Cell Structure
Chapter 6
IB Biology
Prokaryotes vs. Eukaryotes
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Prokaryotes:
Prokaryotes have no
nucleus or membrane
bound organelles
Most have a cell wall
Many have flagella
Very primitive
Origin: 3.5 BYA
Ex- Bacteria
Eukaryotic Cells
• “Eu” = true “Karyo” = kernal (nucleus)
• “YOU are a Eukaryote”
• Have a nucleus
• Have membrane-bound organelles.
• First appeared in fossil records 1.5 bya
• All members of the following kingdoms
have this type of cell: Protocista, Fungi,
Plantae, Animalia.
Prokaryotes/Eukaryotes**
Prokaryotes
Eukaryotes
No nucleus
Nucleus
“Naked” DNA
DNA associated with proteins
DNA in cytoplasm
DNA in an envelope (nucleus)
No mitochondria
Mitochondria
70s ribosomes
80s ribosomes
No organelles
organelles
Reproduce by binary fission
Reproduce by mitosis
Ex.- Bacteria
Ex.- all other cells
Note: s = subunits
Prokaryotic Cell
Bacterium:
Prokaryotic Cells
Escherichia coli
What do all cells
have in common?
•Cell membrane
•Cytoplasm/cytosol
•Genetic material
•Ribosomes
Cell Membrane
• A selectively
permeable
phospholipid
bilayer that
forms a barrier
between the
cell and its
environment
Cytoplasm/cytosol
•Liquid substance that all
chemical reactions of life
take place in
Has dissolved ions,
macromolecules
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Genetic MaterialChromosomes
• DNA is found as
either organized
chromosomes
(eukaryotes) or
single, loosely
packed chromosome
(prokaryotes)
Ribosomes
• Two-piece protein•
based organelle that
makes proteins in both
major types of cell
Varies structurally in
prokaryotes (70S)and
eukaryotes (80S).
Generalized Animal Cell
Generalized Plant Cell
Differences between cells
Plants Lack:
Animals Lack:
1. Lysosomes
2. Centrioles
3. Flagella or Cilia
1. Chloroplasts
2. Vacuoles
3. Cell Walls
4. Plasmodesmata
Eukaryotic Cell Organelles:
Nucleus
• Contains cell’s genetic
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material in form of
chromosomes
Controls most of cell
activities
Site of transcription (1st
step in protein synthesis)
Has a double-membrane
Eukaryotic Cell Organelles:
Nucleolus
• Smaller, dark body
•
inside nucleus
Responsible for
ribosome synthesis
Eukaryotic Cell Organelles:
ER
• ER =Endoplasmic reticulum
• Part of endomembrane
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•
system
Smooth ER: no ribosomes,
synthesizes lipids, detoxifies
substances
Rough ER: studded with
ribosomes, transports
proteins inside cell
Rough ER makes membrane
and proteins
• The rough ER manufactures membranes
• Ribosomes on its surface produce proteins
Transport vesicle
buds off
4
Ribosome
Sugar
chain
1
Polypeptide
3
Secretory
(glyco-) protein
inside transport
vesicle
Glycoprotein
2
ROUGH ER
Eukaryotic Cell Organelles:
Golgi Apparatus (not body)
• Part of endomembrane system
• The Golgi apparatus consists of
•
stacks of membranous sacs
 These receive and modify ER
products, then send them on to
other organelles or to the cell
membrane
Packages and exports cell
chemicals such as proteins,
carbohydrates and lipids
Eukaryotic Cell Organelles:
Mitochondria
• Converts glucose into ATP
during cell respiration
• Is thought to have been primitive
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prokaryote because:
 Has own genome (mtDNA)
 Directs own division
Highly folded inner membrane
Found in cells that are motile
and contractible
Has a double membrane, with
inner membrane called the
cristae.
MITOCHONDRION
Outer membrane
Inner
membrane
Cristae
Matrix
Eukaryotic Cell Organelles:
Chloroplast
• Found in plant cells and some protists
• Contains chlorophyll
• Responsible for converting carbon dioxide and
water into glucose during photosynthesis
Eukaryotic Cell Organelles:
The Cytoskeleton
-Fibrous proteins (actin & tubulin)
-Roles: Support, cell motility,
biochemical regulation, organelle
movement
-Microtubules:
•thickest (25 nm)
•tubulin protein (hollow rods)
•maintains shape, support, transport,
chromosome separation
-Microfilaments:
•thinnest ( 7 nm)
•actin protein filaments;
•motility, cell division, shape
-Intermediate filaments:
• middle diameter (8-12 nm)
•keratin;
•shape, nucleus anchorage
The Cytoskeleton
Actin subunit
Tubulin
subunit
Fibrous subunits
25 nm
7 nm
MICROFILAMENT
Figure 4.17B
10 nm
INTERMEDIATE
FILAMENT
MICROTUBULE
Basic jobs of each
Microtubules
Microfilaments
Intermediate
-give the cell rigidity
-provide anchors for
organelles
-act as tracks for
organelle
movement
-made of actin
-enable cells to change
shape and move
-reinforce the cell
-anchor certain organelles
Eukaryotic Cell Organelles:
Lysosome
• Vesicle that comes off of
Golgi body containing
hydrolytic digestive
enzymes
Responsible for digestion of
old, worn out cell parts and
cells
Also digests nutrients
**Found extensively in
Macrophages (WBC’s)
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Eukaryotic Cell Organelles:
Centriole
• Found only in animal
cells
• Composed of
•
microtubules in triplet
arrangement
Organizes microtubules
that attach to
chromosomes during
cell division
Eukaryotic Cell Organelles:
Vacuole
• Small ones in animal cells
• Large ones found in plant
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cells, stores water to
maintain turgor pressure
Can accumulate wastes,
pigments in plant cells
Eukaryotic Cell Organelles:
Peroxisomes
• Single membrane
• Oxidative organelle
***strips e-’s (H’s) from
substances
Produce hydrogen peroxide
(H2O2) in cells
Metabolism of fatty acids;
detoxification of alcohol
(liver)
Hydrogen peroxide then
converted to water
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Eukaryotic Cell Organelles:
Cell Wall
• Found only in plants
• Made of cellulose
• Non-living
• Has small pores
called
plasmodesmata,
which allows
materials in and out.
Eukaryotic Cell
Organelles: Cilia/Flagella
• Cilia:
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short hairlike
projections used in
cellular movement
Flagella: whiplike
projection used in
cellular movement
 Structure
in
prokaryotes is slightly
different
ECM: Extracellular Matrix**
• Extracellular matrix (ECM) composed
of (located on outside of cell):
-Proteins & Carbodydrate
-Specifically:
-glycoproteins
-glycolipids
-integrins
-fibronectins
-collagen (50% of all protein in the body)
Extracellular Matrix (ECM) - Pg. 118-120
Animal cells secrete or produce:
Glycoproteins:
•proteins covalently bonded to
carbohydrate
Collagen
(50% of protein in human body
•embedded in proteoglycan
(another glycoprotein-95%
carbohydrate)
Fibronectins
bind to receptor proteins in
plasma membrane called
integrins
(cell communication?)
Functions: support,
adhesion,
movement**
ECM’s in Plants**
Cell Walls are an ECM.
-maintain shape
-prevents excessive water
uptake, and
-holds the plant up against
the force of gravity.
Samples of Various Types
of Cells
• Protists may have contractile
vacuoles
– These pump out excess water
Nucleus
Contractile
vacuoles
Figure 4.13B
• Cell, stained for mitochondria,
actin, and nucleus
Figure 4.1x
• Prokaryotic cells, Bacillus
polymyxa
Figure 4.4x1
• Prokaryotic cell, E. coli
Figure 4.4x2
• Pili on a prokaryotic cell
Figure 4.4x3
• Prokaryotic flagella
Figure 4.4x4
• Prokaryotic and eukaryotic cells
compared
Figure 4.4x5
• Paramecium, an animal cell
Figure 4.5Ax
• Plant cells
Figure 4.5Bx1
• Chloroplasts in plant cells
Figure 4.5Bx2
• Nuclei (yellow) and actin (red)
Figure 4.6x
Red Blood Cells