Chapter 13: Intracellular Membrane Traffic

Question 1

What important concept is maintained during intracellular membrane trafficking?

Answer 1

topological equivalence

Question 2

What are the 3 types of intracellular membrane trafficking pathways?

Answer 2

1. endocytic
2. biosynthetic-secretory
3. retrieval

Question 3

What pathway involves absorbing extracellular material into the cell?

Answer 3

endocytic pathway

Question 4

what pathway involves the transfer of material from the nuclear envelope/ER to the Golgi, vesicles, or outside of the cell?

Answer 4

Biosynthetic-secretory pathway

Question 5

what pathway involves the transfer of cell material from other pathways back to the ER?

Answer 5

retrieval pathway

Question 6

The endocytic pathway utilizes what protein to aid in intracellular transport?

Answer 6

clathrin

Question 7

Retrograde transport utilizes what protein to aid in intracellular transport?

Answer 7

COP1

Question 8

The synthesis and secretory transport utilize what protein to aid in intracellular transport?

Answer 8

COP2 (+clathrin)

Question 9

Cholesterol receptor-mediated endocytosis is typically regulated by what protein/transport type?

Answer 9

Clathrin; endocytic pathway

Question 10

In what scenario would a cell use COP1 proteins for intracellular membrane transport?

Answer 10

To return proteins that have been mistakenly transported to certain organelles; retrieval/retrograde pathway

Question 11

COP2 proteins are found in what portion of the cell? What is their function?

Answer 11

ER; transport to topologically equivalent spaces

Question 12

What are the 4 basic steps of clathrin-based vesicle formation?

Answer 12

1. coat assembly and cargo selection
2. bud formation
3. vesicle formation
4. uncoating

Question 13

This particular protein attaches to cargo receptors to allow for the association of the clathrin triskeleton

Answer 13

adaptor protein

Question 14

these proteins aid in the vesicular formation of a clathrin-coated membrane

Answer 14

membrane-bending and fissure proteins

Question 15

On what side of the membrane does the clathrin triskeleton bind to?

Answer 15

cytosolic

Question 16

What phenomenon induces the budding and fission of a clathrin-coated vesicle?

Answer 16

clathrin triskeleton bending

Question 17

This is a vesicular formation/fission protein that has contractile function driven by GTP

Answer 17

dynamin helix

Question 18

What are the three steps of directed traffic endocytosis?

Answer 18

1. tethering of vesicle via Rab-GTP
2. docking on membrane via t-snare/v-snare interaction
3. Fusion of vesicle into cell (and release of Rab-GTP)

Question 19

What is required of a protein for COP2 ER transport of it to occur?

Answer 19

exit signal corresponding to cargo receptor

Question 20

What are the 2 possible fates of a resident ER protein?

Answer 20

1. retention signal prevents removal – remains in ER lumen
2. protein is taken up by vesicle formation – diffused out of ER lumen (to topologically equivalent spaces)

Question 21

These are membrane-bound regions between the ER and cis-Golgi network where retrieval transport can occur

Answer 21

vesicular tubular cluster

Question 22

What are the 3 cisternae of the Golgi stack?

Answer 22

1. cis
2. medial
3. trans

Question 23

What are the 3 total regions of the Golgi apparatus?

Answer 23

1. cis Golgi network
2. Golgi stack
3. trans Golgi network (TGN)

Question 24

The cis Golgi network is responsible for what?

Answer 24

Sorting & phosphorylation of oligosaccarides

Question 25

The cis cisternae of the Golgi stack is responsible for what?

Answer 25

removal of Man

Question 26

what is the function of the medial cisterna of the Golgi stack?

Answer 26

removal of Man & addition of GlcNAc

Question 27

what is the function of the trans cisterna of the Golgi stack?

Answer 27

addition of Gal & addition of NANA

Question 28

what is the function of the trans cisterna of the Golgi stack?

Answer 28

addition of Gal & addition of NANA

Question 29

what is the function of the TGN?

Answer 29

sorting & sulfation of tyrosines and carbohydrates

Question 30

what are the 3 major fates of TGN sorting?

Answer 30

1. lysosome 2. plasma membrane 3. secretory vesicle

Question 31

what are the three possible sources of a lysosome?

Answer 31

1. phagosome 2. late endosome 3. autophagosome

Question 32

this vesicular structure is responsible for digesting the cell's own structures (i.e. mitochondrion, chloroplasts)

Answer 32

autophagosome

Question 33

this vesicular structure is formed via the endocytosis of large, foreign structures (i.e. bacterium)

Answer 33

phagosome

Question 34

this vesicular structure is formed via the endocytosis of smaller structures and can mature into another structure when introduced to a product of macropinocytosis

Answer 34

early endosome

Question 35

the addition of the products of macropinocytosis to the products of endocytosis results in what structure?

Answer 35

late endosome

Question 36

What are the 7 basic steps (and the locations where they occur) of lysosomal hydrolase transport to endosomes?

Answer 36

1. Addition of P-GlcNAc (cis Golgi network) 2. uncover M6P signal (Golgi stack) 3. Binding to M6P receptor (TGN) 4. Transport to endosome (transport vesicle) 5. Dissociation @ acidic pH (endosome) 6. Removal of phosphate (endosome) 7. Receptor retrieval (transport vesicle)

Question 37

What is essential in providing the acidic endosomal environment to ensure the dissociation of lysosomal hydrolase precursor from the M6P receptor?

Answer 37

V-type ATP proton pump

Question 38

Where is the dysfunction located at in I-cell disease?

Answer 38

lack of M6P signal (no mannose phosphorylation) on lysosomal hydrolase precursor

Question 39

What is the result of I-cell disease?

Answer 39

insufficient endosomal hydrolase activity--largely effects nervous system

Question 40

What are the 8 basic steps of cholesterol delivery via LDLs?

Answer 40

1. LDL binding to extracellular receptors 2. formation of clathrin coat 3. uncoating 4. fusion into Golgi network 5. LDL transfer to late endosome (& retrieval of LDL receptor) 6. late endosome --> endolysosome 7. release of free cholesterol via hydrolytic enzymes 8. recycling of lysosome

Question 41

this secretory pathway is used to transport/release membrane lipids or soluble proteins in an unregulated membrane fusion; this is often the default for molecules with no target info

Answer 41

constitutive secretory pathway

Question 42

this secretory pathway occurs in response to the activity of an extracellular receptor (via hormones/NTMs) to induce regulated membrane fusion

Answer 42

regulated secretory pathway

Question 43

In what cells to secretory vesicles form?

Answer 43

only in cells that perform excretion functions (i.e. toxicant removal)

Question 44

What is the default fate/location of a protein translocated into the ER lumen (only contains an ER localizing signal)?

Answer 44

extracellular space

Question 45

What is the default fate/location of proteins synthesized via cytosolic transcription?

Answer 45

usually mitochondria/chloroplast--otherwise they remain in cytosol