Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

MCB2050 > Unit 2: Nucleus > Flashcards

Unit 2: Nucleus Flashcards

(57 cards)

Start Studying
1
Q

Eukaryote nucleus

A
  • membrane bund
  • nuclear envelope
  • nuclear pores
  • organized internal nuclear structure (highly regulated)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Characteristics of nucleus

A
  • irregular shape
  • one per cell
  • largest organelle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Two main functioins:

A
  • compartmentalization of cellular genome and activities (DNA replication, transcription, RNA processing)
  • coordination of cellular activities (metabolism, protein synthesis, reproduction)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Nuclear structure components

A
  • nuclear envelope (membrane, lamina, pores)

- nuclear content (chromatin, nucleoplasm, nuclear matrix, nucleolus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

3 functions of nuclear envelope

A
  • separates nuclear content from cytoplasm (genome and cytosol; transcription/translation)
  • selective barrier (regulates certain molecules, composition of nucleus and regulates gene expression)
  • binds nuclear lamina - structural framework
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Nuclear Lamina structure

A
  • thin meshwrok of long filament-like proteins

- bound to inner surface of nuclear envelope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Nuclear functions

A
  • support structure for nuclear envelope

- scaffold for chromatin and nuclear matrix (?) attachment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Progeria

A
  • premature aging
  • point mutation
  • deletion of 150 nucleotides
  • progerin = mutation of lamin A
  • structure of lamina compromised
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Nucleoplasm

A

highly organized fluid-filled interior of nucleus

>30 specialized regions (subdomains) w/ special functions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Choromosomes

A
  • during interphase organized into discrete subdomains within nucleus
  • location related to activity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Interchromosomal channels

A

regions between domains that serve as barriers for unwanted interactions (DNA-DNA and DNA-protein)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Transcriptioin factories

A

active genes (chromatin) from different subdomains extend into interchromosomal channels to form “transcription factories” - where TF are concentrated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Nuclear Speckles

A
  • subdomains where mRNA splicing factors are concentrated - i.e. mRNA processing
  • located in interchromosomal channels next to TF
  • numerus and highly dynamic depending on needs of cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Nucleolus

A
  • most obvious subdomain: irregular, dense; NOT membrane bound
  • 1-5 nucleoli depending on metabolic activity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Function of the nucleolus

A
  • ribosomal biogenesis
  • site of ribosomal rDNA transcription and rRNA processing
  • INITIAL stages of ribosomal subunit assembly (final assembly in cytosol)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Nuclear matrix

A
  • insoluble fibrillar-like protein network (mesh) distributed throughout the nucleoplasm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Role of the nuclear matrix

A
  • structural role (maintain overall shape)

- scaffold (organizing nuclear subdomains and anchoring protein factors)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Nuclear Pores

A
  • inner and outer membranes of nuclear envelope fuse = pore

- gateway between cytoplasm and nucleoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

NPC Structure

A
  • highly conserved in euk.
  • octagonal symmetry of overal structure
  • central scaffold (anchors complex to nuclear envelope)
  • forms an aqueous central channel
  • filament like proteins - FG nucleoporins (Nups) - inner surface of channel lined
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

FG domains

A
  • FG repeats (FG nucleoporins)
  • line inner sruface of channel
  • extended and flexible organization (highly disordered sec. structure)
  • extend into central channel
  • hydrophobic mesh - sieve like gel limits macromolec
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Cytoplasmic and Nuclear rings

A
  • cytoplasmic and nuclear side of NPC

- linked o central scaffold and cytoplasmic filament s or nuclear basket

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Cytoplasmic filaments

A
  • long protein filaments that extend into cytosol on cytosolic side
  • nucl. receptor cargo protein recognition and import
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Nuclear basket

Study These Flashcards
A
  • basket like structure located on nucl side of NPC

- involved in nucl receptor-cargo protein import and export

24
Q

Functions of NPC

Study These Flashcards
A

size exclusion

  • passive diffusion of small molecules (nucleotides etc)
  • regulate mvt (active) of large molecules (RNAs and proteins)
25
What is nucleoplasmin?
- nuclear protein
26
Where is nucleoplasmin synthesized
- cytoplasm, associates with cytoplasmic fillaments and translocates into nucleus
27
Nucleocytoplasmic transport (cytosol to nuclear) requires
- energy - specific protein receptors - unique targeting signals
28
Nuclear Localization Signal is used in
- imported proteins | - mediates targeting of protein from cytosol to nucleus
29
What is a NLS?
- nuclear localization signal - a.a. sequence necessary and sufficient for cytosol to nuclear targetting - recognized by nuclear receptor proteins
30
Necessary? NLS
- sequence cannot be mutated or else the modified protein will fail to target nucleus
31
Sufficient? NLS
- if sequence linked to non-nuclear passenger protein is capable of redirecting fusion protein to nucleus
32
Transport receptors are also known as
Karyopherins - importin - into nucleus - exportin - out of nucleus
33
What is the role of karyopherins?
- mobile proteins responsible for moving (ferrying) protein cargo across nuclear envelope
34
G proteins
- molecular switch in transport process | - i.e. Ran
35
How are G proteins activated?
- weak intrinsic GTPase activity - conformational change - GTP binding and hydrolysis regulates activity and conformation
36
Ran-GTP and Ran-GDP(active/inactive)
Ran GTP = active | RanGDP = inactive
37
Where is there a high concentration gradient of Ran GTP?
- high in nucleus - low in cytoplasm - gradient maintained high Ran-GTP in nucleus maintained by accessory proteins
38
How is Ran-GDP yielded?
- Ran-GDP is yielded in the cytoplasm (deactivated) - GTPase Activating Protein (GAP) - HYDROLYSIS of GTP of Ran-GTP to GDP = Ran-GDP - Ran-GDP then moves (translocates) to the nucleus
39
How is GTP produced?
- produced in the nucleus - Guanine nucleotide Exchange factor (GEF) - GDP is EXCHANGED by GEF - to product Ran-GTP - NOT a PHOSPHORYLATION event (the whole GDP is replaced)
40
What are the accessory proteins involved in maintaining the [Ran-GTP] gradient?
- RCC1 (promotes conversion of Ran-GDP to Ran-GTP (high [Ran-GTP] in nucleus] - Ran-GAP-1 cytosolic protein promotes hydrolysis of Ran-GTP to Ran-GDP (maintains low [Ran-GTP] in cytosol)
41
Ran-GTP gradient determines what?
directionality of nucleocytoplasmic transport
42
What is required for nucleoplasmic transport (energy)?
GTP hydrolysis
43
Step one of Nuclear import
- nascent NLS-containing cargo protein - recognized in cytosol by importin - importin a recognizes and binds basic residues of cargo NLS
44
Importin is a ____ proteins
heterodimeric | - containing a and b subunits (two distinct)
45
Step Two Nuclear Import
- cargo protein- importer complex moves through cytosol towards nucleus - cytoskeleton elements serves as highway for intracellular transport - surface of nucleus (outside) importin b subunit binds cytoplasmic filament at NPC - importin ability to bind to cytoskeleton
46
Step Three Nuclear Import
- cargo protein- importin complex translocaated through aqueous central channel of NPC - cargo-receptor complex interacts with FG-domains - interactions dissolve/untangle FG domain network and allow translocation through channel
47
Step Four Nuclear Import
- cargo-receptor complex associates with nuclear basket on inner NPC - cargo-receptor complex binds toRan-GTP via importin b - released from NPC and disassembled in nucleoplasm - success import NLS - containing cargo into the nucleus
48
Step Five Nuclear Import
- Ran-GTP bound importin b subunit moves back to cytosol due to [Ran-GTP] gradient - in cytosol, Ran-GTP hydrolyzed
49
What hydrolyzes Ran-GTP in cytosol?
RanGap1
50
What happens after RanGTP is hydrolyzed in cytosol?
- Ran-GDP released from importin b - importin b used for another round of protein import - Ran-GDP moves back to nucleus due to gradient
51
What converts Ran-GDP back to RanGTP?
- accessory protein RCC1 in the nucleus
52
What happens to importin a (and cargo proteins) in the nucleus (after import)?
- need to move back into the cytosol - nuclear export | - importin a binds exportin (karyopherin)
53
How are other cargo proteins brought back to the cytoplasm?
- Nuclear export signal (NES) - specific sequence of a.a. - LxxLxxL - leucine motif
54
How does the imporitina- exportin complex move into the nucleus?
- binds Ran-GTP - high RanGTP conc in nucleus - RanGTP promotes stable assembly and transports to cytosol
55
What happens to Ran-GTP in the cytosol after nuclear export?
- GTP on Ran-GTP is hydrolyzed by Ran-Gap1 | - Ran-GDP hydrolyzed releases exportin and releases importin a
56
What happens to importin a and exportin once they are brought back into the cytosol?
- importin a is used for another round of nuclear import Ran-GDP - exportin moves back into the nucleus for another round of export
57
How do some proteins move into the nucleus without a NLS?
- piggyback nuclear protein import - nascent protein lacking NLS binds NLS containing protein in cytosol - targeting and import of protein-protein complex mediated by importin receptors

MCB2050 (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions