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Eukaryotic Cells
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Eukaryotic organisms
Algae
 Protozoa
 Fungi
 Plants
 Animals
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Eukaryotic Cells
FLAGELLA AND CILIA
 CELL WALL and GLYCOCALYX
 PLASMA MEMBRANE
 CYTOPLASM
 MEMBRANE-BOUND ORGANELLES
 NON-MEMBRANE-BOUND Structures
– RIBOSOMES
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FLAGELLA AND CILIA
Flagella are used for cellular locomotion
 Cilia are used for locomotion or for moving
substances along the surface of the cell.
 Flagella are few and long. Algae of the genus
Euglena use flagella for locomotion
 Cilia are more numerous and shorter. Protozoa
use cilia for locomotion.

– Ciliated cells of the human respiratory system move
mucous and debris along the surface of the cells in
the bronchial tubes and trachea to clear the lungs.
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Prokaryotic flagella rotate, but the eukaryotic
flagellum moves in a wavelike manner.
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Flagella and Cilia
5 b
Figure 4.23a,
MICROTUBULES
Both flagella and cilia are anchored to the
plasma membrane by a basal body, which
consists of nine pairs of microtubules
arranged in a ring, plus another two
microtubules in the center of the ring, an
arrangement called a 9 + 2 array.
 Microtubules are made up of a protein
called tubulin.
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Microtubules are made from tubulin
 9 pairs + 2 arrangements
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Figure 4.23c
CELL WALL and GLYCOCALYX
Most non-animal eukaryotic cells (such as
plants) have cell walls, although they are
much simpler than those of prokaryotic
cells.
 Algae, fungi, and plants have cellulose in
their cell walls instead of peptidoglycan.
 Eukaryotic cells that lack a cell wall and
have direct contact with the environment
may have a glycocalyx, which is a sticky
carbohydrate.
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CELL WALL and GLYCOCALYX
The glycolcalyx strengthens the cell
surface, helps attach cells together, and
contributes to cell-cell recognition.
 Eukaryotic cells do not contain
peptidoglycan.
 Antibiotics such as penicillins and
cephalosporins only act against
peptidoglycan and therefore do not affect
human eukaryotic cells.
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Flagella with
microtubules
Cell wall
Plasma
membrane
Figure10
4.22a
PLASMA MEMBRANE
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The plasma membrane of eukaryotic and prokaryotic
cells is very similar in function and structure.
Eukaryotic membranes have different proteins, and also
contain carbohydrates, which serve in cell to cell
recognition.
– Bacteria take advantage of these sites and attach
there.
Eukaryotic plasma membranes also contain sterols,
which are complex lipids not found in prokayriotic
plasma membranes (with the exception of Mycoplasma).
– Sterols help the membranes resist lysis from
increased osmotic pressure.
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PLASMA MEMBRANE
Substances can cross the plasma membrane by
diffusion or active transport, or a mechanism
called endocytosis.
 This occurs when a particle pushes on the
plasma membrane until it surrounds the particle,
encloses it, and it pushes its way into the cell.
The cell membrane invaginates.
 This process is called phagocytosis when the
plasma membrane projects a pseudopod (false
foot), engulfs the particle and brings it the cell.
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White Blood Cell Pseudopod
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CYTOPLASM
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Located inside the plasma membrane and outside the
nucleus.
Only eukaryotic cytoplasm has a cytoskeleton:
– Microfiaments
– Microtubules
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Cytoskeleton provides support and shape, and assists in
transporting substances through the cell.
They can also move the entire cell, as in phagocytosis.
The movement of cytoplasm from one part of the cell to
another to distribute nutrients is called cytoplasmic
streaming. Cytoplasmic streaming video
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
Cytoplasmic streaming video
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CYTOPLASM
Many of the important enzymes found in
prokaryotes float around freely in the
cytoplasm. But in eukaryotes, the
enzymes are contained within organelles.
 The definition of an organelle is “a
miniature organ that is bound by a
membrane”, similar to the plasma
membrane.
 Ribosomes are not organelles because
they do not have a membrane.
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MEMBRANE-BOUND
ORGANELLES
–NUCLEUS
–ER
–GOLGI COMPLEX
–LYSOSOMES
–VACUOLES
–MITOCHONDRIA
–CHLOROPLASTS
–PEROXISOMES
–CENTRIOLES
NOTE: Ribosomes are NOT membrane bound, so they are not organelles
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NUCLEUS
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Usually the largest structure in the cell.
Contains almost all of the cell’s hereditary information
(DNA).
Some DNA is also found in mitochondria and in the
chloroplasts of photosynthetic organisms.
The nucleus is surrounded by a double membrane
called the nuclear envelope which has tiny channels
(nuclear pores) which allow the nucleus to
communicate with the cytoplasm.
Within the nucleus are one or more nucleoli which are
condensed regions of chromosomes where ribosomal
RNA is being synthesized.
The nucleus also contains some proteins called
histones, which are like spools the DNA wraps around
to organize it.
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Nucleus
Nucleolus
Figure19
4.22a
Nucleus
204.24
Figure
Histones: Protein that DNA
wraps around
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NUCLEUS
Chromatin: a thread-like mass of dormant DNA.
 Chromatin shortens and thickens into
chromosomes during replication.
 Prokaryotic chromosomes do not undergo this
process, do not have histones, and are not
enclosed in a nuclear envelope.
 Eukaryotic cells divide by mitosis and meiosis;
these processes do not occur in prokaryotic
cells.
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Endoplasmic Reticulum
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An extensive network of channels which are
continuous with the nuclear envelope.
Rough ER is studded with ribosomes, the
sites of protein synthesis.
Proteins synthesized by ribosomes that are
attached to rough ER enter the channels within
the ER to be processed and sorted.
Thus, rough ER are protein factories.
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Endoplasmic
Reticulum
244.25
Figure
Endoplasmic Reticulum
Smooth ER extends from the rough ER to
form a separate network.
 Smooth ER does not have any ribosomes.
 It contains unique enzymes; it synthesizes
phospholipids, fats, and steroids such as
estrogen and testosterone.
 In liver cells, the enzymes of smooth ER
detoxify drugs.
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GOLGI COMPLEX
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Most of the proteins synthesized by ribosomes
from rough ER are transported to other
regions of the cell.
The first step in the transport pathway is
through the Golgi complex.
Proteins synthesized by ribosomes on the
rough ER push their way out until they are
surrounded by a portion of the ER membrane,
which eventually buds to form a transport
vesicle.
This transport vesicle fuses with the Golgi
complex, releasing the proteins into the
channels of the Golgi complex.
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Golgi Complex
Figure 27
2.8
GOLGI COMPLEX
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Within the Golgi complex, the proteins are
modified into glycoproteins and lipoproteins. It
also makes glycolipids.
Some of the processed proteins leave the Golgi
complex in secretory vesicles, which detach
from the Golgi membrane and deliver the
proteins to the plasma membrane, where they
are discharged from the cell.
Some of the processed proteins leave the Golgi
complex in vesicles that are called storage
vesicles.
The major storage vesicle is a lysosome.
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LYSOSOMES
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Lysosomes are formed from the Golgi
complexes and look like membrane-enclosed
spheres.
Unlike mitochondria, lysosomes have only one
membrane and lack internal structure.
They contain as many as 40 different kinds of
powerful digestive enzymes capable of
breaking down various molecules.
They can also digest bacteria that enter the
cell. Human white blood cells, which use
phagocytosis to ingest bacteria, contain large
numbers of lysosomes.
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VACUOLES/VESICLES
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A vesicle is a small container and a vacuole is
a larger container. Both of them are just
spheres surrounded by a membrane.
Made by the Golgi complex
Functions:
– Storage for nutrients such as proteins, lipids, sugars, water
– Store wastes and poisons to prevent toxicity to the cytoplasm
– Used to transport substances within a cell and transport
substances to the outside of the cell
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Vacuoles
Figure31
4.22b
MITOCHONDRIA
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Rod-shaped organelles which appear throughout
the cytoplasm of most eukaryotic cells.
They make most of the cell’s ATP.
There can be as many as 2000 mitochondria in
one cell.
Mitochondria have a double membrane; the
outer membrane is smooth but the inner
membrane is arranged in a series of folds called
cristae.
The center of the mitochondrion is a semi-fluid
substance called the matrix.
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Mitochondrion
334.27
Figure
MITOCHONDRIA
The convolutions of the cristae provide an
enormous surface area on which chemical
reactions can occur.
 Some proteins that function in cellular
respiration, including the enzymes that make
ATP, are located on the cristae, and many of the
metabolic steps involved in cellular respiration
occur in the matrix.
 Mitochondria are called the powerhouses of the
cell because of their central role in ATP
production.
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MITOCHONDRIA
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Mitochondria contain their own
ribosomes and DNA and are able to
replicate themselves and make their own
proteins.
It is theorized that they have evolved
from bacteria millions of years ago,
which have a symbiotic relationship
within the organism.
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Endosymbiotic
Theory
3610.2
Figure
CHLOROPLASTS
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Only found in algae and green plants.
Contains the pigment chlorophyll plus
enzymes required for photosynthesis.
Capable of multiplying on their own
within the cell.
Chloroplasts and mitochondria replicate
by binary fission like bacteria.
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Chloroplast
384.28
Figure
PEROXISOMES
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Similar to lysosomes but they are smaller
Contain one or more enzymes that can oxidize
various substances including alcohol.
The end product of the oxidation reaction is
hydrogen peroxide (H2O2), which is a very
toxic compound.
However peroxisomes also contain the enzyme
catalase, which decomposes hydrogen
peroxide into H2O plus oxygen, so it is safe
within the cell.
Peroxisomes can also be used to digest
bacteria that have invaded the cell.
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CENTROSOME
Located near the nucleus.
 It consists of proteins fibers and two centrioles,
which are cylinders of small fibers.
 They organize the spindles that appear during
mitosis to help the duplicated chromosomes
move towards opposite ends of the cell.
 Each of the two centrioles in the centrosome is
arranged so that the long axis of one centriole is
at a right angle to the long axis of the other.
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Centrioles of the Centrosome
Centrioles
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CENTROSOME
with
centrioles
inside
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NON-MEMBRANE-BOUND
Structures
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RIBOSOMES
– We cannot call these “organelles”
because they do not have a membrane
around them.
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RIBOSOMES
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Attached to the outer surface of rough ER are ribosomes
or floating free in the cytoplasm.
They are the sites of protein synthesis in the cell.
They are larger (80S instead of 70S) and denser than
the ribosomes of prokaryotic cells.
The free ribosomes synthesize proteins which are used
inside the cell.
The ribosomes that are attached to the rough ER
synthesize proteins destined for insertion in the plasma
membrane or for export from the cell.
Ribosomes within the mitochondria synthesize special
mitochondrial proteins.
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Ribosomes
Complete 80S Ribosome
Figure454.19
Figure 46
2.1
PROKARYOTIC
EUKARYOTIC
One circular chromosome, not membranebound
Paired chromosomes, membrane-bound
No histones
Histones present
No organelles
Organelles present: Golgi complex, ER,
mitochondria, chloroplasts
Peptidoglycan cell walls
Polysaccharide cell walls
Reproduce by binary fission
Reproduce by mitosis/meosis
No true nucleus; no nuclear membrane
True nucleus; nuclear membrane; also has nucleoli
Glycocalyx present as capsule or slime
layer
Present in some cells that lack a cell wall
Plasma membrane has no carbohydrates
and lack sterols
Plasma membrane has carbohydrates and sterols
No cytoskeleton
Has a cytoskeleton
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Ribosomes are small (70S)
Ribosomes are large (80S)