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Cell Biology > Chapter 11: The Nucleus > Flashcards

Chapter 11: The Nucleus Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what NEVER transects the inner membrane of the nucleus?

A

the perinuclear space

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2
Q

list the 7 components of the nuclear envelope complex

A
  1. nucleoplasm
  2. perinuclear space
  3. nuclear lamina
  4. nuclear pore complex
  5. IM
  6. OM
  7. endoplasmic reticulum
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3
Q

describe the nucleolus

A

a dense concentrated bundle of DNA where ribosomes are made

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4
Q

list 5 functions of the nuclear envelope

A
  1. structure
  2. barrier
  3. OM contains ribosomes
  4. connection w/ lumen of ER
  5. IM carries nucleus specific proteins
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5
Q

define lamins

A

fibrous proteins that compose the nuclear lamina

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6
Q

what structures are included in the nuclear lamina

A
  • lamin filaments
  • nuclear pores
  • LBR
  • Emerin
  • chromatin

LBR: lamin B receptor

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7
Q

where is the nuclear lamina found?

A

under the IM

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8
Q

how many types of lamins are in mammalian cells? list them.

A

4 types

  1. A
  2. B1
  3. B2
  4. C
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9
Q

lamins can associate w/ the…

A

inner nuclear membrane and chromatin

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10
Q

what is the name for diseases caused by deficiencies of lamins?

A

laminopathies

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11
Q

nuclear pore complexes are channels through which…

A

molecules cross the nuclear membrane

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12
Q

transport across the channels of nuclear pores is said to be

A

selective

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13
Q

FG-NUPs are

A

protein complexes embedded in the channel of nuclear pores

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14
Q

FG- NUPs are mainly composed of

A

phenylalanine

glycine

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15
Q

nuclear pores are __________ in the nucleus memebrane?

A

embedded

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16
Q

what type of symmetry is expressed by nuclear pores?

A

8-spoke symmetry

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17
Q

give examples of what passes through nuclear pores.

A
  • RNAs
  • proteins
  • ribosomes
  • ions
  • transcription factors
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18
Q

How does the cell know which proteins to transport into the nucleus?

A

with nuclear localization signals (NLS)

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19
Q

what are NLSs?

A

specific amino acid sequences that target proteins to the nucleus

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20
Q

NLSs are typically rich in what amino acids?

A

basic amino acids
- lysine & arginine

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21
Q

signal sequences can be located anywhere in the protein but NLSs are specifically located _________ in the protein

A

intrinsically

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22
Q

why is the location of NLSs important?

A
  • they can not be removed
  • allow nucleus specific proteins to return to the nucleus after nuclear envelope dissociation and reassociation
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23
Q

what is the function of importins?

A

to carry proteins into the nucleus

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24
Q

importins recognize..

A

NLSs

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25
Q

importins work in conjunction w/

A

Ran

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26
Q

Ran is a

A

GTP binding protein

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27
Q

what are known as the off/on switches of nuclear transport?

A

G proteins

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28
Q

give 2 examples of G proteins

A
  • GTP
  • GDP
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29
Q

what is the function of Ran-GTP?

A

to hydrolyze Ran-GTP into Ran- GDP

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30
Q

what is the function of Ran-GEF?

A

to exchange the GDP for GTP resulting in Ran-GTP

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31
Q

where does Ran-GTP’s activity occur?

A

in the cytoplasm

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32
Q

where does Ran-GEF’s activity occur?

A

in the nucleus

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33
Q

define karyopherins

A

molecules that are responsible for the transport of compounds in and out of the cell

34
Q

name two types of karyopherins

A
  • importins
  • exportins
35
Q

what are the 2 methods of regulation of nuclear transport?

A
  1. NF-κB
  2. Pho4
36
Q

NF-κB is maintained inactive by

A

inhibitory proteins

37
Q

Pho4 is maintained inactive through

A

phosphorylation

38
Q

How is NF-κB activated?

A

by phosphorylation and proteolysis of IκB

- done according to extracellular signals

39
Q

How is Pho4 activated?

A

by dephosphorylation exposing NLS

40
Q

the nucleolus is the site of…

A

rRNA transcription and ribosomal assembly

41
Q

define heterochromatin

A

condensed chromatin

42
Q

is heterochromatin transcribed?

A

NO

43
Q

define euchromatin

A

chromatin in interphase

44
Q

is euchromatin transcriptionally active?

A

YES

45
Q

chromosomes in the nucleus are organized into

A

discrete functional domains

46
Q

in what ways can chromosomes be organized?

A
  • by polarity
  • into territories
47
Q

where are centromeres and telomers found when the chromosomes are organized by polarity?

A

at opposite ends of the nucleus

48
Q

where are transcribed genes locate in the chromosomal territories?

A

to the periphery

- outer limits ‘edge’

49
Q

where are gene rich chromosomes located?

A

at the center of the nucleus

50
Q

where are gene poor chromosomes located?

A

in the outer limits of the nucleus

51
Q

what does the outward extension of chromosomes suggest?

A

that transcribed genes loop out to facilitate transcription

52
Q

inactive chromosomes associate w/

A

the lamina or the nucleolus

53
Q

what is the function of cohesin

A

to form domain boundaries of transcriptionally active portions

54
Q

what are replication factories

A

discrete clustering of chromatin for efficient transcription

55
Q

what are transcription factories

A

clustered sites of newly synthesized RNA for efficient gene expression

56
Q

transcription factories are highly enriched in

A
  • new mRNAs
  • RNA polymerases
  • transcription factors
57
Q

what is the most prominent nuclear substructure?

A

the nucleolus

58
Q

the nucleolus is the site of

A
  • rRNA processing
  • ribosome assembly
59
Q

what are the 3 distinct regions of the nucleoli?

A
  1. fibrillar center
  2. dense fibrillar component
  3. granular component
60
Q

the fibrillar center is the location of genes encoding for

A

rRNA

61
Q

the fibrillar center is the location of

A

RNA transcription

62
Q

where is rRNA transcribed?

A

at the interface of the fibrillar compartment the dense fibrillar component

63
Q

the dense fibrillar component is the location of

A

pre-rRNA processing

64
Q

the granular component is the location of

A

pre-ribosome assembly

65
Q

what genes are called nucleolar organizing regions?

A

the genes that contain rRNA genes

66
Q

list the 4 nuclear bodies

A
  1. cajal bodies
  2. polycomb bodies
  3. PML bodies
  4. speckles
67
Q

cajal bodies are involved w/ the assembly of…

A
  • snRNPs
  • RNA complexes (telomerase)
68
Q

cajal bodies are the location of

A

snRNPs maturation

69
Q

cajal bodies are enriched w/

A
  • fibrillarin
  • coilin
70
Q

fibrillarin is responsible for

A

RNA methylation

71
Q

nuclear speckles are storage sites for

A

RNA splicing components

72
Q

nuclear speckles are active sites of

A

pre-mRNA splicing

73
Q

nuclear speckles receive _________ from cajal bodies

A

snRNPs

74
Q

PML bodies use transcription factors to

A

induce differentiation

75
Q

PML bodies are found fragmentated in cells from

A

acute promyelocytic leukemia

76
Q

polycomb bodies are sites of

A

gene silencing

77
Q

what method is used for gene repression in polycomb bodies

A

histone methylation

78
Q

what type of chromatin are polycomb bodies likely to associate with

A

heterochromatin

79
Q

after cell division how does the nucleolus reform?

A

by fusing individual nucleoli that have previously formed around chromosomes containing rRNA genes

80
Q

describe the steps in the dissociation of the nuclear envelope

A
  1. Cdk1 phosphorylates lamins creating lamin dimers
  2. nuclear membrane vesicles w/ lamin Bs form
81
Q

which lamins roam freely when the nuclear envelope dissociates?

A

lamins A &C

82
Q

describe the steps in the reformation of the nuclear envelope

A
  1. Cdk1 gets deactivated
  2. lamins are dephosphorylated
  3. vesicles bind to daughter chromosomes
  4. vesicles fuse around chromosomes
  5. individual vesicles fuse together
  6. nuclear lamina & pores reform

Cell Biology (12 decks)

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