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Molecular Bio - Exam I > Lect. 11 - intracellular compts. and protein sorting 1 > Flashcards

Lect. 11 - intracellular compts. and protein sorting 1 Flashcards

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1
Q

plasma membrane

A

outer boundary of cells, bilayer; protective barrier, has transporters, signaling

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2
Q

plasma membrane

A

outer boundary of cells, bilayer; protective barrier, has transporters, signaling

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3
Q

nucleus

A

contains the genome; principal site for DNA and RNA synthesis

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4
Q

Cytoplasm

A

consists of cytosol and cytoplasmic organelles; intermediary metabolism

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5
Q

endoplasmic reticiulum

A

ribosomes attached to it (rER), no ribosomes (smoothER); protein sysntehsis, lipid synthesis, protein folding, storage of Ca.

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6
Q

golgi apparatus

A

stacks of disc like compartments; post-translational changes on proteins and lipids, trafficking

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7
Q

mitochondria

A

outer and inner membrane and matrix; makes ATP, signaling, cell differentiation and cell death

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8
Q

lysossomes

A

contain digestive enzymes that degrade organelles and biomolecules

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9
Q

peroxisomes

A

small vesicular compartments that contain enzymes used in oxidation reactions

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10
Q

what are the 3 topological categories of the cell?

A

nucleus and cytosol; organelles (ER, golgi, endosomes, lysosomes); mitochondria

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11
Q

gated transport

A

b/w nucleus and cytosol through nuclear pore complexes (active transport and free diffusion)

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12
Q

transmembrane transport

A

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

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13
Q

vesicular transport

A

membrane-enclosed transport intermediates move proteins b/w various compartments via vesicle

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14
Q

what guides protein transfer/transport to various compartments?

A

sorting signals

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15
Q

make up of a sorting signal

A

stretch of aas, typically 15-60 residues long; may be localized on N or C terminus or w/i protein sequence.

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16
Q

signal patch

A

formed by multiple scattered sequences in protein

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17
Q

signal peptidase

A

may remove signal after protein reaches final destination

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18
Q

which is more important in a signal sequence; the physical properties or the actual sequence?

A

the physical properties (charge, hydrophobicity, etc. )

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19
Q

what are signal sequences recognized by?

A

complementary receptors

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20
Q

nuclear transport

A

gated, bidirectional, and selective

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21
Q

what proteins are needed in the nucleus for nuclear transport and where do they come from/where are they synthesized?

A

histones, DNA and RNA polymerases, topoisomerases, gene regulatory proteins - imported from cytoplasm - also where they are synthesized

except- tRNA and mRNA are synthesized in the nucleus and exported to the cytosol

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22
Q

Nuclear Pore Complexes (NPCs)

A

composed of 30 different proteins/nucleoporins. arranged in octagonal symmetry w/ one or more aqueous pores.

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23
Q

What direction is transport in NPCs?

A

both directions

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24
Q

What kind of transport in NPCs?

A

passive diffusion of small molecules and facilitated transport

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25
How is transport facilitated in NPCs?
by binding of particles to fibrils extending from NPC
26
Nuclear Localization Signals (NLS)
sorting signals that direct molecules to nucleus; short sequences rich in positively charged aas lysine and arginine
27
where are NLS located?
many different sites on protein - from loops or patches on surface
28
what is the result of NLS?
selective import of proteins into nucleus
29
what recognizes NLS?
nuclear import receptors (NIRs)
30
Nuclear Import Receptors (NIRs)
soluble cytosolic proteins that bind to NLS on protein and to NPC proteins present on fibrils that extend into cytoplasm
31
make up of NPC proteins
they have phenylalanine glycine (FG) repeats; they serve as binding sites for import receptors
32
nucleus
contains the genome; principal site for DNA and RNA synthesis
33
Cytoplasm
consists of cytosol and cytoplasmic organelles; intermediary metabolism
34
endoplasmic reticiulum
ribosomes attached to it (rER), no ribosomes (smoothER); protein sysntehsis, lipid synthesis, protein folding, storage of Ca.
35
golgi apparatus
stacks of disc like compartments; post-translational changes on proteins and lipids, trafficking
36
mitochondria
outer and inner membrane and matrix; makes ATP, signaling, cell differentiation and cell death
37
lysossomes
contain digestive enzymes that degrade organelles and biomolecules
38
peroxisomes
small vesicular compartments that contain enzymes used in oxidation reactions
39
what are the 3 topological categories of the cell?
nucleus and cytosol; organelles (ER, golgi, endosomes, lysosomes); mitochondria
40
gated transport
b/w nucleus and cytosol through nuclear pore complexes (active transport and free diffusion)
41
transmembrane transport
membrane protein translocators directly transport specific proteins from cytosol across an organelle membrane
42
vesicular transport
membrane-enclosed transport intermediates move proteins b/w various compartments via vesicle
43
what guides protein transfer/transport to various compartments?
sorting signals
44
make up of a sorting signal
stretch of aas, typically 15-60 residues long; may be localized on N or C terminus or w/i protein sequence.
45
signal patch
formed by multiple scattered sequences in protein
46
signal peptidase
may remove signal after protein reaches final destination
47
which is more important in a signal sequence; the physical properties or the actual sequence?
the physical properties (charge, hydrophobicity, etc. )
48
what are signal sequences recognized by?
complementary receptors
49
nuclear transport
gated, bidirectional, and selective
50
what proteins are needed in the nucleus for nuclear transport and where do they come from/where are they synthesized?
histones, DNA and RNA polymerases, topoisomerases, gene regulatory proteins - imported from cytoplasm - also where they are synthesized except- tRNA and mRNA are synthesized in the nucleus and exported to the cytosol
51
Nuclear Pore Complexes (NPCs)
composed of 30 different proteins/nucleoporins. arranged in octagonal symmetry w/ one or more aqueous pores.
52
What direction is transport in NPCs?
both directions
53
What kind of transport in NPCs?
passive diffusion of small molecules and facilitated transport
54
How is transport facilitated in NPCs?
by binding of particles to fibrils extending from NPC
55
Nuclear Localization Signals (NLS)
sorting signals that direct molecules to nucleus; short sequences rich in positively charged aas lysine and arginine
56
where are NLS located?
many different sites on protein - from loops or patches on surface
57
what is the result of NLS?
selective import of proteins into nucleus
58
what recognizes NLS?
nuclear import receptors (NIRs)
59
Nuclear Import Receptors (NIRs)
soluble cytosolic proteins that bind to NLS on protein and to NPC proteins present on fibrils that extend into cytoplasm
60
make up of NPC proteins
they have phenylalanine glycine (FG) repeats; they serve as binding sites for import receptors
61
How do receptors + cargo traverse the NPC?
by binding, dissociating, and re-binding to adjacent FG repeats
62
What does nuclear export rely on?
nuclear export signals (NES) on molecules that need to go out of nucleus ; need complementary nuclear export receptors (NER)
63
role of NER in nuclear export
NER bind to cargo present in nucleus and NPC proteins; binding, dissociation and re-binding facilitates transport.
64
What drives nuclear transport?
gradient of Ran conformational states drive nuclear transport in appropriate direction import receptor and cargo enter nucleus by interacting w/ FG repeats on NPC proteins
65
Ran-GTP
binds to complex of import receptor and cargo; binding causes release of cargo; Ran-GTP + import receptor leave nucleus
66
what happens to Ran-GTP in cytoplasm
Ran-GTP is hydrolyzed by Ran-GAP; receptor is released from Ran-GDP and is ready for another cycle
67
Shuttling proteins
some proteins contain both NLS and NES; these proteins shuttle back and forth b/w nucleus and cytosol
68
what is steady state localization dependent upon?
relative rate of transport
69
if rate of import is greater than export . . .
it is considered nuclear and vice versa

Molecular Bio - Exam I (9 decks)

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