The History of
Cells and Cell
Theory
OBJECTIVES:
In this lesson, you will learn:
• how cells were first discovered,
• how the cell theory was developed, and
• the main components of the cell theory
CABBAGE PAPER GAME
CELL THEORY HISTORICAL TIMELINE
HANS and ZACHARIAS
JANSSEN
• Around the year
1590, two Dutch
lens makers by the
name of Hans and
Zacharias
Janssen invented
the first
compound
microscope when
they put two of
their lenses
together in a tube.
A Dutch father-son
team named Hans and
Zacharias Janssen invented the
first so-called compound
microscope in the late 16th
century when they discovered
that, if they put a lens at the top
and bottom of a tube and looked
through it, objects on the other
end became magnified
Hans and Zacharias Janssen
are known for inventing the
compound optical
microscope. They made it in
the 1590's. This contributed
to "The Cell Theory" by
making it easier and more
practical whilst observing
cells.
ROBERT HOOKE
• In 1665, an English scientist, Robert Hooke
discovered and came up with the name
“cells” while looking through a microscope
at a piece of cork.
• Supposedly, the cork (which was made of
dead oak tree tissues) reminded him of the
small rooms that the monks lived in at the
monasteries.
●
Hooke's cells
Robert Hooke
• While observing cork through his
microscope, Hooke saw tiny
boxlike cavities, which he
illustrated and described as
cells. He had discovered plant
cells! Hooke's discovery led to
the understanding of cells as
the smallest units of life—the
foundation of cell theory
•
ANTON VAN
Not longLEEUWENHOEK
after Hooke (around 1683), a
Dutch amateur scientist by the name of
Anton Van Leeuwenhoek observed
some of the first living cells under a
simple (1 lens) microscope.
• He named these small organisms
“animalcules”.
• It is now believed that some of the living
cells he saw were actually protozoa.
• He was the first person to
examine many cells,
including red blood cells. He
was also the first person to see
the nucleus of these blood
cells. Before him, the notion of
cells as the building blocks of
living things was not widely
accepted.
MATTHIAS JACOB
SCHLEIDEN
In 1838 a German botanist
by the name of Matthias
Schleiden viewed plant
parts under microscope
discovered that plant parts
are made of cells.
THEODORE SCHWANN
In 1839 German zoologist by
the name of Theodore
Schwann viewed plants and
animals under a microscope
and discovered that plants
and animals are both made
of cells.
RUDOLPH VIRCHOW
In 1855 a Prussian (modern
day German) physician by the
name of Rudolph Virchow
collaborated his ideas with the
other two scientists and they
developed the Cell Theory.
Q
The Cell Theory
1. All organisms are made of cells.
2. The cell is the basic unit of life in all
living things.
3. All cells come from existing cells.
THIS IS IMPORTANT BECAUSE IT SHOWS THAT
ALL LIVING THINGS SHARE A SIMILAR
STRUCTURE
Cells:
The Basic Units of Life
Definition of Cell
A cell is the smallest unit
that is capable of
performing life functions.
Examples of Cells
Amoeba Proteus
Plant Stem
Bacteria
Red Blood Cell
Nerve Cell
How big is a cell?
• http://www.cellsalive.com/howbig.htm
Two Types of Cells
All cells, whether they are prokaryotic or eukaryotic, have
some common features
Organelles
Organelles are structures that enable
the cell to live, grow and reproduce.
Two Types of Cells
Prokaryotic Cells:
• Have no membrane
covered nucleus
• Have no membrane
- covered organelles
• Have circular DNA
• Are bacteria
Prokaryotic Cells
●
Prokaryotic cell – Unicellular organisms
like bacteria. Notice the DNA is not found in
a nucleus and organelles are absent
(except ribosomes).
Two Types of Cells
Eukaryotic Cells:
• Have a nucleus
• Have a membrane covered organelles
• Have linear DNA
• Are all other cells
Organelles
Organelles are structures that enable
the cell to live, grow and reproduce.
Cell Membrane
• Outer layer of cell
• Allows nutrients
into the cell and
wastes outside of
the cell
“Gate into the
city”
Cell Membrane
Cytoplasm
• Cytoplasm a
jelly-like fluid
contained in
the cell that
holds the
organelles.
The Nucleus
DNA
• The control
center of the
cell
• Contains the
Cell’s DNA
Nucleolus
Nuclear Membrane
“Mayor’s office”
Mitochondria
Outer Membrane
• Power center of
cell
• Provides the
energy the cell
needs to move,
divide, etc.
Inner Membrane
“Electric company of
the cell”
Ribosomes
• Site where
proteins are
made
• Cell parts are
made of
proteins
“Factories of the
cell”
Endoplasmic Reticulum
Endoplasmic Reticulum
Ribosomes
• Transportation
system of cell
• Rough ERribosome's
attached
• Smooth ER- no
ribosome's
“Roadways of the cell”
Golgi Complex
• Packaging house of
cell
• Packages,
processes, and
ships out the
stuff the cell
makes
“UPS of the cell”
Lysosomes
• Digests food
particles and cell
parts
– “Garbage men”
• Protects cell by
digesting foreign
invaders
– “Police men
Vacuole
Vacuole
• Stores water,
food & wastes
Vacuole is largest
organelle in plant
cell
Cell Wall
• Found only in
plant cells
• Protects and
supports the cell
Chloroplasts
• Found only in plant
cells
• Contains
chlorophyll (makes
plants green)
• Where
photosynthesis
takes place
“Typical” Plant Cell
http://waynesword.palomar.edu/images/plant3.gif
• A "raphide crystal" is found in plant cells and has
the primary purpose of "repelling animals away from
plants". The needle-like crystals are made of calcium
oxalate and are shaped like needles.
• How are raphides different from plastids? Rhapides
are elongated, crystals that function in storage and
protection. Plastids create and store food and pigments
and are membrane bound organelles.
• Raphides seem to be a defense mechanism against
plant predators, as they are likely to tear and harm the
soft tissues of the throat or esophagus of a plant predator
chewing on the plant's leaves.
Plants with Raphide Crystals
A druse is a group of crystals of calcium
oxalate,[1] silicates, or carbonates present
in plants, and are thought to be a defense
against herbivory due to their toxicity.
Plant or Animal Cell?
Found in Plant and Animal cells:
• Nucleus
• Golgi Complex
• Mitochondrion
• Lyosomes
• Endoplasmic
Reticulum
• Cell Membrane
• Ribosomes
• Vacuoles
Found only in Plant Cells:
• Chloroplasts
• Cell Wall