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Chapter 7 Biology
Discovery of the Cell
In the mid-1600s, Anton van
Leewenhook used a single lens light
microscope to observe pond water
and discovered a world of tiny
microscopic organism in the water.
In 1665, Englishman, Robert Hooke
used an early compound light
microscope to look at a thin slice of
cork a plant material.
•He observed thousands
of tiny empty chambers,
he called cells now
considered to be the
basic units of life
Development of Cell Theory
In 1838, German botanist, Matthias
Schleiden concluded that all plants
were made of cells.
The next year, German biologists,
Theodore Schwann stated that all
animals were made of cells.
In 1855, German
physician Rudolf
Virchow
concluded that
new cells could
only be
produced from
existing cells
Together the works of these
scientist and others led to the
development of the cell theory the
fundamental concept of biology!
The Cell Theory states:
All things are composed of cells
Cells are the basic units of structure
and functions
New cells are produced from
existing cells
Exploring the Cell
In the 1940s, a
new type of
microscope, the
electron
microscope was
invented
The Electron Microscope uses beams of
electrons instead of natural light to
magnify images and can do so up to
500,000 x the actual size of the image
 The Electron Microscope was better
than the Light Microscope because it
allowed scientists to see the internal
structures within the cell
There are several different types of
Electron Microscopes:
Scanning Electron Microscope
(SEM): scans the surface within the
cell
Fly leg
Transmission
Electron
Microscope
(TEM): allows
scientists to see
internal
structures.
Pine tree
Scanning Tunneling
Microscope (STM):
uses electrons to
investigate the atoms
of the surface of
molecules
2 Types of Cells
With the development and use of the
microscopes, scientists were able to
discover 2 groups of cells that exists in
living organisms all contain:
ribosome
DNA
cell membrane
cytoplasm
1. Prokaryotic Cells: cells that lack
internal membrane-bound
structures called organelles (little
organs)
2. Eukaryotic Cells: cells that
contain internal membranebound structures or organelles
(has a nucleus)
Discovery of the Nucleus
Robert Brown, a Scottish scientist,
was the first to observe as
prominent structure in cells, called
the nucleus
Rudolf Virchow later concluded
that this structure (nucleus) is
responsible for cell division
(reproduction) in living organisms
6 Kingdom System (into which
living organisms belong):
1. Eubacteria-prokaryotic cells ex: E. coli (bacteria)
2. Archaebacteria- prokaryotic cells ex. Methanogens (bacteria)
3. Protista-eukaryotic cells ex. Amoeba, algae
4. Fungi- eukaryotic cells ex. Mushrooms, athlete’s foot
5. Plants- eukaryotic cells ex. Pine, flowers
6. Animals- eukaryotic cells ex. Sponges, humans
NOTE: THE
ONLY
Prokaryotes ON
EARTH ARE
bacteriums
(monerans)
Typical Prokaryotic Cell
DNA
Cell membrane
Typical Eukaryotic Cell
Ch 7.2 Biology Notes
Cell Parts (Organelles)
•Prokaryotic cells
(prokaryotes)-are cells that do
not have a nucleus. They are
the most ancient (oldest) cells
on Earth. Many of these
earliest cells do not use
oxygen to respire.
They used CO2 in the
atmosphere and lived in water
and produced O2 gas as a byproduct. Prokaryotes are ONLY
found in the kingdom Monera.
Eubacteria and Archaebacteria
Domains. They are bacteria.
Eukaryotic cells (eukaryotes)-are
cells that have a nucleus. They are
found in all the other kingdoms:
Plantae, Animalia, Fungi, and
Protista. They are thought to have
evolved from two bacteria living
together symbiotically (both
benefiting).
This is called the
Endosymbiotic Theory. You
have eukaryotic cells!
Mitochondria and
Chloroplast have own
DNA.
Nucleus-directs all activities of the
eukaryotic cell. Surrounded by a
nuclear envelope (membrane)
Nucleolus-organelle inside the
nucleus that make ribosomes
Chromatin-is located in the
nucleus of the cell; contains
strands of DNA.
Chromosomes are condensed
chromatin.
·
·
Plasma
Membrane-a
bilayer (2-layers)
of phospholipids
joined together to
surround the cell.
(Fatty acids +
Phosphate
Group)
Primary Function is to maintain:
Homeostasis
Ribosomes-the site of protein
synthesis. Ribosomes take amino
acids and produce proteins using
the instructions from DNA
 Cytoplasm-the
fluid of the cell.
Also called
cytosol
 Where all
chemical
reactions of
the cell takes
place
Endoplasmic Reticulum (ER)-are cellular pathways used
to transport proteins
 Smooth ER=have no ribosomes
 Rough ER=have ribosomes
 Golgi Apparatus-sort, package, process
proteins. They are the UPS of the cell.
Produces little packages celled vesicles.
Not connected to nucleus
 Vacuoles-in plant cells they are the
largest structure. Responsible for
storing large amounts of water. In
animal cells, they are much smaller and
more numerous. They store food,
enzymes, and other materials needed
by the cell. Sometimes they store waste
products. Some have Contractile
vacuole- to maintain Homeostasis.
Lysosomes-recycle cellular parts.
They can contain digestive
enzymes that break down and
reuse worn-out organelles and
food particles.
 Chloroplasts-are cell organelles that
capture light energy and convert it
into chemical energy (glucose/food)
for plant cells.. Chlorophyll is the
green pigment used to trap light
energy. Chlorophyll also gives plants
their green color (belongs to a group
called plastids). NOTE: The
ultimate source of all energy on
Earth is the SUN!
 Mitochondria-the site of cellular
respiration (ENERGY). They transform
food into energy in the form of ATP
(adenosine triphosphate: a useable form
of energy). Tissues or cells that use a lot
of energy have large numbers of
mitochondria. Muscle cells have more
mitochondria than skin cells.
Powerhouse of the cell.
 NCSCOS: mitochondria is folded to
increase surface area (make more room).
Organelle DNA
 Mitochondria and Chloroplast have own genetic
DNA.
 It is suggested that mitochondria and chloroplast are
descendents of ancient prokaryotes.
 Prokaryotes that use oxygen to generate ATP evolved
into Mitochondria.
 Prokaryotes that carried out photosynthesis evolved
into Chloroplast.
 Microtubules and Microfilaments-are thin,
solid proteins fibers. Many anchor cilia
(hair-like) and flagella (whip-like tail) that
help one-celled organisms to move.
Cell Wall-an inflexible barrier found
in plants. It protects the cell and gives
it support it is made up of cellulose
and has porous fibers that allows
molecules to pass through
Centrioles-found only in animal
cells. Aid(appears) in cellular
division