Download Prokaryotic vs. Eukaryotic

Prokaryotic vs. Eukaryotic
Prokaryotes
• Prokaryotes are unicellular organisms and are found in all
environments. They are the largest group of organisms,
mostly due to the large numbers of bacteria which make up
the bulk of the classification.
• Characteristics:
– No membrane bound nucleus (genetic material dispersed
throughout cytoplasm)
– No membrane-bound organelles
– Simple internal structure
– Most primitive cell type (appeared about four billion years ago)
• Examples:
• Staphylococcus
Eukaryotes
• Eukaryotes, in general, are more advanced than
prokaryotes. There are many eukaryotic
unicellular organisms but there are no
multicellular prokaryotes.
• Characteristics:
–
–
–
–
Membrane bound nucleus
Numerous membrane-bound organelles
Complex structure
Appeared approximately one billion years ago
• Examples:
– Paramecium
– Dinoflagellates
– Canines (Dogs
Organelles
• There are several reasons why cells evolved organelles.
• First, organelles can perform specialized functions.
Organelles as specialized structures:
– Cilia for example - they act as "oars" to help some cells move
• Second, membrane bound organelles act as containers,
separating parts of the cell from other parts of the cell.
Organelles as Containers:
– Lysosome - It contains digestive enzymes that if allowed to
float free in the cell would kill it.
• Third, the membranes of organelles can act as sites for
chemical reactions.
• Organelle membranes as sites for chemical reactions:
– Chloroplast - Photosyntheis as a chemical process occurs
within the structure of this organelle.
Non Membrane Bound
Organelles
• Membrane - thin, pliable layer of tissue
covering surfaces or separating or
connecting regions, structures, or organs
of an animal or a plant.
Ribosomes
•
•
•
•
•
•
•
•
•
Ribosomes are small dot-like structures in cells.
They are often associated with endoplasmic reticulum(ER), to form
rough ER.
It is here that Protein Syntheis occurs.
They are made up of proteins and ribonucleic acid (RNA).
Their only function is to build proteins.
There are two kinds of ribosomes:
– those attached to the endoplasmic reticulum and
– those floating in the cell cytoplasm.
Attached ribosomes make proteins that are used in the ER or
transported within the ER.
Free ribosomes make proteins that are used in the cytoplasm.
Ribosomes are made in the nucleus of the cell and uniquely
enough posess their own form of RNA know as Ribosomal RNA
(rRNA). A ribosome can make the average protein in about one
minute.
Centrioles
• They are not found in higher plant cells.
• Centrioles come in pairs and are
composed of short microtubules arranged
in a cylinder.
• The two centrioles are aligned at right
angles to each other.
• During cell division one centriole moves to
opposite sides of the cell and may function
in cell division.
• The basic structure of the centriole is nine
groups of three microtubules arranged as
a cylinder.
• Each animal cell will have two.
Centrioles (cont’d)
• The spindle fibers that pull the chromosomes
apart during mitosis begin forming in the vicinity of
the centrioles.
• Because of this behavior it was long believed that
centrioles were necessary for animal cell division.
• However, some animal cells can divide when the
centrioles have been removed
• Another possible function of centrioles is that of a
cilia and/or flagella template or plan.
• Centrioles are found in animal cells, and the cells
of most protists also contain them.
• Curiously enough, plant, fungus and red algae
cells are fully capable of dividing without
centrioles.
Microtubules
• All eukaryotic cells will contain a network of
microtubules.
• They are made up of protein molecules and
provide structure, acting as a "skeleton" or
cytoskeleton.
• They serve as "roads" along which cells
can transport organelles and vesicles.
• Chromosomes are pulled apart during
mitosis by microtubules
• Cilia and flagella are composed of
microtubules
Membrane Bound Organelles
Organelles made-up of single
membranes
Vacuoles
• The vacuole acts as a container
• Vacuoles are, in simplest terms, a sac, a
single membrane surrounding solid or liquid
contents.
• There are a wide variety of vacuoles,
containing a wide variety of substances.
• Many plant cells contain a large central
vacuole (50 -90 % of its volume) filled with
water
• A food vacuole in a single celled amoeba
contains the food item that the amoeba has
consumed.
Lysosome
• Lysosomes are sacs that contain digestive
enzymes.
• Lysosomes are used by the cell to digest or
breakdown most complex organic molecules.
• They can either digest substances brought into the
cell or they can digest parts of the cell itself.
• Cells that ingest (eat) other cells surround the
ingested cell with a membrane forming a food
vacuole.
• This food vacuole is then fused with a lysosome
and the cell is digested.
Lysosomes (cont’d)
• Often cells need to tear down parts of themselves
and reuse the materials, Lysosomes do this. For
example, when a tadpole looses its tail in the
process of becoming a frog, the tail cells digest
themselves by the use of lysosomes. The material
from the tail is then used to build legs and other
frog parts!
• The term lysosome comes from two roots, lys
which means breakdown or digest and some
which means body. Therefore the literal translation
is "digesting body".
Vesicles
• Vesicles are the shipping containers within
cells and also carry material out of the cell
• They are a sac surrounded by a single
membrane.
• They are a liquid filled sac.
• Some are formed by pinching off the Golgi
apparatus.
• Vesicles that carry material out of the cell are
called exocytotic vesicles. Those which
bring material into the cell are called
endocytotic vesicles.
Endoplasmic Reticulum
•
•
•
•
•
•
•
•
Endoplasmic reticulum(ER) is a network of folded membranes that
extend through the cytoplasm to the nuclear membrane.
There are two kinds of ER, rough and smooth. Rough has
ribosomes, smooth has no ribosomes. ER is involved in the
transport of materials through the cell.
Endoplasmic reticulum is an extensive network of membranes that
extends from the cell membrane through the cytoplasm to the
nuclear membrane.
The membranes of the ER surround an inner cavity called the
lumen.
The membranes of the ER enclose a series of tubes and flattened
membranous areas.
The ER membranes actually attach to the cell membrane and the
nuclear membrane as well as the Golgi bodies in the cytoplasm.
The basic function of ER is transport. Proteins produced by the
ribosomes are transported to regions of the cell where they are
needed or to the Golgi body for export from the cell.
Smooth ER involved in detoxification of poisons and lipid
synthesis.
Peroxisomes
• Peroxisomes resemble lysosomes in structure and
function.
• They break down amino acids, fatty acids and
alcohol.
• The function of peroxisomes is very similar to
lysosomes, however the reactions in peroxisomes
are more specific.
• These reactions produce hydrogen peroxide which
could harm cells if it were allowed to persist.
• An enzyme (catalase) breaks down the hydrogen
peroxide to water and oxygen, both of which can be
used by the cell.
Golgi Apparatus
• Golgi apparatus (sometimes called the Golgi body)
• The Golgi apparatus consists of stacks of sacs with
vesicles pinching off from the edges of the sacs.
• The function of the Golgi is to "pack up" materials
for export from the cell.
• The vesicles that pinch off from the Golgi apparatus
move to the cell membrane and the material in the
vesicle is released to the outside of the cell. Some
of these pinched off vesicles become lysosomes.
• The two primary functions of the Golgi apparatus is
– : First modification of lipids and proteins;
– and second storage and packaging of materials that will
be exported from the cell. It is the "shipping department"
of the cell
Mitochondria
• They are the main energy producers in cells.
• There is a single outer membrane and a folded inner
membrane.
• This results in a sac with two inner compartments
which are separated by the inner membrane.
• The first compartment is between the outer and
inner membranes, the outer compartment is inside
the inner membrane.
• Mitochondria are usually shaped like stubby cigars
but sometimes they are round.
Mitochondria (cont’d)
• They use complex molecules and oxygen to
produce a high energy molecule known as
ATP.
• To do this mitochondria carry on a process
called aerobic respiration.
• Because of its role in energy production the
mitochondria has been called the
"powerhouse of the cell".
• They are very abundant in cells that require
lots of energy such as muscle cells.
Mitochondria (cont’d)
• All the mitochondria in your body came from your
mother.
• Mitochondria are not part of the genetic code in the
nucleus of your cells, fathers only give genes to
their children.
• Mothers give genes and cytoplasm to their children
in their egg cells, since mitochondria are in the
cytoplasm and reproduce themselves they only are
inherited from mothers.
• Geneticists have used this feature of mitochondria
to study maternal family lines and rates of evolution.
Chloroplasts
• Chloroplasts are the site of photosynthesis in eukaryotic
cells.
• Because of their green color chloroplast are the only
organelles that can easily be seen with a light microscope.
• There is a single membrane surrounding the chloroplast.
• This membrane surrounds a fluid called the stroma.
• Floating in the stroma are stacks of disks made up of
membranes, these are the grana.
• The grana resemble a stack of coins, however instead of
coins this stack is made up of individual hollow disks called
thylakoids.
• Chlorophyll, the green compound which gives chloroplasts
their color, is found in the membranes of the thylakoids.
Chloroplasts (cont’d)
• The light reactions take place on the
membranes of the grana.
• The dark reactions (also called lightindependent reactions and/or CalvinBenson Cycle) take place in the stroma.
• Chloroplasts, like mitochondria, contain
their own DNA and reproduce themselves.
Both have these characteristics of
prokaryotes (bacteria)
Cilia and Flagella
• These whiplike appendages extend from the surface of many
types of eukaryotic cells.
• If there are many of them, they are called cilia;
• if only one, or a few, they are flagella.
• Flagella also tend to be longer than cilia but are otherwise
similar in construction.
• Cilia and flagella move liquid past the surface of the cell.
• For single cells, such as sperm, this enables them to swim.
• For cells anchored in a tissue, like the epithelial cells lining our
air passages, this moves liquid over the surface of the cell
(e.g., driving particle-laden mucus toward the throat).
Cell Wall
• a non-living secretion of the cell membrane,
composed of cellulose
• contains pits (openings) that make it totally
permeable
• The cell wall is rigid (up to many micrometers in
thickness) and gives plant cells a very defined
shape.
• The cell wall is the reason for the difference
between plant and animal cell functions.
• Because the plant has evolved this rigid structure,
they have lost the opportunity to develop nervous
systems, immune systems, and most importantly,
mobility.
Cell Membrane
• While the plant cell has a rigid cell wall, an animal cell
membrane is a flexible lipid bilayer.
• The lipid molecules (mostly phospholipids) that make up the
membrane have a polar, hydrophilic head and two
hydrophobic hydrocarbon tails.
• There are three different major classes of lipid molecules phospholipids, cholesterol, and glycolipids.
• Different membranes have different ratios of the three lipids.
• What makes the membrane truly special is the presence of
different proteins on the surface that are used for various
functions such as cell surface receptors, enzymes, surface
antigens, and transporters.
Cytoplasm
• is defined as the material that lies within the cytoplasmic
membrane, or the membrane that surrounds a cell.
• It contains none of a cell's genetic material, because this is
contained in the nucleus.
• It does, however, contain a lot of water, and the other
organelles of the cells.
• It provides a platform upon which they can operate within the
cell. It is made up of proteins, vitamins, ions, nucleic acids,
amino acids, sugars, carbohydrates and fatty acids.
• All of the functions for cell expansion, growth and replication
are carried out in the cytoplasm of a cell.
The Cell Nucleus
•
•
•
•
•
•
•
•
•
•
The cell nucleus forms the package for our genes and their
controlling factors.
It functions to:
Transport regulatory factors & gene products via nuclear pores.
Produce messages (messenger Ribonucleic acid or mRNA) that
code for proteins
Store genes on chromosomes
Organize genes into chromosomes to allow cell division.
Produce ribosomes in the nucleolus
Organize the uncoiling of DNA to replicate key genes
The nucleus is the control center and exists only in eukaryotes.
The nucleus contains the genetic information for the cell in the form
of DNA and RNA.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
. Organelles are labelled as follows:
Nucleolus
Nucleus
Ribosome
Vesicle
Rough endoplasmic reticulum
Golgi apparatus (or "Golgi body")
Cytoskeleton
Smooth endoplasmic reticulum
Mitochondrion
Vacuole
Cytosol
Lysosome
Centriole
A Comparison of Plant and Animal
Cells
• Plant cells have a cell wall, but animal cells do not.
• Plant cells have chloroplasts, but animal cells do
not.
• Plant cells generally have a more rectangular
shape because the cell wall is more rigid. Animal
cells have a round or irregular shape because they
do not have a cell wall.
• Plants cells usually have one or more large
vacuole(s), while animal cells have smaller
vacuoles, if any are present.
Your Turn
• Pg. 34 # 1,2,4,5,7,9,11