KEY DIFFERENCES — PLANT CELL vs ANIMAL CELL ⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
PLANT CELL |
ANIMAL CELL |
| Cell wall | Present (cellulose) | Absent |
| Plastids | Present | Absent |
| Large central vacuole | Present | Absent or small |
| Centrioles | Absent in almost all plant cells ⭐ | Present |
| Plasmodesmata | Present | Absent |
A CELL MEMBRANE (Plasma Membrane)
Fluid Mosaic Model (Singer & Nicolson, 1972) ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Model proposed by | Singer & Nicolson (1972) ⭐ |
| Main composition | Lipids & Proteins (also carbohydrates) |
Lipid Bilayer ⭐⭐
↔ Swipe table sideways to view full columns
| COMPONENT |
POSITION |
NATURE |
| Polar heads |
Outer sides (facing aqueous environment) |
Hydrophilic ⭐ |
| Non-polar tails |
Inner side (sandwiched between) |
Hydrophobic ⭐ |
| Major lipids |
— |
Phospholipids (Phosphoglycerides) ⭐ |
| Also contains |
— |
Cholesterol |
Proteins ⭐⭐
↔ Swipe table sideways to view full columns
| TYPE |
LOCATION |
DETAIL |
| Integral (Intrinsic) |
Partially or totally buried in the membrane ⭐ |
Deeply embedded |
| Peripheral (Extrinsic) |
Lie on the surface of membrane ⭐ |
Easily extracted |
Fluidity ⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Basis | Quasi-fluid nature of lipids ⭐ |
| Consequence | Enables lateral movement of proteins within the lipid bilayer ⭐ |
Human RBC Membrane Composition ⭐
↔ Swipe table sideways to view full columns
| COMPONENT |
PERCENTAGE |
| Protein | ~52% |
| Lipid | ~40% |
⚡ EXAM TRAP
NEET 2012, 2026 (reinforced): Membrane of human RBC has approximately 52% protein and major phospholipids are arranged in a bilayer with hydrophobic tails facing inward.
⚡ EXAM TRAP
NEET 2026: Glycocalyx is present on the outer surface of plasma membrane in prokaryotes.
Functions of Fluid Nature of Membrane ⭐
• Cell growth • Secretion • Endocytosis • Cell division • Formation of intercellular junctions
Transport Across Membrane ⭐⭐
↔ Swipe table sideways to view full columns
| TYPE |
DIRECTION |
ENERGY REQUIRED |
EXAMPLES |
| Passive transport |
High → Low conc. (along gradient) |
No |
Simple diffusion, Osmosis, Facilitated diffusion |
| Active transport |
Low → High conc. (against gradient) |
Yes (ATP) ⭐ |
Na⁺/K⁺ Pump ⭐ |
| TRANSPORT MODE |
DETAIL |
| Simple diffusion | Neutral solutes move along conc. gradient |
| Osmosis | Movement of water by diffusion (high to low concentration) ⭐ |
| Facilitated diffusion |
Polar molecules cannot pass through nonpolar lipid bilayer → require carrier proteins ⭐ |
| Active transport |
Against concentration gradient; ATP-dependent; e.g., Na⁺/K⁺ Pump |
⚡ EXAM TRAP
NEET 2021: Active transport — Na⁺/K⁺ Pump; requires ATP; against concentration gradient.
B CELL WALL (Eukaryotic — Plants)
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Nature | Non-living, rigid structure ⭐ |
| Position | Outer covering for plasma membrane (in fungi & plants) |
Composition in Different Groups ⭐
↔ Swipe table sideways to view full columns
| GROUP |
CELL WALL COMPOSITION |
| Algae |
Cellulose, Galactans, Mannans, Minerals (CaCO₃) ⭐ |
| Other plants |
Cellulose, Hemicellulose, Pectins, Proteins ⭐ |
| Bacteria |
Peptidoglycan |
Primary vs Secondary Cell Wall ⭐
↔ Swipe table sideways to view full columns
| FEATURE |
PRIMARY CELL WALL |
SECONDARY CELL WALL |
| Found in | Young plant cells | Mature cells |
| Growth | Capable of growth ⭐ | Growth capacity diminished |
| Position | Outer | Formed on inner side (towards membrane) ⭐ |
Middle Lamella ⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Composition | Mainly Calcium pectate (Ca²⁺ pectates) ⭐ |
| Function | Holds / glues neighbouring cells together ⭐ |
• Plasmodesmata ⭐: Traverse cell wall & middle lamella; connect cytoplasm of neighbouring cells.
• Functions of Cell Wall ⭐: Gives shape to cell; protects from mechanical damage & infection; helps in cell-to-cell interaction; provides barrier to undesirable macromolecules.
C ENDOMEMBRANE SYSTEM
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Definition | Different membranous organelles with coordinated functions |
| Includes | ER, Golgi complex, Lysosomes, Vacuoles ⭐ |
| Does NOT include |
Mitochondria, Chloroplast, Peroxisomes ⭐⭐ (functions NOT coordinated with endomembrane system) |
⚡ EXAM TRAP
NEET 2021, 2023, RE-NEET 2026 (reinforced): Endomembrane system includes endoplasmic reticulum, Golgi complex, lysosomes and vacuole — mitochondria, chloroplast and peroxisomes are NOT part of it.
C1. Endoplasmic Reticulum (ER) ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Structure | Network of tiny tubular structures scattered in cytoplasm |
| Function | Divides intracellular space into two compartments: Luminal (inside ER) & Extra-luminal (cytoplasm) ⭐ |
Two Types of ER ⭐⭐⭐
↔ Swipe table sideways to view full columns
| TYPE |
FEATURE |
MAJOR FUNCTION |
| RER (Rough ER) |
Ribosomes attached on outer surface ⭐ |
Protein synthesis & secretion ⭐; Glycoprotein formation |
| SER (Smooth ER) |
No ribosomes (smooth appearance) |
Lipid synthesis ⭐ (including steroidal hormones in animal cells) |
• ⭐ RER is extensive & continuous with outer membrane of nucleus.
• RER frequent in cells actively involved in protein synthesis & secretion.
⚡ EXAM TRAP
NEET 2013, 2015, 2018, RE-NEET 2026 (reinforced): Smooth ER is major site for synthesis of lipids (steroidal hormones in animal cells). Rough ER bears ribosomes on its surface (protein synthesis). Lipid synthesis does NOT occur in RER!
C2. Golgi Apparatus ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Discovered by | Camillo Golgi (1898) ⭐ |
| Structure | Many flat, disc-shaped sacs called Cisternae ⭐ |
| Cisternae diameter | 0.5–1.0 µm |
| Arrangement | Stacked parallel to each other; concentrically arranged near nucleus |
Cis & Trans Faces ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FACE |
SHAPE |
ALTERNATE NAME |
FACES TOWARDS |
| Cis face |
Convex ⭐ |
Forming face |
Towards ER / Nucleus ⭐ |
| Trans face |
Concave ⭐ |
Maturing face |
Towards plasma membrane |
| KEY FACT |
DETAIL |
| Cis & Trans faces | Entirely different but interconnected ⭐ |
| Close association with | Endoplasmic Reticulum ⭐ |
| Materials from ER |
Fuse with cis face → move towards trans face → released from trans face |
| Proteins modified |
In cisternae of Golgi → released from trans face (NOT cis face) ⭐ |
Functions ⭐⭐
• ⭐ Packaging of materials (for intracellular delivery or secretion outside cell)
• Modification of proteins synthesised by ER ribosomes
• ⭐⭐ Major site of formation of Glycoproteins & Glycolipids (Glycosylation)
⚡ EXAM TRAP
NEET 2014, 2015, 2018, 2019, 2020, 2021, 2023, 2024, 2025 (reinforced): Vesicles from ER fuse with cis face of Golgi, are modified in cisternae, and released from trans face for packaging and delivery; Golgi = major site for glycoprotein & glycolipid formation.
C3. Lysosomes ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Structure | Membrane-bound vesicular structures ⭐ |
| Formed by | Process of packaging in the Golgi apparatus ⭐⭐ (NOT ER) |
| Enzymes | Rich in hydrolytic enzymes (hydrolases) ⭐ — lipases, proteases, carbohydrases |
| Optimal pH | Acidic pH ⭐ (enzymes inactive at alkaline pH) |
| Can Digest ⭐ | Carbohydrates, Proteins, Lipids, Nucleic acids |
⚡ EXAM TRAP
NEET 2016, 2019, 2022: Lysosomes — formed by packaging in Golgi (NOT ER); contain hydrolytic enzymes active at acidic pH (inactive at alkaline pH!).
C4. Vacuoles ⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Structure | Membrane-bound space in cytoplasm |
| Membrane | Bound by a single membrane called Tonoplast ⭐⭐ |
| In plant cells | Can occupy up to 90% of cell volume ⭐ |
| Contents ⭐ | Water, Cell sap, Excretory products, Other materials not useful for cell |
Tonoplast Function ⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Function | Facilitates transport of ions & materials against concentration gradient into the vacuole ⭐ |
| Result | Concentration significantly higher in vacuole than in cytoplasm |
Special Vacuoles ⭐
↔ Swipe table sideways to view full columns
| ORGANISM |
VACUOLE TYPE |
FUNCTION |
| Amoeba | Contractile vacuole | Osmoregulation & excretion ⭐ |
| Protists | Food vacuoles | Formed by engulfing food particles |
D MITOCHONDRIA
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Visibility | Not easily visible without specific staining |
| Number | Variable — depends on physiological activity of cell ⭐ |
| Shape | Sausage-shaped or cylindrical ⭐ |
| Diameter & Length | Diameter 0.2–1.0 µm (average 0.5 µm); Length 1.0–4.1 µm |
| Membrane | Double membrane-bound ⭐⭐ |
| Division | Divide by fission ⭐ |
Structure ⭐⭐⭐
↔ Swipe table sideways to view full columns
| COMPONENT |
DETAIL |
| Outer membrane |
Continuous limiting boundary; more permeable (permeable to monomers) ⭐ |
| Inner membrane |
Forms infoldings called Cristae ⭐⭐; relatively less permeable ⭐ |
| Two aqueous compartments |
Outer compartment (perimitochondrial space) & Inner compartment (matrix) |
| Cristae |
Infoldings of inner membrane towards matrix ⭐; increase surface area ⭐ |
| Matrix | Dense, homogeneous substance filling inner compartment |
Matrix Contents ⭐⭐
↔ Swipe table sideways to view full columns
| CONTENT |
DETAIL |
| DNA | Single, circular, double-stranded DNA molecule ⭐ |
| RNA | A few RNA molecules |
| Ribosomes | 70S type ⭐ (required for protein synthesis within mitochondria) |
| Enzymes | Components for protein synthesis |
Function ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Main function | Site of aerobic respiration ⭐ |
| Product | Cellular energy in the form of ATP |
| Called | 'Power Houses' of the cell ⭐⭐ |
⚡ EXAM TRAP
NEET 2015, 2016, 2017, 2019, 2021, 2024, 2026, RE-NEET 2026 (reinforced): Mitochondrial inner membrane encloses matrix; cristae increase surface area; both mitochondria and plastids have circular DNA and are double membrane bound. Mitochondria = 'Power Houses' of cell!
E PLASTIDS
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Found in | All plant cells & Euglenoids ⭐ |
| Size | Large — easily observed under microscope |
Three Types (Based on Pigments) ⭐⭐
↔ Swipe table sideways to view full columns
| TYPE |
PIGMENTS |
COLOUR GIVEN |
FUNCTION / DETAIL |
| Chloroplast |
Chlorophyll & Carotenoid ⭐ |
Green |
Trapping light energy for photosynthesis |
| Chromoplast |
Fat-soluble carotenoid pigments (Carotene, Xanthophyll, etc.) ⭐ |
Yellow, Orange, Red ⭐ |
Give colour to plant parts |
| Leucoplast |
No pigments (Colourless) ⭐ |
— |
Storage of nutrients |
⚡ EXAM TRAP
NEET 2013, 2024, RE-NEET 2026 (reinforced): Chromoplast is a plastid that stores xanthophyll/carotene (fat-soluble carotenoids giving yellow, orange, red colour).
Leucoplast — Three Subtypes ⭐⭐
↔ Swipe table sideways to view full columns
| SUBTYPE |
STORES |
EXAMPLE |
| Amyloplast | Carbohydrates (Starch) ⭐ | Potato |
| Elaioplast | Oils & Fats | — |
| Aleuroplast | Proteins | — |
Chloroplast — Detailed Structure ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Shapes | Lens-shaped, Oval, Spherical, Discoid, Ribbon-like |
| Length & Width | Length 5–10 µm; Width 2–4 µm |
| Number |
1 per cell in Chlamydomonas ⭐; 20–40 per cell in mesophyll cells ⭐ |
| Membrane | Double membrane-bound ⭐; Inner membrane relatively less permeable |
Internal Structure ⭐⭐
↔ Swipe table sideways to view full columns
| COMPONENT |
DETAIL |
| Stroma |
Space limited by inner membrane; contains enzymes for carbohydrate & protein synthesis ⭐; contains circular dsDNA ⭐, 70S ribosomes |
| Thylakoids |
Flattened membranous sacs in stroma ⭐; arranged in stacks like piles of coins = Grana ⭐ |
| Grana (sing.: Granum) |
Stacks of thylakoids ⭐; site of light reactions |
| Stroma lamellae |
Connect thylakoids of different grana |
| Thylakoid lumen |
Space enclosed by thylakoid membrane |
| Chlorophyll |
Present in thylakoids (NOT in stroma) ⭐ |
| DNA |
Small, double-stranded, circular ⭐ |
| Ribosomes |
70S (smaller than cytoplasmic 80S) ⭐ |
| Stroma |
Site of dark reactions |
⚡ EXAM TRAP
NEET 2014, 2015, 2021, 2024: Chloroplast structure — double membrane, stroma contains circular dsDNA and 70S ribosomes; thylakoids stacked into grana.
F RIBOSOMES
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Discovered by | George Palade (1953) ⭐ |
| Composition | RNA + Proteins |
| Membrane | NOT surrounded by any membrane ⭐ |
| Function | Protein synthesis ('Protein factory') ⭐⭐ |
Two Types ⭐⭐
↔ Swipe table sideways to view full columns
| TYPE |
FOUND IN |
SUBUNITS |
| 80S |
Eukaryotes (cytoplasm) |
60S + 40S ⭐ |
| 70S |
Prokaryotes, also in Mitochondria & Chloroplasts |
50S + 30S ⭐ |
• ⭐ 'S' unit = Svedberg unit — indirectly measures density & size (sedimentation coefficient).
• Location of Ribosomes in Eukaryotic Cells ⭐: Free in cytoplasm, attached to RER, within Chloroplasts, within Mitochondria.
⚡ EXAM TRAP
NEET 2019, 2025, 2026, RE-NEET 2024 (reinforced): Eukaryotic ribosomes are 80S with 60S and 40S subunits, prokaryotic ribosomes are 70S with 50S and 30S subunits — each ribosome has two subunits. Ribosomes are non-membrane bound organelles found in both prokaryotic and eukaryotic cells!
G CYTOSKELETON
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Composition |
Elaborate network of filamentous proteinaceous structures ⭐ |
Three Components ⭐
↔ Swipe table sideways to view full columns
| COMPONENT |
DETAIL |
| Microtubules |
Constitute spindle fibres, centrioles, cilia, flagella ⭐ |
| Microfilaments |
Solid linear elements; diameter ~6 nm; made of actin monomer ⭐ |
| Intermediate filaments |
— |
• Functions ⭐⭐: Mechanical support, Motility, Maintenance of cell shape.
⚡ EXAM TRAP
NEET 2014, 2016, 2023, 2026 (reinforced): Network of microtubules, microfilaments and intermediate filaments in cytoplasm is called cytoskeleton; functions = mechanical support, motility, shape maintenance.
H CILIA & FLAGELLA
↔ Swipe table sideways to view full columns
| FEATURE |
CILIA |
FLAGELLA |
| Nature | Hair-like outgrowths of cell membrane | Hair-like outgrowths of cell membrane |
| Size | Small ⭐ | Longer than cilia ⭐ |
| Function | Work like oars → move cell or surrounding fluid | Responsible for cell movement |
| Emerge from | Basal body ⭐ | Basal body ⭐ |
| Covering | Covered with plasma membrane | Covered with plasma membrane |
Axoneme (Core Structure) ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Core called | Axoneme ⭐ |
| Microtubule arrangement | 9 + 2 array ⭐⭐ |
| 9 peripheral | Doublets (radially arranged) |
| 2 central | Singlets |
| Central tubules | Connected by bridges; enclosed by central sheath |
| Radial spokes | 9 in number; connect central sheath to one tubule of each peripheral doublet ⭐ |
| Peripheral doublets | Connected by linkers |
⚡ EXAM TRAP
NEET 2024: Axoneme = core of cilia/flagella; 9+2 arrangement of microtubules.
I CENTROSOME & CENTRIOLES
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Centrosome | Organelle containing two cylindrical structures called centrioles ⭐ |
| Centriole orientation | Two centrioles lie perpendicular to each other ⭐ |
| Surrounding material | Amorphous pericentriolar material |
| Centriole organisation | Like a Cartwheel ⭐⭐ |
Centriole Structure ⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Peripheral fibrils | 9 evenly spaced peripheral fibrils of tubulin protein ⭐ |
| Each fibril | A triplet ⭐ (contrast: cilia/flagella = doublets) |
| Adjacent triplets | Linked to each other |
| Central part | Hub (proteinaceous; in proximal region) ⭐ |
| Hub ↔ peripheral triplets | Connected by radial spokes (protein) |
| Microtubule arrangement | 9 + 0 ⭐⭐ (NO central tubules — contrast with cilia/flagella 9+2) |
| FEATURE |
DETAIL |
| Functions ⭐⭐ | Form basal body of cilia & flagella; Form spindle fibres during cell division in animal cells ⭐⭐ |
| In plant cells | Absent in almost all plant cells ⭐ |
| Non-membrane-bound | Yes ⭐ |
⚡ EXAM TRAP
NEET 2014, 2020, 2024: Centriole = Cartwheel organisation; 9+0 arrangement; forms basal body of cilia/flagella & spindle fibres.
Cilia/Flagella vs Centriole — Microtubule Comparison ⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
CILIA / FLAGELLA |
CENTRIOLE |
| Arrangement | 9 + 2 | 9 + 0 |
| Peripheral type | Doublets | Triplets |
| Central microtubules | 2 singlets (present) | Absent (hub instead) |
J NUCLEUS
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| First described by | Robert Brown (1831) ⭐ |
| Chromatin named by | Flemming ⭐ |
Nuclear Envelope ⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Structure | Two parallel membranes (double membrane-bound) ⭐ |
| Perinuclear space | Space between the two membranes (10–50 nm) ⭐; forms barrier between nucleus & cytoplasm |
| Outer membrane | Continuous with ER ⭐; bears ribosomes on it ⭐ |
| Nuclear pores | Formed by fusion of both membranes ⭐ |
| Pore function | Passage for movement of RNA & Protein molecules (both directions) ⭐ |
⚡ EXAM TRAP
NEET 2015, 2021: Nuclear envelope outer membrane continuous with ER and bears ribosomes; Nuclear pores allow passage of RNA & protein in both directions.
Number of Nuclei ⭐
↔ Swipe table sideways to view full columns
| CONDITION |
EXAMPLE |
| Normally | One nucleus per cell |
| More than one | Paramecium, Liquid endosperm of coconut |
| No nucleus (at maturity) |
RBCs of many mammals ⭐; Sieve tube cells of vascular plants ⭐ |
• Interphase Nucleus ⭐: = Nucleus of a cell when it is NOT dividing. Contains: Chromatin, Nuclear matrix (Nucleoplasm), Nucleoli (one or more).
Nucleolus ⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Shape | Spherical |
| Membrane | Non-membrane-bound ⭐ |
| Content | Continuous with rest of nucleoplasm |
| Function | Site of active ribosomal RNA (rRNA) synthesis ⭐⭐ |
| Size & number | Larger & more numerous in cells actively carrying out protein synthesis ⭐ |
⚡ EXAM TRAP
NEET 2018, 2020, 2024, 2026 (reinforced): Nucleolus — non-membrane-bound; site for active ribosomal RNA (rRNA) synthesis; larger in cells with active protein synthesis.
Chromatin ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Structure | Highly extended & elaborate nucleoprotein fibres ⭐ |
| During cell division | Condense → form chromosomes ⭐ |
| Contains | DNA + Basic proteins (Histones) ⭐ + Some non-histone proteins + RNA |
| Human cell | ~2 metres of DNA thread distributed among 46 chromosomes (23 pairs) |
⚡ EXAM TRAP
NEET 2015, RE-NEET 2024: Chromatin = DNA + Histones + Non-histone proteins + RNA.
Chromosomes ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Primary constriction | = Centromere ⭐ |
| Kinetochores | Disc-shaped structures on sides of centromere ⭐ |
| Centromere function | Holds two chromatids of a chromosome together |
| Secondary constriction | Non-staining; at constant location |
| Satellite | Fragment / part of chromosome after secondary constriction ⭐ |
Types Based on Centromere Position ⭐⭐⭐
↔ Swipe table sideways to view full columns
| TYPE |
CENTROMERE POSITION |
ARMS |
| Metacentric | Middle ⭐ | Two equal arms |
| Sub-metacentric | Slightly away from middle ⭐ | One shorter arm + one longer arm |
| Acrocentric | Close to one end ⭐ | One extremely short arm + one very long arm |
| Telocentric | Terminal (at the end) ⭐ | One arm only |
⚡ EXAM TRAP
NEET 2021, 2022, 2024, RE-NEET 2024: Chromosome classification based on centromere position — know all four types!
K MICROBODIES
↔ Swipe table sideways to view full columns
| FEATURE |
DETAIL |
| Structure | Membrane-bound minute vesicles |
| Contents | Various enzymes |
| Present in | Both plant & animal cells ⭐ |
⚡ EXAM TRAP
NEET 2021: Microbodies — membrane-bound; contain enzymes; present in both plant & animal cells.