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All About Cells
Microscopes and the Cell Theory
At lot of times,
when we think of a
object, we think of
it as it is today.
For example, a cell
phone.
So when we think of cell phones, we
think of the ones we see today.
The ones that we know and many of
us use.
But what about the original cell
phones?
Just as there are difference between
the cell phones we use now and the
original cell phones, there are also
differences in the microscopes we
use today and what the original
scientists who first looked at cells
had available to them.
Historical microscope images, and
more, can be found at:
http://www.techinst.com/
antiquecollection.html
 The observations and conclusion of
many scientists helped to develop the
current understanding of the cell.
 Robert Hooke
 Anton van Leeuwenhoek
 Matthias Schleiden
 Theodor Schwann
 Rudolph Virchow
 Early Scientists
 Robert Hooke (1665)
 Observed a cork slick
and saw that it
seemed to be made
up of tiny, empty
chambers.
 Hooke called these
chambers cells,
because they
resembled the tiny
rooms of a monastery.
 Early Scientists
 Anton van Leeuwenhoek
(1674)
 Used a single-lense
microscope to observe
pond water
 Saw tiny living organisms,
which he called
“animalcules” and we
know today as bacteria
Matthias
Schleiden (1838)
– concluded that
all plants are
made up of cells
Theodor
Schwann (1839)
– concluded that
all animals are
made up of cells
Rudolph
Virchow (1855) –
proposes that all
cells come from
preexisting cells,
completing the
cell theory
 Cells are the basic unit of life.
 The cell theory states that:
 All living things are composed of cells
 Cells are basic units of structure and function in living
things
 New cells are produced from existing cells
 Remember, before the Cell Theory, we had
Spontaneous Generation – that life can arise
from nonliving matter.
 The scientists who worked to disprove this
idea are:
 Redi
 Spallanzani
 Pasteur
 Common Microscope Types:
 Light microscope – living organisms, but low resolution
 Electron microscopes - view details 1000 times smaller
than visible in light microscopes. Non-living specimens.
Requires vacuum.
 Scanning Probe microscopes – Can operate in air, and
can show DNA, protein molecules, and even single
atoms.
 Light Microscope
 Electron Microscopes
 Transmission Electron microscopes – requires thin
specimens, can view cell structures and large protein
molecules.
 Electron microscopes
 Scanning Electron microscopes – 3D
 Scanning Probe Microscopes
PROKARYOTES
DNA
Cells that have genetic
material that is not
contained in a nucleus;
called a nucleoid region
EUKARYOTES
Cells that contain a
nucleus in which their
genetic material is
separated from the rest
of the cell
Size
0.2-10μm
5-100μm
Organization
Usually single-celled;
generally smaller than
Eukaryotes
Can be single celled,
but often multicellular
Examples
Bacteria
Plants, animals,
protists, fungi