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BIO353 > Chapter 15 - Protein Sorting to Intracellular Compartments pt. 1 > Flashcards

Chapter 15 - Protein Sorting to Intracellular Compartments pt. 1 Flashcards

1
Q

Organelle duplication and growth requires a supply of what?

A

1) New lipids to make more membranes

2) New proteins, both membrane proteins and soluble proteins, that will occupy the interior of the organelle

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2
Q

Proteins for organelle duplication and growth must be ___ and accurately ___ to their destined organelles.

A

sorted, delivered

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3
Q

What instructs the correct delivery of proteins to their targeted organelles?

A

Amino acid sequence.

Similar to how a letter has a mailing address.

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4
Q

What are the two types of protein synthesis?

A

1) Synthesis from free polyribosomes

2) Synthesis from membrane-bound polyribosomes

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5
Q

What type of proteins does synthesis from free polyribosomes create?

A

Proteins floating freely in the cytosol.

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6
Q

What type of proteins does synthesis from free polyribosomes NOT create?

A

Transmembrane proteins nor proteins that are going to be exoctyosed from the cell.

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7
Q

(T/F) Synthesis from membrane-bound polyribosomes evolved along with internal membrane structures.

A

True

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8
Q

Synthesis from membrane-bound polyribosomes creates what types of proteins?

A

Membrane associated proteins and proteins in endomembrane vesicles.

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9
Q

Synthesis from membrane-bound polyribosomes are present only what kind of cells?

A

Eukaryotic

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10
Q

A polyribosome is a messenger RNA that has multiple ribosomes on its progressing from its ___ to ___ end.

A

5’, 3”

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11
Q

For both cases of protein synthesis, a polyribosome starts of as a what?

A

As a monoribosome (i.e., one ribosome).

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12
Q

Which end of the messenger RNA does polyribosomes start?

A

The 5’ end in the cytosol.

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13
Q

Where do sorting signals direct proteins?

A

To their target organelles

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14
Q

The synthesis of virtually all proteins begins where? What are some exceptions?

A

On ribosomes inside the cytosol. Some exceptions are mitochondria and chloroplast proteins.

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15
Q

What happens to proteins that lack sorting signals?

A

These proteins will remain in the cytosol.

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16
Q

Where are some examples sorting signals will direct proteins?

A

The nucleus, mitochondria, chloroplast, and the ER.

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17
Q

How can an organelle transport a protein across its membrane(s) which are normally impermeable to large and hydrophilic molecules?

A

Proteins from the cytosol move into:

1) Nucleus via nuclear pores
2) ER, mitochondria, or chloroplasts
3) Proteins move onward from ER

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18
Q

For nucleus proteins what types of gates and transport do proteins rely on?

A

Selective gates which actively transport the proteins.

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19
Q

How do proteins transverse across the membrane of the ER, mitochondria, or chloroplasts?

A

By protein translocation in the membrane. Protein must be unfolded and “snake” across the membrane.

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20
Q

Proteins that move onward from one compartment of the endomembrane system to another are transported by what?

A

Transport vesicles

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21
Q

How do proteins move onward from one compartment to the next?

A

They pinch off from one compartment and then fuse with the membrane of a second compartment.

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22
Q

What do proteins usually deliver when being transported to another compartment?

A

Soluble cargo proteins and membrane proteins.

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23
Q

How does the nuclear envelope get lipids and membrane proteins?

A

By backfilling along the appropriate lipid layer because the lipids themselves are not covalently linked and the membranes are contiguous.

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24
Q

How are proteins transported through the nucleus?

A

Via nuclear pores

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25
Q

The protein meshwork in the center of the nuclear envelope: each protein has a ___.

A

short repeated sequence; FGs.

26
Q

The protein meshwork in the center of the nuclear envelope and nuclear pores of repeated sequences that ___ to each other.

A

Bind

27
Q

The protein meshwork in the center of the nuclear envelope and nuclear pores form a mesh to prevent what?

A

Large molecules passing through.

28
Q

What are protruding both sides of the pore complex inside the nuclear envelope and nuclear pores?

A

Protein fibrils

29
Q

Protein fibrils ___ to form a basket-like structure on the nuclear side of nuclear pores.

A

converge

30
Q

Proteins destined to the nucleus must display what sorting signal?

A

Nuclear Localization Signal (NLS)

31
Q

What is the Nuclear Localization Signal (NLS)

A

It serves as both a mailing addresses and a ticket for protein transport.

32
Q

What signal is used when NSL is recognized by proteins?

A

Nuclear Import Receptor (NIR)

33
Q

Which signal directs the protein complex to a nuclear pore by grabbing the tentacle-like cytosolic fibrils?

A

Nuclear Import Receptor (NIR).

34
Q

Once in the pore, NIR grabs onto the ___ of the meshwork proteins, opening a ___ through the pore.

A

FG repeats, passage

35
Q

NIR bumps along the nuclear pore from one FG to another until what?

A

Enters the nucleus

36
Q

NIR and the cargo protein dissociates from each other thereby what?

A

Completing the delivery.

37
Q

Which cycle of active transport transports protein into, and out of, the nucleus?

A

Ran-GTP cycle

38
Q

In the nucleus, ___ protein encounters a ___ called Ran, which carries a GTP.

A

NIR-cargo, GTPase

39
Q

Ran binds to ___, causing the release of cargo protein.

A

NIR

40
Q

Which complex is transported back to the cytosol after the release of a cargo protein?

A

NIR-Ran-GTP

41
Q

Ran hydrolyzes what in the cytosol with the help of Ran GAP?

A

GTP

42
Q

What does GTP stand for?

A

GTPase Activating Protein

43
Q

NIR dissociates with ___, and ready to transport another nuclear protein.

A

Ran-GDP

44
Q

What type of conformation do proteins remain while being transported via nuclear pores?

A

Fully folded

45
Q

At what speed do proteins travel through nuclear pores?

A

Very high speeds - about 1000 translocations per second.

46
Q

Import and export of proteins via nuclear pores share what?

A

Similar mechanisms

47
Q

Which organelle(s) have their own genome, which can make some of their own proteins?

A

Mitochondria and Chloroplast

48
Q

Though they make some of their own proteins, most of Mitochondria and Chloroplasts’s ___ are encoded by the nuclear genome and imported from the cytosol.

A

Protein

49
Q

How many membranes do mitochondria and chloroplasts have?

A

Two

50
Q

Do proteins pass through both membranes of mitochondria and chloroplasts?

A

Yes

51
Q

How do mitochondria and chloroplasts get proteins from the cytosol?

A

From proteins already synthesized on free polyribosomes. Hence, post-translational transport.

52
Q

How do mitochondria and chloroplast obtain lipids?

A

By lipid transporters

53
Q

By lipid transporters, mitochondria and chloroplasts extract ___ from the ER and deliver them to these organelles.

A

Phospholipids

54
Q

For protein transport into mitochondria and chloroplasts, the protein precursor protein is ___ and its ___ is recognized and bound by a specific ___ on the outer membrane, which is associated with a pore-forming ___ protein.

A

unfolded, signal sequence, receptor protein, translocator.

55
Q

For protein transport into mitochondria and chloroplasts, which precursor complex diffuses laterally until it meets a second translocator on the inner membrane?

A

protein-receptor-translocator complex

56
Q

For protein transport into mitochondria and chloroplasts, the two translocators transport the protein across both the ___ and ___ membrane.

A

outer, inner

57
Q

(T/F) For protein transport into mitochondria and chloroplasts, after translocator transport the protein across both the outer and inner membrane, the signal peptide is then cleaved off.

A

True

58
Q

For protein transport into mitochondria and chloroplasts, how do chaperones assist protein transport?

A

1) Keeping protein unfolded in the cytosol.
2) Pulling proteins across the membrane.
3) Promoting correct protein folding in the matrix

59
Q

For protein transport into chloroplasts, which proteins share the same transport mechanisms as mitochondria matrix protein?

A

Stroma proteins.

60
Q

For protein transport into chloroplasts, for proteins destined to the thylakoid lumen, what are the two signal peptides?

A

1) One for chloroplast stroma, which will be cleaved off in stroma.
2) This will expose the second signal peptide for thylakoid lumen.

61
Q

For protein transport into chloroplasts, the exposed thylakoid signal peptide will target the ___ to the ___ via a similar mechanisms as the one for stroma proteins.

A

protein, lumen

62
Q

How do you identify an unknown protein and study the function of this protein after identification?

A

Looking for a storing signal amino acid sequence.

BIO353 (8 decks)

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