2. Shape and Size
• Morphologically diverse- plants, animals, eukaryotic microbes
• Eukaryotic microbes- fungi, protists--> protozoa and algae
• Larger than bacteria and archaeal cells
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3. Cell organization
• Membrane bound organelles
• Appendages : Flagella; Cilia Different: made of protein microtubules
(9+2)
• Cell wall is chemically simpler
• Plasma membrane similar--larger, some can use phagocytosis, or
pinocytosis
• Cytosol aka. Cytoplasm fluid matrix, cytoskeleton of protein tubes and
fibers to anchor structures, provide shape, and transport material
within cell
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6. Cell Envelope
• Consists of PM and external layers
• Many eukaryote microbes lack CW
• CW diverse if present
• PM- lipid bilayer with sphingolipids and sterols
• Increased sphingolipids—strength of PM
• Pack closely than phospholipids
• Eukaryotes withstand osmotic pressure without CW—closely packed
sphingolipids
• Lipids inside differ from those outside-asymmetric
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7. • Use passive diffusion, facilitated diffusion and active
transport
• Endocytosis– to bring materials into the cell
• CW differs in various eukaryotic microbes
oProtists-algae, CW layered
• Contain high number of polysaccharides, cellulose and
pectin
• Also inorganic substances, silica and calcium carbonate
oFungi, CW rigid
• Contain cellulose, chitin and glucan
• Rigid CW chemically simpler than bacterial peptidoglycan
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8. Cytoplasm
• Important part of the cell
• Cytosol—cytoplasmic matrix, organelles location
• Location of important biochemical processes
• Cytoskeleton- helps organize contents of the cytoplasm
• Cytoskeleton large dynamic network composed of 3 parts:
• Actin filament- microfilament
• Intermediate filament
• Microtubules
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10. Actin filaments Intermediate filaments Microtubules
4-7nm in diameter 10nm in diameter Thin cylinders of 25nm diameter
Form variety of structures—depend
on cell type
Variety of functions Tubulin-4-5 nm diameter, helical
arrangement- cylinder with 13
subunits per turn
Composed of actin protein Composed of keratin and vimentin
proteins
Spherical protein subunits: α-
subunit and β-subunit
Same molecular weight but
different aa
Amoeboid movement, endocytosis,
Cytokinesis and movement of some
structures within the cell
Identified only in animals
Nuclear lamina- support nuclear
envelope
Position cells within organelles
Link cells--tissues
Spindle apparatus separate Chrs-
meiosis and mitosis
Found within cilia and flagella
Found in structures requiring
support
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11. Organelles of the secretory and endocytic
pathways
• Secretory pathway-system that moves materials to various sites
within the cell, to PM or cell exterior
• Endocytic pathway-system that moves materials into the cell from
outside
• Endoplasmic reticulum
• Lysosomes
• Golgi apparatus
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12. Endoplasmic reticulum
• Irregular network- branching and fusing membranous tubules
• 40-70nm diameter
• Flattened sacs- cisternae
• Rough Endoplasmic reticulum-RER– covered with ribosomes large
amount of proteins to be secreted
• Smooth Endoplasmic reticulum-SER– lack ribosomes produce large
amount of lipids
• Transport proteins, lipids, and other materials
• Synthesize materials it transports
• Lipids and proteins synthesized by ER-associated enzymes and ribosomes
• Major site of Cell membrane synthesis
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13. Golgi apparatus
• Composed of flattened saclike cisternae
• Complex network of tubules and vesicles located at the edges of
cisternae
• Dictyosome– 4-8 cisternae stacked on each other
• Dictyosome has two faces which differ: cis and trans
• cis- close to ER, trans- furthest from ER: both differ in thickness,
enzyme content and degree of vesicle formation
• GA, packages and prepares material for secretion
• Cell membrane development and packages cell products
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15. Lysosomes
• Membrane-bound vesicles found in most eukaryotes
• Involved in intracellular digestion
• Contain hydrolases, hydrolyse molecules
• Maintain an acidic environment by pumping protons into
their interior
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16. Organelles Involved in Genetic Control of the
Cell
• Nucleus
• Membrane-bound spherical structure that houses genetic material of
eukaryotic cell
• Contain chromosomes—exact number depends on organismcell type and
stage in life cycle
• Contains dense fibrous material called chromatin
–complex of DNA, histones, and other proteins
–five types of histones: H1, H2A, H2B, H3, and H4
• 8 histones form an ellipsoid—DNA wraps around forming Nucleosome-a
structural unit of a eukaryotic chromosome
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19. • Nuclear envelope
–double membrane structure that delimits nucleus
-NE consists of inner and outer membranes separated
by perinuclear space
–continuous with ER
–penetrated by nuclear pores
communicationtransport
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20. Nucleolus
• Organelle but not membrane enclosed
• Important in ribosome synthesis
–directs synthesis and processing
of rRNA
–directs assembly of rRNA to
form partial ribosomal subunits
–ribosomes mature in cytoplasm
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21. Ribosomes
• Larger than bacterial and archaeal cells
• Sedimentation coefficient of 80S
• Consists of 60S subunit and 40S subunit
• 6OS consists of 3 rRNA molecules: 5S, 28S and 5.8S as well as 50
proteins
• 40S consists of 1 rRNA molecule: 18S and 30 proteins
• Associated with ER or free in cytoplasm
•60S is bound subunit to RER
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22. Organelles involved in energy conservation
Mitochondria
• “The power houses of the cell” are found in most eukaryotic cells
• Site of tricarboxylic acid cycle activity
• Site where ATP is generated by electron transport and oxidative
phosphorylation
• About the same size as bacterial cells
• Reproduce by binary fission as do bacterial cells
• 2 membranes (inner and outer) separated by intermembrane space-6-8nm
• Outer membrane similar to Gram-negative bacteria OM- contains porin
• Inner membrane has infoldings– cristae, location of enzymes and electron
carriers
• DNA enclosed in circle
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25. Hydrogenosomes
• Organelles involved in energy conservation–
anaerobic protists and fungi
• Bound by double membrane
• Lack DNA and cristae
• ATP is generated by fermentation process rather than
respiration
• Also generates CO2, H2 and acetate
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26. Chloroplasts
• Plastid organelle—synthesis and storage of food reserves
• Pigment-containing organelles observed in plants and algae
• The stroma (a matrix) is within inner membrane
–contains DNA, ribosomes, lipid droplets, starch granules, and
thylakoids
• thylakoids
–flattened, membrane-delimited sacs
–grana (s., granum) – stacks of thylakoids
–site of light reactions (trapping of light energy to generate ATP,
NADPH, and oxygen)Photosynthesis (Stroma)
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28. External structures
Cilia and Flagella
• Associated with motility
• Flagella (s., flagellum)
–100-200 μm long
–move in undulating fashion
• Cilia (s., cilium)
-5-20 μm long
–beat with two phases, working like oars
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30. Structure
• Membrane bound cylinders 0f 0.2 µm diameter
• Matrix contains axoneme
• Axoneme: 9 doublets microtubules around 2 central microtubules
9+2 pattern of microtubules
• Basal body
–at base of flagellum or cilium
–directs synthesis of flagella and cilia
• Microtubules similar to cytoplasmic microtubules
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