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From Flashcardlet > Microanatomy: Nucleus: Structure and Function > Flashcards

Microanatomy: Nucleus: Structure and Function Flashcards

1
Q

Major events that take place in nucleus (in relation to central dogma) (2)

A
  • Transcription (DNA –> pre mRNA)

- Splicing (pre mRNA –> mature mRNA)

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1
Q

Dynamics of nuclear envelope

A

Breaks down during mitosis

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2
Q

Functions of nuclear envelope (2)

A
  • Forms a barrier to separate nuclear material from cytoplasm
  • Anchors nucleus within the cell
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3
Q

Nucleus

A

Major organelle that allows chromatin to be separated from the cytoplasm by the nuclear envelope

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4
Q

Nuclear Envelope (definition)

A

2 membrane system that encloses a perinuclear cisterna and consists of inner nuclear membrane and outer nuclear membranes that are continuous at the nuclear pore complexes

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5
Q

Components of nucleus (4)

A
  • Nuclear envelope
  • Nucleolus
  • Nucleoplasm (matrix and granules)
  • Chromatin
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6
Q

Nuclear Matrix (structure)

A

Protein latticework that fills the nucleus

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7
Q

Nucleolus is where (2)

A

synthesis of rRNAs and assembly of ribosomal subunits takes place

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9
Q

Nuclear matrix (function) (3)

A
  • Anchors chromosomes for DNA replication and transcription complexes
  • Reinforces nuclear envelope
  • Plays a role in structural organization of chromatin
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10
Q

Chromatin consists of (2)

A

DNA and protein

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11
Q

Major functions of nucleus (3)

A
  • Dynamic center of cell
  • Synthesis, processing, and storage of DNA and RNA
  • Synthesis of structural and regulatory proteins
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12
Q

Outer nuclear membrane (structure) (3)

A
  • Continuous in some locations with RER
  • Is studded with ribosomes
  • Surrounded by loosely arranged mesh of intermediate filaments
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13
Q

Outer nuclear membrane (function) (2)

A
  • Contains ribosomes, which synthesize proteins for outer and inner nuclear membranes
  • Major site of protein synthesis
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14
Q

Inner nuclear membrane (structure) (3)

A
  • Continuous with outer membrane at nuclear pore complexes
  • Faces nuclear contents
  • Is separated from nuclear material and supported on inner surface by nuclear lamina
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15
Q

Nuclear lamina is composed of (2)

A

-Intermediate filament-like proteins called lamins

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16
Q

Nuclear lamina (purpose/function) (2)

A
  • Help organize nuclear envelope and perinuclear chromatin

- Serves as attachment site for nuclear RNAs and chromosomes

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17
Q

Perinuclear space (structure) (3)

A
  • Space between outer and inner nuclear membranes
  • Continuous with lumen of RER
  • Proteins are found in this space
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18
Q

Nuclear Pore Complex (function) (9)

A
  • Sites of nucleo-cytoplasmic communication
    • Small molecules are transported bidirectionally by passive diffusion
    • Active transport
  • Attachment point for nucleoskeletal proteins
  • Transport macromolecules between nucleus and cytoplasm
    • Nuclear import and export
      • Import of polymerases, things that need to get into nucleus
      • Export of mRNAs after they’ve been spliced
    • Use Nuclear localization signals
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19
Q

Nucleolus (function) (2)

A
  • Site of rRNA synthesis and assembly of ribosomal subunits
20
Q

How ribosomal subunits are constructed (5)

A
  • rRNA synthesized in nucleolus
  • rProteins synthesized in cytoplasm and transported into nucleus
  • rRNA and rProtines are combined in nucleolus to form ribosomal subunit

Overview:

- Subunits are assembled in cytoplasm
- Subunits are transported out of nucleus
21
Q

3 regions of Nucleolus (5)

A
  • Nuclear organizing region
  • Fibrillar region (where rRNA precursors are transcribed)
  • Granular region (where ribosomal subunits are assembled)
22
Q

Nuclear Matrix (purpose) (7)

A
  • Aids in organizing nucleoplasm
  • Associated with:
    • DNA replication sites
    • rRNA and mRNA transcription and processing
    • steriod recepor-binding sites
    • Carcingoen-binding sites
    • Heat-shock proteins
    • DNA virus and viral proteins
23
Q

Nucleoplasm (structure) (3)

A
  • Does not include chromosomes or nucleolus
  • 2 components:
    • Nuclear matrix
    • Nuclear granules
23
Q

Nucleoplasm: Nuclear granules (purpose)

A
  • May be sites of mRNA processing
24
Q

Nucleoplasm: Nuclear Matrix (structure) (4)

A
  • Nuclear lamina
  • Residual ribonucleoprotein network
  • Fibular elements
  • May contain components that facilitate gene expression
26
Q

DNA and associated proteins in the nucleus are present as (2)

A
  • Heterochromatin

- Euchromatin

26
Q

Basic structural unit of chromatin

A

Nucleosome

27
Q

Degree of packaging of DNA is governed by (2)

A

Histones and non-histone proteins

28
Q

Many nucleosomes are linked by

A

A DNA linker to give a beads-on-a-string appearance

30
Q

Hierarchy of nucleosomes (3)

A

Nucleosomes –> chromatin fibers –> chromosomes (order of increasing compaction)

31
Q

Heterochromatin (4)

A
  • More coiled
  • Less active
  • In interphase
  • Scattered throughout nucleoplasm
32
Q

Cell proliferation is

A
  • a cyclic process involving alternating phases of DNA synthesis and cell division (mitosis)
32
Q

Euchromatin (3)

A
  • Less coiled
  • More active
  • In interphase
33
Q

Chromosomes are (3)

A
  • Thread-like, highly coiled structures in the nucleus which appear during cell division
  • Carry genetic information in the form of genes
  • Consist of chromatin (heterochromatin and euchromatin) that is folded into loops
34
Q

Mitosis is when

A
  • cell division occurs
35
Q

Phases of Cell Cycle (6)

A
  • Mitosis
  • Interphase
    • S-phase
    • G1
    • G2
    • G0
36
Q

S phase is when

A

DNA replication occurs

37
Q

G2 is the

A

Interval between S-phase and mitosis

38
Q

G1 phase is when (2)

A
  • Cell growth occurs

- It is the most variable phase

39
Q

G0 phase is

A

A state for cells that exit the cell cycle temporarily or permanently

40
Q

3 checkpoints regulating the cell cycle

A
  • Start/G1 checkpoint

- G2 checkpoint

41
Q

G2 checkpoint

A
  • Cell enters mitosis after all DNA replication is complete
42
Q

G1 checkpoint (3)

A

Checks to make sure:

- cell has grown big enough
- cell has all necessary resources
- environment is favorable
43
Q

Apoptosis is

A

programmed cell death

45
Q

Apoptosis is regulated by (5)

A
  • Regulatory genes which leads to activation of caspases.

- Caspases cause degradation of chromosomes, lamin, and nucleoskeleton

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