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Cells
- Robert Hooke (~ mid 1600’s)
 Looked at cork & many plants through a very simple microscope.
 All plants had similar structure when viewed through microscope.
 Looked like a lot of “little boxes”.
 Reminded him of rooms that monks lived in so he called them
cells.
 He was looking at the remains of dead cells.
- Anton van Leeuwenhoek (~ mid 1600’s)
 Created a more powerful microscope
 First to view living cells.
- 150 years later, all information about cells was organized into a
unified theory called Cell Theory which has 3 parts:
1) All living things are composed of one or more cells.
2) Cells are the basic units of structure and function in an
organism.
3) Cells come only from the reproduction of existing living cells.
* Part 3 is only true now in time – not true 3.5 billion years ago!
- Cell sizes range from micrometers or microns (1/1000000 meters) to
meters in length. Most are microscopic. Some are large – egg cell
and some are long - nerve cell in giraffe leg is 2.2 meters in length.
- Cells come in a variety of shapes and the shape is based on its
function.
1) Flat cells – skin cells cover the body
2) Long cells – nerve cells transmit messages to different areas
3) Shape changers – white blood cells can move through narrow
openings to track down diseases.
- Cells contain many small organs or organelles (“elle” = small/tiny)
that perform a lot of different functions, a lot like organs in the
body. Ex: Brain controls body, nucleus in cell controls cell.
- Two major categories of cells:
1) Prokaryotic (“Pro” – before, “karyo” – nucleus)
a. Contains no membrane-bound nucleus
b. No membrane-bound organelles
c. Size ranges mainly from .001 - .1 microns
d. Evolved 3.5 billion years ago
e. Bacteria is the only type of prokaryote currently living
2) Eukaryotic (“Eu” – true, “karyo” – nucleus)
a. Contains a “true” nucleus – nucleus is membrane bound
b. Most organelles are membrane bound
c. Size ranges mainly from .002 - 50 microns
d. Evolved 1.5 billion years ago
e. All other cells besides bacteria