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Cell Theory

Cell Unit: Day 1

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What is a scientific theory?

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Robert Hooke

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  • English scientist 1635-1703
  • Discovered cells in cork
  • Named cells-cells

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Anton van Leeuwenhoek

  • Dutch Scientist (1632-1723)
  • Built microscopes
  • First person to see living cells

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Other scientists to contribute to cell theory:

  • Matthias Schleiden (1838) Concluded that all plants are composed of cells.

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  • Theodor Schwann (1839) Concluded that all animals are composed of cells.

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  • Rudolf Virchow (1855) Concluded that cells only come from other cells.

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Cell Theory:

  • All living organisms are composed of one or more cells

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  • Cells are the basic units of structure and function in an organism

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  • Cells come from other living cells

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What technology has allowed us to understand cells?

  • Before microscopes we were not aware of microorganisms such and unicellular protists and bacteria.
  • As we have improved microscopes we can see greater detail in the cells.
  • DNA analysis techniques have also helped us learn more about cells, this helps us understand how different organisms are related.
  • Other chemical analysis of proteins, RNA, etc have also helped us gain an even deeper understanding of cells.

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Prokaryotic vs. Eukaryotic Cells

Prokaryotic Cell

Eukaryotic Cell

No Nucleus/ DNA in cytoplasm

Nucleus/ DNA in nucleus

No membrane bound organelles

Membrane bound organelles

Usually smaller than Eukaryotic cells

Usually bigger than prokaryotic cells

Evolved 3.5 billion years ago

Evolved 1.5 billion years ago

Archaebacteria and Eubacteria

Fungi, Protist, Plant, and Animal

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Cell Examples

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Eukaryotic Cells

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Prokaryotic Cells