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Cell Theory
THE CELL THEORY GREW
OUT OF THE WORK OF
MANY SCIENTISTS AND
IMPROVEMENTS IN THE
MICROSCOPE.
 Many
scientists
contributed to
the cell theory.
ROBERT HOOKE

He was the first person to look at cells and
named them. He looked at cork cells which
are not living.
 It
is the bark of a tree so they are dead
plant cells. They are small squares and
they reminded him of the small rooms
in a monastery called cells
ANTON VAN LEEUWENHOEK

Credited with improving the microscope. (Zacharias
Janssen is credited with discovering/creating
microscope). Leeuwenhoek’s microscope could
magnify 200x the human eye! Today’s microscopes
can magnify up to 1500!
MATTHIAS SCHLEIDEN
was a German botanist
(scientist who studies
plants.)
 He found that the plant
parts he examined were
made of cells. He made
the generalization that
all plants were made of
cells.

THEODOR SCHWANN
Studied animals. His microscopic investigations of
animal parts led him to generalize that all animals are
made of cells
 After looking at Schleiden’s work ,he further proposed
that all organisms are made of cells.

RUDOLF VIRCHOW- OMNIS CELLULA C CELLULA”: ALL
CELLS FROM CELLS (1855)


German doctor that said that new plant cells arise
only from existing plant cells, and new animal cells
arise only from existing animal cells.
Building off the work of Redi (1668) who disproved the
idea of spontaneous generation in his experiments
about rotting meat.
LOUIS PASTEUR-GERM THEORY
1856-Used the microscope to discover that tiny, onecelled (eukaryotic) yeast created alcoholic
fermentation and that other one-celled, rod-shaped
organisms (prokaryotic bacteria) caused beverages
to spoil.
 Pasteur (1864) designed a flask experiment that
disproved the idea of spontaneous generation once
and for all!

Ask me why I don’t
have anthrax!
images from “amoeba Mike” and Britannica


Early studies led to the development of the cell theory.
The Cell theory has three principles.
1) All organisms are made of cells.


Early studies led to the development of the cell theory.
The Cell theory has three principles.
1) All organisms are made of cells.
2) All existing cells are produced by other living cells.


Early studies led to the development of the cell theory.
The Cell theory has three principles.
1) All organisms are made of cells.
2) All existing cells are produced by other living cells.
3) The cell is the most basic unit of life.

There are two cell types: eukaryotic cells and
prokaryotic cells: Comparing cell types

There are two cell types: eukaryotic cells and
prokaryotic cells.
Eukaryotic cells have a
nucleus (true nucleus)which contains
DNA that forms many chromosomes.

nucleus
cell membrane

There are two cell types: eukaryotic cells and
prokaryotic cells.
Eukaryotic cells have a
nucleus.
 Eukaryotic cells have
membrane-bound
organelles.

nucleus
organelles
cell membrane

There are two cell types:
eukaryotic cells and
prokaryotic cells.


Prokaryotic cells do not
have a nucleus.
nucleus
Prokaryotic cells do not
have membrane-bound
organelles, but they do have
some organelles like ribosomes.
organelles
cell membrane
cytoplasm

There are two cell types: eukaryotic cells and
prokaryotic cells.

Prokaryotic cells do not
have a nucleus, but they have one chromosome
and “extra” circular pieces of DNA called
“plasmids”. Draw a circular plasmid in your bottom
cell diagram on your notes and label it “plasmid
DNA”.
EUKARYOTIC CELLS VS PROKARYOTIC BACTERIA
CELLS
Organelles
Nucleus
Eukaryotic
DNA/Chromatin
Cytoplasm
Cell membrane
Prokaryotic
Plasmid DNA
DNA/Chromatin
Cytoplasm
Cell membrane