CHAPTER : THE FUNDAMENTAL UNIT OF LIFE
1️⃣ Discovery of Cell & Cell Theory
🔹 Discovery
Robert Hooke
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Observed cork under microscope (1665)
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Coined the term “Cell”
Robert Brown
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Discovered nucleus (1831)
Purkinje
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Coined the term Protoplasm
🔹 Cell Theory
Schleiden and Schwann
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All plants & animals are made of cells
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Cell is structural & functional unit of life
Virchow
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All cells arise from pre-existing cells
2️⃣ Types of Organisms
🔹 Unicellular
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Made of single cell
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Example: Amoeba, Bacteria
🔹 Multicellular
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Made of many cells
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Division of labour present
3️⃣ Structure of Cell
Every cell has:
🔹 Plasma Membrane
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Outermost covering
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Selectively permeable
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Allows diffusion & osmosis
🔹 Cell Wall (Plant cells only)
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Made of cellulose
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Provides shape & rigidity
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Prevents bursting
4️⃣ Diffusion & Osmosis
🔹 Diffusion
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Movement from high → low concentration
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Example: O₂, CO₂ exchange
🔹 Osmosis
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Movement of water through semi-permeable membrane
| Solution Type | Effect on Cell |
|---|---|
| Hypotonic | Cell swells |
| Isotonic | No change |
| Hypertonic | Cell shrinks |
5️⃣ Nucleus
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Controls activities of cell
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Contains chromosomes
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Chromosomes contain DNA
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Functional units of DNA = Genes
🔹 Prokaryotic Cells
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No nuclear membrane
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Example: Bacteria
🔹 Eukaryotic Cells
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True nucleus present
6️⃣ Cytoplasm
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Jelly-like substance
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Contains organelles
7️⃣ Cell Organelles
🔹 Endoplasmic Reticulum (ER)
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Transport system
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RER → Protein synthesis
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SER → Lipid synthesis
🔹 Golgi Apparatus
Camillo Golgi
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Packaging & secretion
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Forms lysosomes
🔹 Lysosomes
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Digestive enzymes
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Called “Suicide bags”
🔹 Mitochondria
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Powerhouse of cell
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Produces ATP
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Has own DNA
🔹 Plastids (Plant cells only)
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Chloroplast → Photosynthesis
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Leucoplast → Storage
🔹 Vacuole
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Storage sac
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Large in plant cells
8️⃣ Cell Division
🔹 Mitosis
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Growth & repair
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2 identical daughter cells
🔹 Meiosis
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Formation of gametes
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4 daughter cells
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Chromosome number reduced