Transcript 1.2 Ultrastructure of cells

Essential Idea
Eukaryotes have a much more complex cell
structure than prokaryotes.
All cells share certain characteristics
♦ Cells tend to be microscopic.
♦ All cells are enclosed by a membrane.
♦ All cells are filled with cytoplasm.
♦ Plasma membrane
♦ Chromosomes (carry genes)
♦ Ribosomes (make proteins)
There are two cell types:
1. Prokaryotes
nucleus
2. Eukaryotes
organelles
cell membrane
Prokaryotes
Assessment Statement
Draw and label a diagram of the ultrastructure
of Escherichia coli (E. coli) as an example of
a prokaryote. The diagram should show the
cell wall, plasma membrane, cytoplasm, pili,
flagella, ribosomes and nucleoid (region
containing naked DNA).
Draw and label a prokaryote
E. Coli – A representative prokaryote (bacteria)
Prokaryotes are cells that
do not have a nucleus
The do not have any
membrane bound
organelles
All bacteria are prokaryotes
Diagram of E. Coli
Prokaryotes
The
general size of a prokaryotic
cell is about 1-2 um.
Note the absence of membrane
bound organelles
There is no true nucleus with a
nuclear membrane
The ribosome's are smaller than
eukaryotic cells
The slime capsule is used as a
means of attachment to a surface
Only flagellate bacteria have the
flagellum
Plasmids are very small circular
pieces of DNA that maybe
transferred from one bacteria to
another.
Prokaryotes
•
Example Eshericha coli (E.
coli)
•
In a prokaryotic cell, DNA is
circular and in the cytoplasm
called the nucleoid
Prokaryote cellular structure function
Assessment Statement
Annotate the E. coli diagram with the functions of each
named structure.
Annotate: Label & Function
Prokaryote cellular structure function
Cell Wall:
Made of a murein (not cellulose), which is a glycoprotein or peptidoglycan (i.e. a
protein/carbohydrate complex). There are two kinds of bacterial cell wall, which are
identified by the Gram Stain technique when observed under the microscope. Gram
positive bacteria stain purple, while Gram negative bacteria stain pink. The technique is
still used today to identify and classify bacteria. We now know that the different staining
is due to two types of cell wall
Plasma membrane:
Controls the entry and exit of substances, pumping some of them in by active transport.
Cytoplasm:
Contains all the enzymes needed for all metabolic reactions, since there are no organelles.
Ribosome:
The smaller (70 S) type are all free in the cytoplasm, not attached to membranes (like RER).
They are used in protein synthesis which is part of gene expression.
Nucleoid:
Is the region of the cytoplasm that contains DNA. It is not surrounded by a nuclear
membrane. DNA is always a closed loop (i.e. a circular), and not associated with any
proteins to form chromatin.
Prokaryote cellular structure function
Flagella:
These long thread like attachments are generally considered to be for movement. They have
an internal protein structure that allows the flagella to be actively moved as a form of
propulsion. The presence of flagella tends to be associated with the pathogenicity of the
bacterium. The flagella is about 20nm in diameter. This structure should not be confused
with the eUkaryotic flagella seen in protoctista.
Pilli:
These thread like projections are usually more numerous than the flagella. They are
associated with different types of attachment. In some cases they are involved in the
transfer of DNA in a process called conjugation or alternatively as a means of preventing
phagocytosis.
Slime Capsule:
A thick polysaccharide layer outside of the cell wall, like the glycocalyx of eukaryotes. Used
for sticking cells together, as a food reserve, as protection against desiccation and
chemicals, and as protection against phagocytosis. In some species the capsules of
many cells in a colony fuse together forming a mass of sticky cells called a biofilm.
Dental plaque is an example of a biofilm.
Prokaryote cellular structure function
Plasmids:
Extra-nucleoid DNA of up to 400 kilobase pairs. Plasmids can self-replicate particularly
before binary fission.
They are associated with conjunction which is horizontal gene transfer.
It is normal to find at least one anti-biotic resistance gene within a plasmid. This should not
be confused with medical phenomena but rather is an ecological response to other
antibacterial compounds produced by other microbes. Commonly fungi will produce antibacterial compounds which will prevent the bacteria replicating and competing with the
bacteria for a resource.
conjugation
Direct contact between bacterial cells in which plasmid DNA is transferred between a donor
cell and a recipient cell.
There is no equal contribution to this process, no fertilisation and no zygote formation. It
cannot therefore be regarded as sexual reproduction.
Binary Fission – Asexual Reproduction in Prokaryotes
Prokaryotes
reproduce by
binary fission
They
copy their circular
chromosome
The
cell grows longer with
the two chromosomes
attached to the inside
membrane
The
membrane pinches
together in the centre
Two
daughter cells are
formed
Prokaryote Binary Fission
(a). Reproduction signal: The cell receives a
signal, of internal or external origin that initiates
the cell division. E.coli replicates about once
every 40 minutes when incubated at 37o C. If
however we increase the concentration of
carbohydrate nutrients that the cell is supplied
with then the division time can be reduced to 20
minutes. There is a suggestion here that an
external signal (nutrient concentration) is acting
as the reproductive signal.
(b). Replication of DNA: bacterial cells have a
single condensed loop of DNA. This is copied by
a process known as semi-conservative
replication to produce two copies of the DNA
molecule one for each of the daughter cells. The
replication begins at a single point (ori)on the
loop of DNA. The process proceeds around the
loop until two loop have been produced, each a
copy of the original. The process finishes at a
single point on the loop of DNA called the ter
position.
Prokaryote Binary Fission
(c).
Segregation of DNA: One DNA loop will be
provided for each of the daughter cells.
As the new loops form the ori site becomes
attached to some contractile proteins that pull the
two ori sites, and therefore the loops, to opposite
ends of the cell. This is an active process that
requires the bacteria to use energy for the
segregation.
(d). Cytokinesis: Cell separation.
This occurs once the DNA loop replication and
segregation is complete. The DNA completes a
process of condensing whilst the plasma
membrane begins to form a 'waist' or constriction
in the middle of the cell. As the plasma membrane
begins to pinch and constrict the membrane fuses
and seals with additional new membrane also
being formed.
Prokaryote cell
Pili
Nucleoid
Ribosomes
Plasma
membrane
Bacterial
chromosome
Cell wall
Capsule
Flagella
0.5 µm
A typical
rod-shaped
bacterium
A thin section through the
bacterium Bacillus
coagulans (TEM)
Binary Fission Animation
http://www.classzone.com/books/hs/ca/sc/bio
_07/animated_biology/bio_ch05_0149_ab_fi
ssion.html
Prokaryotes Animation
Watch Animation of Prokaryotes Structure and
function.
http://www.wiley.com/legacy/college/boyer/04
70003790/animations/cell_structure/cell_str
ucture.swf
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::50
0::500::/sites/dl/free/0073375225/594358/Bi
naryFission.swf::BinaryFission
Eurkaryotic Cell Characteristics

Eukaryotic cells have a nucleus that contain its DNA

Eukaryotic cells have membrane-bound organelles.
 Nucleus
 Mitochondria
 Chloroplasts (plants only)

Eukaryotes are bigger than Prokaryotes

Animal and plant cells are eukaryotes
Human Liver Cells
Draw a Eukaryotic Liver Cell
Assessment Statement
Draw and label a diagram of the ultrastructure
of a liver cell as an example of an animal
cell. The diagram should show free
ribosomes, rough endoplasmic reticulum
(rER), lysosome, Golgi apparatus,
mitochondrion and nucleus. The term Golgi
apparatus will be used in place of Golgi
body,
Draw a Eukaryotic Liver Cell
N: Nucleus
PM: plasma membrane
M: mitochondria
rER: Rough endoplasmic
reticulum
GA: Golgi apparatus
L: Lysosome
MV: Microvilli
Annotate Diagram
Assessment Statement
Annotate the E. coli diagram with the functions of each
named structure.
Annotate: Label & Function
Nucleus
Nucleus: This is the largest of the
organelles. The nucleus contains
the chromosomes which during
interphase are to be found the
nucleolus.
The nucleus has a double
membrane with pores(NP).
The nucleus controls the cells
functions through the expression of
genes.
Some cells are multi nucleated
such as the muscle fibre
Plasma Membrane
Plasma membrane: controls which
substances can enter and exit a cell.
It is a fluid structure that can
radically change shape.
The membrane is a double layer of
water repellant molecules.
Receptors in the outer surface
detect signals to the cell and relay
these to the interior.
The membrane has pores that run
through the water repellant layer
called channel proteins.
Mitochondria:..
Mitochondria: location of aerobic
respiration and a major synthesis of
ATP region..
Double membrane organelle.
Inner membrane has folds called
cristae. This is the site of oxidative
phosphorylation.
Centre of the structure is called the
matrix and is the location of the Krebs
cycle.
Oxygen is consumed in the synthesis
of ATP on the inner membrane
The more active a cell the greater the
number of mitochondria.
Rough endoplasmic reticulum (rER).
rER form a network of
tubules with a maze like
structure.
In general these run away
from the nucleus
The 'rough' on the reticulum
is caused by the presence of
ribosomes.
Proteins made here are
secreted out of the cell
Ribosomes:
the free ribosome
produces proteins for
internal use within the
cell.
Golgi apparatus.
Modification of proteins
prior to secretion.
proteins for secretion are
modified
possible addition of
carbohydrate or lipid
components to protein
packaged into vesicles
for secretion
Lysozyme:
Vesicles in the above
diagram that have
formed on the golgi
apparatus.
Containing hydrolytic
enzymes.
Functions include the
digestion of old
organelles, engulfed
bacteria and viruses.
Vocabulary Practice (12 mnutes)
1.
2.
3.
4.
5.
6.
free ribosomes,
rough endoplasmic
reticulum (rER)
lysosome,
Golgi apparatus,
mitochondrion
and nucleus
3 minutes – One student
gives function –the other
identifies organelle
3 minutes -- Switch
3 minutes – One student
gives organelle –the
other describes function
3 minutes -- Switch
IB Assessment Statement
Identify structures from liver in electron
micrographs of liver cells.
Videos
Video about Animal Cells
http://www.youtube.com/watch?v=cj8dDTHGJBY&feature=BF
a&list=PL3EED4C1D684D3ADF&lf=context
Video about Plant Cells
http://www.youtube.com/watch?v=9UvlqAVCoqY&list=SP3EE
D4C1D684D3ADF
Video about Cells in general
https://www.youtube.com/watch?v=yZu6DfcPHr8&feature=pl
ayer_embedded#t=6
Self Test: What organelle is it?
Self Test: What organelle is it?
Self Test: What organelle is it?
Self Test: What organelle is it?
Self Test: What organelle is it?
IB Assessment Statement
2.3.4 Compare prokaryotic and eukaryotic cells.
Prokaryote vs. Eukaryote
Only organisms of the domains Bacteria and
Archaea consist of prokaryotic cells
Protists, fungi, animals, and plants all consist
of eukaryotic cells
Prokaryote cell
Pili
Nucleoid
Ribosomes
Plasma
membrane
Bacterial
chromosome
Cell wall
Capsule
0.5 µm
Flagella
A typical
rod-shaped
bacterium
A thin section through the
bacterium Bacillus
coagulans (TEM)
Eukaryote
cells
Flagellum
ENDOPLASMIC RETICULUM (ER
Nuclear envelope
Rough ER
Smooth ER
NUCLEUS
Nucleolus
Chromatin
Centrosome
Plasma membrane
CYTOSKELETON
Microfilaments
Intermediate filaments
Microtubules
Ribosomes:
Microvilli
Golgi apparatus
Peroxisome
Mitochondrion
Lysosome
In animal cells but not plant cells:
Lysosomes
Centrioles
Flagella (in some plant sperm)
Prokaryotes vs. Eukaryotes
nucleus
organelles
cell membrane
cytoplasm
Prokaryotic vs. Eukaryotic
Prokaryotic vs. Eukaryotic
IB ASSESSMENT STATEMENT
State three differences between plant and animal cells.
Eukaryotes
•
All eukaryotes have the same following
components:
•
•
•
•
•
•
Ribosomes
Mitochondria
Nucleus
Endoplasmic Reticulum (ER)
Rough ER
Golgi body apparatus
Eukaryotic: Plant vs. Animal
Plants
Animals

Cell Wall


Chloroplasts
NO

General Rectangular
Shape

NO cell wall
Chloroplast
Irregular shape
Small

Vacuoles
Large Vacuoles
Stores

Stores polysaccharide in
the form of STARCH
polysaccharide in
the form of Glycogen
LE 6-9a
Flagellum
ENDOPLASMIC RETICULUM
(ER
Rough ER Smooth ER
Nuclear
envelope
Nucleolu
s
Chromatin
NUCLEUS
Centrosome
Plasma
membrane
CYTOSKELE
TON
Microfilaments
Intermediate filaments
Microtubules
Ribosome
s:
Microvilli
Golgi apparatus
Peroxisom
e
Mitochondrio
n
Lysosom
e
In animal cells but not plant
cells: Lysosomes
Centrioles
Flagella (in some plant
sperm)
LE 6-9b
Nuclear
envelope
NUCLEUS
Nucleolus
Rough
endoplasmic
reticulum
Chromatin
Smooth
endoplasmic
reticulum
Centrosome
Ribosomes
(small brown dots)
Central vacuole
Golgi
apparatus
Microfilaments
Intermediate
filaments
Microtubules
CYTOSKELETON
Mitochondrion
Peroxisome
Chloroplast
Plasma
membrane
Cell wall
Plasmodesmata
Wall of adjacent cell
In plant cells but not animal cells:
Chloroplasts
Central vacuole and tonoplast
Cell wall
Plasmodesmata
A representative plant cell and a diagram of a ‘’Typical’’ Plant Ce
Other Eukaryotes – Protists
Paramecium and Ameoba
Plants vs. Animals
Plant Vs. Animal
Nature of Science
Developments in scientific research follow
improvements in apparatus—the invention
of electron microscopes led to greater
understanding of cell structure. (1.8)
http://www.history-of-the-microscope.org
Assignment: History of the Microscope
Webquest
The electron microscope
• Invented in Germany (1930’s)
• Able to view samples 200 times
smaller than light microscopes
• Invention of the electron
microscope revealed a whole
new level of cellular detail.
Resolution - comparison
Eye
Light
Microscope
Electron
microscope
Resolution
Millimetres
(mm)
0.1
Micrometres Nanometres
( m)
(nm)
100
100,000
0.0002
0.2
200
0.000001
0.001
1