Cell Theory and
Prokaryote vs.
Eukaryote
Characteristics #1 of Living Things:
-Living things are organized
What is a Cell?
1. Cell – Basic unit of living things.
2. Organisms are either:
a)Unicellular – made of one
cell such as bacteria and amoebas.
OR
b)Multicellular – made of
many cells such as plants
and animals.
Multicellular Organization
tissue
cell
organ
organism
A group of similar cells is called a tissue.
A group of similar tissues is called an organ.
A group of organs working together form an
organ system or organism
Scientists to Remember
1.Anton van Leeuwenhoek (1674)
a)Father of Microscopy
b)Saw tiny living things in pond water.
Scientists to Remember
1.Robert Hooke (1665) – Observed “cells” in cork
a)Named box-shaped structures as “cells”
Other Scientists
1.Matthias Schleiden (1838) – Plants are made of cells.
2.Theodor Schwann (1839) – Animals are made of cells.
3.Rudolf Virchow (1855) – New cells come from existing
cells.
4.Janet Plowe (1931) – Cell membrane is a physical
structure.
5.Lynn Margulis (1970) – Organelles were once free-living
cells.
Cell Theory
1.Confirmed discoveries that all scientists
believe to be true about cells:
a)All organisms (living things) are composed of
one or more cells.
b)The cell is the basic unit of (life) structure
and organization of organisms.
c)All (new) cells come from preexisting cells.
Microscopes
1.Light Microscope – magnifies tiny
organisms up to 1,000 times.
-Uses light and lenses.
-We use these.
2.Electron Microscope – magnifies
up to a million times.
-Uses electrons.
The Discovery of Cells
before
nucleus
true
nucleus
Eukaryotes
1. Has a nucleus with a nuclear envelope
2. Bigger and more complex than prokaryotes
3. Have membrane bound Organelles (golgi, ER,
lysosomes…etc)
4. DNA – double-stranded and forms chromosomes
(highly organized)
5. Can be unicellular OR multicellular organisms
6. Sexual Reproduction by Meiosis
7. Ex: animals, plants, fungi
Prokaryotes
1.
2.
3.
4.
5.
NO nucleus
NO membrane bound organelles (just ribosomes)
ALL are unicellular
Smaller than eukaryotic cells
Forerunner to eukaryotic cells (smaller and more
simple)
6. DNA – single strand and circular
7. Asexual Reproduction by Binary Fission
8. Ex: ALL Bacteria
Similarities
1. Contain all four macromolecules
a) lipids, carbohydrates, proteins, and nucleic acids
2. Both have ribosomes
3. Both have DNA
4. Similar Metabolism
5. Both can be unicellular
6. Have cell/plasma membranes or cell wall
Eukaryote VS. Prokaryote Picture
Prokaryotic Cell Reproduction
Binary Fission
Eukaryotic Cell Reproduction
Mitosis: cell reproduction for growth
and replacement of cells. This makes
identical copies (clones)
Meiosis: cell reproduction for the
production of gametes, such as egg and
sperm (sex cells)
How did organelles evolve?
1.Biologists generally believe
that eukaryotes evolved from
prokaryotes.
2.In 1981, Lynn Margulis
popularized the
“endosymbiont theory.”
Endosymbiotic Theory
1.The Endosymbiotic Theory states that present day
eukaryotic cells evolved from the uniting of several
types of primitive prokaryotic cells
a)Some organelles (mitochondria and chloroplasts)
might have been were originally prokaryotes that
were involved in a symbiotic relationship
Endosymbiotic Theory
1. A prokaryote ancestor “eats” a
smaller prokaryote
2. The smaller prokaryote evolves a
way to avoid being digested, and lives
inside its new “host” cell kind of like a
pet.
Endosymbiotic Theory
•Endo = inside
Symbiont = friend
Endosymbiotic Theory
1.The small prokaryotes that can do
photosynthesis evolve into chloroplasts, and
“pay” their host with glucose.
2.The smaller prokaryotes that can do aerobic
respiration evolve into mitochondria, and
convert the glucose into energy the cell can use.
3.Both the host and the symbiont benefit from the
relationship
Endosymbiotic Theory
1.Chlorella are tiny green cells that live
inside some amoeba... endosymbiosis may
still be evolving today!