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B-2.1 Recall the three major tenets of cell theory (all living things are
composed of one or more cells; cells are the basic units of structure and
function in living things; and all presently existing cells arose from
previously existing cells).
B-2.3 Compare the structures and organelles of prokaryotic and
eukaryotic cells.
B-2.4 Explain the process of cell differentiation as the basis for the
hierarchical organization of organisms (including cells, tissues, organs,
and organ systems).
- used a compound microscope to look at
cork (from bark of a tree) & he saw empty
boxlike structures that he named “cells”.
used a simple microscope to look at pond
water.
- was the first to observe microorganisms
in pond water.
-
Onion cells Elodea cells
-
Cork cells
studied numerous plant parts under the
microscope and declared “ALL PLANTS
ARE MADE OF CELLS!”
-
Cheek cells
Amphibian Blood
Used a microscope to observe numerous
animal tissues and declared “ALL
ANIMALS ARE MADE OF CELLS!”
- observed living cells dividing and
declared “ALL CELLS COME FROM
OTHER LIVING CELLS!”
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All living things are composed of one or more cells.
Cells are the basic unit of structure of all living things.
◦ The lowest level of structure capable of performing all the activities of
life is the cell.
◦ A unicellular organism is composed of one cell and all of life’s activities
occur within that single cell.
◦ In a multicellular organism, each cell carries on most of the major
functions of life.
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All presently existing cells arose from previously existing
cells.
◦ The ability of cells to divide to form new cells is the basis for all
reproduction (both sexual and asexual) and for the growth and repair of
all multicellular organisms
Organisms may be:
 Unicellular- Composed of
one cell
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Multicellular-composed of
many cells
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Most cells are microscopic and are only 10 to 50
µm in size
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Three Basic Types of Cells:
Animal Cell
Plant Cell
Bacterial Cell
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Despite the diversity among cells these features
are common to all cell types
Plasma Membrane
◦ The cells outer boundary that acts as a barrier between
the inside and the outside of a cell
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Cytoplasm
◦ The region of the cell within the plasma membrane that
includes the fluid and all of the organelles (except the
nucleus)

Control Center
◦ Where the DNA is located
◦ Some cells have a nucleus and others do not
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Prokaryotic cells do not have a true nucleus
◦ “Pro—No”
◦ Kary- “nucleus”
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DNA is not completely separated from the rest of
the cell by a nuclear membrane (envelope) and is
not arranged in strands called chromosomes
Do not contain mitochondria but they can obtain
energy from either sunlight or from chemicals in
their environment.
No internal bound organelles
Two types of prokaryotes: Archaea & Bacteria
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Earliest from of life found on earth and our found
in extreme environment
Methanogens–produce methane gas as waste of
their “digestion” or process of making energy
Halophiles- live in salty environments
Thermophiles –live in extremely hot environments
Psychrophiles –live in unusually cold temperatures
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Microscopic organisms that are found
everywhere, except for extreme environments
Most are helpful, not harmful.
Essential for human life:
◦ Bacteria coexists with humans and other organisms at
all times
◦ Help us make vitamins, breakdown waste and maintain
our atmosphere
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Examples
◦ Escherichia coli (E.coli) lives in the intestines where it
helps us digest food and produce vitamin K
◦ Bacillus anthracis causes anthrax a deadly disease
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Smaller than Eukaryotic cells
Nucleoid region contains the DNA
Contains ribosomes (without membrane) to
make proteins in their cytoplasm
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Eu= “True”
Kary- “Nucleus
Organisms made up of one or more cells that
have a nucleus
Cytoplasm with Membrane-bound Organelles
◦ Organelles-intracellular bodies that perform
specific functions that support life
◦ Much larger than prokaryotic cells
Animal Cell
Plant Cell
Prokaryotic
Eukaryotic
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Cells of different organisms and even cells within the
same organism are very diverse in terms of shape, size
and internal organization.
The STRUCTURE of a cell relates to its FUNCTION
An adult human is composed of approximately 100
trillion cells and has over 200 different types of
specialized cells.
Ex. Nerve cells—long extension
Skin cells- flat and plate like
Bacteria- Rod, round or spiracle shape
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A single cell (fertilized egg) gives rise to many different
types of cells, each with a different structure and
corresponding function.
Cell division results in an increase number of cells
Cell differentiation- creates specialized in structure and
function.
Various types of cells (blood, muscle, or epithelial cells)
organize
Cells Tissues Organs Organ systems  Organisms
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Nearly all of the cells of a multicellular organism
have exactly the same chromosomes and DNA.
During differentiation, only specific parts of the
DNA are activated
The parts of the DNA that are activated determine
the structure and function of the specialized cell.
Because all cells contain the same DNA, all cells
initially have the potential to become any type of
cell.
Once a cell differentiates, the process cannot be
reversed.
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Stem cells are unspecialized cells that
continually reproduce themselves and have,
under appropriate conditions, the ability to
differentiate into one or more types of
specialized cells.
Embryonic Stem Cells -Have not yet
differentiated into various cell types
Adult Stem Cells- Found in bone marrow
Scientists have recently demonstrated that both
types of stem cells differentiate into specialized
cells under the right laboratory culture
conditions.
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