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Biology · Quick Reference
Lesson 1 — Cell Theory Cheat Sheet
In one line: All life is made of cells, the cell is life's basic unit, and every cell comes from a pre-existing cell.
Key Ideas
1Schleiden & Schwann (1839). All organisms are composed of cells.
2Virchow (1855). All cells arise from pre-existing cells.
3Prokaryote. No nucleus, 1–10 µm — bacteria, archaea.
4Eukaryote. Has a nucleus, 10–100 µm — animals, plants, fungi.
5Cell = basic structural & functional unit of every living thing.
Microscopy
Light microscope resolution
0.2 µm
Electron microscope resolution
0.2 nm (1000x better)
TEM
Internal structure
SEM
Surface structure