Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Y1 Cellular Biochemistry and Biology > L16: Moving Into The Nucleus > Flashcards

L16: Moving Into The Nucleus Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is the defining feature of a eukaryotic cell?

A

The membrane-bound nucleus.

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

What is the role of lysosomes in the cell?

A

They enable protein turnover through a low pH environment for protein unfolding and degradation.

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

Why is compartmentalisation important in eukaryotic cells?

A

It allows distinct environments for specialised functions, protects the local environment, and regulates interactions and cellular processes.

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

Name three mechanisms of molecular exchange between cellular compartments.

A

Gated transport, transmembrane transport, and vesicular transport.

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

What is the function of the nuclear pore complex (NPC)?

A

It enables the gated transport of proteins and molecules between the cytoplasm and the nucleus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are FG-Nups, and what is their role in the NPC?

A

FG-Nups are intrinsically disordered proteins with phenylalanine-glycine repeats that form a hydrogel, acting as a selective barrier within the NPC.

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

What happens in the genetic disease progeria regarding Lamin A processing?

A

Mutations prevent the final cleavage of prelamin A, causing defective nuclear architecture and DNA damage.

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

How does mislocalisation of proteins lead to disease?

A

For example, mutations in ATP7B, a copper metabolism protein, can lead to toxic copper buildup, causing liver and neurological damage.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the structural organisation of the nuclear envelope?

A

It consists of an inner and outer phospholipid bilayer, supported by the nuclear lamina.

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

Describe the nuclear lamina and its function.

A

It is a network of filaments made of Lamin proteins (A, B, and C) that provide structural support to the nuclear envelope and aid in DNA replication and regulation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the significance of the nuclear localisation sequence (NLS)?

A

It is an amino acid sequence required for the translocation of transcription factors and other proteins into the nucleus.

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

What is unique about the nucleus in eukaryotic cells?

A

It separates gene expression (in the nucleus) from mRNA translation (in the cytoplasm), allowing precise regulation.

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

How does vesicular transport contribute to cellular processes?

A

It enables protein and molecule transport via membrane fusion, such as in secretion and endocytosis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the three main types of nucleoporins (Nups) in the nuclear pore complex?

A

Core scaffolding Nups (outer, inner, and transmembrane), FG-Nups, and linker Nups.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is the hydrogel barrier in the NPC formed?

A

By weak interactions between phenylalanine residues in FG-Nups, creating a selective barrier for molecular transport.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the two types of chromatin seen in the nucleus, and what do they signify?

A

Heterochromatin (dark, silenced genes) and euchromatin (light, active genes).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the nuclear envelope, and how is it related to the endoplasmic reticulum?

A

The nuclear envelope is a double phospholipid bilayer continuous with the endoplasmic reticulum.

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

What is the primary function of the nucleolus?

A

It is essential for ribosome biogenesis.

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

What happens to the nuclear pore complex during the cell cycle?

A

It is dismantled and rebuilt with each cell cycle as the nuclear envelope breaks down and reforms.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the approximate size and transport capacity of the nuclear pore complex?

A

It has a diameter of 35 nanometres and can transport up to 16 proteins per second.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How does the mutation in the nuclear localisation sequence (NLS) affect Swyer Syndrome?

A

It prevents the transcription factor SRY from entering the nucleus, disrupting male sex development.

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

Why is oxidative stress contained within mitochondria?

A

To prevent reactive oxygen species (ROS) from damaging other cellular components.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the significance of laminin A processing?

A

Proper processing ensures nuclear envelope integrity and prevents diseases like progeria.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How do neurons exemplify the importance of compartmentalisation?

A

Gene expression occurs in the nucleus, but proteins must be transported to synapses for their function.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the role of motor proteins in intracellular transport?

A

They move vesicles along the cytoskeleton to specific cellular destinations.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Why is the production of reactive oxygen species (ROS) tightly regulated?

A

Excess ROS can cause cellular damage if not metabolised into less toxic compounds.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the role of signal peptides in protein secretion?

A

They direct proteins to the endoplasmic reticulum for secretion or membrane integration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What structural feature of the NPC facilitates its symmetric design?

A

The eightfold symmetry of its core structure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What does the ‘phenylalanine-glycine (FG)’ motif in FG-Nups enable?

A

The formation of hydrogels that selectively filter nuclear transport.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How do vesicles contribute to endocytosis?

A

By allowing the uptake of extracellular molecules into the cell through membrane fusion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What cellular problem arises from the mislocalisation of AVP2?

A

It leads to dehydration due to impaired water regulation in cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is the importance of compartmentalisation in eukaryotic cells?

A

It enables control of interactions, regulation of local environments, specialisation of cellular functions, and protection from toxic metabolites.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

How does the low pH of lysosomes benefit cellular processes?

A

It enables protein unfolding and degradation while preventing damage to other parts of the cell.

34
Q

What are the three main types of transport mechanisms across cellular compartments?

A

Gated transport (e.g., nuclear-cytoplasmic exchange), transmembrane transport (e.g., protein folding through membranes), and vesicular transport (e.g., endocytosis and exocytosis).

35
Q

What happens when ATP7B, a protein responsible for copper metabolism, is mislocalised?

A

It causes copper buildup, leading to liver failure and neurological problems.

36
Q

Why is the NPC referred to as a ‘molecular sieve’?

A

It allows passive diffusion of small molecules while controlling the active, gated transport of larger proteins.

37
Q

What is the role of Lamin proteins in the nuclear lamina?

A

They provide structural support to the nucleus, assist in DNA replication, and regulate gene expression.

38
Q

What is the function of phenylalanine in FG-Nups within the NPC?

A

Its aromatic properties create weak interactions that form the hydrogel barrier for selective transport.

39
Q

How does the uncoupling of gene expression and mRNA translation benefit eukaryotic cells?

A

It allows precise regulation and coordination of these processes.

40
Q

Why is the processing of prelamin A important for nuclear structure?

A

Proper processing ensures nuclear envelope stability and prevents diseases like progeria, where defective processing disrupts nuclear architecture.

41
Q

How does vesicular transport maintain cellular communication?

A

By enabling the movement of molecules and proteins between cellular compartments or into and out of the cell.

42
Q

Describe the structural complexity of the nuclear pore complex (NPC).

A

The NPC is the largest protein complex in the cell, comprising over 500 proteins organised in an eightfold symmetric structure.

43
Q

What structural feature of FG-Nups makes them flexible and functional in the NPC?

A

Their intrinsically disordered nature with interspaced phenylalanine-glycine motifs.

44
Q

What is the consequence of mutating phenylalanine in FG-Nups to serine?

A

It disrupts the hydrogel barrier, making the nuclear pore overly porous.

45
Q

What are some diseases caused by mislocalisation of transcription factors?

A

Disorders like Swyer syndrome, where mutations prevent proper nuclear localisation and disrupt gene expression.

46
Q

Why does the nuclear pore complex need to be rebuilt during the cell cycle?

A

It is dismantled as the nuclear envelope breaks down during mitosis and must be reassembled afterward to resume nuclear transport.

47
Q

What enables rapid delivery of prelamin A to the nuclear envelope?

A

Farnesylation of the C-terminal motif, which aids in targeting and initial localisation before further processing.

48
Q

How do mutations in the nuclear localisation sequence (NLS) affect proteins?

A

They prevent proteins from entering the nucleus, impacting processes like gene regulation and contributing to diseases.

49
Q

Why is the nucleus considered the ‘command centre’ of the cell?

A

It houses genetic material, regulates gene expression, and coordinates cellular functions through communication with the cytoplasm.

50
Q

What is the function of the nuclear lamina’s Lamin-associated proteins?

A

They tether Lamins to the inner nuclear membrane and aid in nuclear structural stability and gene regulation.

51
Q

How do oxidative phosphorylation and ROS production in mitochondria exemplify compartmentalisation?

A

Reactive oxygen species (ROS) are confined and detoxified within mitochondria, preventing damage to other cellular regions.

52
Q

How does the NPC facilitate energy-dependent transport?

A

The NPC uses gradients (e.g., Ran-GTP/GDP) and interactions with specific transport receptors (importins/exportins) to drive energy-dependent transport.

53
Q

How does the FG hydrogel in the nuclear pore complex influence movement?

A

The FG hydrogel does not direct movement but allows random diffusion, guided by the Ran-GTP gradient to promote transport directionality.

54
Q

What is the role of phosphorylation adjacent to the NLS in SV40 Large T antigen?

A

Phosphorylation adjacent to the NLS increases recognition by importin alpha, enhancing nuclear import.

55
Q

What happens to importins after releasing their cargo in the nucleus?

A

Importins are recycled back to the cytoplasm to pick up new cargo, driven by the Ran-GTP/GDP gradient.

56
Q

Why is the nuclear pore complex important for messenger RNA (mRNA) export quality control?

A

The NPC ensures only properly spliced and processed mRNAs are exported, preventing defective mRNA from entering the cytoplasm.

57
Q

How can a single amino acid substitution mimic phosphorylation?

A

Replacing serine with aspartic acid mimics a phosphate group, allowing the protein to behave as if it were phosphorylated.

58
Q

What defines the direction of protein movement through the NPC?

A

The Ran-GTP gradient, with high Ran-GTP in the nucleus and high Ran-GDP in the cytoplasm, drives directionality.

59
Q

How do exportins work in nuclear export?

A

Exportins bind cargo and Ran-GTP in the nucleus, move through the NPC, and release cargo in the cytoplasm when Ran-GTP is hydrolysed to Ran-GDP.

60
Q

What is the function of the protein NFX1 in mRNA export?

A

NFX1 recognises the 3’ cap of mature mRNA and facilitates its localisation to the nuclear pore complex for export.

61
Q

How does a conformational change induced by phosphorylation regulate nuclear import?

A

Phosphorylation can expose or hide the NLS, altering recognition by importins and thus controlling nuclear import.

62
Q

What is the role of Gle1 and DDX19 in mRNA export?

A

These proteins create a cytoplasmic gradient that facilitates mRNA movement out of the nucleus without relying on Ran-GTP.

63
Q

How does phosphorylation regulate NFAT localisation?

A

Phosphorylation of NFAT retains it in the cytoplasm, while dephosphorylation by calcineurin allows nuclear import during T-cell activation.

64
Q

Why do importins alpha and beta work as a team?

A

Importin alpha binds the cargo’s NLS, and importin beta interacts with FG nucleoporins, enabling coordinated transport through the NPC.

65
Q

What is the role of RanGEF and where is it located?

A

RanGEF is a nucleus-localised protein that loads GTP onto Ran, maintaining high levels of Ran-GTP in the nucleus.

66
Q

What happens to Ran-GTP once it reaches the cytoplasm?

A

Ran-GTP is hydrolysed to Ran-GDP by RanGAP, maintaining the cytoplasmic Ran-GDP gradient.

67
Q

How is the NPC structured to enable selective transport?

A

The NPC contains FG nucleoporins forming a selective barrier, recognising transport receptors like importins and exportins.

68
Q

What determines the high concentration of Ran-GTP in the nucleus?

A

RanGEF, a protein tethered to chromatin in the nucleus, facilitates the conversion of Ran-GDP to Ran-GTP, maintaining high nuclear levels of Ran-GTP.

69
Q

How does the phosphorylation of proteins influence nuclear export?

A

Phosphorylation can alter the nuclear export sequence (NES), either enhancing or inhibiting the recognition by exportins.

70
Q

Why is the localisation of RanGAP crucial for maintaining the Ran-GTP gradient?

A

RanGAP is localised on the cytoplasmic filaments of the NPC, where it hydrolyses Ran-GTP to Ran-GDP, sustaining the cytoplasmic Ran-GDP levels.

71
Q

What happens during the export of proteins via exportins?

A

Exportins bind cargo and Ran-GTP in the nucleus, translocate them through the NPC, and release cargo in the cytoplasm after Ran-GTP hydrolysis.

72
Q

How does the NPC recognise mRNA for export?

A

The NPC uses export proteins like NXF1, which bind to processed mRNA at its 3’ cap to guide it to the pore for export.

73
Q

What is the role of the NPC in quality control of mRNA export?

A

The NPC ensures mRNA is fully processed, including capping, splicing, and 3’ end formation, before allowing export to the cytoplasm.

74
Q

What type of amino acid sequence is commonly found in Nuclear Export Sequences (NES)?

A

NES are typically rich in leucine residues, which are recognised by exportins for nuclear export.

75
Q

How does phosphorylation influence the viral protein SV40 Large T antigen?

A

Phosphorylation near its NLS enhances recognition by importin alpha, significantly increasing nuclear import efficiency.

76
Q

What is the relationship between Ran-GTP hydrolysis and nuclear export?

A

Hydrolysis of Ran-GTP to Ran-GDP in the cytoplasm releases exportins and cargo, completing the export cycle.

77
Q

How does calcineurin regulate NFAT nuclear import?

A

Calcineurin dephosphorylates NFAT in response to high calcium levels, exposing the NLS and enabling nuclear import.

78
Q

Why is RanGAP located on the cytoplasmic side of the NPC?

A

Its location ensures the hydrolysis of Ran-GTP to Ran-GDP occurs as transport components exit the nucleus, sustaining the gradient.

79
Q

What is the purpose of the basket-like structure at the NPC?

A

The basket helps position mature mRNAs for export by interacting with export factors like TPR and NXF1.

80
Q

How is the hydrogel-like environment of the NPC maintained?

A

FG nucleoporins create a selective hydrogel that allows transport proteins to dock while restricting passive diffusion of larger molecules.

81
Q

What is the role of Gle1 in mRNA export?

A

Gle1 works with DDX19 at the cytoplasmic filaments of the NPC to create a gradient that facilitates mRNA export without Ran-GTP.

82
Q

How do mutations in the NLS affect protein localisation?

A

Mutations in the NLS can prevent proteins from entering the nucleus, causing them to remain in the cytoplasm.

Y1 Cellular Biochemistry and Biology (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions