1.2 Ultrastructure of Cells
This electron micrograph shows the
complexity of cells in the panceas
Two Fundamentally Different Cell
Architectures
A prokaryotic cell
A eukaryotic cell
1.2.U1 Prokaryotes have a simple cell structure without
compartmentalization
Prokaryote means “before
nucleus”
http://www.wiley.com/college/boyer/0470003
790/animations/cell_structure/cell_structure.
htm
Prokaryotic
 Cell
wall
 pili
 Plasma
membrane
 Flagella
 Ribosomes
(70 S)
 Nucleoid
(region containing DNA)
Prokaryotic Structures &
Functions
Cell Wall
 protects and maintains shape
 Composed of peptidoglycan (carbprotein)
 Some have additional layer to adhere to
structures (teeth, skin)
Plasma Membrane
 Controls movement of materials in and
out
 Role in binary fission
 Cytoplasm is the complete interior
 No compartments
 DNA most visible structure
Pili
Prokaryotic Structures &
Fucntions
These hollow, hairlike structures made of
protein allow bacteria to attach to other
cells and specialized pili have a role in
conjugation
Flagella
 The purpose of flagella (sing., flagellum) is
motility.
 Flagella are long appendages which rotate
by means of a "motor" located just under
the cytoplasmic membrane.
 Bacteria may have one, a few, or many
flagella in different positions on the cell.

http://highered.mcgrawhill.com/sites/007337525x/student_view0/exercises_3590/bacterial_locomotion.html
Prokaryotic Structures &
Functions
Ribosomes
 site of protein synthesis
 small made up of two parts that come
together, can be in large numbers
 70S
Note: S Svedberg unit, a measure of
the rate of sedimentation in
centrifugation rather than size and
accounts for why fragment names do
not add up (70S is made of 50S and
30S).
Prokaryotic Structures &
Functions
Nucleoid region


DNA in the bacterial cell is
generally confined to this
central region.
Though it isn't bounded by a
membrane, it is visibly
distinct from the rest of the
cell interior.
Plasmid
A plasmid is a DNA molecule that is separate from, and can replicate
independently of, the chromosomal DNA. They are double stranded
and, in many cases, circular. Plasmids usually occur naturally in
bacteria, but are sometimes found in eukaryotic organisms
1.2.A2 Prokaryotes divide by binary fission
http://www.classzone.com/books/hs/c
a/sc/bio_07/animated_biology/bio_c
h05_0149_ab_fission.html
• asexual reproduction
• semiconservative
replication (unit 2.7 U1)
•2 DNA loops attach to
membrane
•Membrane elongates
and pinches off forming
two cells
•Daughter cells are
clones (genetically
identical)
Drawing #1 Please complete in your
sketchbook.
 You
must be able
to draw and label a
diagram of the
ultrastructure of a
prokaryotic cell
based on electron
micrographs.
 The
organelles
previously discussed
must be included in
your drawing.
Similarities Between
Prokaryotes & Eukaryotes
1.
DNA
1.
Plasma membrane (a.k.a. “cell
3.
Cytoplasm
4.
Ribosomes
membrane”)
Differences
Prokaryote
Eukaryote
DNA ring no protein
2. DNA free
3. No mitochondria
4. 70 S ribosomes
5. No internal compartmentalization
6. Less than 10 micrometers
chromosomes
nucleus
mitochondria
80 S
organelles
greater than 10
micrometers
1.
1.2.U2 Eukaryotes have a
compartmentalized structure
Electron
micrograph
of a
mammalian
cell
Why
compartmentalize?
Eukaryotic cells
An idealized animal cell.
An idealized plant cell
Eukaryotic:Animal, algae,
protozoa, fungi and Plant cells
This shows the
organelles of a liver
cell
Eukaryotic cells are usually 5 to 100
micrometers, nucleus is membrane
bound, have membrane bound
organelles
1 micrometer= 0.001mm
1nanometer= 0.001 µ m
1.2.A1 Structure and function of organelles within exocrine
gland cells of the pancreas (animal cell) and within palisade mesophyll
cells of the leaf (plant cell)
Palisade
mesophyll
cells
Pancreas
cell
The Nucleus
• Generally spherical with
double membrane
• Pores in membrane
• Contains genetic
information in
chromosomes/chromatin
(DNA + histone proteins)
Two meters of human DNA fits into a
nucleus that’s 0.000005 meters across!
The Mitochondrion
Think of the mitochondrion as the powerhouse of the cell.
Worn out mitochondria may
be an important factor in
aging
•
•
•
•
•
•
•
•
Has a double membrane (smooth outer and
folded inner)
Folds are called cristae
Shape varies
Site of energy production (ATP) during
cellular respiration
they have their own DNA
large surface for cellular metabolism
produces and contains its own ribosomes
(70S type)
Can reproduce independently
Free ribosomes
Bound ribosomes are
attached to another
organelle called the
endoplasmic reticulum and
their protein products are
shipped out of the cell
The Endoplasmic
Reticulum (ER)
Endoplasmic
Reticulum
Smooth ER
-no ribosomes
-lipid synthesis
- Fewer of
these exist in
pancreatic cells
Rough ER
•
•
•
•
•
Consists of flattened membrane
sacs called cisternae
Often located near the nucleus
80 S ribosomes attached to
outside
Synthesizes proteins which are
transported by vesicles to the golgi
apparatus before secretion out of
the cell
Pancreatic exocrine cells would
have an abundance of these do to
the constant production of
digestive enzymes
Golgi apparatus
The Golgi collects,
packages, modifies and
distribute materials the cell
makes (especially protein)
Golgi in the cytoplasm of a macrophage in
lung tissue
• Like the ER it is composed of
flattened sacs called cisternae
• However, it has no ribosomes
and is often near the plasma
membrane
• Cisternae are shorter and more
curved than those on ER
Vesicles



A single membrane with
fluid inside
Very small
Used to transport
materials outside of cell
http://bcs.whfreeman.com/thelifewire/c
ontent/chp04/0402002.html
The Lysosome
•Intracellular
•arise from golgi
•Spherical with a single
membrane
Functions: Contain digestive enzymes
•Breakdown ingested food
•Breakdown damaged or unwanted
organelles
•Cell suicide (a.k.a “suicide sac”)
Stains dark in
micrographs
due to high
concentration
of enzymes
Many diseases (e.g. Tay-Sachs)
are caused by lysosome
malfunction
http://highered.mheducation.com/sites/0
072495855/student_view0/chapter2/ani
mation__lysosomes.html
The Lysosome
This bacterium about to be eaten by an immune system cell will
spend the last minutes of its existence within a lysosome.
Vacuoles
• Store food, waste,
toxins, water
• Increase SA to
volume ratio
• Allow plants to be
rigid
Cilia and Flagella
Cilia
Flagella
tiny
•
hair like projections
contains microtubules
used to move the cell or
move the fluids next to the
cell
•
•
Thin projection from
cell surface
Contains
microtubules
Used for movement
Lung cilia
Mature plant cells do not contain these structures but
some plant gametes do
Microtubules and Centrioles
IN PLANTS
NOT ANIMALS!
The Chloroplast
Think of the chloroplast as the solar panel of the plant cell.
•
•
•
•
•
•
Starch
granules
maybe
present if
producing
lots of
food!
Contain double membrane
same size as bacteria
Has own DNA
has 70 S ribosomes
can reproduce on own
Inside are stacks of
thylakoids (discs of
flattened membrane)
• Usually oval in shape
• Site of photosynthesis
(production of
carbohydrates)
Only plants and algae have chloroplasts
Granumflattened sacs
like solar
panels
(increase SA)
Stroma-fluid,
contains
enzymes and
chemicals
Cell Wall
• Extracellular
component not an
organelle
• Secreted by all plant
cells (also fungi and
some protists)
• In plants it contains
mostly cellulose
• Cellulose is
permeable, strong
and hard to digest
(little maintenance
required)
IN PLANTS
NOT
ANIMALS!
Plant
Differences
vs.
Animal
Cell wall
Chloroplasts
Large vacuoles
Carbs stored as starch
No centrosome
Fixed angular shape
http://www.youtube.com/watch?v=LP7xAr2
FDFU&feature=related
http://www.youtube.com/watch?v=GigxU1
UXZXo&feature=fvwrel
none
none
small or none
glycogen
centrosome
flexible, rounded
http://library.thi
nkquest.org/C0
03763/flash/gai
a1.htm
Magnification- is how
large the object will
appear compared to its
actual size
Electron Micrographs
A rat liver cell (with color enhancement to show
organelles).
Perioxsome

Similar to
lysosomes except
peroxisomes bud
off from the
endoplasmic
reticulum

Have many roles
and/or involvement
in producing bile,
fatty acid
breakdown,
cholesterol, myelin
production, getting
rid of H2O2 etc…
Extracellular Matrix-animal cells
composed of collagen and glycoproteins (sugar and protein)
form fibres, anchor to the plasma membrane to strengthen it,
cell to cell interaction
possible altering of gene expression,
leads to coordination of cell action
may be involved in directing stem cells,
and possibly cell migration and movement
The Cytoskeleton
The name is
misleading. The
cytoskeleton is the
skeleton or
scaffolding of the cell,
but its also like the
muscular system as
well, able to change
the shape of cells in a
flash.
An animal cell
A Cytoskeleton Gallery
The Cytoskeleton in Action
A macrophage using the cytoskeleton to “reach out” for a hapless
bacterium.
The Cytoskeleton in Action
Membrane ruffles on a crawling cell.
Centrosome
usually a pair of centrioles
-Assemble microtubules for structure and
movement
-cell division
- higher plants produce microtubules even
though they do not have centrioles
-