Cell Structure
Biology · कोशिका संरचना
📋Quick Overview
The cell is the basic structural and functional unit of life. Cell theory was proposed by Schleiden (plants, 1838) and Schwann (animals, 1839). Rudolf Virchow added 'Omnis cellula e cellula' (every cell arises from a pre-existing cell). Robert Hooke first observed cells in cork (1665). Cells are broadly divided into Prokaryotic (no true nucleus — bacteria) and Eukaryotic (true nucleus — plants, animals, fungi).
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Robert Hooke (1665) = first observed cells in cork. Leeuwenhoek = first observed living cells (bacteria) under microscope.
📖Plant Cell vs Animal Cell
📖Cell Organelles — Functions
| Organelle | Nickname | Function |
|---|---|---|
| Nucleus | Brain/Control center of cell | Controls all cell activities, contains DNA (genetic material), has nuclear membrane |
| Mitochondria | Powerhouse of the cell | Cellular respiration → produces energy (ATP). Has its own DNA. Double membrane. |
| Ribosome | Protein factory | Protein synthesis. Found on Rough ER and free in cytoplasm. Smallest organelle. |
| Chloroplast | Kitchen of the cell | Photosynthesis (only in plant cells). Contains chlorophyll. Has own DNA. Double membrane. |
| Endoplasmic Reticulum (ER) | Transport network | Rough ER = has ribosomes (protein transport). Smooth ER = no ribosomes (lipid synthesis, detox). |
| Golgi Apparatus (Golgi Body) | Post office / Packaging center | Modifies, packages, and ships proteins and lipids. Forms lysosomes. |
| Lysosomes | Suicide bags of the cell | Contain digestive enzymes. Break down waste, old organelles, foreign materials. Can destroy the cell itself. |
| Vacuole | Storage tank | Stores water, nutrients, waste. Large in plant cells, small/absent in animal cells. |
| Cell Membrane | Gatekeeper | Selectively permeable. Controls what enters and exits the cell. Made of lipid bilayer. |
| Centrosome | Division organizer | Helps in cell division (forms spindle fibres). Present in animal cells only. |