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1. Fundamentals of Cytology
Cytology = Study of Cells | Cyto = Cell | Logy = Study
Cell kya hai?
Cell life ki structural aur functional unit hai โ matlab ye zindagi ki sabse chhoti building block hai.
Cell โ Tissue โ Organ โ Organ System โ Organism (yahi order hai!)
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2. Discovery of Cell
๐ชจ Dead Cell
Robert Hooke ne 1665 mein cork mein dead cell dekhi.
Inhe Father of Cytology kehte hain.
๐ง Living Cell
Antonie van Leeuwenhoek ne 1674 mein pond water mein living cell dekhi.
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3. Cell Theory
1
Schleiden & Schwann (1838)
Sabhi living organisms cells se bane hain, aur cell life ki basic unit hai.
2
Rudolf Virchow (1855) โ "Omnis cellula e cellula"
Matlab: naye cells hamesha purane cells se bante hain. Naye cells suddenly nahi aate!
โ ๏ธ Exception: Viruses
- Viruses Cell Theory ko follow nahi karte.
- Inke paas protoplasm ya organelles nahi hote โ sirf DNA/RNA + Protein Coat (Capsid).
- Ye semi-living hote hain โ reproduce karne ke liye host cell chahiye.
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4. Key Cellular Facts
Largest Cell (Human)
๐ฅ Ovum (female sex cell)
Smallest Cell (Human)
๐ฌ Sperm (male sex cell)
Largest Cell in Male
๐ง Neuron (also longest!)
Smallest Cell in Women
๐ฉธ RBC (Red Blood Cell)
Largest Cell (Overall)
๐ฆ Ostrich's Egg
Smallest Cell (Overall)
๐ฆ Mycoplasma (bacteria)
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5. Cell Membrane
Kya hoti hai?
- Ise Plasma Membrane bhi kehte hain.
- Thin, elastic aur flexible structure hoti hai.
- Animal cells mein outermost covering, plant cells mein cell wall ke andar hoti hai.
Composition (Kya bani hoti hai?)
Proteins 50% Lipids 50%
Lipids ke 2 types: Phospholipids Cholesterol
Lipids = organic molecules jo water mein dissolve nahi hote par non-polar solvents mein hote hain (fats & waxes).
Functions (Kya kaam karti hai?)
- ๐ก๏ธ Protective barrier โ bodyguard ki tarah
- ๐ Cell ko shape deti hai
- ๐ฆ Internal contents ko protect karti hai
- ๐ช Substances ki movement control karti hai โ Selectively Permeable Membrane
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6. Movement Across Cell Membrane
Diffusion
No Energy Needed
- High โ Low concentration movement
- Rate: Gases > Liquids > Solids
- Example: Agarbatti ki khushbu
Osmosis
Water Movement
- Water ka movement semi-permeable membrane se
- High โ Low concentration
- No energy, equilibrium tak chalta hai
Active Transport
Energy Required
- Low โ High concentration
- Reverse Osmosis bhi kehte hain
- Cellular energy (ATP) chahiye
| Solution Type | Description | Effect on Cell | Solute vs Solvent |
|---|---|---|---|
| Isotonic | Normal solution | No change in size | Solute = Solvent |
| Hypotonic | Dilute solution | Cell swells (Turgidity) | Solute < Solvent |
| Hypertonic | Concentrated solution | Cell shrinks (Plasmolysis) | Solute > Solvent |
Turgor Pressure: Hypotonic solution mein cell mein pani ghusta hai โ cell phool jata hai โ Turgor pressure badhta hai โ Cells ka growth aur enlargement hota hai.
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7. Cell Wall
Key Points
- Sirf Plant, Bacteria, Fungus, Algae mein hoti hai โ Animal cells mein NAHI.
- Cell wall living structure nahi hai.
- Cell membrane ke bahar hoti hai.
- Freely permeable hai (unlike selectively permeable cell membrane).
- Rigidity, shape, structural support aur protection deti hai.
๐ฟ Plant
Cellulose
๐ฆ Bacteria
Peptin / Peptidoglycan
๐ Fungi
Chitin
๐ Algae
Cellulose / Pectin
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8. Cytoplasm
Kya hota hai?
- Plasma membrane aur nuclear envelope ke beech ka fluid.
- Saare cell organelles cytoplasm mein hi hote hain.
- Cytosol: Water-based fluid portion (aqueous part).
- Cytoplasmic Inclusions: Non-living components โ pigments, nutrients etc.
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9. Nucleus & Nucleoplasm
Nucleus โ "Brain of the Cell"
- Discovery: Robert Brown, 1831
- Cell ke center mein hota hai.
- Eukaryotic cell ka sabse bada organelle hai (double-membraned).
- Double-layered nuclear membrane nucleus ko cytoplasm se alag karti hai.
- Saare cell organelles ki activities control karta hai.
Protoplasm = Cell membrane + Cytoplasm + Nucleus โ ye cell ka living material hai. Isme nucleic acids, proteins, lipids aur carbohydrates hote hain.
Nucleoplasm
- Purkinje ne 1839 mein term diya.
- Thick fluid se bana hota hai โ chromatin fibers (DNA + proteins) hote hain.
- Nucleolus: Non-membrane-bound structure โ ribosome biogenesis (banane) ke liye.
- Chromatin material: DNA + Proteins (mainly Histones) ka complex.
Euchromatin
Loosely packed โ active (transcription hoti hai)
Heterochromatin
Tightly packed โ inactive (transcription nahi hoti)
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10. Chromosomes & DNA
Chromosomes
- Thread-like structures jo nucleus mein hote hain โ DNA aur genes carry karte hain.
- Genetic information ek cell se doosre mein le jaate hain.
- Components: DNA + Proteins (Histones)
- Human mein total: 46 chromosomes = 23 pairs
- 22 pairs = Autosomal | 1 pair = Sex (XX female, XY male)
DNA
- Genetic information carry karta hai.
- Genes: DNA ke functional segments โ next generation ko info transfer karte hain.
- Discovery: Friedrich Miescher (1869)
- Double-Helical Structure: Watson and Crick (1953)
Nucleotide = Phosphate + Deoxyribose + Nitrogenous Base
Base Pairs: Guanine โ Cytosine | Adenine โ Thymine (DNA)
RNA mein: Adenine โ Uracil (Thymine ki jagah)
Base Pairs: Guanine โ Cytosine | Adenine โ Thymine (DNA)
RNA mein: Adenine โ Uracil (Thymine ki jagah)
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11. Types of Cells
| Feature | Prokaryotic Cell | Eukaryotic Cell |
|---|---|---|
| Size | 1โ10 ยตm | 10โ100 ยตm |
| Nucleus | Absent | Present |
| Nucleolus | Absent | Present |
| Cell Organelles | Absent | Present |
| Chromosome | Single | More than one |
| Examples | Bacteria, Cyanobacteria, Mycoplasma | Plant & Animal cells |
Common to both: Cell membrane, Cytoplasm, Ribosomes
Nucleoid: Bacterial cell mein nucleus jaisi region jo membrane se bound nahi hoti.
Nucleoid: Bacterial cell mein nucleus jaisi region jo membrane se bound nahi hoti.
Bacterial Flagellum
- Microscopic hair-like structures โ cell ki locomotion (movement) ke liye.
- Helical structure โ flagellin protein se bana.
- 3 parts: Basal Body Hook Filament
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12. Cell Organelles
Mitochondria
Powerhouse of the Cell
- Discovery: Kolliker (1857)
- Size: 1โ2 ยตm, Sausage shape
- ATP (Adenosine Triphosphate) synthesis karta hai โ Energy currency
- Apoptosis (programmed cell death) mein role
- Apna DNA aur ribosomes hote hain
- 2 membranes: Outer (porous) + Inner (ATP synthesis)
Ribosomes
Protein Factory
- Discovery: George E. Palade (1955)
- No membrane hoti in mein
- Protein synthesis ke liye essential
- Both prokaryotes & eukaryotes mein hote hain
Endoplasmic Reticulum
Transport System
- Sac-like network of structures
- Plasma membrane โ Nuclear membrane se connected
- RER: Ribosomes present โ Protein synthesis
- SER: No ribosomes โ Lipid/fat synthesis + Detoxification (liver mein cytochrome P450)
Golgi Bodies
Post Office of Cell
- Discovery: Camillo Golgi (1898)
- Vesicles, cisternae, vacuoles se bana
- Cis face: Convex, nucleus ki taraf (receiving)
- Trans face: Concave, plasma membrane ki taraf (shipping)
- Proteins & lipids packaging + dispatch
- Simple sugars โ Complex sugars banata hai
- Lysosomes banata hai
Lysosomes
Suicide Bag of Cell
- Digestive enzymes (made in RER) se filled
- Cell ka waste disposal system
- Cell damage hone par burst hote hain โ apni hi cell digest karte hain
Vacuoles
Storage Bags
- Membrane-bound, solid/liquid filled sac
- Plants: Large (50โ90% cell volume), permanent, cell sap store karte hain, turgidity dete hain
- Animals: Small, numerous, temporary, glucose/glycogen/protein store karte hain
- Waste products temporarily stored in vacuoles
Peroxisomes
Detox Center
- Very long chain fatty acids ko break karta hai (beta oxidation)
- Catalase enzyme hoti hai โ Harmful HโOโ โ Water + Oโ
- Free radical scavengers โ cell ko detoxify karte hain
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13. Plastids
Plastids sirf plant cells mein hote hain, animal cells mein nahi. Inke paas apna DNA aur ribosomes hote hain.
Chloroplasts
Photosynthesis
- Green plastids โ chlorophyll pigment hota hai
- Yellow/orange pigments: Xanthophyll, Carotenes
- Chlorophyll mein Magnesium (Mgยฒโบ) hota hai โ solar energy capture ke liye
Chromoplasts
Color Provider
- Different pigments โ color provide karte hain
- Tomato red โ Lycopene
- Chilli red โ Capsanthin
- Anthocyanin โ fruits/veges ka color
- Yellow color โ Xanthophyll
Leucoplasts
Storage (Colorless)
- Amyloplast โ Carbohydrates store
- Aleuroplast โ Proteins store
- Elaioplast โ Fats store
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14. Cell Division
Cell division = ek parent cell 2 ya zyada daughter cells mein divide hoti hai.
Division ki Zaroorat Kyun?
- 1๏ธโฃ Organism ka growth
- 2๏ธโฃ Old, dead, injured cells ko replace karna
- 3๏ธโฃ Gamete formation (Meiosis se)
| Feature | Mitosis | Meiosis |
|---|---|---|
| Cells | Somatic (body) cells | Germ (reproductive) cells |
| Nucleus divides | Once | Twice |
| Daughter cells | 2 | 4 |
| Chromosome number | Diploid (2n) โ same as parent | Haploid (n) โ half of parent |
| Genetic identity | Identical to parent | Different from parent |
| Purpose | Growth, repair, asexual reproduction | Gamete formation (egg & sperm) |
| Genetic variation | No | Yes (crossing over) |
| Malfunction leads to | Cancer (uncontrolled division) | Down's, Klinefelter's, Turner's syndrome |
Mitosis ke Phases (PMAT)
- Prophase: Chromosomes condense aur visible ho jaate hain
- Metaphase: Chromosomes cell ke equator pe align ho jaate hain
- Anaphase: Sister chromatids separate ho jaate hain, opposite poles pe jaate hain
- Telophase: 2 new nuclei form hote hain
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15. Cell Cycle
Interphase (I phase)
3 sub-phases hoti hain:
- G1 Phase (Gap 1): Cell grow karta hai, normal functions karta hai, DNA replication ki preparation
- S Phase (Synthesis): DNA replicate hota hai โ har chromosome ki 2 identical copies ban jaati hain
- G2 Phase (Gap 2): Cell aur grow karta hai, ensure karta hai ki DNA replication complete ho gayi, mitosis ke liye ready hota hai
M Phase (Mitotic Phase)
Cell ka nucleus aur cytoplasm divide hote hain.
- Karyokinesis: Nucleus ka division (Prophase โ Metaphase โ Anaphase โ Telophase)
- Cytokinesis: Cytoplasm ka division
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16. DNA Replication
DNA Replication = Cell apna exact DNA copy banata hai cell division se pehle โ taaki har naye cell ko same genetic information mile.
Semi-Conservative Replication
2 new double-stranded DNA molecules bante hain โ har ek mein ek original strand aur ek naya strand hota hai.
Enzymes (DNA Replication ke liye)
Helicase
DNA ko unwind/unzip karta hai (๐)
Topoisomerase
DNA ko tangle hone se rokta hai
DNA Primase
Replication initiate karta hai (new strands produce)
DNA Polymerase
DNA ki amount double karta hai (Builder ๐๏ธ)
DNA Ligase
DNA strands ko join karta hai (Gluer ๐)
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17. Endocytosis vs Exocytosis
๐ฝ๏ธ Endocytosis โ Cell Eating/Drinking
- Active transport ka ek type
- Cell external materials ko engulf karta hai โ vesicle banata hai andar laane ke liye
- Phagocytosis: Cell eating
- Pinocytosis: Cell drinking
- Example: Amoeba food particles trap karta hai
๐คฎ Exocytosis โ Cell Vomiting
- Cell molecules ko bahar transport karta hai
- Vesicles cell membrane se fuse hote hain โ contents extracellular space mein release hote hain
- Vomited particles = undigested residues from endocytosis โ enzymes & hormones
Amoeba Digestion Steps
1. Ingestion 2. Digestion 3. Absorption 4. Assimilation 5. Egestion
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18. Cytoskeleton & Centrosome
Cytoskeleton
- Cell ko structural support deta hai.
- Cell movement mein help karta hai.
Centrosome โ MTOC
- Microtubule Organizing Center โ cell division aur structure regulate karta hai.
- Microtubules organize karta hai โ cell structure, movement aur division ke liye essential.
- Har centriole ek cylindrical structure hai jเฅ microtubules se bana hai โ 9+0 arrangement.
Microtubules
Hollow, cylindrical structures โ tubulin proteins se bane hain. Cell ka cytoskeleton form karte hain, structural support, movement aur cell division mein role.
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19. Animal Cell vs Plant Cell
| Feature | Animal Cell | Plant Cell |
|---|---|---|
| Cell Wall | Absent โ | Present โ |
| Chloroplast | Absent โ | Present โ (photosynthesis) |
| Shape | Small, irregular/round | Almost rectangular |
| Vacuoles | Small, numerous | Large (50โ90% volume) |
| Plastids | Absent โ | Present โ |
| Mitochondria | More in number | Less in number |
| Reserve Food | Glycogen | Starch |
| Centrosome | Present | Generally Absent |