Lecture 4- Intracellular Transport

Question 0

Posttranslational Translocation

Answer 0

Proteins are translocated in the ER after they are translated by free ribosomes

Question 1

What is Fluid phase endocytosis

Answer 1

A non-selective means for bringing extracellular contents & fluid into the cell

Question 2

What are the 2 forms of endocytosis

Answer 2

1) Fluid phase

2) Receptor mediated

Question 3

What is Receptor-mediated endocytosis

Answer 3

Specific receptor molecules line the extracellular portion of the vesicle and look to bind to a specific ligand. They are then closed off and covered by a coated pit

Question 4

Cotranslational Translocation

Answer 4

Proteins are translocated directly in to ER lumen during translation by the ribosome

Question 5

What are the 2 types of coatamers

Answer 5

1) COPI

2) COPII

Question 6

COPI

Answer 6

Coats vesicles moving between Golgi stacks

Question 7

COPII

Answer 7

Coats vesicles leaving ER and heading toward cis-Golgi face

Question 8

Which way does the exocytoplasmic leaflet face in the ER

Answer 8

Luminal/endoplasmic compartment

Question 9

What are v-SNARE and t-SNARE

Answer 9

v-SNARE is a receptor coming off the vesicle looking for a specific target area
t-SNARE is a receptor coming off the membrane looking for a specific vesicle

Question 10

Adaptin

Answer 10

Binds cathrin to the transmembrane receptor molecule

Question 12

Which way does the protoplasmic leaflet face in the ER

Answer 12

Cytoplasmic/cytosolic compartment

Question 13

What are the 2 departments of the ER

Answer 13

1) Luminal (endoplasmic/internal) compartment

2) Cytoplasmic (cytosolic/external) compartment

Question 15

Clathrin

Answer 15

• Coats pits of receptor-mediated endocytosis
• Coats secretory vesicles of regulated exocytosis
• Anchors transmembrane receptors to vesicle
• Immediately removed after vesicle forms and enters cell

Question 15

What are NSF and SNAP and what is their role in fusion

Answer 15

• NSF and SNAP are proteins that mediate the connection b/w the v-SNARE and t-SNARE
• NSF is on the vesicle side
• SNAP is on the membrane side

Question 15

What are the 3 types of ER and how do they differ

Answer 15

1) Smooth ER- has no ribosomes on the cytoplasmic face
2) Rough ER- has ribosomes on the cytoplasmic face
3) Transitional ER- location where vesicles exit toward the cis-Golgi face

Question 16

What is an NLS and where is it found?

Answer 16

Nuclear Localization Signal-Signal to send a protein to the nucleus
Found anywhere on a nascent polypeptide

Question 17

How are proteins marked for transport to the mitochondria?

Answer 17

N-terminal signal sequence (can be cleaved off)

Question 18

How does protein transport from the ribosome to the inner mitochondrion take place?

Answer 18

Hsp70 keeps protein partially folded
TOM complex moves protein through both membranes with ATP
Hsp60 helps with final folding

Question 19

What are the two forms of Microtubular Transport and what proteins are involved?

Answer 19

Anterograde Transport- cell body to axon terminus (involves Kinesins)
Retrograde Transport- axon terminus to cell body (involves dynein)

Question 20

Myosin II

Answer 20

Found in muscle and non-muscle cells
Paired molecules linked by tails
Moves toward plus end of actin

Question 21

Myosin I

Answer 21

Found in all cells
Tail binds to vesicles
Moves toward plus end of actin

Question 22

Myosin V

Answer 22

Found in all cells
Two heads and double tail
Tail binds to vesicles
Moves toward plus end of actin

Question 23

Kinesin

Answer 23

Found in all cells
Two heads bind to microtubules
Tail binds to vesicles
Moves toward plus end of microtubule (anterograde)

Question 24

Dynein

Answer 24

Found in all cells Two heads bind to microtubules Tail binds to vesicles Moves toward minus end of microtubule (retrograde)