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Molecular Biology Test II - Jourdan > Intracellular Compartments and Protein Sorting 1 > Flashcards

Intracellular Compartments and Protein Sorting 1 Flashcards

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0
Q

What is a nucleus?

A

Principal site for DNA and RNA synthesis

Contains the genome

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1
Q

What is a plasma membrane?

A

Outer boundary of cells, and a bilayer

It is a protective barrier with transporters and signaling

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2
Q

What is cytoplasm?

A

Consists of cytosol and cytoplasmic organelles

And is an intermediary metabolism

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3
Q

What is Endoplasmic Reticulum ER?

A

Ribosomes attach to the rough ER and the smooth ER has no ribosomes
It is a place for proteins synthesis, lipid synthesis, protein folding, and storage of calcium

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4
Q

What is the golgi apparatus?

A

Stacks of disc-like compartments

-post-translational changes on proteins and lipids occur here and also trafficking

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5
Q

What does the mitochondria do?

A

Makes ATP, signaling, cell differentiation and cell death.

Has an outer and inner membrane and matrix

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6
Q

What are lysosomes?

A

The digestive system of the cell: contain digestive enzymes that degrade organelles and biomolecules

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7
Q

What are peroxisomes?

A

Small vesicular compartments that contain enzymes used in oxidation reactions

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8
Q

what 3 topological categories does the cell divide into?

A

Nucleus and cytosol
Organelles in secretory and endocytic pathways
Mitochondria

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9
Q

How does the nucleus and cytosol communicate?

A

Through nuclear pore complex. Topologically they are the same and one organelle

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10
Q

What are organelles in secretory and endocytic pathways?

A

ER, Golgi, Endosomes, and lysosomes

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11
Q

How do organelles in secretory and endocytic pathways communicate?

A

Through vesicles

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12
Q

What allows topologically equivalent organelles to communicate with each other and with the cell exterior?

A

Membrane budding and fusion allows the lumen of each of these compartments to communicated

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13
Q

What are the types of protein trafficking?

A

Gated transport
Transmembrane transport
Vesicular transport

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14
Q

What type of protein trafficking is between the nucleus and cytosol through nuclear pore complexes?

A

Gated transport

Active transport and free diffusion

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15
Q

What is transmembrane transport?

A

Membrane proteins translocators directly transport specific proteins from cytosol across an organelle membrane

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16
Q

What is vesicular transport?

A

Membrane-enclosed transport intermediates that move proteins between various compartments via vesicles

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17
Q

What guides protein transfer/transport to various compartments?

A

Sorting signals

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18
Q

What are sorting signals?

A

Stretch of amino acids, typically 15-60 residues long

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19
Q

Where may sorting signals be localized?

A

On N or C terminus or within the protein sequence

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20
Q

What forms a signal patch?

A

Multiple scattered sequences in protein may form signal patch

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21
Q

What may remove the signal after protein reaches final destination?

A

Signal peptidase

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22
Q

Signal sequences are both necessary and sufficient for ____________

A

Protein targeting

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23
Q

What is more important than actual sequence in a sorting signal?

A

Physical properties of the sequence (e.g. charge, hydrophobicity)

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24
What are signal sequences recognized by?
Complementary receptors
25
Describe nuclear transport?
Gated, bidirectional, and selective
26
What proteins are needed in nucleus?
Histones, DNA and RNA polymerases, topoisomerases, and gene regulatory proteins
27
Where are proteins needed in the nucleus imported from?
The cytoplasm where they are synthesized
28
What proteins are synthesized in the nucleus and exported to cytosol?
tRNA and mRNA molecules
29
What are nuclear pore complexes?
(NPCs) Perforate nuclear envelope in eukaryotes
30
What is the molecular mass of NPCs?
About 125 million Da
31
What is the NPC composed of?
30 different proteins or nucleoporins
32
What is the arrangement of NPCs?
Octagonal symmetry with one or more aqueous pores
33
How many NPCs does the nuclear envelope have?
3000-4000 NPCs
34
What direction does the NPCs transport molecules?
Both directions
35
What type of transport do NPCs do?
Passive diffusion of small molecules and facilitated transport
36
What is transport facilitated by in NPC?
Binding of particles to fibrils extending from NPC
37
What are Nuclear localization signals?
(NLS) Sorting signals that direct molecules to nucleus Short sequences rich in positively charged amino acids lysine and arginine
38
What are NLS located on? What do they form?
Many different sites on protein and form loops or patches on surface
39
What do NLS result in?
Selective import of proteins into nucleus
40
What are NLS recognized by?
Nuclear import receptors (NIRs)
41
What does each NIR recognize specifically?
A subset of cargo proteins
42
What are NIRs?
Soluble cytosolic proteins that bind to NLS on protein and to NPC proteins present on fibrils that extend into cytoplams
43
What do NPC proteins have? What is their purpose?
Phenylalanine glycine (FG) repeats which serve as binding sites for import receptors
44
How do receptors plus its cargo traverse NPC?
By binding, dissociating, and re-binding to adjacent FG repeats
45
What happens once the cargo passes the NPC?
It is released inside the nucleus and NIR returns to cytoplasm
46
What types of binding occurs with nuclear import receptors?
Direct binding with 3 different cargo proteins | and indirect binding via adaptor protein
47
What is nuclear export?
Works similar to import but in opposite direction. It transports cargo out of the nucleus
48
What does nuclear export rely on?
Nuclear export signals (NES) on molecules that need to go out of the nucleus
49
What receptors are needed?
Need complementary nuclear export receptors (NER)
50
What does NER bind to?
Cargo present in nucleus and NPC proteins
51
What facilitates transport during nuclear export?
Binding, dissociation and re-binding
52
Where is the cargo released during nuclear export?
Into cytoplasm
53
What drives nuclear transport in appropriate direction?
Gradient of Ran conformational states
54
How does the import receptor and cargo enter the nucleus?
By interacting with FG repeats on NPC proteins
55
What binds to complex of import receptor and cargo?
Ran-GTP
56
What does the binding of Ran-GTP to complex of import receptor and cargo cause?
The release of cargo
57
What leaves the nucleus after cargo is released in the nucleus?
Ran-GTP and import receptor
58
What happens to Ran-GTP in the cytoplasm?
It is hydrolyzed by Ran-GAP and the receptor is released from the Ran-GDP (hydrolyzed ran-gtp) and is ready for another cycle
59
Some proteins contain both ____ and _____
NLS and NES
60
Where do proteins with both NLS and NES shuttle back and forth?
Between nucleus and cytosol
61
What does the steady state localization dependent upon?
Relative rate of transport
62
If rate of import is greater than export, ________
It is considered nuclear, and vise versa
63
What can the changing rate of import/export change?
Location of protein
64
Gene regulatory proteins transport is _________
Stringently controlled
65
What is kept out of nucleus until needed?
Gene regulatory proteins
66
Gene regulatory protein transport is controlled by what?
By NLS and NES being turned on and off
67
What mechanisms are used to turn on and off the NLS and NES on gene regulatory proteins?
Phosphorylation, proteolysis, and binding to inhibitory proteins

Molecular Biology Test II - Jourdan (9 decks)

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