The History of the Cell

How did we discover cells?
–Discovery made possible by
the invention of the
microscope
–Mikros = small
–Skopein = look
Microscopes and Cells

1600’s.
–Anton van
Leeuwenhoek
first described
living cells as
seen through a
simple
microscope.
Microscopes and Cells
–Robert Hooke used the first
compound microscope to
view thinly sliced cork cells.
•Compound scopes
use a series of lenses
to magnify in steps.
•Hooke was the first
to use the term
“cell”.
Robert Hooke's
Drawing of Cork Cells
Actual cork cells
Microscopes and Cells

1830’s.
–Mathias Schleiden
identified the first plant
cells and concluded that
all plants were made of
cells.
- Theodore Schwann
made the same
conclusion
about animal cells.
Plant and Animal Cells
Cell Theory:
 All
organisms are composed of
one or more cells.
 The cell is the basic unit of life
 All cells come from preexisting
cells.
All Cells
Cells do have some basic structures in
common
1) Cell membrane
2) DNA
3) Ribosomes
4) Cytoplasm

All cells have a membrane



cell membrane =
plasma membrane
Function – controls what
enters and exits the cell,
helps to maintain cell
homeostasis
NOT the same as cell
wall (only some cells)
(more coming in ch. 8)
All cells have DNA code



DNA is a nucleic acid
What is the purpose of
DNA (and nucleic
acids in general)?
Again, more details
coming later in
genetics unit (ch. 13)
All cells have ribosomes


They look like tiny
dots in overall cell
If DNA has protein
code, ribosomes
build the protein
according to the
code
All cells have ribosomes

Ribosome sliding along a nucleic acid,
reading its code to assemble amino
acids together into a protein
Two Basic Cell Types
1)
Prokaryotic Cells:
– Lack internal
compartments (organelles)
– No true nucleus.
– All are single-celled
(unicellular) organisms.
– Examples: bacteria
– Smaller, simpler cells than
eukaryotes
Two Basic Cell Types
2) Eukaryotic Cells
– Have several internal structures
(organelles).
– True nucleus.
– Either unicellular or multicellular.
– plants and animals, fungi, protists
– Much more complex and larger then
prokaryotic cells
Simple to complex…



Prokaryotic cells are simple
Eukaryotic cells are complex
Can you guess which type may have
evolved from which type?
Eukaryotic from Prokaryotic
Prokaryotes vs. Eukaryotes
Now compare the two groups side by side:
Prokaryotes




No definite nucleus
No membrane bound organelles
All are bacteria!
Unicellular
Eukaryotes




Have a defined nucleus
have membrane-bound organelles
plants, animals, protists, or fungi
May be single or multi-cellular
Now think of what Prokaryotes and Eukaryotes have in common and
use them to complete the following bubble map. Remember the
characteristics of all living things!!
Prokaryotes vs. Eukaryotes
Prokaryotes vs. Eukaryotes
Ask if you have a different
answer.
DNA
No
organelles
organelles
cytoplasm
Unicellular
Prokaryotes
Eukaryotes
Defined
Nucleus
Cell
membrane
Multi or
Unicellular
No nucleus
Ribosomes