*Cell*
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“Cell” word comes from Robert Hooke in 1665. He saw dead cork cells under
microscope and thought they looked like tiny “rooms” — “cellula” in Latin = small
room.
*1. What is a Cell?*
*Cell* = The smallest unit of life that can live and do all functions on its own.
Just like bricks make a building, cells make your body, plants, animals, bacteria
— everything living.
*2 types of cells in nature:*
**Type****Prokaryotic Cell****Eukaryotic Cell**
--- cell
**Meaning**“Pro” = before, “Karyon” = nucleus“Eu” = true, “Karyon” = nucleus
**Nucleus**No true nucleus. DNA lies free in cellHas true nucleus with nuclear
membrane
**Size**Very small — 0.1 to 5 micrometersBigger — 10 to 100 micrometers
**Examples**Bacteria, Blue-green algaePlants, animals, fungi, humans —
including you!
**Organelles**Few, no membrane-bound organellesMany membrane-bound
organelles
Today we’ll study *Eukaryotic cell* because your body is made of it.
*2. Cell Structure — “Cell ka naksha”*
Imagine cell is a mini city. Each part = one department. All parts together = “Cell
Organelles”.
**Organelle****Structure****Function / Job****City Example**
**1. Cell Membrane / Plasma Membrane**Thin, flexible, double layer of fat +
protein**Gatekeeper**. Controls what enters/exits cell. Protects cellCity
boundary wall + security gate
**2. Cell Wall**Only in plant cells. Made of cellulose. Hard & rigidGives
shape, protection, support to plant cellFort wall around plant city. Animal cells
don’t have it
**3. Cytoplasm**Jelly-like, watery fluid filling whole cell**Factory floor**. All
organelles float here. Chemical reactions happen hereWater + space inside city
where all work happens
**4. Nucleus**Big, round, covered by double membrane with pores**Brain +
Control room**. Has DNA. Controls all cell activities, growth, reproduction
Mayor’s office + library of instructions
**5. Nucleolus**Dark spot inside nucleusMakes **ribosomes**Room
inside mayor office where security guards made
**6. Mitochondria**Oval, double membrane. Inner membrane folded
**Powerhouse**. Makes ATP energy from food + oxygen. “Cellular respiration”
happens herePower plant of city. Gives electricity
