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Cells
For centuries, scientists had no idea that the human body consists of trillions of cells.
What piece of technology made the discovery of cells possible? Answer: The microscope!
History In 1665 Robert Hooke
made a simple microscope and looked at a piece of cork. What did he see? Small, box-shaped
structures that he called “cells” because they reminded him of cells in which monks lived.
History During the late 1600’s,
Dutch scientists Anton van Leeuwenhoek designed his own microscope and looked at pond water and milk.
What did he see? Living organisms that they
never knew were there!
History 1838 German scientist
Matthias Schleiden studied plants and concluded that all plants are made of cells.
History 1839 another
German scientist, Theodor Schwann reported that animal tissues are also made of cells.
History 1855 Virchow proposed
that all cells are produced from the division of existing cells.
Cell Theory The observations of all of these scientists
were summarized as what we know today as “Cell Theory”
1. All living organisms are composed of one or more cells.
2. Cells are the basic unit of structure of all living organisms.
3. Cells come from pre-existing cells.
Microscope TechnologyMicroscopes have enabled scientists to
study cells in detail!
Compound Light Microscopes These are the
microscopes we use in class.
Consists of a series of glass lenses and uses light to produce an image.
Compound Light Microscope
Electron Microscopes
Transmission Electron Microscope (TEM); Electrons are used to view an object at
500,000x Give a cross section view of the object
Scanning Electron Microscope (SEM); Uses electrons to produce a 3-D image of an
object.
Electron Microscopes
Prokaryotic Eukaryotic
Cells
•Cells without membrane-bound organelles•No true Nucleus•Smaller than Eukaryotic•Ex. Bacteria
•Cells with membrane-bound organelles•Contain a true nucleus•Larger than prokaryotic •Ex. Animals, Plants, Fungi, Protist
Eukaryotic vs. Prokaryotic