1. Cell Theory Timeline

2. What is a cell?
The basic unit of structure and function of life.

3. 1665: Robert Hooke
Builds compound microscopes and first to observe cork cells.

4. Late1600’s: Anton van Leeuwenhoek
Builds simple, powerful microscopes
Observes many single celled organisms, (like blood cells, animal sperm cells, & bacteria from his own teeth! He called them “animalcules” )

5. 1824: Henry Dutrochet All living things are made of cells
1831: Robert Brown
Cells have a nucleus

6. 1838: Matthias Schleiden Concludes all plants are made of cells
1839: Theodor Schwann Concludes all animals are made of cells.

7. Purkinje (1838): Jelly-like substance in cells called protoplasm
Shultze (1861): protoplasm is the basis for life
Dujardin (1860s): organisms can be unicellular

8. 1855: Virchow
Concludes that all cells come from pre-existing cells

9. Cell Theory All organisms are composed of one or more cells.
Cells are the basic units of structure and function in an organism.
Cells come only from the reproduction of existing cells.

10. Cell Diversity
Shape: There are many cell shapes. The function of the cell influences the shape of the cell.
For example, skin cells are flat, nerve cells have extensions.

11. Skin Cells
Nerve cell

12. Size
Different types of cells have different sizes.
0.1 μm – 100 μm
The size of a cell is limited by the surface area-to volume ratio.

13. Surface area-to-volume Ratio
larger
As the cell gets ______, the surface-area-to-volume ratio gets _________.
If the cell grows beyond a certain limit, not enough material will be able to cross the membrane fast enough to provide for the increased volume.
smaller

14. Surface area-to-volume ratio
Length of side
Surface Area
Volume
Surface Area/ Volume 1 2 4 6 1 6 8 3 24 96 64
3/2 = 1.5

15. Surface area-to-volume ratio
Materials must enter through the surface.
The bigger the cell, the smaller the surface area-to-volume ratio.
If a cell is too large, there is not enough surface area to allow materials to pass through quickly enough.

16. Types of Cells
Prokaryotic vs. Eukaryotic

17. Prokaryotic Cells

18. Very simple cell
Generally smaller
NO membrane-bound organelles (compartments)
No true nucleus.
DNA is found in the nucleoid region and is NOT separated by a membrane.
Example is bacteria.

19. Eukaryotic Cell

20. More complex cells
Generally bigger
Contains membrane-bound organelles
Has a true nucleus
Region of where DNA is stored and is separated by a membrane.
Examples are animals & plants

21. Pop Quiz! Who is credited for first seeing cells?
According to the Cell Theory, where do all cells come from?
Which cells are simpler: Prokaryotic or Eukaryotic?
Which cells contain membrane-bound organelles?
Which type of cells do you have?

22. Viewing Cells
Label, name, and state the functions of the parts of a compound microscope

23. Light Microscope Simple microscope: magnifying glass
Uses light to produce enlarged image
Light rays bend when passing through lens
Simple microscope: magnifying glass
Compound microscope: 2 lenses
Multiply the magnification of each lens to get the total magnification.

24. Onion Cells

26. Stage clips: hold slide in place Diaphragm: adjusts amount of light
Course adjustment: moves stage up and down to focus
Fine adjustment: focuses on a smaller scale
Eyepiece contains the ocular lens
Nosepiece: holds objective lenses
High power, medium power, low power