Cell Discovery

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Cell Discovery Cell Theory
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It all started with an invention.

• The first microscope
• Zacharias Jansen, 1595, Middleburg, Holland
• It launched great leaps in Astronomy and Biology.
  
• Some of the first great observations with it were
  made by

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Robert Hooke (1635-1703)

• Designed microscopes
• Discovered and documented
• the first cells in 1665
• Named them after the cells in
• which a monk sleeps.

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Micrographia
Hooke released a book of detailed drawings and
observations Micrographia, 1665
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Antony van Leeuwenhoek (1632-1723)

• A tradesman from Holland
• who became fascinated with
• Hookes book
• Discovered bacteria, free-
• living protists, sperm cells,
• blood cells, nematodes, etc.
• Became an expert lens grinder and made over 500
  simple microscopes
• Acute eyesight and lens grinding skill let him
  build microscopes that were capable of 200X
  magnification

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Antony van Leeuwenhoek
. . . my work, which I've done for a long time,
was not pursued in order to gain the praise I now
enjoy, but chiefly from a craving after
knowledge, which I notice resides in me more than
in most other men. And therewithal, whenever I
found out anything remarkable, I have thought it
my duty to put down my discovery on paper, so
that all ingenious people might be informed
thereof. Antony van Leeuwenhoek. Letter of June
12, 1716
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Spontaneous Generation
The theory that life comes from non-living matter.
Francisco Redi in 1688 proved that flies do not
come from rotting meat.
Louis Pasteur in 1862 proved that microorganisms
do not arise spontaneously from nutrient broths.
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Beginnings of Cell Theory

• 1838 Mattias Schleiden stated that all plant
  tissues consisted of cells
• 1839 Theodore Schwann stated that all animal
  tissues consisted of cells
• Each conjectured that there was a nucleus
• 1858 Rudolf Virchow combined the two ideas and
  added that all cells come from pre-existing
  cells, formulating the Cell Theory

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Rudolf Virchow 1821-1902

• Cell Theory
• every cell originates from another existing cell
  like it
• All living things are composed of one or more
  cells
• In organisms, cells are the basic units of
  structure and function.
• All cells are produced only from existing cells.

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Modern Microscopes

• Some of the light microscopes here are capable of
  1000x magnification.
• That is about the limit of a light microscopes
  magnification without losing clarity (called
  Resolving Power).
• Due to the width of visible lights wavelength
• The electron microscope was introduced in the
  1950s and uses the wavelength of electrons to
  increase the resolving power by 100x.
• Approx. 100,000x magnification!!
• Cell Biology advanced rapidly as cellular
  organelles were clearly seen for the first time.

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Resolving Power
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Electron Microscopes

• Works by scanning a beam of electrons over a
  prepared specimen.
• After passing over the object, scattered
  electrons are collected and formed into a 2-D or
  3-D image.

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Transmission Electron Microscope (TEM) magnifies
a slice of a sample. (Rabbit trachea cilia)
Modern Microscopes
Scanning Electron Microscope (SEM) shows 3D image
of the (Rabbit trachea cilia)
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A modern TEM
Limitations Specimen must be prepared
(killed). FOV very small. Very time consuming.
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A Modern SEM
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Fruit fly with four eyes under an SEM