamorphosis.
  • Cockroach (Periplaneta): chitinous exoskeleton; tracheal respiration (spiracles → tracheae → tracheoles); open circulation; Malpighian tubules (excretion); mouthparts (labrum, mandibles, maxillae, labium); compound eyes; reproductive systems distinct (ootheca in ♀).
  • High-yield contrasts: epithelial types & locations; connective tissue components; muscle features; excretory organs by organism; frog vs. cockroach vs. earthworm systems.
Important Figures
Diagram of simple squamous, cuboidal, columnar, ciliated and stratified epithelium
Major epithelial types and typical sites.
Areolar, adipose, dense regular, cartilage and bone diagrams
Connective tissues: proper, supporting, and fluid.
Skeletal, smooth and cardiac muscle microstructure
Muscle tissue microstructure and features.
Neuron with dendrites, soma, axon and synapse
Neuron structure; direction of impulse.
Labelled diagram of cockroach mouthparts
Cockroach mouthparts—labrum, mandibles, maxillae, labium.
Cockroach tracheal system showing spiracles, tracheae and tracheoles
Tracheal system in cockroach (gas exchange).
Quick Summary

Learn one clean table for tissue classes (key features + sites). Memorise the hallmark traits of frog, earthworm, and cockroach—especially respiration types, circulation, excretion, and reproduction. Most NEET stems are recognition or “match the following” across these features.

Practice Quiz (10 MCQs)
Downloads
Revision Sheet (PDF) Figure Pack (PNG, ZIP) Tissue Tables (Print PDF)
Cross-links

Related chapters: Anatomy of Flowering Plants · Cell: The Unit of Life · Neural Control & Coordination

08 Cell: The Unit of Life

Summative Weightage: High Updated: 03 Sep 2025
Chapter Notes
  • Cell theory: Schleiden & Schwann; Virchow’s extension—cells arise from pre-existing cells.
  • Prokaryote vs eukaryote: nucleoid (no true nucleus), 70S ribosomes, simple cytoskeleton vs membrane-bound organelles, 80S ribosomes (70S in mitochondria/chloroplasts).
  • Cell envelope & wall: bacteria—glycocalyx (capsule/slime), cell wall (peptidoglycan), plasma membrane; Gram +/− differences.
  • Plasma membrane: Fluid Mosaic Model; transport—passive (diffusion, facilitated), osmosis; active transport (pumps); endocytosis/exocytosis.
  • Endomembrane system: ER (RER—protein; SER—lipid, detox), Golgi (cis→trans; glycosylation, packaging), lysosomes (acid hydrolases, autophagy), vacuoles (plant cell tonoplast, storage, turgor).
  • Mitochondria: double membrane, cristae, matrix; own DNA/ribosomes (70S); ATP synthesis; semi-autonomous.
  • Plastids: proplastid → chloroplast (grana—thylakoids with chlorophyll; stroma with Rubisco), chromoplast, leucoplast (amyloplast, elaioplast, aleuroplast); circular DNA, 70S ribosomes.
  • Ribosomes: 70S (50S+30S) in prokaryotes & organelles; 80S (60S+40S) in cytosol of eukaryotes.
  • Cytoskeleton: microtubules, microfilaments (actin), intermediate filaments—shape, transport, movement, spindle.
  • Cilia & flagella (eukaryotic): 9+2 axoneme; dynein arms; basal body = centriole-like 9×3.
  • Centrosome/centrioles: present in animals (usually absent in higher plants); centriole = 9 triplets.
  • Nucleus: nuclear envelope with pores; nucleolus (rRNA synthesis); chromatin (euchromatin/heterochromatin); chromosomes—centric positions; histones; karyotype.
  • Microbodies: peroxisomes (H2O2 metabolism, photorespiration); glyoxysomes (seed lipid → sugars).
  • Exam targets: 70S vs 80S, organelle functions, 9+2 vs 9×3, chloroplast structure, endomembrane membership (which organelles are/aren’t part of it).
Important Figures
Fluid mosaic model with proteins and lipids
Fluid Mosaic Model—integral & peripheral proteins; transport pathways.
ER-Golgi-lysosome-vacuole trafficking pathways
Endomembrane system: RER/SER → Golgi → lysosome/vacuole/exocytosis.
Mitochondrion with cristae and matrix
Mitochondrion: cristae, matrix, 70S ribosomes & circular DNA.
Chloroplast with grana and stroma
Chloroplast: grana thylakoids, stroma (Rubisco), starch grains.
Comparison of 70S and 80S ribosomes
Ribosomes: 70S vs 80S (subunits indicated).
9 plus 2 axoneme and basal body 9x3
Cilium/flagellum: 9+2 axoneme; basal body (centriole) 9×3.
Quick Summary

Cells are the structural and functional units of life. Remember who belongs to the endomembrane system (ER, Golgi, lysosomes, vacuoles) and who does not (mitochondria, plastids, peroxisomes). Distinguish 70S/80S ribosomes, 9+2/9×3 arrangements, and organelle DNA. Link form to function—why cristae increase surface area, why chloroplasts have grana, and how cytoskeleton drives movement.

Practice Quiz (10 MCQs)
Downloads
Revision Sheet (PDF) Organelle Diagrams (PNG, ZIP) Prokaryote vs Eukaryote Table (PDF)
Cross-links

Related chapters: Structural Organisation in Animals · Biomolecules · Cell Cycle & Cell Division

09 Biomolecules

Summative Weightage: High Updated: 03 Sep 2025
Chapter Notes
  • Biomacromolecules vs micromolecules: macro (>10 kDa)—polysaccharides, proteins, nucleic acids; micro—monosaccharides, amino acids, nucleotides, lipids (often non-polymeric).
  • Carbohydrates: mono (glucose, fructose), di (sucrose, lactose, maltose), poly (starch—amylose+amylopectin, glycogen, cellulose β-1→4). Reducing sugars possess free carbonyl; sucrose is non-reducing.
  • Amino acids & proteins: 20 standard amino acids (zwitterions); peptide bond condensation; levels—primary (sequence), secondary (α-helix/β-sheet via H-bonds), tertiary (R-group interactions), quaternary (subunits). Fibrous vs globular proteins.
  • Enzymes: biological catalysts; active site; cofactor classes—prosthetic group (tightly bound), coenzyme (organic, e.g., NAD+), metal activators. Michaelis–Menten: Vmax, Km; factors—temperature, pH, [S], [E], inhibitors (competitive/non-competitive).
  • Lipids: triglycerides (esterified glycerol + 3 fatty acids), phospholipids (membrane), steroids (cholesterol), waxes; saturated vs unsaturated FAs (cis double bonds → fluidity).
  • Nucleic acids: nucleotide = pentose (ribose/deoxyribose) + phosphate + base (purines A,G; pyrimidines C,T,U). DNA: antiparallel double helix; A=T (2 H-bonds), G≡C (3 H-bonds); Chargaff’s rules. RNA types: mRNA, tRNA, rRNA.
  • Metabolic concepts: metabolism = anabolism + catabolism; metabolic pathways are enzyme-mediated and regulated; ATP is the common energy currency.
  • Tests/identification (qualitative): Benedict’s/Fehling’s for reducing sugars; Biuret/Xanthoproteic for proteins; iodine for starch (blue-black).
  • High-yield tables: linkages (glycosidic α/β; peptide; phosphodiester), examples of cofactors, sugar–polysaccharide relationships, base-pairing and GC% implications (Tm).
  • NEET cues: classify sugars; deduce protein level; enzyme kinetics logic; identify lipid types; DNA vs RNA features; match cofactor to enzyme.
Important Figures
Examples of mono-, di-, and polysaccharides with linkages
Carbohydrate classes and key linkages.
Protein levels: primary to quaternary with α-helix and β-sheet
Protein structural hierarchy and bonds involved.
Michaelis–Menten curve showing Km and Vmax
Michaelis–Menten curve: Vmax and Km.
Phospholipid bilayer with cholesterol molecules
Phospholipid bilayer; cholesterol and fluidity concept.
DNA double helix with base pairing A=T and G≡C
DNA double helix and base-pairing rules.
Nucleotide anatomy: base, pentose sugar, phosphate
Nucleotide components and phosphodiester linkage.
Quick Summary

Biomolecules underpin cell structure and function. Track building blocks → polymers → bonds and the rules of recognition (reducing vs non-reducing sugars, α/β linkages, protein levels, DNA vs RNA). For enzymes, remember Km (affinity) and Vmax, and how temperature, pH, and inhibitors modulate activity.

Practice Quiz (10 MCQs)
Downloads
Revision Sheet (PDF) Enzyme Kinetics Sheet (PDF) Carb/Protein/Nucleic Acid Tables (PDF)
Cross-links

Related chapters: Cell: The Unit of Life · Cell Cycle & Cell Division · Respiration in Plants

10 Cell Cycle & Cell Division

Summative Weightage: High Updated: 03 Sep 2025
Chapter Notes
  • Cell cycle phases: Interphase (G1 → S → G2) + M phase (mitosis/cytokinesis). G0 = quiescent (non-dividing, metabolically active).
  • Checkpoints & regulation: G1/S, G2/M and spindle (M) checkpoints. Cyclins bind CDKs → phosphorylate targets; p53/p21 can arrest cycle on DNA damage.
  • S phase: DNA replication (semiconservative); centriole duplication (animals). DNA content doubles (C→2C); ploidy (n) unchanged.
  • Mitosis (equational): Prophase (chromatin condenses; spindle forms), Metaphase (chromosomes at equator; max condensation), Anaphase (centromeres split; sister chromatids → opposite poles), Telophase (reformation of nuclear envelope; cytokinesis).
  • Cytokinesis: animals—cleavage furrow (actin ring); plants—cell plate (phragmoplast, vesicles from Golgi).
  • Meiosis (reductional + equational): Meiosis I reduces chromosome number (2n→n) via separation of homologues; Meiosis II resembles mitosis (sister chromatids separate).
  • Meiosis I—Prophase I substages: leptotene, zygotene (synapsis via synaptonemal complex), pachytene (crossing over; chiasmata), diplotene, diakinesis.
  • Significance: mitosis—growth/repair, genetic stability; meiosis—gamete formation, genetic variation (independent assortment + recombination).
  • Key contrasts: centromere behaviour (splits in mitosis & meiosis II, not in anaphase I), chromosome number changes, sites of crossing over, spindle attachment patterns.
  • Exam cues: identify stages from micrographs/schematics; S-phase vs mitosis changes; animal vs plant cytokinesis; order of Prophase I; “what halves?” type questions.
Important Figures
Schematic of G1, S, G2, M with checkpoints
Cell cycle phases & major checkpoints.
Diagrams of prophase, metaphase, anaphase, telophase with cytokinesis
Mitosis stages and cytokinesis types.
Leptotene, zygotene, pachytene, diplotene, diakinesis sequence
Prophase I substages and key events.
Synaptonemal complex and chiasma formation
Crossing over at pachytene; chiasmata visible in diplotene.
Reduction in meiosis I versus equational division in meiosis II
Reductional (I) vs equational (II) division logic.
Cell plate formation vs cleavage furrow
Plant cell plate vs animal cleavage furrow.
Quick Summary

Interphase prepares; M phase executes division. Mitosis keeps ploidy constant and distributes identical chromatids. Meiosis I halves chromosome number by separating homologues; meiosis II separates sister chromatids. Control is by cyclin-CDK checkpoints; errors trigger arrest. For NEET, decode micrographs by centromere status, chromosome number, and presence of synapsis/chiasmata.

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Related chapters: Biomolecules · Cell: The Unit of Life · Photosynthesis in Higher Plants

11 Photosynthesis in Higher Plants

Summative Weightage: High Updated: 03 Sep 2025
Chapter Notes
  • Overall process: 6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O (in presence of light & chlorophyll). O2 comes from photolysis of water.
  • Pigments: chlorophyll a (primary), chlorophyll b, carotenoids (carotenes & xanthophylls). Absorption spectrum vs action spectrum (Emerson’s enhancement effect).
  • Chloroplast: thylakoids (PSII in grana; PSI in stroma lamellae), stroma with enzymes of C3 cycle; ATP synthase on CF0–CF1.
  • Light reactions (photochemical):
    • Non-cyclic photophosphorylation: PSII (P680) → PQ → Cyt b6f → PC → PSI (P700) → Fd → NADP+ (makes ATP + NADPH + O2).
    • Cyclic photophosphorylation (PSI only): ATP only; no O2 or NADPH.
    • Photolysis of water at PSII releases O2, H+, e−; proton gradient drives ATP synthase (chemiosmosis).
  • Dark reactions (biosynthetic): C3 cycle (Calvin–Benson) in stroma: carboxylation (RuBisCO fixes CO2 to RuBP) → reduction (uses ATP/NADPH) → regeneration (RuBP).
  • Photorespiration (C2 cycle): RuBisCO oxygenase at high O2/low CO2, high temperature; involves chloroplast–peroxisome–mitochondrion; reduces photosynthetic efficiency.
  • C4 pathway (Hatch–Slack): Kranz anatomy; PEP carboxylase fixes HCO3− to form C4 acids (malate/aspartate) in mesophyll → decarboxylated in bundle sheath → CO2 fed to C3 cycle; minimizes photorespiration.
  • CAM plants: nocturnal CO2 fixation; stomata open at night—water conservation.
  • Factors affecting photosynthesis: light intensity/quality, CO2 concentration, temperature, water; Blackman’s law of limiting factors; light saturation and CO2 compensation point.
  • NEET focuses: PS I vs PS II differences; cyclic vs non-cyclic; RuBisCO dual activity; C3 vs C4 vs CAM features; site of O2 evolution; chemiosmosis components.
Important Figures
Chloroplast showing grana, stroma and thylakoids
Chloroplast: grana thylakoids (PSII-rich) & stroma lamellae (PSI-rich).
Z-scheme showing PSII to PSI electron flow
Z-scheme: PSII (P680) → PQ → Cyt b6f → PC → PSI (P700) → Fd → NADP+.
Proton gradient across thylakoid membrane driving ATP synthase
Chemiosmosis: H+ gradient drives ATP synthase (CF0–CF1).
Calvin cycle carboxylation, reduction, regeneration steps
Calvin cycle: RuBP carboxylation → reduction → regeneration.
Photorespiration across chloroplast, peroxisome and mitochondrion
Photorespiration (C2 cycle) organelle interplay.
Comparison table C3, C4 and CAM pathways and anatomy
C3 vs C4 vs CAM: key enzymes, anatomy, conditions.
Quick Summary

Light reactions capture energy as ATP and NADPH while splitting water to release O2. The Calvin cycle fixes CO2 into sugars in the stroma. Photorespiration wastes energy under high O2/heat; C4 and CAM strategies concentrate or time-shift CO2 to reduce it. For NEET, lock in PSII vs PSI roles, cyclic vs non-cyclic outputs, RuBisCO’s dual nature, and anatomical signatures of C4/CAM.

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Related chapters: Respiration in Plants · Biomolecules · Plant Growth & Development

12 Respiration in Plants

Summative Weightage: High Updated: 03 Sep 2025
Chapter Notes
  • Cellular respiration: controlled oxidation of substrates to release energy captured as ATP. Involves glycolysis, pyruvate oxidation, TCA cycle, and electron transport/oxidative phosphorylation.
  • Glycolysis (Embden–Meyerhof–Parnas): cytosol; glucose → 2 pyruvate; net gain = 2 ATP + 2 NADH (per glucose). Key irreversible steps: hexokinase, phosphofructokinase-1 (PFK-1), pyruvate kinase.
  • Fates of pyruvate: (a) Aerobic—pyruvate dehydrogenase complex → acetyl-CoA (mitochondrial matrix); (b) Anaerobic fermentation—lactate (in some tissues) or ethanol + CO2 (yeast/plants).
  • Link reaction: pyruvate + CoA + NAD+ → acetyl-CoA + CO2 + NADH (pyruvate dehydrogenase).
  • TCA cycle (Krebs): matrix; acetyl-CoA + oxaloacetate → citrate → … → OAA; yields (per acetyl-CoA) 3 NADH, 1 FADH2, 1 GTP(ATP), 2 CO2.
  • ETS & OxPhos: inner mitochondrial membrane; complexes I–IV pass electrons to O2 (terminal acceptor) forming H2O; proton gradient powers ATP synthase.
  • P/O ratios (textbook convention): NADH ≈ 3 ATP; FADH2 ≈ 2 ATP (modern values ~2.5/1.5, but NCERT often uses classic estimates; keep consistent in answers).
  • Respiratory Quotient (RQ): CO2 produced / O2 consumed; carbohydrates ≈ 1, fats < 1, organic acids > 1.
  • Alternative pathways: Pentose phosphate pathway (PPP) generates NADPH + ribose-5-P; in plants, cyanide-resistant respiration via alternative oxidase (AOX) (thermogenic tissues).
  • Regulation & factors: substrate availability, O2, ADP/ATP ratio, enzymes (PFK-1 as key control point), temperature; Pasteur effect (aeration suppresses fermentation).
Important Figures
Glycolysis steps from glucose to pyruvate with ATP and NADH accounting
Glycolysis overview and energy yield.
TCA (Krebs) cycle with NADH, FADH2 and GTP outputs
TCA cycle outputs per acetyl-CoA.
Electron transport chain across inner mitochondrial membrane and ATP synthase
ETC complexes I–IV and chemiosmotic ATP synthesis.
Alcoholic and lactic fermentation pathways from pyruvate
Alcoholic vs lactic fermentation.
RQ values for carbohydrates, fats and organic acids
Respiratory quotient (RQ) concept and examples.
Plant alternative oxidase pathway schematic
Cyanide-resistant respiration (AOX) in plants.
Quick Summary

Respiration harvests energy via glycolysis → acetyl-CoA → TCA → ETC, with ATP made by oxidative phosphorylation. Plants also show PPP and an alternative oxidase route. Track where each step occurs (cytosol vs mitochondrion), the coenzymes produced, and classic exam values for ATP yield and RQ.

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Related chapters: Photosynthesis in Higher Plants · Biomolecules · Plant Growth & Development

13 Plant Growth & Development

Summative Weightage: Medium–High Updated: 03 Sep 2025
Chapter Notes
  • Concepts of growth: irreversible increase in size/dry mass due to cell division & enlargement. Phases—lag, log/exponential, stationary; sigmoid (S) curve. Arithmetic vs geometric growth; RGR, NAR (qualitative awareness).
  • Meristems: apical, intercalary, lateral. Differentiation (cells specialise), Dedifferentiation (mature cells regain meristematic activity → cambium), Redifferentiation (specialise again).
  • Plant growth regulators (PGRs): Auxins, Gibberellins (GAs), Cytokinins (CKs), Abscisic acid (ABA), Ethylene.
    • Auxin (IAA): cell elongation (acid growth), apical dominance, adventitious/root initiation, vascular differentiation, phototropism & geotropism, parthenocarpy (in some fruits).
    • Gibberellins (e.g., GA3): stem elongation (bolting), break seed/tuber dormancy, germination (aleurone → α-amylase), flowering in LD plants (some).
    • Cytokinins (kinetin, zeatin): cell division, delay senescence (antisenescence), promote lateral bud growth, morphogenesis (high CK:Aux → shoot).
    • Abscisic acid (ABA): stress hormone; stomatal closure; promotes dormancy; antagonistic to GAs/auxin.
    • Ethylene: gaseous; fruit ripening (climacteric), triple response (hypocotyl thickening, reduced elongation, horizontal growth), abscission, epinasty.
  • Photoperiodism: response to day length; SDP, LDP, Day-neutral. Critical day length; leaves perceive the signal; florigen concept.
  • Phytochrome: photoreversible pigment—Pr (absorbs red ~660 nm) ⇄ Pfr (absorbs far-red ~730 nm); Pfr usually active form. Red followed by far-red reverses responses.
  • Vernalization: cold-induced flowering (e.g., cereals, biennials); stimulus often perceived at the shoot apex/embryo; reversible by devernalization (warming).
  • Tropisms & nasties: photo-, geo-, thigmo-, chemo-tropism (directional) vs nastic movements (non-directional; e.g., seismonasty in Mimosa).
  • Dormancy & seed germination: dormancy broken by scarification/stratification, GA treatment; germination requires water, O2, suitable temperature; ABA maintains dormancy.
  • Apical dominance: auxin from apical bud suppresses lateral buds; removal of apex or CK application releases branching.
  • NEET cues: hormone-function tables; red–far red reversibility; GA–aleurone–amylase axis; critical day length logic; dedifferentiation vs redifferentiation; dormancy breakers.
Important Figures
Sigmoid growth curve showing lag, log and stationary phases
Sigmoid growth curve and growth phases.
Map of five plant hormones with major actions
Five PGRs: core actions and interactions.
Short-day vs long-day response around critical day length
Photoperiodic responses and critical day length.
Interconversion between Pr and Pfr by red and far-red light
Phytochrome: Pr ⇄ Pfr photoreversibility.
Gibberellin stimulating aleurone to release amylase
GA induces α-amylase from aleurone during germination.
Diagram of phototropism and geotropism
Tropisms: directional growth responses.
Quick Summary

Growth follows a sigmoid trajectory governed by meristems and hormones. Auxin elongates and enforces apical dominance; GAs elongate, break dormancy and aid germination; CKs drive division and delay senescence; ABA enforces dormancy and stress responses; ethylene ripens fruit and modulates growth. Flowering is timed by day length (photoperiodism) and cold cues (vernalization), sensed via phytochrome and the shoot apex.

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Related chapters: Photosynthesis in Higher Plants · Respiration in Plants · Excretory Products & Their Elimination

14 Breathing & Exchange of Gases

Summative Weightage: High Updated: 03 Sep 2025
Chapter Notes
  • Human respiratory tract: nares → nasal cavity → pharynx → larynx (glottis/epiglottis) → trachea (C-shaped cartilaginous rings) → primary/secondary/tertiary bronchi → bronchioles → terminal bronchioles → respiratory bronchioles → alveolar ducts → alveoli (gas exchange). Lungs covered by double-layered pleura (pleural fluid reduces friction).
  • Mechanics of breathing: Inspiration—diaphragm contracts & flattens; external intercostals lift ribs → ↑ thoracic volume, ↓ intrapulmonary pressure (air in). Expiration—passive recoil (and internal intercostals/abdominals in forceful expiration). Compliance & surfactant reduce alveolar surface tension (Type II pneumocytes).
  • Lung volumes & capacities (textbook values at rest): TV ≈ 500 mL; IRV ≈ 2500–3000 mL; ERV ≈ 1000–1100 mL; RV ≈ 1100–1200 mL; VC = TV+IRV+ERV; TLC = VC+RV; FRC = ERV+RV; IC = TV+IRV.
  • Partial pressures (mmHg; sea level): Alveolar air ~ PO₂ 104, PCO₂ 40; Oxygenated blood (systemic arterial) similar; Deoxygenated venous blood ~ PO₂ 40, PCO₂ 45. Diffusion follows gradients & Fick’s law; exchange across respiratory membrane (thin, ~0.5 μm).
  • O₂ transport: ~98.5% as oxyhaemoglobin (HbO₂), ~1.5% dissolved. Oxyhaemoglobin dissociation curve—sigmoid; right shift (reduced affinity) by ↑PCO₂, ↑[H⁺] (↓pH), ↑temperature, ↑2,3-BPG (Bohr effect) → facilitates unloading in tissues.
  • CO₂ transport: ~70% as bicarbonate (HCO₃⁻) in plasma, ~23% as carbamino-Hb, ~7% dissolved. Chloride shift (Hamburger phenomenon) maintains ionic balance. Haldane effect: deoxygenated Hb carries more CO₂/H⁺—enhances CO₂ uptake in tissues and release in lungs.
  • Regulation of breathing: medullary respiratory centers (DRG/VRG) and pontine centers; central & peripheral chemoreceptors (↑PCO₂/↑[H⁺] primary driver; severe hypoxia stimulates peripheral chemoreceptors). Stretch receptors (Hering–Breuer reflex) in infants/forced breathing.
  • Pulmonary disorders (NEET-relevant): asthma (bronchoconstriction/inflammation), emphysema (alveolar wall destruction ↓ surface area), chronic bronchitis/COPD, pneumonia (exudate), pneumothorax (collapsed lung). Smoking—ciliary paralysis, ↑mucus, emphysema risk.
  • Key formulas/logics: Minute ventilation = TV × RR; Alveolar ventilation ≈ (TV − dead space) × RR; Diffusion ∝ (Area × ΔP × solubility) / (Thickness).
  • Exam focuses: volumes/capacities mapping; curve shifts (Bohr/Haldane); majority forms of O₂/CO₂ carriage; surfactant role; site of regulation; disorder→mechanism.
Important Figures
Human respiratory tract from nasal cavity to alveoli
Conducting vs respiratory portions of the airway.
Spirogram showing TV, IRV, ERV, RV and capacities
Spirogram with volumes and capacities.
Layers of respiratory membrane and capillary network
Respiratory membrane and diffusion path.
Oxyhaemoglobin dissociation curve with right and left shifts
Oxyhaemoglobin curve; Bohr shift factors.
Conversion of CO2 to bicarbonate and chloride shift
CO₂ transport forms & chloride shift.
Medullary and pontine centers with chemoreceptors
Neural & chemical control of breathing.
Quick Summary

Air moves in by pressure gradients created by thoracic mechanics; gases diffuse across a thin, huge-area respiratory membrane. O₂ binds Hb sigmoidal-ly; right shifts aid unloading in active tissues. CO₂ travels mainly as bicarbonate with chloride shift support. Medullary centers tune rate/depth, driven largely by CO₂/H⁺. Master the spirogram and the curve logic—these dominate NEET stems.

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Related chapters: Body Fluids & Circulation · Neural Control & Coordination · Excretory Products & Their Elimination

15 Body Fluids & Circulation

Summative Weightage: High Updated: 03 Sep 2025
Chapter Notes
  • Body fluids: blood (plasma + formed elements), tissue fluid (interstitial), lymph (returns excess interstitial fluid; immune functions).
  • Plasma: ~55% of blood; water, ions, nutrients, gases, hormones, wastes; proteins—albumin (oncotic pressure), globulins (immunity), fibrinogen (clotting).
  • Formed elements: RBCs (biconcave, anucleate; Hb; life ~120 d), WBCs (neutrophils, eosinophils, basophils, monocytes, lymphocytes), platelets (thrombocytes).
  • Blood groups: ABO—A, B antigens; plasma antibodies anti-B/anti-A; universal donor O−, universal recipient AB+ (practical caveats). Rh system—Rh+/Rh−; erythroblastosis fetalis risk in Rh− mother carrying Rh+ fetus.
  • Coagulation (clotting): cascade → prothrombin → thrombin (Ca2+ dependent) → fibrinogen → fibrin; platelets + clotting factors; anticoagulants (heparin); vitamin K for synthesis of some factors.
  • Heart anatomy: four chambers; valves—tricuspid (RA→RV), bicuspid/mitral (LA→LV), semilunars (aortic & pulmonary). Coronary circulation nourishes heart; blockage → angina/infarction.
  • Conduction system: SA node (pacemaker) → AV node → AV bundle (Bundle of His) → bundle branches → Purkinje fibres → ventricular systole (apex-to-base).
  • Cardiac cycle (avg HR ~75/min): atrial systole → ventricular systole → joint diastole. Heart sounds: S1 (AV valves close), S2 (semilunars close). Stroke volume ~70 mL; Cardiac output = HR × SV (~5 L/min at rest).
  • ECG: P wave—atrial depolarisation; QRS—ventricular depolarisation; T—ventricular repolarisation. PR interval—AV conduction; ST segment—ischemia evaluation.
  • Vessels & pressure: arteries (thick, elastic), arterioles (resistance), capillaries (exchange), veins (valves). BP ~120/80 mmHg (adult); MAP ≈ diastolic + 1/3 pulse pressure. Local control by Starling forces (hydrostatic vs oncotic) across capillaries.
  • Regulation: autonomic (symp ↑HR/↑SV; para ↓HR), baroreflex (carotid/aortic), hormones (ADH, RAAS, ANP), local metabolites (NO).
  • Key disorders: anemia, leukemia, thrombocytopenia; hypertension; atherosclerosis; myocardial infarction; heart failure; varicose veins; edema (lymphatic blockade/protein loss).
  • NEET focuses: ABO–Rh logic incl. erythroblastosis; conduction pathway & ECG mapping; heart sounds & valve events; Starling forces; CO formula; order of blood flow.
Important Figures
Pie/diagram of plasma and formed elements
Blood: plasma vs formed elements.
ABO and Rh blood group compatibility chart
ABO & Rh compatibility; erythroblastosis concept.
Simplified coagulation cascade to fibrin
Coagulation: prothrombin → thrombin → fibrin.
Four chambers and valves with blood flow direction
Heart chambers, valves, and blood flow.
SA node to Purkinje fibre conduction pathway
Conduction pathway and pacemaker order.
ECG lead II tracing with P, QRS, T
ECG waves and intervals.
Quick Summary

Blood carries gases, nutrients and immune factors; plasma proteins hold fluid in the vasculature. The heart pumps via an intrinsic conduction system coordinated with valves, producing distinct sounds and ECG waves. Pressure and resistance control flow through different vessels; excess interstitial fluid returns via lymph. For NEET, master ABO–Rh rules, ECG mapping, valve–sound timing, and CO/BP calculations.

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Related chapters: Breathing & Exchange of Gases · Excretory Products & Their Elimination · Neural Control & Coordination

16 Excretory Products & Their Elimination

Summative Weightage: High Updated: 03 Sep 2025
Chapter Notes
  • Nitrogenous wastes: Ammonotelic (ammonia—many aquatic animals), Ureotelic (urea—mammals, elasmobranchs), Uricotelic (uric acid—birds, reptiles).
  • Human excretory system: pair of kidneys → ureters → urinary bladder → urethra. Kidney: cortex, medulla (pyramids), pelvis.
  • Nephron (functional unit): renal corpuscle (Bowman’s capsule + glomerulus) and tubule (PCT → loop of Henle → DCT → collecting duct). Cortical vs Juxtamedullary nephrons (long loops; concentrate urine).
  • Urine formation—three steps:
    • Glomerular filtration (ultrafiltration; GFR ≈ 125 mL/min, ~180 L/day; NFP & filtration membrane).
    • Tubular reabsorption (selective—glucose, amino acids, ions, water; mostly at PCT).
    • Tubular secretion (H+, K+, NH4+, drugs; acid–base balance).
  • Counter-current system: loop of Henle (descending permeable to water; ascending to salts) + vasa recta → medullary osmotic gradient (NaCl + urea) → concentrated urine.
  • Juxtaglomerular apparatus (JGA): JG cells (renin) + macula densa monitor perfusion/NaCl; initiates RAAS → angiotensin II (vasoconstriction) → aldosterone (Na+ reabsorption).
  • Hormonal control: ADH/vasopressin (↑water reabsorption via aquaporins in CD), Aldosterone (↑Na+ reabsorption, K+ secretion), ANP (natriuresis; opposes RAAS), PTH (↑Ca2+ reabsorption, ↓PO₄³⁻).
  • Acid–base balance: kidneys reabsorb HCO₃⁻ and secrete H+ (via buffers like phosphate/ammonia); maintain blood pH ~7.4.
  • Micturition reflex: stretch receptors → spinal reflex; detrusor contraction + sphincter relaxation (voluntary control via external urethral sphincter).
  • Urine characteristics (typical): 1–1.5 L/day; pH ~6; urea main nitrogenous waste; also creatinine, uric acid, ions.
  • Disorders: renal calculi (kidney stones), glomerulonephritis, UTI, oliguria/anuria, diabetes insipidus (ADH deficiency), chronic kidney disease (CKD) → dialysis/transplant, gout (↑uric acid).
  • NEET targets: pathway & parts; GFR numbers; JGA–RAAS logic; counter-current & role of urea; hormone effects; acid–base handling; disorder–defect match.
Important Figures
Kidney showing cortex, medulla, pyramids and pelvis
Kidney gross anatomy: cortex–medulla–pelvis.
Nephron with glomerulus, PCT, loop of Henle, DCT and collecting duct
Nephron & associated vasculature.
Layers of filtration membrane and pressures driving GFR
Filtration membrane & net filtration pressure.
Loop of Henle and vasa recta counter-current system
Counter-current multiplier & exchanger.
Juxtaglomerular apparatus and RAAS cascade
JGA and RAAS regulation.
ADH, aldosterone and ANP actions on collecting duct
Hormonal control of water/Na+ handling.
Quick Summary

Kidneys filter ~180 L/day, reclaim essentials and secrete wastes. A medullary gradient, built by loop of Henle and vasa recta with urea recycling, lets ADH fine-tune water reabsorption for concentrated urine. RAAS raises pressure and Na+ reabsorption; ANP and ADH balance fluid–electrolyte status. For NEET, connect numbers (GFR), parts (JGA, PCT), and hormones to outcomes (dilute vs concentrated urine).

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Related chapters: Breathing & Exchange of Gases · Body Fluids & Circulation · Locomotion & Movement

17 Locomotion & Movement

Summative Weightage: Medium–High Updated: 03 Sep 2025
Chapter Notes
  • Types of muscle: Skeletal (striated, voluntary, multinucleate), Cardiac (striated, involuntary, intercalated discs), Smooth (non-striated, involuntary; visceral walls).
  • Muscle fibre ultrastructure (skeletal): sarcolemma, sarcoplasm, SR (Ca2+ store), T-tubules; myofibrils with sarcomeres (Z–Z). Bands/lines: A band (myosin), I band (actin), H zone (within A), M line, Z line.
  • Thin filament: actin (F-actin), tropomyosin, troponin (T, I, C). Thick filament: myosin with heads (ATPase) + hinge.
  • Sliding filament theory: AP at NMJ → ACh → depolarisation → T-tubules trigger SR Ca2+ release → Ca2+ binds troponin C → tropomyosin shifts → cross-bridge cycle (attach–power stroke–detach–recock) using ATP → sarcomere shortens (I, H decrease; A constant).
  • Energy for contraction: ATP immediate; phosphocreatine buffer; anaerobic glycolysis; aerobic metabolism for sustained work.
  • Muscle mechanics: motor unit; twitch, summation, incomplete/complete tetanus; tone; fatigue (metabolite accumulation). Isotonic vs isometric contraction; length–tension relation.
  • Human skeleton overview: axial (skull, vertebral column, ribs, sternum) + appendicular (limbs, girdles). Bone types: long, short, flat, irregular, sesamoid. Microscopic bone: osteon (Haversian system), osteocytes in lacunae.
  • Joints (articulations): fibrous (immovable), cartilaginous (slightly movable), synovial (freely movable: hinge, ball-and-socket, pivot, saddle, gliding, condyloid). Components: synovial cavity, cartilage, capsule, ligaments.
  • Common disorders: myasthenia gravis (autoimmune NMJ), Duchenne muscular dystrophy (genetic), tetany (hypocalcaemia), cramps, arthritis (osteo-/rheumatoid), gout (uric acid crystals), sprain/dislocation, osteoporosis (↓bone mass).
  • NEET targets: band changes during contraction; sequence NMJ→Ca2+→troponin; muscle type features; joint types/examples; osteon parts; isotonic vs isometric; disorder→defect mapping.
Important Figures
Sarcomere with A, I, H bands and Z, M lines
Sarcomere: A/I/H bands; Z & M lines.
Myosin head cycle: attach, power stroke, detach, recock
Cross-bridge cycle & ATP usage.
Motor neuron terminal releasing acetylcholine at NMJ
NMJ: ACh-mediated depolarisation.
Twitch summation leading to tetanus graph
Twitch, summation & tetanus.
Axial and appendicular skeleton labeled
Axial vs appendicular skeleton.
Types of synovial joints with examples
Synovial joint types & examples.
Quick Summary

Movement arises from sliding of actin over myosin when Ca2+ exposes binding sites and myosin heads cycle ATP. Sarcomeres shorten (I & H shrink; A unchanged). Bones and synovial joints convert muscle force into levered motion. For NEET, remember NMJ→Ca2+→troponin, what band lengths change, and hallmark features of joint types and muscle classes.

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Related chapters: Excretory Products & Their Elimination · Neural Control & Coordination · Chemical Coordination & Integration

18 Neural Control & Coordination

Summative Weightage: High Updated: 03 Sep 2025
Chapter Notes
  • Organisation: CNS (brain + spinal cord) and PNS (cranial/spinal nerves) with somatic & autonomic (sympathetic “fight–flight”, parasympathetic “rest–digest”). Enteric plexuses regulate gut.
  • Neuron: cell body (soma), dendrites, axon (axon hillock = trigger zone). Myelination by Schwann cells (PNS) or oligodendrocytes (CNS); Nodes of Ranvier enable saltatory conduction.
  • Resting membrane potential: ~ −70 mV (Na⁺/K⁺ gradients + leak channels; Na⁺/K⁺-ATPase maintains). Action potential: threshold → rapid Na⁺ influx (depolarisation) → K⁺ efflux (repolarisation) → brief hyperpolarisation; refractory periods ensure one-way travel.
  • Synapse: mostly chemical (presynaptic Ca²⁺ influx → vesicle fusion → neurotransmitter release; postsynaptic EPSP/IPSP via receptors). Summation—temporal & spatial. Electrical synapses via gap junctions (fast, rare in humans).
  • Spinal cord & reflexes: grey inside, white outside (opposite of brain). Reflex arc = receptor → sensory neuron → (interneuron) → motor neuron → effector. Knee-jerk is monosynaptic; withdrawal is polysynaptic.
  • Brain overview:
    • Forebrain: cerebrum (cortex lobes, corpus callosum), thalamus (relay), hypothalamus (homeostasis, temperature, hunger, endocrine link via pituitary; circadian regulation).
    • Midbrain: visual/auditory reflex centres; cerebral peduncles.
    • Hindbrain: cerebellum (coordination, balance), pons & medulla (vital centres—cardio-respiratory, vomiting, swallowing).
  • Meninges & CSF: dura–arachnoid–pia; cerebrospinal fluid cushions, maintains ionic milieu.
  • Autonomic effects (examples): sympathetic ↑HR, bronchodilation, pupil dilation; parasympathetic ↓HR, bronchoconstriction, pupil constriction, ↑GI motility.
  • Eye (vision): cornea + lens focus image on retina; photoreceptors—rods (dim, rhodopsin) & cones (color, fovea high acuity). Accommodation by ciliary muscle; phototransduction via opsins → hyperpolarisation of photoreceptors.
  • Ear (hearing & balance): external ear → tympanum → ossicles amplify → oval window → cochlear fluid → organ of Corti (hair cells) → auditory nerve. Vestibular apparatus (utricle/saccule: linear; semicircular canals: angular acceleration). Eustachian tube equalises pressure.
  • NEET Focus: AP phases & ion movements; myelinated vs unmyelinated speed; reflex arc path; brain part–function map; sympathetic vs parasympathetic effects; rod vs cone traits; cochlea vs vestibular roles; common neurotransmitters (ACh, GABA, glutamate, dopamine, NE).
Important Figures
Neuron with dendrites, axon, myelin and a chemical synapse
Neuron structure & chemical synapse steps.
Action potential phases with ion fluxes
AP: depolarisation (Na⁺ in), repolarisation (K⁺ out), refractory.
Forebrain, midbrain and hindbrain labelled
CNS regions and key functions.
Reflex arc components from receptor to effector
Monosynaptic vs polysynaptic reflex arcs.
Eye showing cornea, lens, iris, retina, fovea and optic nerve
Eye optics & retina (rods vs cones, fovea).
Cochlea and semicircular canals with macula and crista ampullaris
Cochlear hearing vs vestibular balance sensors.
Quick Summary

Neurons encode signals as action potentials and transmit via chemical synapses where Ca²⁺-triggered neurotransmitter release drives EPSPs/IPSPs. CNS integrates; PNS executes; autonomic branches balance organ functions. Eye focuses light onto a cone-rich fovea; ear transduces sound in cochlea and senses head movement via vestibular organs. For NEET, couple ion flow with AP phases, map brain parts to functions, and keep rod/cone and cochlear/vestibular contrasts straight.

Practice Quiz (10 MCQs)
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Related chapters: Locomotion & Movement · Chemical Coordination & Integration · Body Fluids & Circulation

19 Chemical Coordination & Integration

Summative Weightage: High Updated: 03 Sep 2025
Chapter Notes
  • Endocrine vs exocrine: Endocrine glands are ductless, release hormones into blood; exocrine use ducts (e.g., sweat, digestive enzymes). Many organs are mixed (e.g., pancreas).
  • Hormone chemistry & signaling: Peptide/protein/amine hormones act via membrane receptors & second messengers (cAMP, IP3/DAG, Ca2+); Steroid & thyroid hormones act via intracellular/nuclear receptors to alter gene transcription.
  • Hypothalamus→Pituitary axis: Hypothalamic releasing/inhibiting hormones (TRH, CRH, GnRH, GHRH, somatostatin, dopamine) regulate anterior pituitary (adenohypophysis) via hypophyseal portal system. Posterior pituitary (neurohypophysis) stores & releases hypothalamic ADH and oxytocin.
  • Anterior pituitary hormones: GH (growth; ↑IGF-1), TSH (→ thyroid), ACTH (→ adrenal cortex), LH/FSH (→ gonads), Prolactin (lactation), MSH (melanocytes in some animals). Feedback loops maintain homeostasis.
  • Thyroid: follicles produce T3/T4 (iodine-containing; ↑BMR, growth, CNS development); parafollicular C cells make calcitonin (↓Ca2+). Parathyroid secretes PTH (↑Ca2+, ↓PO43−; bone resorption, kidney reabsorption, ↑calcitriol).
  • Adrenal glands: Medulla—epinephrine/norepinephrine (acute stress). Cortex zones: glomerulosa (mineralocorticoids—aldosterone), fasciculata (glucocorticoids—cortisol), reticularis (androgens).
  • Pancreas (Islets of Langerhans): β—insulin (↓blood glucose; ↑uptake/glycogenesis/lipogenesis), α—glucagon (↑blood glucose; glycogenolysis/gluconeogenesis), δ—somatostatin (paracrine).
  • Pineal: melatonin (circadian rhythms). Thymus: thymosin (T-cell maturation). GI/Kidney/Heart: gastrin, secretin, CCK; EPO & renin (→ RAAS); ANP (↓Na+/BP).
  • Integration with nervous system: stress → hypothalamus (CRH) → ACTH → cortisol; medulla via sympathetic preganglionic fibres (ACh→chromaffin cells) releases catecholamines.
  • Key disorders (NEET-high yield):
    • GH: excess before epiphyseal closure → gigantism; after → acromegaly. Deficiency → dwarfism.
    • Thyroid: hypothyroidism (cretinism in infants; myxedema in adults); hyperthyroidism (Graves’—exophthalmos); goitre (iodine deficiency).
    • PTH: hypocalcemic tetany (↓PTH); bone demineralisation (↑PTH).
    • Adrenal: Addison’s (↓cortisol/aldosterone), Cushing’s (↑cortisol), hyperaldosteronism (Conn’s).
    • Pancreas: Diabetes mellitus—Type 1 (autoimmune β-cell loss), Type 2 (insulin resistance); acute hypoglycaemia vs chronic complications.
    • ADH: diabetes insipidus (polyuria, dilute urine).
  • NEET cues: hormone→source→target→effect tables; second messenger vs nuclear receptor; feedback diagrams; cortex zonation (G→F→R); insulin vs glucagon actions; classic symptom clusters.
Important Figures
Hypothalamic releasing hormones regulating anterior and posterior pituitary
Hypothalamus→Pituitary axis & feedback.
Second messenger pathways: cAMP and IP3/DAG with Ca2+
Peptide/amine hormone second messengers.
Steroid/thyroid hormone binding intracellular receptor affecting transcription
Steroid & thyroid hormones act via nuclear receptors.
Thyroid follicles and parathyroid location with calcitonin and PTH roles
Thyroid–parathyroid and Ca2+ regulation.
Adrenal cortex zones glomerulosa, fasciculata, reticularis and medulla
Adrenal: zona G–F–R & medulla outputs.
Islet of Langerhans cells alpha, beta and delta with hormones
Islet hormones: insulin vs glucagon.
Quick Summary

Hormones coordinate long-range regulation. Peptides/amines signal via membrane receptors and second messengers; steroids/thyroid hormones regulate transcription via nuclear receptors. The hypothalamus–pituitary axis orchestrates thyroid, adrenal and gonadal function with tight negative feedback. Master cortex zonation (G–F–R), insulin/glucagon antagonism, Ca2+ control by PTH vs calcitonin, and signature endocrine syndromes.

Practice Quiz (10 MCQs)
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Revision Sheet (PDF) Hormone Tables (PDF) Feedback Loops & Zonation (PNG)
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Related chapters: Neural Control & Coordination · Body Fluids & Circulation · Plant Growth & Development