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First Semester/Mini 1 part 1
golgi, endosome, and membrane trafficking
21
Biology
Graduate
12/07/2010

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Cards

Term
Describe signal-mediated signal sorting to lysosome
Definition

- from trans-golgi to lysosome (requiring clathrin)

- Cis-golgi adds a mannose-6-phosphate (M6P) to a N-linked oligosaccharide from ER 

-M6P is directly linked to a lysosome & looses its affinity after vesicle binds to lysosome

Term
Describe Vesicular Transport
Definition

-where membranes & proteins carried as cargo

-regulated by spontaneous aggregation

-requires clathrin, COPI or COPII as machinery to promote budding

 

 

Term
Significance of COP I
Definition

- A retrograde transport

- Transports proteins from golgi to ER

Term
Significance of COP II
Definition

- A anterograde Transfer

- Transfers vesicles from rER to golgi

Term
Importance of Clathrin
Definition

- mediates endocytosis

1. Of vesicles from plasma membrane

2. Of vesicle movement from trans-golgi to lysosome

- it also regulates secretory vesicles

- influenza virus will enter but has an escape mechanism in order to avoid being degraded by lysosomes

Term
Signal used for target membrane in Vesicular Transport
Definition

-SNARES --used for targeting & drive fusion reaction

-V-snares for vesicles

-T-smares for target membrane

- snares are not found in mitochondria nor perxiosomes because there is no vesicular transport

Term
Signal used to promote vesicle fusion from target membranes in Vesicular Transport 
Definition

-RABs (a small GTP binding protein)

-gets tethering proteins close allowing v & t snares to bind before vesicle is fused

- after fusion

- NSF and SNAPS are soluble proteins required for breaking of v & t snares apart for recycling

Term
Constitutive Secretory Pathway
Definition

-The default pathway

-From ER to golgi to secretory vesicles to plasma membrane

- doesnt require a specific signal

Term
What is a Golgi Apparatus?
Definition

- totally dependent on microtubles

- a organelle where proteins and lipids are transferred from ER, modified, and sorted

- Sorting Signals

1. ER retention

- KDEL sequence (BIB a chaperone protein)

2. Golgi retention 

- for cis, medial, trans golgi

Term
Secretory Pathway
Definition

- from ER to golgi, the N-linked sugar is trimmed and receives a O-linked sugar 

 

Term
Importance of O-linked Glycosylation
Definition

- sugars including serine and threonine

- referred to as glycoproteins & glycolipids composed of sialic acid (NANA)

- its the only carbohydrate group with a negative charge facing the extracellular space

Term
Glycolipids
Definition

- formed in the golgi

- thick rim of carbohydrate around the plasma membrane called glycocalyx

-protects 

-important for cellular recognition 

-located on noncytosolic side

Term
How are secretions regulated? 
Definition

-insulin secretion, acteylcholine or glutamine requires a chemical signal before the secretory vesicle move to plasma membrane, fuse & release contents

- increase in Ca  causes a release in secretory vesicles from cytoskeleton (under the PM)

- Dynein & kinesin will transport vesicles along microtubles

Term
What are lipid rafts?
Definition

- formed from cluster cholesterol, spingomyelin, and phosphatidycholine (GPI-linked protein)

- are in the trans golgi network

 

Term
What happens during EXOCYTOSIS?
Definition

-Secrete molecules into extracellular fluid

Term
What happens during ENDOCYTOSIS?
Definition

- Bring molecules into the cell from extracellular fluid

- via Phagocytosis and pinocytosis

- mediated by clathrin (recycles between it assembled and unassembled state)

ex/ LDL binds to LDL cell-surface receptor proteins which is bound to adaptin and clathrin

Term
Phagocytosis
Definition

1. material contains the "eat me" signal to be opsinized

- pseudopods

2. Coated surface by IgG antibody

 

Term
Down regulation of receptors
Definition

EGF assemble in coated pits after the binding of ligand & becomes trapped & targeted for lysosome degrations

Term
Importance of Caveolae
Definition

- A lipid raft that requires the protein caveolin

- Caveolin causes the invagination

- Never pinches off like clathrin coated pits 100% of the time

- Molecules are only for endocytosis 

- its entry afford those microbes protection from the degradation in lysosomes 

- only fuses with ER and Golgi NOT lysosome

- The GPI anchor protein can act as a sorting signal 

Term
What is a early endosome?
Definition

- A drop in pH separates the ligand from receptor

- receptor gets recycled 

- doesnt contain digestive enzymes

Term
What is a late endosome?
Definition

- a early endosome thats fused with vesicle containing lysosomal hydrolases

- will mature into a secondary lysosome

- Acid hydorlasis dissociate from the M6P which gets recycled back to the trans-golgi

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