1. Cell Theory
(Ch. 7 Section 1)

2. Historical Background - Hooke
Term “cell” first used by Robert Hooke (1665, England)
He looked at cork plant samples through an early compound microscope
The empty cork chambers he called cells.
Also made great discoveries in physics, chemistry, astronomy and architecture

3. Historical Background - Leeuwenhoek
Dutch, mid-1600’s
Father of Microbiology
Perfected early microscopes and their use
Discovered single-celled organisms
First to make many observations at the cellular level: bacteria, muscle fibers, blood flow, etc…

4. Historical Background – Germans
1838 – Schleiden: all plants are made of cells
1839 – Schwann: all animals are made of cells
1855 – Virchow: new cells can only emerge from two previous cells dividing
All of these discoveries lead to the Cell Theory

5. Cell Theory Cell Theory basically states 3 things:
All living things are composed of cells
(some unicellular, some multi-cellular)
2) Cells are the basic unit of structure and function in living things
(Different cell types look and function differently)
3) New cells are produced from existing cells
(different types of cell division)

6. New discoveries… Cellular structure and function is very complex
Cells seem to have their own machinery
Organelles work together to make the cell a small factory – more complex and efficient than any human factory
Discoveries made possible by better microscopes, biochemistry, DNA research

7. Better Scopes
Transmission Electron Microscopes (TEM’s): electrons pass through thins slices of specimens to create the image
TEM’s show cell structure and protein molecule structure
Scanning Electron Microscopes (SEM’s):
electrons bounce off specimen to create a 3-D image
Electron microscopes can only work in a vacuum so only non-living, preserved specimens can be used

8. Pollen under SEM

9. Better Scopes
Scanning Probe Microscopes developed in 1990’s use a probe instead of an electron beam
Can even show images at atomic level
Vacuum not necessary
Used to show protein structure, DNA, other cellular structures

10. Arrangement of atoms on silicon surface

11. Prokaryotic vs. Eukaryotic
All cells are bound by a cell membrane and at some point carry DNA
Prokaryotic cells have no nucleus to hold the DNA
Eukaryotic cells have a nucleus as well as other internal membranes
Eukaryotic cells are more complex
Eukaryotic cells are generally larger
Bacteria – Prokaryotic,
Most others – Eukaryotic