Springfield Central High School
What is a cell?
What are the key concepts to understand this unit?
Where do cells fit into the order of scale studied in biology?
How old are the oldest known fossils of cells?
What is the significance of Stanley Miller’s experiment?
What are the two types of cells?
How do the two types of cells differ?
What are the key characteristics of a plant cell?
What are the key characteristics of an animal cell?
What are organelles?
What are the three points to the cell theory?
Who were the scientists involved in the discovery of the cell theory?
What is the cell membrane and why is it so important to life?
Why are the definition of cells and the characteristics of life similar?
Central Concepts: Cells have specific structures and functions that make them
distinctive. Processes in a cell can be classified broadly as growth, maintenance, and
reproduction.
•2.1 Relate cell parts/organelles (plasma membrane, nuclear envelope, nucleus,
nucleolus, cytoplasm, mitochondrion, endoplasmic reticulum, Golgi apparatus,
lysosome, ribosome, vacuole, cell wall, chloroplast, cytoskeleton, centriole, cilium,
flagellum, pseudopod) to their functions. Explain the role of cell membranes as a
highly selective barrier (diffusion, osmosis, facilitated diffusion, active transport).
•2.2 Compare and contrast, at the cellular level, the general structures and degrees
of complexity of prokaryotes and eukaryotes.
•2.3 Use cellular evidence (e.g., cell structure, cell number, cell reproduction) and
modes of nutrition to describe the six kingdoms (Archaebacteria, Eubacteria, Protista,
Fungi, Plantae, Animalia).
Cells are small packages that have all the characteristics of life. These
packages are surrounded by a special double layer of fat known as a
phospholipid bilayer, which separates the outer environment from the
cell's inner environment.
The separation of the outer environment from the inner environment
allows the cell to maintain homeostasis.
A definition of a biological cell: the smallest unit that can
perform all life processes; cells are surrounded by a membrane
and contain DNA and cytoplasm.
There are two types of cells:
Prokaryote and Eukaryote. You
should already know that a
prokaryote cell does not have a
nucleus or any self-contained
organelles; while a eukaryote cell
does have a nucleus and can have
other self-contained organelles.
A. Types of organisms that are
Prokaryotes and Eukaryotes
B. Prokaryote celled organisms:
Archaea
Eubacteria
C. Eukaryote celled organisms:
Protist (aka. protoctista)
Fungus
Plant
Animal
•Prokaryote cells are always single celled organisms, which do not contain
a nucleus or other membrane bond structures.
•There are two types of prokaryote cells.
•Archaea (aka Archaebacteria)
•Eubacteria
Let’s look at a labeled drawing and actual photographs of prokaryotes
•Some prokaryotes can consume rocks, hydrogen gas, metal even uranium.
•In addition to oxygen, prokaryotes can "breathe" things like carbon dioxide,
metals, and salts.
•Prokaryotes can live in some of the most extreme environments on Earth!
•Archaea are the most thermophilic (heat loving) organisms known!
•The oldest microbial fossils are about 3.8 billion years old!
•Microbes can be found almost everywhere on Earth.
•Some places scientists have not yet found bacteria are in magma and in
some places in the Atacama Desert of South America!
•There are about 200 species of bacteria in your mouth.
•1,000 bacteria can fit on the tip of a pin.
•There are more bacterial cells than human cells in your body.
•Your skin contains about 1 trillion bacterial cells.
•Bacteria were first discovered in the 1670s by van Leeuwenhoek.
•There are more prokaryotes on your hand than there are people on the
planet.
Facts from: http://sciences.unlv.edu/desertsurvivors/Pages/episode2.htm
•Bacteria and archaea are
prokaryotes, or single-celled
microscopic organisms that have
no nucleus, unlike your cells.
•Bacterial cells have a cell wall, cell
membrane, cytoplasm, DNA, and
ribosomes.
•Bacterial cells can be spherical, rod
shaped, or spiral shaped.
Rods = bacilli (singular form is bacillus)
Spirals = spirilla (singular form is
spirillum)
Spheres = cocci (singlular form is
coccus)
•Archaea are single celled organisms that have similar structure as the
Eubacteria.
•However, the Archaea are genetically and biochemically quite
different from the Eubacteria.
•Archaea produce proteins and replicate their DNA differently
than do the eubacteria.
•Archaea like eukaryotes use the DNA code for the amino acid
methionine as a start codon.
•Archaea are extremophiles, which means that they love extreme
environmemts.
•Archaea are believed to be closely related to the early cells from billions
of years ago, when all earth environments were extreme.
•Many scientists see the evolutionary link between prokaryotes and
eukaryotes to be made from the archaea
•Eubacteria aka bacteria aka germs.
•Eubacteria are the common single celled organisms that lack a nucleus
and membrane bound structures.
•We usually associate bacteria with the pathogens that cause many
illnesses.
•However, most Eubacteria exist as ditritivores or symbionts and not
pathogens.
Different
Forms
Different
Functions
•Eukaryote cells are cells that contain a phospholipid bilayer
membrane bound nucleus and other phospholipid
membrane bound structures (known as organelles).
•Eukaryote cells have membrane bound compartments in
them.
•These compartments can have a separate chemical
environment than the rest of the cell.
•This allows for a wider variety of chemistry within
the cell and therefore a more complex form of life
Let’s have a look at an example of a eukaryote cell: an animal cell
•One of the distinguishing characteristics of eukaryotic cells is that they
have small membrane enclosed structures called organelles.
•Organelle means “little organ”, so organelles are like the organs of a cell.
•Organelles have various forms and perform various functions.
• The presence of a certain organelle will allow a cell to perform the
organelles function; this allows for some of the diversity between different
cell types.
Refer to this Web page
http://biology.clc.uc.edu/courses/bio104/cells.htm
Animal cells are eukarotic; they have a
nucleus.
Animal cells have other organelles; make
special note that animal cell vacuoles are
small. Animal cells lack chloroplasts.
Animal cells have a cell membrane; they do
not have a cell wall.
Plant cells are eukaryotic; they have a nucleus.
Plant cells have other organelles; make
special note that plant cell vacuoles are large.
Plant cells have chloroplasts.
Plant cells have a cell membrane, and they
have a cell wall made of the polysaccharide
cellulose.
•Plant cells are distinguished by
having a nucleus, a cellulose cell wall,
chloroplasts, and a large vacuole.
•Since plant cells are eukaryotes,
plant cells must have a membrane
bound nucleus to store the cell’s DNA
•A cell wall made from the sugar
cellulose if found around the plant
cells.
•Most plant cells contain the
organelle for photosynthesis known
as chloroplast.
•Plant cells have sap filled large
vacuoles.
•Plant cells have other organelles
found in eukaryote cells such as:
endoplasmic reticulum, golgi body,
mitochondria, and nucleolus.
•Animal cells are distinguished by
their lack of any cell wall; animal
cells have an undefined shape;
animal cells are surrounded by a
phospholipid bilayer membrane;
animal cells have a centrosome to
help with cell division. Naturally
animal cells have nuclei.
•Animal cells have no definite shape
because animal cells have no cell
wall.
•Animal cells can take different
forms to allow them to perform
different functions.
•Animal cells have other organelles
found in eukaryote cells such as:
endoplasmic reticulum, golgi body,
mitochondria, nucleolus, lysosome,
and small vacuole.
•The diversity of cells allows for the
diversity of life.
•Evolution has selected for this
diversity of life stategies and forms
of cells.
•Some cells survive as single celled
organisms: such as both types of
prokaryotes and some eukaryotic
protist.
•Other cells work independently
within a multicelled organism: such
as blood cells
•While other cells that have similar
functions are organized into tissues
which in turn can form the organs
that make up complex living things
like you and me.
Different
Forms
Different
Functions
What is a cell?
What are the two major types of cells?
What organisms have the two types of cells ?
Are there more human cells or bacteria cells in your body?
What structure are found in prokaryote cells?
What are the shapes that bacteria can be found taking?
How do the two types of cells differ?
What are the key characteristics of a plant cell?
What are the key characteristics of an animal cell?
What are organelles?
Scientists now feel that the archaea or the eubacteria are more closely
related to eukaryotes?
What is a phospholipid bilayer?
Similar cells can be organized into what layer of scale in biology?