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State Board · Class 11 · Biology

Lesson 5: Cell Structure and Organization

7 concepts · 56 practice questions with answers · Free to read

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Cell, history and cell theory

Link to Std 9–10

This deepens the basic cell structure of Std 9–10 (cell wall, nucleus, mitochondria, chloroplast) to the structure and function of every organelle.

From daily life

A wall is built brick by brick and a body is built cell by cell; the smallest cells are invisible to the eye while an ostrich egg is the largest example.

Simple definition

Cell = structural and functional unit of life, capable of independent existence. Cell theory: Schleiden (1838) and Schwann (1839) stated that plants and animals are made of cells; Virchow (1855): new cells arise from pre-existing cells by division.

Cell-theory timeline and cell sizesRoad to the cell theory1665Hooketerm ‘cell’1670sLeeuwenhoekliving cells1838Schleidenplants = cells1839Schwannanimals = cells1855Virchowcell from cellCell sizes (log scale)0.3 µmMycoplasma3–5 µmBacteria10 µmRBC100 µmHuman egg15 cmOstrich eggLongest cells: nerve cellsLight microscope ~1000×; electron microscope ~500,000×

In the figure : Top: timeline of the cell theory; below: cell sizes on a log scale.

Rule 1 : Postulates of the modern cell theory — All organisms consist of cells; new cells arise from old; the cell is the unit of structure and function; total cell activity gives organism activity; cells transform energy; cells contain DNA and RNA.

  • Easy : ‘Omnis cellula e cellula’ = every cell from a cell (Virchow).
  • Medium : The word cell was used by Robert Hooke (1665) in ‘Micrographia’.
  • Exam-type (CET) : Totipotency = ability of a cell to form a whole organism (embryonic stem cells).

Rule 2 : Cell sizes and microscopes — Smallest: Mycoplasma 0.3 µm; bacteria 3–5 µm; largest: ostrich egg (~15 cm); longest: nerve cell. Light microscope ~1000×, electron microscope ~500,000×. Purkinje–Mohl: protoplasm; Robert Brown: nucleus; Golgi; Porter: ER; de Duve: lysosome.

  • Easy : Cell size is usually in µm; 1 µm = 10⁻⁶ m.
  • Medium : An electron microscope shows cell organelles.
  • Exam-type (CET) : Virchow filled the gap (how are new cells formed?).
Remember

Hooke 1665 (cell), Schleiden 1838, Schwann 1839, Virchow 1855; smallest Mycoplasma.

Common mistake and CET trap

‘Virchow coined cell’ is wrong (Hooke). Trap: swapping Schleiden (plants) and Schwann (animals) is wrong.

Shortcut

Memory clue : "HSSV: Hooke → Schleiden → Schwann → Virchow".

Spot the difference

ScientistYearContribution
Hooke1665Term cell
Schleiden1838Plants = cells
Schwann1839Animals = cells
Virchow1855Cell from cell

Practice questions

Easy
  1. 1What is a cell?
  2. 2Who used the term cell?
  3. 3Who proposed the cell theory?
Medium
  1. 4Contribution of Virchow?
  2. 5Largest and smallest cells?
  3. 6What is totipotency?
Challenging
  1. 7Three postulates of modern cell theory.
  2. 8Advantage of an electron microscope?
Show answers (try them yourself first)
  1. 1Structural and functional unit of life.
  2. 2Robert Hooke (1665).
  3. 3Schleiden and Schwann.
  4. 4New cells arise from pre-existing cells.
  5. 5Ostrich egg; Mycoplasma.
  6. 6Capacity of a cell to give a whole organism.
  7. 7Organisms are cellular; cells from cells; cell = unit.
  8. 8Very high magnification; shows cell interior.

Prokaryotic cell

From daily life

The bacteria that set curd have no nuclear membrane; their DNA lies loose in the cytoplasm.

Simple definition

Prokaryotic cell = a cell without a definite nucleus or membrane-bound organelles (bacteria, cyanobacteria). The cell envelope has three layers: glycocalyx + cell wall + plasma membrane.

A prokaryotic cellplasmidflagellumglycocalyx (slime/capsule)cell wall + membranenucleoid (circular DNA)70S ribosomes (50S + 30S)Prokaryote: no nuclear membrane or membrane organelles; mesosome; plasmid (F, R)Gram +ve = peptidoglycan; Gram −ve = murein | pili = contact; fimbriae = clinging

In the figure : Bacterial cell: cell envelope, nucleoid, plasmid, 70S ribosomes, flagellum.

Live figure

Prokaryotic cell

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Rule 1 : Cell envelope and motility — Glycocalyx = slime layer (loose) or capsule (tough). Cell wall: peptidoglycan (Gram +ve), murein (Gram −ve) – mechanical strength. Plasma membrane = phospholipid bilayer. Motility by flagella; basal body (motor) + filament + hook. Pili = contact; fimbriae = clinging. Gram staining: Hans Christian Gram.

  • Easy : Mesosome = membrane infolding; wall formation, respiration, DNA replication.
  • Medium : Cyanobacteria have chromatophores (photosynthetic pigments).
  • Exam-type (CET) : The basal body is often called the smallest motor in the world.

Rule 2 : Interior: DNA, ribosomes, plasmids — Genetic material = single circular DNA (nucleoid), no histones so no chromatin; attached to mesosome. Plasmid = small circular DNA: F-plasmid (reproduction), R-plasmid (antibiotic resistance). Ribosomes 70S = 50S + 30S. Cytoplasm has reserve granules (glycogen, cyanophycean starch, sulphur).

  • Easy : A special DNA replication pattern: theta model.
  • Medium : R-plasmid makes bacteria resist antibiotics.
  • Exam-type (CET) : 70S refers to sedimentation rate (Svedberg).
Remember

Prokaryote: no nucleus, 70S ribosomes, circular DNA, plasmid, mesosome.

Common mistake and CET trap

‘Prokaryotes have mitochondria’ is wrong. Trap: ‘histones present’ is wrong.

Shortcut

Memory clue : "Pro = Primitive, no nucleus; 70S = 50 + 30".

Spot the difference

PointProkaryoteEukaryote
Nuclear membraneAbsentPresent
Ribosomes70S80S
Membrane organellesAbsentPresent

Practice questions

Easy
  1. 1What is a prokaryotic cell?
  2. 2Three layers of the cell envelope.
  3. 3Who developed Gram staining?
Medium
  1. 4What is a plasmid?
  2. 5Functions of F and R plasmids.
  3. 6Function of mesosome.
Challenging
  1. 7Difference between pili and fimbriae.
  2. 8Two differences between prokaryote and eukaryote.
Show answers (try them yourself first)
  1. 1A cell lacking nuclear membrane and membrane organelles.
  2. 2Glycocalyx, cell wall, plasma membrane.
  3. 3Hans Christian Gram.
  4. 4Small circular extra DNA in bacteria.
  5. 5F: reproduction; R: antibiotic resistance.
  6. 6Wall formation, respiration, DNA replication.
  7. 7Pili: intercellular communication; fimbriae: clinging.
  8. 8Nuclear membrane absent/present; ribosomes 70S/80S.

Cell wall and plasma membrane

From daily life

A ripe fruit turns soft as pectin in its wall dissolves; the plasma membrane works like a fence, letting in what is needed and keeping out the rest.

Simple definition

Cell wall = rigid outer covering in plants, fungi and some protists. Plasma membrane = lipid bilayer + proteins; fluid mosaic model (Singer–Nicholson, 1972); selectively permeable.

Plasma membrane and cell wallFluid mosaic model (Singer–Nicholson 1972)channelperipheral proteinhydrophilic headhydrophobic tailsperipheralintegralPlant cell wall: outside to insideMiddle lamellaPrimary wallSecondary wallPlasma membranepectin; firstcan growafter growth; pitsselectively permeablePassive: along gradient, no energy | Active: ATP, against gradient (Na⁺/K⁺ pump)Plasmodesmata = cytoplasmic bridges between neighbouring cells

In the figure : Top: fluid mosaic model; below: layers of a plant cell wall and transport.

Rule 1 : Cell wall — Middle lamella (pectin, Ca and Mg pectate; first, from the cell plate), primary wall (young cell, can grow), secondary wall (after growth stops; pits). Algae: cellulose, galactans, mannans, CaCO₃; other plants: hemicellulose, pectin, lignin; cutin, suberin, silica deposited. Plasmodesmata connect neighbouring cells.

  • Easy : Suberin in root endodermis; cutin in leaf epidermis.
  • Medium : Cellulose = rigidity; pectin = cementing material.
  • Exam-type (CET) : Meristematic cells have only a primary wall.

Rule 2 : Plasma membrane and transport — Thickness about 75 Å; phospholipids are amphipathic (hydrophilic heads + hydrophobic tails) in a bilayer. Proteins: integral (span the bilayer, channels) and peripheral. Passive: simple diffusion, osmosis – no energy. Active: against the gradient, ATP (Na⁺/K⁺ pump). Polar molecules need carrier proteins.

  • Easy : ‘Icebergs in a sea’: proteins move in the lipid sea (fluidity).
  • Medium : Water channels = integral proteins.
  • Exam-type (CET) : Endomembrane system: ER, Golgi, lysosomes, vacuoles, nuclear envelope; not mitochondria/chloroplasts.
Remember

Passive = no energy; active = ATP + against gradient; Singer–Nicholson 1972.

Common mistake and CET trap

‘Animals have a cell wall’ is wrong. Trap: ‘proteins are fixed’ is wrong (fluid).

Shortcut

Memory clue : "ML-PW-SW: Middle → Primary → Secondary (outside to inside)".

Spot the difference

TransportEnergyExample
Simple diffusionNoO₂, CO₂
OsmosisNoWater
Active transportATPNa⁺/K⁺ pump

Practice questions

Easy
  1. 1Who proposed the fluid mosaic model?
  2. 2What does amphipathic mean?
  3. 3Integral vs peripheral proteins.
Medium
  1. 4What forms the middle lamella?
  2. 5What are plasmodesmata?
  3. 6Active vs passive transport.
Challenging
  1. 7Why does a ripe fruit soften?
  2. 8When is the secondary wall laid?
Show answers (try them yourself first)
  1. 1Singer and Nicholson (1972).
  2. 2One end water-loving, the other water-repelling.
  3. 3Integral span the membrane; peripheral lie on the surface.
  4. 4Pectin, Ca/Mg pectate.
  5. 5Cytoplasmic bridges between neighbouring cells.
  6. 6ATP, against gradient / no energy, along gradient.
  7. 7Pectin dissolves.
  8. 8After primary wall growth stops.

Cytoplasm, ER and Golgi complex

From daily life

A factory receives raw material, makes goods, packs and dispatches them. In a cell the ER makes, the Golgi packs and vesicles dispatch.

Simple definition

Cytoplasm (cytosol) = the jelly-like material of the cell; ER = network of membranous tubules and sacs (cisternae); Golgi complex = stacks of cisternae – modifies and packs secretions.

ER and Golgi relationshipnucleusRough ERSmooth ERvesicleGolgi complexcistranssecretion,lysosomeRough ER: ribosomes; proteins (e.g. insulin secretion), membrane buildingSmooth ER: lipids/steroids, detox (liver), Ca²⁺ store (muscle)Golgi: cis (receive) → modify + pack → trans (dispatch); makes pectinER absent in: mature RBCs and ova

In the figure : Nucleus → rough ER → vesicle → Golgi (cis → trans) → outside / lysosome.

Live figure

Cytoplasm, ER and Golgi complex

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Rule 1 : Cytoplasm and ER — Cytosol holds water, sugars, amino acids, enzymes; cyclosis = streaming. ER runs from the nuclear envelope to the cell membrane; over 50% of cell membrane. Rough ER: ribosomes; secretory proteins, builds membrane. Smooth ER: lipids/steroids (adrenal, testes), detoxification (liver), Ca²⁺ store (muscle). ER absent: mature RBCs, ova.

  • Easy : Cells making insulin have abundant rough ER.
  • Medium : Smooth ER in liver = drug/alcohol detox.
  • Exam-type (CET) : Cytoplasm = raw material + site of metabolism.

Rule 2 : Golgi complex — Stacks of cisternae (0.5–1 µm); cis (receiving) and trans (dispatching) faces; ER vesicles fuse at cis; secretions are modified (glycoproteins, glycolipids) and leave from trans as vesicles. Golgi also makes non-cellulose polysaccharides like pectin. Golgi cisternae are not connected like ER. Lysosomes arise from Golgi.

  • Easy : Cis = near (toward ER); trans = far.
  • Medium : Discovered by Camillo Golgi (1838).
  • Exam-type (CET) : Cisternal maturation model: cisternae themselves mature from cis to trans.
Remember

Rough ER = proteins; smooth ER = lipids/detox; Golgi = modify and pack (cis → trans).

Common mistake and CET trap

‘Smooth ER has ribosomes’ is wrong. Trap: ‘Golgi cisternae are connected like ER’ is wrong.

Shortcut

Memory clue : "RER = Ribosomes + Protein; SER = Steroids + Safe (detox)".

Spot the difference

OrganelleFunctionKey
Rough ERProteinsRibosomes
Smooth ERLipids, detoxNo ribosomes
GolgiModify, packcis/trans

Practice questions

Easy
  1. 1What is cytosol?
  2. 2What is cyclosis?
  3. 3Which cells lack ER?
Medium
  1. 4Function of rough ER.
  2. 5Two functions of smooth ER.
  3. 6Explain cis and trans faces.
Challenging
  1. 7Which form the endomembrane system?
  2. 8One difference between Golgi and ER.
Show answers (try them yourself first)
  1. 1The fluid part of the cytoplasm.
  2. 2Streaming movement of cytoplasm.
  3. 3Mature RBCs and ova.
  4. 4Synthesis and transport of proteins.
  5. 5Lipid/steroid synthesis; detox; Ca²⁺ storage.
  6. 6cis = receiving; trans = dispatching.
  7. 7ER, Golgi, lysosomes, vacuoles, nuclear envelope.
  8. 8ER cisternae are connected; Golgi's are not.

Lysosomes, vacuoles and microbodies

From daily life

As a garbage truck breaks down waste, a lysosome digests old material in the cell.

Simple definition

Lysosome = membrane-bound vesicle with hydrolytic enzymes (act at acidic pH). Vacuole = sac bounded by a tonoplast holding cell sap. Microbodies = small membrane-bound sacs: sphaerosome, peroxisome, glyoxysome.

Types of lysosomes and microbodiesLysosomesGolgiPrimaryinactive enzymesfoodold organelleSecondaryAutophagicHeterophagic (foreign)Autophagic = ‘suicide bag’residualbodyLysosome enzymes: hydrolases (amylase, protease, lipase); acidic pHVacuole: tonoplast; cell sap; turgor; contractile vacuole in ParamoeciumMicrobodies: sphaerosome (fat store), peroxisome (H₂O₂ breakdown), glyoxysome (fat → sugar)Acrosome = modified lysosome of sperm (hyaluronidase)

In the figure : Types of lysosomes, plus vacuoles and microbodies in brief.

Rule 1 : Lysosomes — Formed from Golgi; enzymes inactive (primary) → fuse with foreign material/old organelles to form active secondary lysosomes (heterophagic/autophagic). Residual body = undigested remains. Autophagic = ‘suicide bag’. Acrosome = lysosome (hyaluronidase). Metamorphosis, destroying cancer cells (T-lymphocytes). Tay-Sachs: lipase deficiency → fat accumulates, brain damaged.

  • Easy : Amoeba food vacuole = intracellular digestion.
  • Medium : Macrophages engulf bacteria and destroy them with lysosomes.
  • Exam-type (CET) : Lysosomes do not digest their own membrane (protein shape).

Rule 2 : Vacuoles and microbodies — Vacuole: large in plant cells (central vacuole up to 90%); tonoplast; cell sap hypertonic; maintains turgor; pigments (petal colour); contractile vacuole in Paramoecium (excretion + osmoregulation). Microbodies: sphaerosome (fat storage, endosperm), peroxisome (makes and breaks H₂O₂; alcohol in liver), glyoxysome (fat → sugar in germinating seeds).

  • Easy : Central vacuole stores water and salts.
  • Medium : Glyoxysome = in germinating seeds, until photosynthesis begins.
  • Exam-type (CET) : Tonoplast = vacuole membrane.
Remember

Lysosome = digestion + ‘suicide bag’; vacuole = turgor; peroxisome = H₂O₂; glyoxysome = fat → sugar.

Common mistake and CET trap

‘Lysosome enzymes always active’ is wrong (initially inactive). Trap: ‘tonoplast = lysosome membrane’ is wrong.

Shortcut

Memory clue : "Lyso = lysis (break down); Tono = Tonic (vacuole)".

Spot the difference

OrganelleFunctionExample
LysosomeDigestionMacrophage
VacuoleTurgor, storageCentral vacuole
PeroxisomeH₂O₂ breakdownLiver

Practice questions

Easy
  1. 1Where do lysosomes arise?
  2. 2Type of lysosomal enzymes?
  3. 3Why is it called a suicide bag?
Medium
  1. 4Acrosome is a modified ___?
  2. 5What is a tonoplast?
  3. 6Function of contractile vacuole.
Challenging
  1. 7Function of peroxisome.
  2. 8Where are glyoxysomes found and what do they do?
Show answers (try them yourself first)
  1. 1From the Golgi complex.
  2. 2Hydrolases (amylase, protease, lipase).
  3. 3It digests the cell's own old organelles.
  4. 4Lysosome.
  5. 5Membrane around the vacuole.
  6. 6Excretion and osmoregulation.
  7. 7Forms H₂O₂ and converts it to water.
  8. 8Germinating seeds; convert fat to sugar.

Mitochondria, plastids and ribosomes

From daily life

A phone battery stores and delivers energy; in a cell mitochondria deliver ATP and chloroplasts make food from sunlight.

Simple definition

Mitochondrion = double-membraned energy factory (cristae, oxysomes). Plastids = leucoplast, chromoplast, chloroplast. Ribosome = membrane-less protein factory; 70S (prokaryote) and 80S (eukaryote).

Mitochondrion and chloroplastmatrixMitochondrion: cristae, oxysomes (F₁–F₀)double membrane; matrix has DNA + 70S ribosomesATP synthase = F₁ headstromagranumChloroplast: thylakoids, grana, stromadouble membrane; DNA + 70S ribosomesLeuco- / chromo- / chloroplastRibosomes: prokaryote 70S (50S + 30S) | eukaryote 80S (60S + 40S)Svedberg (S) = sedimentation unit; 1 S = 10⁻¹³ s | 70S in mitochondria/plastidsEndosymbiont theory: engulfed bacteria became mitochondria / chloroplasts

In the figure : Structure of mitochondrion and chloroplast; ribosome sizes and the endosymbiont theory.

Live figure

Mitochondria, plastids and ribosomes

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Rule 1 : Mitochondria — Double membrane: outer (porin; permeable), inner (cristae; selectively permeable). Matrix: circular DNA, 70S ribosomes, Krebs cycle enzymes. Inner membrane bears oxysomes (F₁ head = ATP synthase, F₀ = proton channel). Absent in RBCs and prokaryotes.

  • Easy : ‘Powerhouse of the cell’ = makes ATP.
  • Medium : Cristae = folds of the inner membrane; increase surface area.
  • Exam-type (CET) : Having DNA and ribosomes, mitochondria divide on their own.

Rule 2 : Plastids and ribosomes — Leucoplast (colourless; storage: amyloplast starch, elaioplast oil, aleuroplast proteins), chromoplast (carotene, xanthophyll; red/yellow), chloroplast (chlorophyll; grana + stroma + thylakoids; 20–40 in mesophyll). Ribosome: rRNA + protein, Palade 1953; 80S = 60S + 40S; free (enzymes) and bound (secretory proteins); polyribosomes.

  • Easy : White potato = leucoplast; red hibiscus petal = chromoplast.
  • Medium : Ribbon-shaped in Spirogyra; one large chloroplast in Chlamydomonas.
  • Exam-type (CET) : Venkatraman Ramakrishnan: 2009 Nobel (Chemistry) for ribosome structure.
Remember

Mitochondria = ATP (oxysomes); chloroplast = food (grana); ribosome = proteins (70S/80S).

Common mistake and CET trap

‘Ribosome has a membrane’ is wrong. Trap: ‘mitochondria have 80S’ is wrong (70S).

Shortcut

Memory clue : "Mito = ATP machine; Chloro = chlorophyll + grana".

Spot the difference

OrganelleMembraneKey
MitochondrionDoubleCristae, oxysomes
ChloroplastDoubleGrana, thylakoids
RibosomeNone70S / 80S

Practice questions

Easy
  1. 1Why are mitochondria called powerhouses?
  2. 2What are cristae?
  3. 3Function of oxysomes?
Medium
  1. 4Three kinds of leucoplast.
  2. 5Pigments of chromoplast?
  3. 6Parts of a chloroplast.
Challenging
  1. 7Prokaryotic vs eukaryotic ribosomes.
  2. 8What is the endosymbiont theory?
Show answers (try them yourself first)
  1. 1They make ATP.
  2. 2Folds of the inner membrane.
  3. 3Proton pumping and ATP synthesis.
  4. 4Amyloplast, elaioplast, aleuroplast.
  5. 5Carotene, xanthophyll.
  6. 6Grana, stroma, thylakoids, stromal lamellae.
  7. 770S (50S+30S) / 80S (60S+40S).
  8. 8Mitochondria and chloroplasts arose from bacteria living inside cells.

Nucleus, cytoskeleton, cilia and centrioles

From daily life

A principal runs a school; in a cell this is the nucleus, holding DNA, chromosomes and instructions.

Simple definition

Nucleus = control centre with a double nuclear envelope, nucleoplasm, nucleolus and chromatin. Cytoskeleton = microtubules, microfilaments, intermediate filaments. Cilia/flagella = movement; centriole = 9 triplets.

Nucleus and the 9+2 structure of cilianucleolusNucleus: nuclear envelope (double)nucleopores, nucleoplasm, chromatinEuchromatin = active | Heterochromatin = inertCilia / flagella section: 9 + 29 outer doublets + 2 central; radial spokesCentriole = 9 triplets (cartwheel)Cytoskeleton: microtubules (tubulin), microfilaments (actin), intermediate filamentsCilia = short, many (oars) | flagella = long, few | basal body from centrioleCentrosome forms the spindle; near nucleus in animal cells

In the figure : Nucleus, the 9+2 structure of cilia/flagella, centriole and cytoskeleton.

Rule 1 : Nucleus — Nuclear envelope: two membranes, perinuclear space (10–50 nm), nucleopores. Outer membrane joins ER; inner lined by nuclear lamina. Nucleoplasm (karyolymph) has chromatin (DNA + histones) and nucleolus (rRNA + ribosomal proteins; makes ribosomes). Euchromatin = active; heterochromatin = inert. Human cells have 46 chromosomes.

  • Easy : The nucleolus has no membrane.
  • Medium : Nucleopores regulate exchange of molecules.
  • Exam-type (CET) : Robert Brown (1881) discovered the nucleus.

Rule 2 : Cytoskeleton, cilia/flagella and centrioles — Microtubules (tubulin), microfilaments (actin), intermediate filaments → shape, motility, division. Cilia: short, many, oar-like; flagella: long, few. Structure: basal body (from centriole), basal plate, shaft = axoneme 9+2 (9 doublets + 2 central), radial spokes, sheath. Centrosome: 2 centrioles at right angles; each with 9 triplets, cartwheel; forms spindle and gives basal bodies.

  • Easy : 9+2 = cilia/flagella; 9 triplets = centriole/basal body.
  • Medium : Centrosome lies near the nucleus in animal cells.
  • Exam-type (CET) : A bacterial flagellum differs structurally from a eukaryotic one.
Remember

Nucleus = DNA + nucleolus; cilia/flagella = 9+2; centriole = 9 triplets.

Common mistake and CET trap

‘Centriole = 9+2’ is wrong (9 triplets). Trap: ‘nucleolus has a membrane’ is wrong.

Shortcut

Memory clue : "Cilia = 9+2; centriole = 9 triplets (3×9)".

Spot the difference

StructureArrangementFunction
Cilia / flagella9 + 2Movement
Centriole9 tripletsSpindle, basal body
NucleolusNo membraneRibosome biogenesis

Practice questions

Easy
  1. 1Function of nucleolus?
  2. 2Function of nucleopores?
  3. 3Euchromatin vs heterochromatin.
Medium
  1. 4Three parts of the cytoskeleton.
  2. 5Cilia vs flagella.
  3. 6What does 9+2 mean?
Challenging
  1. 7Structure of a centriole.
  2. 8Function of centrosome?
Show answers (try them yourself first)
  1. 1Makes rRNA and ribosomes.
  2. 2Exchange between nucleus and cytoplasm.
  3. 3Active, extended / inert, condensed.
  4. 4Microtubules, microfilaments, intermediate filaments.
  5. 5Cilia short and many; flagella long and few.
  6. 69 peripheral doublets and 2 central fibrils.
  7. 79 triplet microtubules; cartwheel.
  8. 8Forms spindle; gives basal bodies.

Quick revision of the whole lesson

ConceptKey fact
Cell theoryHooke 1665 → Schleiden 1838 → Schwann 1839 → Virchow 1855
Prokaryote70S, nucleoid, plasmid, mesosome
Membrane / wallFluid mosaic 1972; ML → PW → SW
ER / GolgiRER proteins; SER lipids; Golgi cis → trans
Lysosome / vacuoleDigestion, suicide bag; tonoplast
Mito / plastid / ribosomeATP; grana; 70S vs 80S
Nucleus & beyondNucleolus; 9+2; centriole = 9 triplets

🎯 Most important points for the exam

  • Timeline of the cell theory.
  • Prokaryote vs eukaryote.
  • Fluid mosaic model and transport types.
  • Functions of ER, Golgi and lysosome.
  • Mitochondria / chloroplast structure, 70S–80S.
  • Cilia (9+2) and centriole (9 triplets).
Study mantra

Understand the concept → draw the figure → memorise the key points → solve questions yourself.