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The Cell
I. Cell Theory
A. Famous Scientists
1. Anton von Leeuwenhoek (1665): A Dutch businessman who used the
microscope to examine the quality of the cloth he traded.
a) He was the first person to see
microorganisms in a drop
_______________________
of water.
_______________________
b) He called them ____________
animalcules.
I. Cell Theory
A. Famous Scientists
1. Robert Hooke (1674):
An English physicist who used the microscope to look at a thin slice of cork.
cork is
a) He discovered that _____________
made of many small chambers.
____________________________
cells after
b) He called them ________
monastery rooms.
________________________
c) Hooke’s work inspired other
scientists to search for cells
elsewhere.
3. Mathias Schleiden (1823): A German botonist – plant specialist.
all plants are
a) He discovered that _____________
made up of cells.
____________________________
4. Theodore Schwann (1839): Another German scientist
all animals are
a) He discovered that _____________
Sideburns
made up of cells.
____________________________
Not to be confused with…
cells
cells
5. Rudolf Virchow (1855):
A German physicist who realized that all cells
come from pre-existing cells.
B. The discoveries made by these scientists led to the formation of the cell theory:
The cell is the basic unit of structure and function in living things.
1. __________________________________________________________
All living things are made up of cells.
2. __________________________________________________________
All cells come from pre-existing cells.
3. __________________________________________________________
Exceptions…
II. Microscopy
light microscope was invented in the 1600s and
A. The ________________
opened a whole new world to biologists.
B. Magnification: How much larger an object appears
C. Resolving Power (resolution):
Measure of clarity/detail of an image
Ex. What appears to be one
star, may actually be
two stars when viewed
with a high-resolution
telescope.
D. Light Microscope (LM)
1. Produce image by focusing light on specimen.
2. Resolution is limited by wavelength of visible light
a) LMs can resolve objects ≥ 0.2 µm (micrometer… 10-6meter)
b) Clear magnification up to 1,000X
3. Dead or live specimens
4. Various dyes can be used to improve visibility
a) Lugol’s Iodine solution – stains starch in plant cells
b) Methylene Blue – stains animal cells
Light Microscope Parts
Body Tube
Revolving
Nosepiece
Eyepiece
(Ocular Lens)
Arm
Objective
Lens
Stage
Stage Clips
Diaphragm
Light Source
Coarse Adjustment
Fine Adjustment
Base
E. Electron Microscope (EM)
1. Uses electromagnets to focus a beam of electrons
on/through a specimen.
2. Much shorter wavelength than visible light:
a) Higher magnification
b) Resolve objects ≥ 0.1 nm (nanometer… 10-9meter)
First EM was built
by Ernst Ruska &
Max Knoll at
Berlin Tech in
the late 1920’s
Vladimir Zworykin (seated)
& James Hillier
Demonstrate an early
electron microscope.
This model stood
10 feet high and
weighed half a ton!
3. Two types of Electron Microscopes:
a) Transmission EM (TEM):
Aims electron beam through a thin section of the specimen
b) Scanning EM (SEM): Scans the surface of the specimen
Cilia in
rabbit
trachea
Table Salt
Human Hair
(split end)
Human Hair
Follicle
Blood Cells
Pollen
Fly’s Eye
Spinnerets
Of a spider
Diatoms