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A Handbook of Biology

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A cell is the fundamental, structural and functional unit of all living

organisms.

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Robert Hooke: (Father of cytology) Discovered cell.

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Anton Von Leeuwenhoek: First observed and described a live cell.

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Robert Brown later discovered the nucleus

The invention of the compound & electron microscopes revealed

all the structural details of the cell.

ÇËLL THËØRÝ

Matthias Schleiden (1838), a botanist, observed that all plants are

composed of different kinds of cells.

Theodore Schwann (1839), a zoologist, found that cells have 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.

Schleiden & Schwann formulated the cell theory. (AIPMT 1993)

Rudolf Virchow (1855) first explained that cells divide and new cells

are formed from pre-existing cells (Omnis cellula-e cellula). He

modified the cell theory. (NEET 2019)

Cell theory states that

(i) All living organisms are composed of cells and products of cells.

(ii) All cells arise from pre-existing cells

Viruses are exception to cell theory.

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All cells contain

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Cytoplasm: A semi-fluid matrix where cellular activities and chemical

reactions occur. This keeps the cell in ‘living state’.