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Cell Theory and Modern Cell Theory

Robert Hooke was the first to describe cell and he published his observation in his book Micrographia (1670). He sliced a piece of cork and placed under his microscope. He observed honey comb like structural units and called it as the “cell”.
Robert Hooke
Leeuwenhoek (1674) was the first one to observe live cells under microscope. He observed many things including bacteria under his primitive microscope and drew beautiful sketches of his observations.
If you want to see this classical book, follow this link
Cell theory was actually a generalization of observations made by many scientists around the world.
Cell theory was proposed by Theodor Schwann, Matthias Schleiden and Rudolf Virchow
cell theory
The three tenets are
1. All living organisms are composed of one or more cells (Schwann and Schleiden, 1838-39).

2. The cell is the basic structural and functional unit of life (Schwann and Schleiden, 1838-39).
Schleiden proposed that new cells arise from within the old cells, specifically from the nucleus. This was corrected by Rudolf Virchow who proposed “Theory of cell lineage” stating that “omnis cellulae e cellula” (all cells arise from pre-existing cells).

3. All cells arise from pre existing cells by cell division (Rudolf Virchow, 1858).

Modern cell theory
Some more points are added with the advancement of our knowledge in cytology and molecular biology.
• The cell contains hereditary information DNA which is passed on from cell to cell during cell division
• All cells are basically the same in chemical composition and metabolic activities
• All basic chemical and physiological functions are carried out inside the cells (digestion, movement etc)
• A cells activity depends on the activities of sub cellular structures within the cell (organelles, plasma membrane etc)

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