Download Eukaryotic cells

The Discovery of the Cell
What is the cell theory?
The cell theory states:
- All living things are made up of cells.
- Cells are the basic units of structure and function in living things.
- New cells are produced from existing cells.
Fig. 6-3cd
TECHNIQUE
(c) Phase-contrast
(d) Differential-interferencecontrast (Nomarski)
RESULTS
Comparing Prokaryotic and Eukaryotic Cells
• Basic features of all cells:
– Plasma membrane
– Semifluid substance called cytosol
– Chromosomes (carry genes)
– Ribosomes (make proteins)
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• Eukaryotic cells are characterized by having
– DNA in a nucleus that is bounded by a
membranous nuclear envelope
– Membrane-bound organelles
– Cytoplasm in the region between the plasma
membrane and nucleus
• Eukaryotic cells are generally much larger than
prokaryotic cells
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• The plasma membrane is a selective barrier
that allows sufficient passage of oxygen,
nutrients, and waste to service the volume of
every cell
• The general structure of a biological membrane
is a double layer of phospholipids
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-7
Outside of cell
Inside of
cell
0.1 µm
(a) TEM of a plasma
membrane
Carbohydrate side chain
Hydrophilic
region
Hydrophobic
region
Hydrophilic
region
Phospholipid
Proteins
(b) Structure of the plasma membrane
• The logistics of carrying out cellular metabolism
sets limits on the size of cells
• The surface area to volume ratio of a cell is
critical
• As the surface area increases by a factor of n2,
the volume increases by a factor of n3
• Small cells have a greater surface area relative
to volume
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Fig. 6-8
Surface area increases while
total volume remains constant
5
1
1
Total surface area
[Sum of the surface areas
(height  width) of all boxes
sides  number of boxes]
Total volume
[height  width  length 
number of boxes]
Surface-to-volume
(S-to-V) ratio
[surface area ÷ volume]
6
150
750
1
125
125
6
1.2
6
A Panoramic View of the Eukaryotic Cell
• A eukaryotic cell has internal membranes that
partition the cell into organelles
• Plant and animal cells have most of the same
organelles
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BioFlix: Tour Of An Animal Cell
Fig. 6-9a
Nuclear
envelope
ENDOPLASMIC RETICULUM (ER)
Flagellum
Rough ER
NUCLEUS
Nucleolus
Smooth ER
Chromatin
Centrosome
Plasma
membrane
CYTOSKELETON:
Microfilaments
Intermediate
filaments
Microtubules
Ribosomes
Microvilli
Golgi
apparatus
Peroxisome
Mitochondrion
Lysosome
Concept 6.3: The eukaryotic cell’s genetic
instructions are housed in the nucleus and carried
out by the ribosomes
• The nucleus contains most of the
DNA in a eukaryotic cell.
• The DNA is organized into long
strands called chromosomes
which are the genetic information
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The Nucleus: Information Central
•Ribosomes use the
information from the
DNA to make
proteins
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• In the nucleus, DNA and proteins form genetic
material called chromatin
• Chromatin condenses to formchromosomes
• The nucleolus is located within the nucleus
and is the site of ribosomal RNA (rRNA)
synthesis
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Ribosomes: Protein Factories
• Ribosomes carry out protein
synthesis in two locations:
– In the cytosol (free ribosomes)
– On the outside of the endoplasmic
reticulum or the nuclear envelope
(bound ribosomes)
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Fig. 6-11
Cytosol
Endoplasmic reticulum (ER)
Free ribosomes
Bound ribosomes
Large
subunit
0.5 µm
TEM showing ER and ribosomes
Small
subunit
Diagram of a ribosome
The Endoplasmic Reticulum: Biosynthetic Factory
• The endoplasmic reticulum (ER) accounts for
more than half of the total membrane in many
eukaryotic cells
• There are two distinct regions of ER:
– Smooth ER, which lacks ribosomes
– Rough ER, with ribosomes studding its
surface
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Fig. 6-12
Smooth ER
Rough ER
ER lumen
Cisternae
Ribosomes
Transport vesicle
Smooth ER
Nuclear
envelope
Transitional ER
Rough ER
200 nm
Functions of Smooth ER
• The smooth ER
– Synthesizes lipids
– Metabolizes carbohydrates
– Detoxifies poison
– Stores calcium
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Functions of Rough ER
• The rough ER
– Has bound ribosomes, which secrete
proteins
– Distributes transport vesicles, proteins
surrounded by membranes
– Is a membrane factory for the cell
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The Golgi Apparatus: Shipping and
Receiving Center
• The Golgi
• Functions of the Golgi apparatus:
– Sorts and packages materials made in the ER
into transport vesicles
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Fig. 6-13
cis face
(“receiving” side of
Golgi apparatus)
0.1 µm
Cisternae
trans face
(“shipping” side of
Golgi apparatus)
TEM of Golgi apparatus
Lysosomes: Digestive Compartments
• A lysosome is a membranous sac
of enzymes that can digest
macromolecules
• Lysosomal enzymes can digest
proteins, fats, polysaccharides, and
nucleic acids
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• Some types of cell can engulf another cell by
phagocytosis; this forms a food vacuole
• A lysosome fuses with the food vacuole and
digests the molecules
• Lysosomes also use enzymes to recycle the
cell’s own organelles and macromolecules, a
process called autophagy
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Fig. 6-14a
Nucleus
1 µm
Lysosome
Lysosome
Digestive
enzymes
Plasma
membrane
Digestion
Food vacuole
(a) Phagocytosis
Concept 6.5: Mitochondria and chloroplasts
change energy from one form to another
• Mitochondria
are the sites of cellular
respiration, a metabolic
process that generates
ATP or ENERGY
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MITOCHONDRIA
Concept 6.6: The cytoskeleton is a network of fibers
that organizes structures and activities in the cell
• The cytoskeleton is a network of
fibers extending throughout the
cytoplasm
• It organizes the cell’s structures
and activities, anchoring and
supporting many organelles
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Fig. 6-20
Microtubule
0.25 µm
Microfilaments
Roles of the Cytoskeleton: Support, Motility, and
Regulation
• The cytoskeleton helps to support the cell and
maintain its shape
• It interacts with motor proteins to produce
motility
• Inside the cell, vesicles can travel along
“monorails” provided by the cytoskeleton
• Recent evidence suggests that the
cytoskeleton may help regulate biochemical
activities
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Centrioles
• In many cells, microtubules grow out from a
centrosome near the nucleus
• In animal cells, the centrosome has a pair of
centrioles, each with nine triplets of
microtubules arranged in a ring and function to
help separate chromosomes during cell
division (Mitosis)
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Fig. 6-22
Centrosome
Microtubule
Centrioles
0.25 µm
Longitudinal section Microtubules Cross section
of one centriole
of the other centriole
Cilia and Flagella
• Cilia and Flagella, are
appendages of some cells
that help them move or to
move substances on their
surfaces
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