Transcript Ch04_lecturestudents2nd

4.5 What Roles Do Membranes Play In Eukaryotic Cells?
 The endoplasmic reticulum forms channels within the
cytoplasm
ribosomes
smooth ER
rough ER
smooth ER
rough ER
vesicles
(a) Endoplasmic reticulum may be rough or smooth
(b) Smooth and rough ER
Fig. 4-7
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4.5 What Roles Do Membranes Play In Eukaryotic Cells?
 The _______ ER is studded with
ribosomes
• the site where proteins are made.
 The _______ ER lacks ribosomes
• makes phospholipids and
cholesterol.
 Together, the rough and smooth ER are
the sites of new membrane synthesis
for the cell.
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4.5 What Roles Do Membranes Play In Eukaryotic Cells?
 The Golgi apparatus sorts, chemically alters, and
packages important molecules.
• This organelle looks like a stack of flattened sacs.
• Its membranes are derived from the ER.
• Vesicles containing preformed molecules from the ER are
transferred to the Golgi for further processing.
• Once the molecular work of the Golgi has been done, new
vesicles bud off and travel elsewhere in the cytoplasm,
where they fuse with membranes of other organelles, such
as the plasma membrane.
• A major role of the Golgi is to add sugar molecules to
proteins formed in the ER and to pass them on to other
places in the cell.
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4.5 What Roles Do Membranes Play In
Eukaryotic Cells?
 The Golgi apparatus
Protein-carrying
vesicles from the
ER merge with the
Golgi apparatus
Golgi
apparatus
Vesicles carrying
modified proteins
leave the Golgi
apparatus
Fig. 4-8
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4.5 What Roles Do Membranes Play In
Eukaryotic Cells?
 An antibody protein is synthesized on
ribosomes of the rough ER.
 Formed antibody is packaged into vesicles that
travel to the Golgi, where carbohydrates are
attached to protein to make an antibody.
 The vesicle containing antibody leaves the Golgi
and goes to the plasma membrane, where it
fuses with it.
 The antibody inside the vesicle is released to the
outside of the cell (to the blood), where it helps
defend the body against infection.
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4.5 What Roles Do Membranes Play In Eukaryotic
Cells?
 Lysosomes are vesicles that serve
as the cell’s ______________
system.
• They are formed as buds from the
Golgi.
• Lysosomes contain digestive
enzymes that they receive from
Golgi during their production.
• In the cytoplasm, they digest
defective organelles or pieces of
membrane into component parts
that can be recycled.
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4.6 What Other Structures Play Key Roles In
Eurkaryotic Cells?
 Vacuoles regulate _________ and
store substances.
• They are fluid-filled sacs surrounded by
a single membrane.
• Many plant cells have a large central
vacuole.
• Vacuoles hold water and help maintain
the proper water balance of the cell.
• Vacuoles can also serve as dump sites
for hazardous waste that can’t be
excreted.
• They can also store sugars and amino
acids, which can be used for energy.
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4.6 What Other Structures Play Key Roles In
Eurkaryotic Cells?
 Mitochondria extract ________ from food
molecules.
• Mitochondria provide the energy needed
for all cellular processes.
• Energy is obtained from ________
molecules in mitochondria and is stored in
_______ molecules.
• Once formed, ATP can be used anywhere
in the cell where energy is needed.
• Mitochondria have a complex set of outer
and inner membranes, used in the
process of energy production.
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4.6 What Other Structures Play Key Roles In
Eurkaryotic Cells?
 Chloroplasts capture _______ energy.
• Only _______ cells contain chloroplasts.
• Chloroplasts capture energy from
__________ and store it in ________
molecules.
• They are the site of ________________,
the process upon which all life depends.
• Like mitochondria, chloroplasts contain
both outer and inner membranes.
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4.6 What Other Structures Play Key Roles In
Eurkaryotic Cells?
 The cytoskeleton provides shape, support, and
movement.
• All organelles in the cell do not float about the cytoplasm,
but instead, are attached to a network of protein fibers
called the cytoskeleton.
 Several type of protein fibers make up the cytoskeleton.
• Microfilaments: thin fibers
• Intermediate filaments: medium-sized fibers
• Microtubules: thick fibers
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4.6 What Other Structures Play Key Roles In
Eurkaryotic Cells?
 The cytoskeleton
plasma
membrane
microfilaments
mitochondrion
microtubules (red)
intermediate
filaments
ribosomes
endoplasmic
reticulum
microtubule
nucleus
vesicle
microfilaments (blue)
(a) Components of the cytoskeleton
(b) Cell with stained cytoskeleton
Fig. 4-9
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4.6 What Other Structures Play Key Roles
In Eurkaryotic Cells?
 __________ move fluid past the cell
 __________ move the cell
• Cilia and flagella are slender, movable extensions of the
plasma membrane.
• They contain microtubules that extend along their length.
• They may be used to move small animals (flagellum) or
particle-containing fluids past a surface (cilia).
• Differences between cilia and flagella lie in their length,
number, and the direction of force generated.
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4.6 What Other Structures Play Key Roles In
Eurkaryotic Cells?
 Cilia provide force parallel to the plasma membrane,
which can be described as a
“rowing” motion.
propulsion of fluid
power stroke
plasma membrane
return stroke
cilia lining
the trachea
(a) Cilium
Fig. 4-10a
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4.6 What Other Structures Play Key Roles In
Eurkaryotic Cells?
 Flagella provide a force perpendicular to plasma
membrane, like the engine on a motorboat.
direction of locomotion
propulsion of fluid
continuous propulsion
flagellum
of human
sperm
(b) Flagellum
Fig. 4-10b
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4.7 What Are The Features Of Prokaryotic Cells?
 Prokaryotic cells:
• are much smaller than eukaryotic cells, are more
abundant, and are very reproductively successful.
• have a simple internal structure.
• are surrounded by a stiff cell wall, which provides shape
and protection.
• some move with a whiplike flagellum.
• have a single, circular strand of DNA attached to the
plasma membrane, concentrated in an area called the
nucleoid, which lacks a membrane.
• no membrane-enclosed organelles.
• cytoplasm contains ribosomes used for protein synthesis.
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4.7 What Are The Features Of Prokaryotic
Cells?
 A generalized prokaryotic cell
chromosome
(nucleoid region)
ribosomes
food granule
prokaryotic
flagellum
cell wall
cytoplasm
plasma membrane
Fig. 4-11
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