Week 2 Vesicular Transport Module Flashcards Preview

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Flashcards in Week 2 Vesicular Transport Module Deck (48)
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1
Q

what are three functions of vesicular transport?

A

deliver newly made molecules to their final destinations, communicate with the extracellular environment, ingest extracellular particles and solutes.

2
Q

What are the two major pathways of vesicular transport

A

secretory pathway and the endocytic pathway

3
Q

what is the function of the secretory pathway

A

delivers newly made molecules to their proper position outside the cell

4
Q

what is the function of the endocytic pathway

A

delivers extracellular components to the inside of the cell

5
Q

where does secretory vesicular transport begin?

A

ER

6
Q

In general vesicles ____ off the _______ and fuse to the _______ while carrying _____

A

bud, donor compartment, target compartment, cargo

7
Q

describe the role of protein coating in vesicle budding. what two functions does the coat play?

A

vesicles require a protein coat for budding. the protein coat helps pinch vesicle off donor membrane and helps sort sort the cargo

8
Q

what are the three major protein coating proteins?

A

clathrin, COPI and COPII

9
Q

Describe the structure of clathrin. how does this relate to function?

A

3 heavy chains and 3 light chains form a triskelion which forces vesicle into rounded shape.

10
Q

How does clathrin bind the membrane of budding vesicles? (what is the binding cascade?)

A

Clathrin binds adaptin, adaptin binds cargo receptor, cargo receptor binds cargo

11
Q

What is the role of dynamin in vesicle formation?

A

pinches off vesicle

12
Q

what accounts for the variation in cargo carried by vesicles?

A

different adaptin molecules bind different cargo receptors in different regions of the cell.

13
Q

What happens to the clathrin coat prior to the vesicle reaching the target compartment?

A

clathrin and adaptin are released from the vesicle and recycled

14
Q

how does the vesicle find its way to the target compartment?

A

it moves along cytoskeletal elements within the cytoplasm

15
Q

which proteins are responsible for docking and recognition of vesicles to target compartments?

A

Rab located on the vesicle binds the tethering protein located on the target membrane

16
Q

which proteins are largely responsible for the fusion of the vesicle with the target membrane?

A

v-snare on the vesicle and t-snare on the target compartment

17
Q

What types (3) of modifications or proteins occur in the ER?

A

Cys-Cys Disulfide bonds (interchain and intrachain)

lipid membrane anchors (addition of lipids that covalently anchor protein to the membrane

The initial glycosylation of proteins occurs in the ER

18
Q

Oligosaccharides are generally added to which residues on a polypeptide chain?

A

Asparagine (Asn)

19
Q

what is the difference between N-lonked and O-linked glycoproteins?

A

N-linked: oligasaccharide added to Asn residue

O-linked: added to Ser or Threonine

20
Q

what is the role of dolichol?

A

dolichol is a special membrane lipid in the ER that transfers its oligasaccharide group to the newly translated polypeptide

21
Q

Describe the selectivity of exit from the ER

A

protein exit from the ER is highly selective. The ER uses chaperone proteins to ensure proteins fold correctly. If a protein cant be made to fold correctly it is degrade in cytosol

22
Q

what is the difference between cis-golgi network and trans-golgi network?

A

Cis: where vesicles enter the golgi

Trans: where vesicles exit the golgi

23
Q

Vesicles that exit the golgi are destined to go where?

A

endosome or plasma membrane

24
Q

as a vesicle moves through the golgi what happens to its contents?

A

further sorting and modification of sugars and proteins

25
Q

What are the two pathways of exocytosis

A

constitutive secretion, regulated secretion

26
Q

describe constitutive secretion. what cells do this? role?

A

constantly occuring and seen in all cells. supplies PM with new proteins and lipids and releases things to extracellular space

27
Q

describe regulated secretion. what cells do this? role?

A

release of vesicle contents to extracellular space in response to specific stimulus (receptor activation). only seen ins specialized secretory cells such as endocrine cells

28
Q

what is the pathway of an ER protein from the ER to lysosome?

A

ER–>cis golgi–>trans golgi–>endosome–>lysosome

29
Q

what is the role of lysosome? what type of enzymes to they house?

A

sites of molecular degradation. House acid hydrolases (nucleases, proteases, lipases)

30
Q

describe the pH of a lysosome. how is it maintained?

A

acidic (pH about 5. compare to pH 7.2 see in cytosol). maintained through hydrogen pumps

31
Q

where are all lysosomal proteins translated?

A

by ER bound ribosomes

32
Q

what protects acid hydrolases from the acidic environment of the lysosome?

A

acid hydrolases are heavily glycosylated in the ER to protect them from the low pH

33
Q

what is the role of Mannose-6-phosphate? where is it added?

A

Mannose-6-phosphate is added to lysosomal acid hydrolases within the GOLGI. M6P binds M6P receptors of clathrin coated vesicles. These vesicles are targeted to endosomes.

34
Q

compare early and late endosomes. Location? Acidity?

A

early: located near PM, slightly acidic (pH of 6.2)
late: located in interior of cell, more acidic (pH of 5.5). will mature into lysosome

35
Q

what is I-cell disease? cause? results?

A

enzyme that adds M6P (within golgi) is defective. therefore acid hydrolases are not targeted to endosomes and end up in blood.

36
Q

What are the three types of endocytosis?

A

phagocytosis, pinocytosis, receptor-mediated endocytosis

37
Q

What is phagocytosis? where is it seen?

A

ingestion of large particles (bacteria and cell debris). immune cells

38
Q

what is pinocytosis? where is it seen?

A

ingestion of fluid and small molecules. seen in all cells

39
Q

What is receptor-mediated endocytosis? what does it accomplish?

A

a mechanism that allows concentrated uptake of specific molecules

40
Q

what offsets the loss of membrane through pinocytosis?

A

constiutive secretion

41
Q

is pinocytosis clatherin dependent?

A

it can be, but not always

42
Q

describe the process of receptor-mediated endocytosis

A

specific cargo bind cargo receptors on (facing extracellular space)–>clathrin coated pits are formed (adaptin binds cargo receptor, clathrin binds adaptin)–> the vesicle buds INTO the cell and is ready to fuse

43
Q

What is the role of early endosomes?

A

sort endocytosed material

44
Q

what are the fates of receptors used in receptor mediated endocytosis?

A
  1. recycled to PM
  2. degraded by lysosome
  3. transocytosis: travel across a cell
45
Q

how does the cargo know to release when it contacts an early endosome? what if it doesnt release?

A

the light acidic pH of the early endosome triggers cargo release. If the cargo is not released it will have the same fate as the receptor.

46
Q

how is cholesterol transported in blood?

A

transported as LDL: a core of cholesterol with a lipid monolayer that is organized by a protein.

47
Q

How do cells take in cholesterol from blood?

A

LDL receptors locate LDL and entire LDL molecule is taken up (receptor mediated endocytosis)

48
Q

what is familial hypercholesterolemia caused by?

A

mutation in LDL receptor that results in excess LDL cholesteron in blood

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