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BC3003: Introduction to Cell Biology & Biomembranes > Cellular Logistics: Vesicular Traffic - Secretion & Endocytosis > Flashcards

Cellular Logistics: Vesicular Traffic - Secretion & Endocytosis Flashcards

1
Q

Where is cargo transported from and to in Foward Transport in the secretory pathway?

A

ER to cis-Golgi

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2
Q

Where is cargo transported from and to in Reverse Transport in the secretory pathway?

A

cis-Golgi to ER

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3
Q

Is Forward Transport Anterograde or Retrograde transport?

A

Anterograde

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4
Q

Is Reverse Transport Anterograde or Retrograde transport?

A

Retrograde

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5
Q

Which type of coated vesicles is involved in Forward Transport?

A

COPII coated vesicles

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6
Q

Which type of coated vesicles is involved in Reverse Transport?

A

COPI coated vesicles

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7
Q

In Reverse Transport, what sequence mediates the retrieval of most missorted soluble ER resident proteins to the ER?

A

C-terminal KDEL sequences
(Lys-Asp-Glu-Leu)

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8
Q

In Reverse Transport, what sequence mediates the retrieval of transmembrane ER resident proteins?

A

C-terminal KKXX sorting signal
(Lys-Lys-X-X)

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9
Q

Which model is widely favoured for transport through the Golgi?

A

Cisternal Progression Model

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10
Q

What type of vesicles mediate forward transport through the Golgi?

A

Retrograde vesicles

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11
Q

Which coated vesicles mediate retrograde vesicular transport in the cisternal progression model of transport through the Golgi?

A

COPI

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12
Q

What method can be used to study the secretory pathway?

A

Pulse-Chase Method

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13
Q

What is involved in the Pulse part of the Pulse-Chase Method?

A
  • Tissue is exposed briefly to radioactive H3 Leucine
  • H3 Leucine incorporated into newly synthesised protein
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14
Q

What is involved in the Chase part of the Pulse-Chase Method?

A

Subcellular localisation of labelled proteins examined at various timepoints

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15
Q

How many classes of secretion (sec) mutants have been identified in the study of secretion pathways in yeast?

A

5 classes

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16
Q

What type of coated vesicles mediate transport from Trans-Golgi to Endosomes?

A

Clatharin Coated Vesicles with associated Adapter Proteins (AP

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17
Q

What is the structure of Clatharin?

A

Three limbed structure called a Triskelion

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18
Q

How does Clatharin achieve a curved structure?

A

Triskelions polymerise to form a curved polygonal lattice

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19
Q

What is the inner layer of the Clatharin coated vesicles composed of?

A

Adapter protein complexes

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20
Q

What is the final step of vesicle budding for Clatharin coated vesicles?

A

Budding Off

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21
Q

What does Budding Off require for Clatharin coated vesicles?

A

GTP hydrolysis

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22
Q

Which GTPase forms a ring around the “neck” of a Clatharin coated vesicle in order for it to bud off?

A

Dynamin

23
Q

TRUE OR FALSE:
GTPases are required for pinching off of COPI and COPII vesicles

A

False.
They are NOT required

24
Q

TRUE OR FALSE:
In the the secretory and endocytic pathways, the outer Clatharin coat remains the same but the adapter proteins and sorting signals on the cargo proteins are different?

A

True.

25
Q

What Adapter Proteins are involved in trafficking vesicles from Golgi to Endosomes?

A

AP1 or GGA

26
Q

What Adapter Proteins are involved in trafficking vesicles from Plasma Membrane to Endosomes?

A

AP2

27
Q

What Adapter Proteins are involved in trafficking vesicles from Golgi to Lysosomes?

A

AP3

28
Q

TRUE OR FALSE:
Sorting signals on cargo proteins or cargo receptors interact with Clathrin?

A

False.
Sorting signals interact with the adapter proteins

29
Q
A
30
Q

What type of modification happens on Sorting Signals on proteins heading to the lysosomes?

A

Carbohydrate modifications
* Mannose-6-phosphate

31
Q

Where does sorting signal modification occur?

A

cis-Golgi

32
Q

What are the steps involved in Sorting Signal modification?

A
  1. Attachment of phosphorylated N-acetylglucosamine (GlcNAc) to Mannose
  2. Removal of N-acetylglucosamine to leave Mannose-6-phosphate (M6P)
33
Q

What are the TWO enzymes involved in the carbohydrate modification of Sorting Signals?

A
  1. GlcNAc phosphotransferase
  2. Phosphodiesterase
34
Q

What type of proteins do Mannose-6-phosphate (M6P) receptors bind to?

A

Proteins with M6P modified oligosaccharides

35
Q

What pH causes release to M6P tagged cargo proteins in endosomes?

A

Low pH (5 - 5.5)

36
Q

How are lysosomal storage diseases characterised?

A

Absence of one or more lysosomal enzymes

37
Q

Which enzyme do cells lack in I-cell disease (lysosomal storage disease)

A

N-acetylglucosamine phosphotransferase

38
Q

TRUE OR FALSE:
Lysosomal enzymes are NOT tagged with Mannose-6-phosphate in I-cell disease

A

True

39
Q

What happens to enzymes in I-cell disease?

A

Enzymes are secreted instead of being sorted

40
Q

What are the TWO types of secretory vesicles of the secretory pathway?

A
  1. Constitutive
  2. Regulated
41
Q

What is an example of a Constitutive secretory vesicle?

A

Serum albumin release from hepatocytes

42
Q

What is an example of a Regulated secretory vesicle?

A

Neurotransmitter release from synapses

43
Q

What serves as a sorting signal for Regulated secretion?

A

Selective aggregation of proteins

44
Q

Where does proteolytic cleavage occur on secreted proteins in secretory vesicles?

A

C-terminal to dibasic motifs
(Lys and Arg)

45
Q

What are TWO types of Endocytosis?

A
  1. Pinocytosis
  2. Receptor mediated endocytosis
46
Q

What does Receptor Mediated Endocytosis involve?

A

Binding of an extracellular ligand to a receptor

47
Q

What are THREE examples of ligands that are endocytosed?

A
  1. Transferrin (iron binding protein)
  2. Low-density lipoprotein
  3. Growth factors and hormones
48
Q

What is a Low-Density Lipoprotein (LDL) comprised of?

A
  • ApoB protein
  • Phospholipid shell
  • Cholesterol in core
49
Q

What is Familial Hypercholesteromia (High Cholesterol) caused by?

A

Mutations in the LDL receptor

50
Q

What did the study of disease causing mutations in the LDL receptors lead to?

A

Identification of the NPXY sorting signal for endocytosis

51
Q

Where does NPXY sorting signal bind to?

A

AP2

52
Q

What is the function of Transferrin?

A

Transports iron in the bloodstream
* from the intestine and liver
* to cells in all tissues of the body

53
Q

What binds to the Transferrin Receptors on the plasma membrane and is endocytosed?

A

Ferrotransferin

BC3003: Introduction to Cell Biology & Biomembranes (15 decks)

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