Lecture 12: Exocytosis, Endocytosis, and recycling Flashcards Preview

BIOC 341 > Lecture 12: Exocytosis, Endocytosis, and recycling > Flashcards

Flashcards in Lecture 12: Exocytosis, Endocytosis, and recycling Deck (43):
1

Exocytosis

Transport from the trans golgi network to the cell exterior

2

Constitutive vs regulated secretion

A image thumb
3

What are the three sorting possibilities in the TGN?

  1. Signal-mediated diversion to lysosomes via endosomes (mannose-6-phosphate receptors)
  2. Signal-mediated diversion to secretory vesicles (for regulated secretion)
  3. Constitutive secretory pathway

4

____ help mark organelles and membrane domains in the late secretory pathway

Phosphoinositides

5

Regulated secretory vesicles are also called secretory _____ based on their appearance under the electron microscope

granules or dense-core granules 

A image thumb
6

How does proteolytic processing occur in the late Golgi and within secretory vesicles?

Different peptide hormones can be made from the same pre-protein in different cell types 

7

What are the 5 stages of synaptic vesicle fusion?

A image thumb
8

Compound exocytosis? example?

Compound exocytosis - vesicle-vesicle fusion as well as vesicle PM fusion 

Ex-mast cell degranulation

9

GLUT4 translocation is an example of ____. How does this work?

  • regulated excretion
  • Insulin binds to insulin receptor -> sends an intracellular signal that causes glucose receptors to reloacte to the PM -> causes an influx of glucose into cell

10

What are 4 examples of regulated exocytosis leading to plasma membrane enlargement?

A image thumb
11

Secretion is _____ in polarized cells. How is this possible?

  • directional
  • The apical plasma membrane of epithelial cells have a different protein content than the basolateral plasma membrane 

12

What are two ways that polarized exocytosis and transcytosis occur?

A image thumb
13

Apical sorting may involve lipid microdomains called lipid rafts. How?

Only proteins with longer transmembrane domains can go into the raft phase.

14

Endocytosis

Internalization of external material including proteins located on the plasma membrane 

15

3 types of endocytosis?

  1. Receptor-mediated endocytosis
  2. phagocytosis
  3. pinocytosis

16

Receptor-mediated endocytosis

• Cellular uptake of macromolecules usually en route to the lysosome 

• Ingestion of metabolites 

– Cholesterol through LDL and the LDL receptor 

– Iron via the transferrin receptor 

• Termination of cell surface events (ie signaling) 

17

Phagocytosis

• “cellular eating” 

• Ingestion of large particle such as microorganisms or dead cells (usually >250 nm in diameter) 

• Usually triggered 

18

Pinocytosis

• “cellular drinking” 

• Ingestion of fluids and solutes (~100 nm in diameter) 

• Constitutive 

19

COPII coats vesicles in the ___

ER- heading out toward PM

20

COPI coats vesicles in the ___

TGN- heading back towards ER

21

Clathrin coats vesicles at the ___

PM, Early and late endosome

22

Mechanism of endocytosis 

  • Coat proteins are used to deform the membrane and form a coated vesicle 
    • primary coat protein is clathrin

23

Clathrin coats are composed of ___

the clathrin complex (a triskelion-3 heavy chains and 3 light chains) and clathrin adaptors 

24

The diversity of clathrin coats (ie budding form different compartments) is generated by...

using different adaptors 

25

____ proteins link integral membrane proteins to clathrin

Adaptor

26

What is responsible for uncoating clathrin coated vesicles?

  • “Uncoating ATPase”
    • Cytosolic HSP70 family member

27

How does the clathrin adpator AP2 work?

  • When AP2 is bound to phosphoinositides and cargo recpetors, it opens and allows clathrin to bind

28

Unlike internal membranes, vesicles derived from the plasma membrane require help of _____for membrane fission 

dynamin

29

What is dynamin? Whar does it do?

• Dynamin is a GTPase that constricts the neck of the newly formed coated pit to form a vesicle

30

Why do PM derived vesicles require the help of dynamin?

– Different phospholipid bilayer composition

– Increased membrane stiffness 

– Regulation of internalization (sometimes a pit is good) 

31

Low density lipoprotein (LDL) particles are responsible for... 

import of cholesterol esters into the cell

32

How does import of extracellular cholesterol occur?

A image thumb
33

What are the three potential fates of endocytosed membrane proteins?

  1. degradation in the endolysosome
  2. recycling
  3. transcytosis

34

_____ form as early endosomes mature to late endosomes. 

  • Multivesicular bodies (MVBs) 
    • This process separates and sequesters material (particularly membrane proteins) to be degraded from material to be recycled. 

35

membrane proteins are marked for inclusion into MVBs by ____

ubiquitin, which detaches just before formation of intralumenal vesicles 

36

___ proteins are responsible for sorting into and formation of MVBs

ESCRT

37

MVB formation is the same process as ____

virus budding from the PM

38

How does synaptic vesicle recycling occur?

A image thumb
39

What are the specialized types of endocytosis?

• Phagocytosis 

• Pinocytosis 

• Transcytosis

40

Phagocytosis occurs by...

psuedopod formation

41

How are psuedopods formed?

Pseudopod formation is driven by actin polymerization and reorganization in response to specific phosphoinositide generation. 

42

Macropinocytosis

A image thumb
43

What are caveolae?

Membrane invaginations, similiar to an endocytosed vesicle that has failed to detach from the PM