Microscope
and
Cell Theory
Notes
I. MICROSCOPE
A. Field of View: Lighted area when looking
through the eyepiece
1. Low power (40x) (total magnification is
40x = objective magnification x eyepiece
magnification)
4 mm = 4000 Mm
2. Medium power (100x)
2 mm – 2000 Mm
*As magnification increases, our field of
view decreases.
*Mm (micrometer) 1000 Mm = 1 mm
B. Resolution: ability to distinguish 2
objects as separate = clarity
* fine adjustment is responsible for
resolution
C. “Depth of View” – ability to focus 1 plane
(or dimension) at a time
Blurry
Top thread very clear
CELLS
Cells are the structural, functional,
reproductive units of life
II. History:
A. In 1600s, Anton van Leeuwenhoek, a
Dutch lens grinder, built a microscope
and was the 1st to observe tiny living
organisms.
B. In 1665, Robert Hooke, looked at
cork under the microscope and reported
the existence of cells.
(Hooke coined the term “cells” because
the tiny dark pores reminded him of the
cells where monks slept in their dorms)
C. In 1838 & 1839, botanist Matthias
Schleiden, and zoologist Theodore
Schwann originated the Cell Theory:
1. All organisms are made up of 1 or more
cells, and
2. Cells are the fundamental units of lifethe smallest things that can be called
“living”
Pioneers of Cell Biology
“I made a microscope.
Check it out. Stuff looks
wicked close-up.”
Anton Van Leeuwenhoek
1632-1723
“Totally. This one time? I sliced up a
piece of cork? Looked like it was
made of a bunch of little empty
rooms. Like cells monks live in. We
should totally call them that. Cells.”
“Plants are made of
cells”
“We“We
cancan
put put
all these
all these
other
other
guys’
guys’
research
research
intointo
oneone
theory.”
theory.”
“Animals are
made of cells”
“Cells only come
from other cells.
They can’t come
from nonliving
stuff. Ever.”
Rudolf Virchow
Schleiden
The Cell Theory
Schwann
1. All living things are composed of cells
2. Cells are basic unit of structure and function
in living things
3. All cells come from other cells.
D. In 1855, Rudolf Virchow added a 3rd
statement:
3. Cells arise only by division of other
cells
(Virchow discovered that cells divide
forming new cells)
III. Why do organisms need cells?
A. Cells are miniature life-support
chambers that maintain a special
environment.
B. Homeostasis – maintenance of conditions
within specified limits.
C. Many organisms are unicellular
(consisting of only 1 cell)
--However cell size is limited.
D. Because of size constraints, large
organisms such as animals and plants are
multi-cellular.
* Each cell of a multi-cellular organism
make a specialized contribution to the
body as a whole = division of labor.
IV. Types of Cells
A. Prokaryotic (pro = before; karyon =
nucleus)
1. No nucleus
2. Are bacterial cells (Monera)
3. Believed to have evolved earlier than
eukaryotic cells
4. Have a rigid cell wall
B. Eukaryotic (eu = good, true)
1. Contains a nucleus!
2. Make up the bodies of all organisms other
than bacteria:
(include Algae, Fungi, Protists, Plants, &
Animals!)
V. Cell Parts
A.
Cell Membrane (ALL CELLS have one)
1. Phospholipids—main structural molecule of
cell membrane
a. Phosphate head
• Polar (+ end, - end)
• Hydrophilic (“water-loving”)
b. Two Fatty acid tails
• nonpolar
• Hydrophobic (”water-fearing”)
2. In H2O, phospholipids form a LIPID BILAYER
B.
Fluid Mosaic Model (of cell membrane)
1.
The idea that cell membrane is a fluid, shifting
bilayer containing (besides phospholipids)
a.
b.
Cholesterol—keeps membrane fluid
Proteins with diff. jobs--examples


Move things across membrane
carry “markers” to ID cell
Fluid Mosaic link