Cell Theory and
Prokaryote vs. Eukaryote
What is a Cell?

Cell – Basic unit of living things.
Organisms are either:
 Unicellular – made of one
cell such as bacteria and
amoebas.
 Multicellular – made of
many cells such as plants
and animals.
Scientists to Remember

Robert Hooke (1665) – Observed
“cells” in cork

Anton van Leeuwenhoek (1674)


Father of Microscopy
Saw tiny living things in pond water.
What is a Theory

An accepted principle or statement
based on natural and physical
phenomena that is supported by
data from a collection of repeated
tests by independent researchers.
Cell Theory

Confirmed discoveries that all scientists
believe to be true about cells:
 1. Cells are the basic unit of life.


2. All living things are made of cells.
3. New cells are produced from
existing cells.
The Discovery of Cells
before
nucleus
true
nucleus
Eukaryotes






Has a nucleus
Bigger
Have membrane bound Organelles
(golgi, ER, lysosomes…etc)
DNA inside nucleus
Can be uni- OR multicellular organisms
4 Types:animals, plants, fungi, protist
Eukaryotes
Prokaryotes


NO nucleus
NO membrane bound organelles
- just ribosomes




ALL are unicellular
Smaller
DNA – single strand and circular
ALL Bacteria
Prokaryotes
Similarities
1.
2.
3.
Can be unicellular
Contain all four biomolecules
Have organelles in common
- Plasma membrane, Cytoplasm, DNA, Ribosomes
The Endosymbiotic
Theory



The endosymbiotic theory is the idea
that a long time ago, prokaryotic
cells engulfed other prokaryotic cells
by endocytosis. This resulted in the
first eukaryotic cells.
Explains the origin of eukaryotic cells
Explains the origin of certain
membrane-bound organelles
What Exactly Happened?
Evidence in support of the
endosymbiotic theory:
Similarities between mitochondria,
chloroplasts, & prokaryotes:
 Circular DNA
 Ribosomes
 Binary fission
- division in half