1. Cells and the Origin of Cell Theory

2. History of the Cell Theory
Before microscopes, belief in supernatural causes of diseases
Could not see microorganisms
What branch of biology?
Cells = basic units of living organisms

3. Microscopes Originally a hand lens to view quality of cloth
Anton van Leeuwenhoek (mid-1600s) first to examine water under microscope
Credited with development of light microscope

4. Anton von Leeuwenhoek’s Microscope

5. Improvements
Compound light microscope- series of lens to magnify objects (1500x)
Robert Hooke used one to observe cork magnified 30x
Observed small geometric shapes
Dubbed these cells (resembled monk rooms)

6. Hooke’s Microscope

7. Cell Theory
1830’s German scientist Matthias Schleiden realized that plants made up of cells
Theodore Schwann made same determination of animals
= Cell Theory

8. Many resources (including your book) give only credit to Scleiden and Schwann
Original third tenet was spontaneous generation
Rudolph Virchow - "Omnis cellula e cellula”

9. Cell Theory All organisms are composed of one or more cells
The cell is the basic unit of organization of organisms
All cells come from preexisting cells

10. Recent Developments
1940’s were able to use beam of electrons instead of light x
Electron microscope
Scanning Electron Microscope
Transmission Electron Microscope

11. Scanning Electron Microscope
SEM
Electrons are reflected off the surface of the specimen
3D shape

13. Transmission Electron Microscope
TEM
Allows to see inside of cell
Electrons pass through instead of light

14. Size Comparison

15. Prokaryote vs. Eukaryote
With the invention of microscopes, scientists could see two groups of cells
Prokaryotes
Eukaryotes

16. Prokaryote 1-10 m in diameter NO membrane-bound organelles
1 circular DNA molecule located in nucleoid region

17. Plasma membrane, cytoplasm & ribosomes
Most have a cell wall (peptidoglycan)
May have a polysaccharide capsule
Ex. bacteria & cyanobacteria

18. Prokaryotic Cell

19. Eukaryote 10-100 m in diameter
Nucleus & other membrane-bound organelles
2 or more linear DNA molecules located in nucleus
Plasma membrane, cytoplasm & ribosomes some have a cell wall (cellulose or chitin)
Ex. plants, animals, fungi, protista

20. Animal Cell
Animal Cell

21. Plant Cell

22. QUESTIONS?????