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Cell-the unit of life
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, A cell is the fundamental, structural andfunctional unit of all living organisms.
The invention of Compound and Electron
Microscopes revealed the structural details
Anton Von Leeuwenhoek: of the cell.
First observed and described a live cell.
Schleiden & Schwann
formulated the Cell
Theory.
, Malthias Schleiden (1838) observed that plants are composed of cells.
Theodore Schwann (1839) reported that cells had a thin outer layer (plasma membrane).
He also found that plant cells have cell wall.
He proposed a hypothesis that animals and plants are composed of cells and products of
cells.
Rudolf Virchow (1855) explained that cells divided and new cells are formed from pre-
existing cells (Omnis cellula-e cellula). He modified the cell theory.
➢All living organisms are composed of cells
and products of cells.
➢All cells arise from pre-existing cells.
Rudolf Virchow
All cells contain
Cytoplasm: A semi-fluid matrix where cellular activities and chemical reactions occur. This
keeps the cell in ‘living state’.
Ribosomes: Non-membrane bound organelles found in cytoplasm, chloroplasts, mitochondria
and on rough ER.
Based on the functions, shape of cells may
be disc-like, polygonal, columnar, cuboid,
Smallest cells: Mycoplasmas (0.3 µm in thread like, or irregular.
length)
Largest isolated single cell: Egg of ostrich.
Longest cells: E.g. Nerve cell.
Size of bacteria: 3 to 5 µm.
Human RBCs: 7.0 µm in diameter.
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