Lecture 7 - Intracellular Compartments, Membrane Trafficking, and Protein Sorting

Question 1

what are transport vesicles for?

Answer 1

they help exchange material inside the cell since the content inside does not diffuse but rather is exchanged between compartments

Question 2

remember:

Answer 2

• organelle = permanent

- vesicle = transient

Question 3

what are the 2 organelles that are excluded from the similar mechanisms of vesicular transport and exchange of material between intracellular membrane compartments?

Answer 3

• mitochondria

- chloroplasts

Question 4

what is used to synthesize all proteins encoded by the nuclear genome?

Answer 4

a common pool of ribosomes

Question 5

what is Nissl staining for?

Answer 5

for ribosomes in neurons

- they color the entire neuronal cell body inside and used to be called Nissl substance or Nissl body

Question 6

where are membrane proteins synthesized?

Answer 6

next to the place where they will be used and are intercalated into the membrane while synthesized

Question 7

how many polypeptides do mitochondria encode for?

Answer 7

only 13

Question 8

all mitochondria-encoded proteins are ____

Answer 8

membrane-integrated proteins

Question 9

what are the 3 major mechanisms of the membrane-enclosed organelles that import proteins?

Answer 9

1. ) transport through nuclear pores = fully synthesized & folded proteins move through the large pores (nucleus)
2. ) transport across membranes = fully synthesized but unfolded polypeptides are transported thru the membranes & then fold inside the organelles (this is how the mitochondria, chloroplasts, and peroxisomes receive proteins)
3. ) transport by vesicles = membrane-bound (enclosed, secreted, or integrated) are anchored at the membrane of endoplasmic reticulum at the beginning of their synthesis & then special translocase system (translocator) move them into the ER

Question 10

2 of the 3 major mechanisms for organelles importing proteins transport what kind of molecules? and what do they require?

Answer 10

2 of those major mechanisms are for the transport of soluble proteins and membrane proteins for mitochondria and chloroplasts; they require translocases

Question 11

what causes a change in the protein destination?

Answer 11

adding or deleting the signal sequence

Question 12

what molecules does the nuclear pore complex allow to enter or exit the nucleus?

Answer 12

allows ONLY selected macromolecules and large macromolecules to enter or exit the nucleus

Question 13

what does the nuclear import receptor recognize?

Answer 13

the imported proteins that contain nuclear localization signal

Question 14

what does the nuclear import receptor proteins interact with and what do they allow?

Answer 14

interact with cytosolic fibers; allow proteins with nuclear localization signals to enter the nuclear pore thru the meshwork that prevents other proteins from entering the nucleus

Question 15

what are soluble receptors that work by a similar mechanism to nuclear import receptor proteins?

Answer 15

• nuclear export receptors

- nuclear import receptors

Question 16

what is Ran?

Answer 16

a small GTPase that proves the energy of GTP hydrolysis to drive nuclear transport in the appropriate direction

Question 17

what do accessory proteins that cannot cross the pore make?

Answer 17

they make Ran protein exchange GDP to GTP or can make Ran-GTP hydrolyze GTP liberating the receptor and ensuring unidirectional transport