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The Eukaryotic Cell Fig 4.22, page 97
 Eukaryotic cells have many unique features that
distinguish them from prokaryotes
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Cilia
Membrane sterols
Ribosome structure
Membrane bound organelles
 Nucleus
Structures External to Cell
 Tubulin in 9+2 array with
membrane covering
 Flagella
 Function in cell motility
 long in relation to cell size
 Cilia
 Shorter; more numerous
 Move cell or propel substances
across cell
 Glycocalyx
 Carbohydrate coating in animal cells
 Surrounds and stabilizes plasma membrane
 Active in cell-cell recognition
 Cell wall
 Plants, algae, fungi
 Cellulose, chitin, glucan, mannan, silica, calcium
carbonate
 NO PTG!
 Penicillin a “miracle drug”?
 Protozoa have no cell wall but some have a pellicle
surrounding the plasma membrane
Eukaryotic Plasma Membrane
 Similar in structure and function to prokaryote
 Phospholipid bilayer embedded with proteins
 Addition of carbohydrates and sterols (cholesterol,
ergosterol)
 Cell signaling
 Cell recognition
 Stability
 Membrane proteins functions:
 Transport
 Maintain cell integrity
 Attachment of proteins to internal structures
 Receptors for cell signaling
 Proteins in outer layer
 Receptors typically glycoproteins
extracellular fluid (outside)
binding site
phospholipid bilayer
carbohydrate
cholesterol
phospholipid
receptor protein
transport protein
protein filaments
recognition protein
cytoplasm (inside)
 Transport across eukaryotic membrane
 Passive
 Simple and facilitated diffusion; osmosis
 Active
 Active transport; endocytosis; exocytosis
 Endocytosis
 Bring in material from surrounding environment
 Pinocytosis or Phagocytosis
 Exocytosis
 Releases contents into external environment
 Cytoskeleton
 Dynamic network of protein filaments (microtubules, actin
filaments, intermediate filaments)
 Anchor organelles, Structural support, Shape alteration,
Movement
10 µm
Column of tubulin dimers
Tubulin dimer
Centrosome
• Pair of centrioles and proteins found near nucleus
– Involved in the assembly of microtubules
10 µm
7 nm
Structural
microfilaments and
role in motility
microtubules (red)
nucleus
microfilaments (blue)
Membrane-bound Organelles
 Compartmentalization
 Allows for division of labor
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Nucleus
Mitochondria and chloroplast
Endoplasmic reticulum
Golgi apparatus
Lysosome and peroxisomes
 Nucleus
 nuclear envelope
 Double membrane with pores
 nucleolus
 sites of rRNA synthesis
 DNA typically in multiple pairs of linear chromosomes
 associated with histones proteins
•Sexual or asexual
reproduction
•mitosis and
meiosis
Endoplasmic Reticulum
-Network of flattened tubules
(cisterns) continuous with
nuclear membrane
-rough ER
-ribosomes present
-Site of protein synthesis
-smooth ER
-no ribosomes
-Site of lipid/fat synthesis
Ribosomes
 80S
 Large 60S and small 40S subunits
 Membrane-bound: Attached to ER & nuclear membrane
 Free: In cytoplasm
 70S
 In chloroplasts and mitochondria
Golgi Body
-Curved cisterns
-Not continuous
-Modifies, packages and secretes
products of ER
- Produces lysosomes and
vacuoles
 Lysosomes
 Formed in Golgi
 Membrane enclosed sacs of digestive enzymes
 Peroxisome
 Oxidation of fatty acids; destroys H2O2
 Formed by dividing perosiomes
 Vacuoles
 Derived from the Golgi
 Store nutrients
 Sequester harmful substances
Mitochondria
- Double membrane
- Inner membrane is folded into cristae
- Site of cellular respiration; ATP production
- 70S ribosomes and circular DNA; divide independently of cell
Figure 4.26
Plastids
- Chloroplasts
- Found in algae and green plants
- Contains chlorophyll pigment
in the coin-like thylakoids
- Stacked thylakoids - grana
-70S ribosomes and circular DNA;
divide independently of cell
Figure 4.27
Endosymbiotic Theory
- Evolution from prokaryotes
to eukaryotes
3.5 billion yrs ago
- prokaryotes dominate
2.5 billion yrs ago
- oxygen accumulates
1.5 billion yrs ago
- 1st nucleated eukaryotes
Extracellular Structures
Structure
Prokaryotic Cells Eukaryotic Cells
Cells wall
Peptidoglycan
(exceptions?)
Other sugars
Flagella
Fibrils of flagillin
Microtubules
Cilia
Absent
Present
Fimbriae/pili
Present
Absent
Intracellular Structures
Structure
Prokaryotic Cells Eukaryotic Cells
Lacks sterols
Plasma membrane
(exceptions?)
Membrane-bound
Absent
organelles
Contains sterols
Present
Cytoskeleton
Present but simple Complex
Ribosomes
70S
80S (exceptions?)
Genetic Structures
Structure
Prokaryotic Cells Eukaryotic Cells
Genetic material
Single circular
chromosome
Paired linear
chromosomes
Location of
genetic material
Nucleoid
True nucleus
Nucleolus
Absent
Present
Histones
Absent
(exceptions?)
Present
Extrachromosomal
Plasmids
DNA
Mitochondria,
chloroplasts,
plasmids
Reproductive Processes
Prokaryotic Cells
Eukaryotic Cells
Reproduction
Asexual only
Sexual & asexual
Cell division
Binary fission
Budding
Fragmenting
Mitosis & meiosis
Conjugation
Sexual
reproduction
Source of genetic
diversity