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

Lecture 12: Exocytosis, Endocytosis, and recycling Flashcards

1
Q

Exocytosis

A

Transport from the trans golgi network to the cell exterior

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2
Q

Constitutive vs regulated secretion

A
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3
Q

What are the three sorting possibilities in the TGN?

A
  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
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4
Q

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

A

Phosphoinositides

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5
Q

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

A

granules or dense-core granules

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6
Q

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

A

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

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7
Q

What are the 5 stages of synaptic vesicle fusion?

A
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8
Q

Compound exocytosis? example?

A

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

Ex-mast cell degranulation

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9
Q

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

A
  • 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
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10
Q

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

A
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11
Q

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

A
  • directional
  • The apical plasma membrane of epithelial cells have a different protein content than the basolateral plasma membrane
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12
Q

What are two ways that polarized exocytosis and transcytosis occur?

A
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13
Q

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

A

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

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14
Q

Endocytosis

A

Internalization of external material including proteins located on the plasma membrane

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15
Q

3 types of endocytosis?

A
  1. Receptor-mediated endocytosis
  2. phagocytosis
  3. pinocytosis
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16
Q

Receptor-mediated endocytosis

A
  • 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)

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17
Q

Phagocytosis

A
  • “cellular eating”
  • Ingestion of large particle such as microorganisms or dead cells (usually >250 nm in diameter)
  • Usually triggered
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18
Q

Pinocytosis

A

• “cellular drinking”

  • Ingestion of fluids and solutes (~100 nm in diameter)
  • Constitutive
19
Q

COPII coats vesicles in the ___

A

ER- heading out toward PM

20
Q

COPI coats vesicles in the ___

A

TGN- heading back towards ER

21
Q

Clathrin coats vesicles at the ___

A

PM, Early and late endosome

22
Q

Mechanism of endocytosis

A
  • Coat proteins are used to deform the membrane and form a coated vesicle
    • primary coat protein is clathrin
23
Q

Clathrin coats are composed of ___

A

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

24
Q

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

A

using different adaptors

25
Q

____ proteins link integral membrane proteins to clathrin

A

Adaptor

26
Q

What is responsible for uncoating clathrin coated vesicles?

A
  • “Uncoating ATPase”
    • Cytosolic HSP70 family member
27
Q

How does the clathrin adpator AP2 work?

A
  • When AP2 is bound to phosphoinositides and cargo recpetors, it opens and allows clathrin to bind
28
Q

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

A

dynamin

29
Q

What is dynamin? Whar does it do?

A

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

30
Q

Why do PM derived vesicles require the help of dynamin?

A

– Different phospholipid bilayer composition

– Increased membrane stiffness

– Regulation of internalization (sometimes a pit is good)

31
Q

Low density lipoprotein (LDL) particles are responsible for…

A

import of cholesterol esters into the cell

32
Q

How does import of extracellular cholesterol occur?

A
33
Q

What are the three potential fates of endocytosed membrane proteins?

A
  1. degradation in the endolysosome
  2. recycling
  3. transcytosis
34
Q

_____ form as early endosomes mature to late endosomes.

A
  • Multivesicular bodies (MVBs)
    • This process separates and sequesters material (particularly membrane proteins) to be degraded from material to be recycled.
35
Q

membrane proteins are marked for inclusion into MVBs by ____

A

ubiquitin, which detaches just before formation of intralumenal vesicles

36
Q

___ proteins are responsible for sorting into and formation of MVBs

A

ESCRT

37
Q

MVB formation is the same process as ____

A

virus budding from the PM

38
Q

How does synaptic vesicle recycling occur?

A
39
Q

What are the specialized types of endocytosis?

A
  • Phagocytosis
  • Pinocytosis
  • Transcytosis
40
Q

Phagocytosis occurs by…

A

psuedopod formation

41
Q

How are psuedopods formed?

A

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

42
Q

Macropinocytosis

A
43
Q

What are caveolae?

A

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

BIOC 341 (24 decks)

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