Download Golgi apparatus

Roles of ER
Rough
Ribosomes synthesize
excreted proteins
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Modify proteins
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Stored in cisternae or
vesicle
Glycosylation of
proteins
Delivery of membrane
associated proteins
Often interacts with the
Golgi
Smooth
Tissue-specific uses
Storage of
carbohydrates
Detoxification reactions
in liver
Synthesizes much of the
new membrane material
Modification of existing
molecules
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ER and Golgi
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Often adjacent in cytoplasm of
cell
Both are membrane producers
Membrane has sides
 Vesicles are produced inside
out
 Vesicle fuses with surface and
excreted proteins are released
and integral proteins are added
along with membrane
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ER often performs first steps of
modification that is later finished
in Golgi
Golgi apparatus
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Complex collection of membrane
Has polarity
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Responsible for secretion
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Cis and trans surfaces
Very prominent in cells that serve secretory
functions-such as epithelial cells
Modifies structures previously synthesized in
the ER
Golgi Function
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Cis face is nearer the center of cell
 Cis face is often adjacent to ER
Trans face is nearer the cell membrane
Activity is directional
 Starts at cis face and moves to trans
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
ER and Golgi
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Synthesis in ER but
modification in Golgi
Similar to an assembly
line
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Options packages are
added in Golgi
Sequential passage
through cisternae (cis to
trans)
Each cisternae contains
different enzymes
Examples of Golgi Function
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Replace sugars placed on glycoproteins
Modification of phospholipid acylgroups and
head groups
Molecule targeting and assembly
Production of vesicles to delivery membrane
associated molecules and excreted molecules to
cell surface
Cell Renewal
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Cells and their molecules age and become less
effective
An important cellular function is renewal
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Old molecules and organelles are recycled
New phospholipids are produced for the
membrane
Toxic molecules need to be collected and
detoxified
Sometimes a cell needs to commit suicide
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Called autolysis or apoptosis
Vesicle Organelles
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Perform many of the renewal functions
Lysosome
Peroxisome
Glyoxisome
Lysosome
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Contains digestive enzymes used to degrade
macromolecules or organelles
Originates in ER but enzymes are activated in
Golgi
Important in macrophages for degradation of
particles acquired via phagocytosis
Used to degrade organelles-autophagy
Fig. 6-14a
Nucleus
1 µm
Lysosome
Lysosome
Digestive
enzymes
Plasma
membrane
Digestion
Food vacuole
(a) Phagocytosis
Fig. 6-14b
Vesicle containing
two damaged organelles
1 µm
Mitochondrion
fragment
Peroxisome
fragment
Lysosome
Peroxisome
Vesicle
(b) Autophagy
Mitochondrion
Digestion
Cell Death
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Sometimes used in development of organism
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Defense against viral or intracellular bacterial
infections
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Hand development
Certain cells are programmed to die at appropriate
times
Self-destruct
Program is started by T cells
Apoptosis is often accomplished by leaky or
popping lysosomes
Peroxisomes
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Contain enzymes to collect free hydrogen and
oxygen and combine into H2O2 (peroxide)
Peroxide is also toxic so they contain enzymes to
degrade into water and oxygen molecules
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Catalase experiment in lab
Peroxisomes are formed by aggregation of lipids
and proteins (not formed in ER)
Many are found in liver cells
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Degrade alcohols into peroxide then into water and
oxygen
Peroxisome pt 2
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Also responsible for degradation of fatty acids in
cytosol
Modify fatty acids and phospholipids and
incorporate into peroxisome membrane
Divide by binary fission
Glyoxysomes
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Specialized peroxisomes found in plant seeds
Recognize appropriate signals and begin to
degrade stored fat in seed
Fat is converted to sugars which allows
seedling to sprout
Once photosynthesis starts, glyoxysomes
degrade