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What are the three different destinations for Golgi shipments
- Lysosomes (signal mediated)
- Plasma Membrane (Default destination)
- Secretory Vesicles (signal mediated)
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Vesicular transport from the golgi ships what materials
Membrane proteins, soluble proteins, and lipids
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In what portions are machinery needed in vesicular transport
- 1. To promote visicle budding
- 2. To target the correct membrane
- 3. To promote visicle fusion
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In order for budding on the Golgi to take place, what machinery is necessary
- One of three coat proteins.
- Clathrin, COPI, COPII
- (Caveolin for caveolae could be considered a fourth)
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How does COP II differ from COP I as a coating protein
- COP II performs packaging of transfer of vesicles from the Rough ER to the cis-Golgi only
- COP I mediates transfer of vesicles through Golgi stacks, and constitutive secretion to plasma membrane (also retrograde transport from Golgi back to ER)
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What is Clathrins role in protein coating
Clathrin mediates endocytosis of vesicles from the plasma membrane, and movement from the trans-golgi to lysosomes secretory vesicles
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What is a V-snare (Vesicle) and a T-snare (Target Membrane)
T-snares are on the target memberane, and V-snares are on the vesicle. When they match up, fusion happens. (Yin Yang kind of deal)
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Why are snares not found on peroxisomes or mitochondria
Because they use other methods like endocytosis and don't need them
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What are a Rabs
They are small proteins that connect with a tethering protein on the target membrane which pull the rabs in like an arm
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How are the the snares removed
NSF and SNAPs break them apart
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What is the golgi apparatus
A membrane bound organelle in eukaryotes where proteins and lipids transfered from the ER are modified and sorted
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What is the difference between the trans face and the cis face of a golgi
The cis face is closer to the ER
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As proteins move through the Golgi what happens to the carbohydrate
The N-linked carbohydrate is trimmed and they receive additional O-linked sugars
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What acid group gives the plasma membrane of the golgi exterior its negative charge
Sialic acid (The only carb with a neg charge)
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Where are glycolipid formed
They are formed in the Golgi
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Where is there no glycosylation
On the cytosol side of the membrane
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What is the glycocalyx
A thick protective rim of carbohydrate around the plasma membrane, also known as a cell coat and is important to cellular recognition
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Transgolgi is used for what
It is considered the sorting station like that of UPS
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What is required to secrete a hormone such as insulin and neurotransmitters
They require a chemical signal to release
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How can the MT's assist with vesicle secretion
They can use the Dynein and Kinesin to move the visicles to the actin to finish the secretion
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What effect can the rise of calcium have in the cytoplasm relating to vesicles
The rise of Ca often triggers the release of secretory vesicles from actin binding proteins
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What is spontaneous aggregaion
A collection of proteins in a vesicle that seems to be a major stimulus in regulated vesicles
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Why are regulated secretory vesicles often darker when viewed in an electron microscope
Due to the aggregation of the contents in the vesicle
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What does the presence of mannose 6-phosphate (M6P) have on lysosomes
It is a signal for targeting newly synthesized lysosomal hydrolase in the trans-Golgi to lysosomes
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KDEL sequence does what
It is a permanent retention signal for the ER (BiP has one)
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Does Golgi have retention signals
Yes, but only some have been identified
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Lectins in the lumen of the Trans golgi
Help to stabilize the lipid rafts
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Where do the components of a lipid raft (some produced in the ER) begin to coalesce
In the trans golgi network
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GPI linked proteins cluster in
Lipid rafts (calveolae)
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Lipid rafts cosist of
- Cholestrol
- Sphingomyelin
- Phosphatidylcholine
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Raft vesicles extruding from the golgi traffic to the surface where they can
Separate into smaller raft compartments
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Exocytosis
The process by which most molecules are secreted from a eukaryotic cell. These are packaged by membrane bound vesicles that fuse with the plasma membrane releasing their contents
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Is Exocytosis used only for garbage
No, newly synthesized or recycled membrane proteins are taken to the membrane sometimes
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Endocytosis
The uptake of material into a cell by an invagination of the plasma membrane. A drop of extracellular fluid always accompanies
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What are the three types of endocytosis
- Phagocytosis - cell eating
- Pinocytosis - cell drinking
- Receptor mediated endocytosis - has to be opsinized
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What are some types of opsinization
- Soluble Chemoattractants released by bacteria
- Antibody activated (coated with IgG)
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Receptor mediated Endocytosis
A way to take up specific molecules from the extracellular fluid
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What are some of the receptors used in receptor mediate endocytosis
LDL and transferrin
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Adaptin
Proteins on the cytosol side that connect the receptors of a specific binding proteins on the extracellular side through clathrins (Middle man)
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What begins the bud formation in receptor mediated endocytosis
Clathrin
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Endosomes
Are the compartments that are the first to receive all endocytoted vesicles
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How does an endosome remove receptors from LDL
It has a relatively low pH that removes them
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What happens to receptors used in Endocytosis following the release of LDL
They return to the cell membrane
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What is the difference between the early endosomes and the late endosomes
- Early endosomes have shed the receptor but not the LDL
- Late endosomes are essentially lysosomes
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Both EGF and ligand receptors are targeted to
Lysosomes for degradation
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What is a primary lysosome
A cytoplasmic cell organelle that buds off from the golgi complex (becomes a secondary when it fuses with the vesicle containing the matter to be ingested)
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EGF receptor
Is another endocytosis receptor, but differs in that it doesn't invaginate until the target molecule is attached (then it attaches to adaptins), and it doesn't recycle for another round
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Caveolae
Means little caves, and are small invaginations of the plasma membrane in many cell types, especially in endothelial cells
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How are caveolae formed
By lipid rafts that have been invaginated
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Where can some of the caveolae go after they pinch off the membrane
They can deliver contents to the ER and Golgi but never lysosomes
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Caveolae are now thought to act as
Signalsomes, a place where signal transductions can take place efficiently
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Many micro organisms like to use caveolae for entry due to
Their not fusing with lysosomes
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