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BIOL1090 > Lecture 23: Nucleus, Nuclear Import, Nucleolus > Flashcards

Lecture 23: Nucleus, Nuclear Import, Nucleolus Flashcards

1
Q

The nucleus function

A
  1. Storage, replication and repair of genetic material
  2. Expression of genetic materials: transcription of mRNA, tRNA and rRNA, and RNA splicing
  3. Ribosome sbiosynthesis
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2
Q

Storage of DNA is aided by

A

Histones which supercoil the DNA into a chromatid

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3
Q

What causes DNA damage?

A

Replication errors, cellular metabolism, chemical exposure, ionization radiation, UV light exposure

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4
Q

During transcription…

A

MRNA, tRNA, rRNA and many more are transcripted. The control of transcription is the promoter region,

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5
Q

RNA splicing

A

Cutting out the introns (non coding regions of RNA) and fudge together the Exons (coding regions of RNA) through the method of spliceosomes

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6
Q

Transcription occurs in the…

A

Nucleus

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7
Q

Coding RNA vs Noncoding RNA

A

Coding - mRNA, types of RNAS that code for proteins
Noncoding - mRNA and tRNA, types of RNAs that DO NOT code for proteins

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8
Q

Noncoding RNA takes place in the…

A

Nucleolus, transcribed from DNA

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9
Q

The nucleus structure

A
  • nuclear envelope: nuclear membrane, nuclear pores, nuclear laminate
  • Nuclear content: chromatin, nucleoplasm, nucleolus
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10
Q

The nuclear envelope structure

A
  • 2 parallel phospholipid bilayers separated by 10-50 nm space
  • outer nuclear membrane (ONM): binds ribosomes and is continuous with RER
  • inner nuclear membrane (INM): has integral proteins and connects to the nuclear lamina
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11
Q

Nuclear envelope functions

A
  • separates nuclear content from cytoplasm
  • separates transcription and translation processes
  • selective barrier that allows limited overeat of molecules between nucleus and cytoplasm - through nuclear pores
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12
Q

The nuclear lamina functions

A
  • supports the nuclear envelope, structural support
  • attachment sites for chromatin
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13
Q

What is the nuclear lamina?

A
  • thin mesh work of IF proteins: Lamins
  • nuclear lamina is bound to inner membrane of the nuclear envelope by integral membrane proteins
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14
Q

Plant cells do have a nuclear lamina but…

A

Not made of lamin protein

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15
Q

Nuclear pores

A
  • gateways between cytoplasm and nucleus
  • 3000-4000 pores
  • found where inner and outer membrane fuses
  • contains complex protein structure that involve arrangement of different type of proteins
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16
Q

Nuclear pore complex (NPC)

A
  • located within nuclear pore
  • composed of nuceoporins (NUPs) - proteins
  • octagonal symmetry
  • projects into cytoplasm and nucleoplasm
  • supramolecular complex
  • passive diffusion for smaller molecules: rapid, 100 molecules/min/pore
  • regulated movement of larger molecules: slow 6 molecules/min/pore
17
Q

Nuclear import: Nuclear localization signal (NLS)

A

Targeting sequence from AA that regulates the movement of proteins into the nucleus. Several positively charge AA within the sequence

18
Q

How does the NLS target proteins to nucleus?

A
  1. Protein with NLS (cargo) interacts with Importin protein in cytoplasm
  2. Cargo complex interacts with FG-NUPs at NPC and enter nucleoplasm
  3. Rap-GTP (G-protein) interacts with importin; cargo dissociates and stays in nucleoplasm
  4. Ran-GTP/Importin complex edits nucleus through NPC
  5. GTP hydrolysed to GDP. Importin released in cytoplasm to find new cargo
    - entire process is controlled
19
Q

Nuclear import and export are important for the following proteins to function

A
  • structural proteins
  • DNA packaging proteins
  • proteins for DNA replication, repair and transcription
  • proteins for RNA processing and export
  • proteins for ribosomes synthesis and export
20
Q

Nucleolus

A
  • largest structure in nucleus
  • function: to make ribosomes
  • not membrane bound
  • consists of two major components: small ribosomal subunits which read RNA and large subunits which join AA to form polypeptide chain

BIOL1090 (11 decks)

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