B: The nucleas (23) Flashcards
What are the functions of the nucleus
- Storage, replication, repair of genetic material
- Expression of genetic material
- Ribosome biosynthesis
Explain how the nucleus stores, replicates, and repairs genetic material
Contains all genetic material - compressed strand of DNA
Integrity of genome is preserved here
– Mechanisms repair any mutations or breakage that can happen
Explain how the nucleus aids in expression of genetic material
Transcription occurs: mRNA, tRNA, rRNA
– Promoter region is upstream: allows transcription factors to bind
rRNA splicing
What is the nuclear envelope made of
Nuclear membrane and ER is continuous base
Ribosomes found on surface of nuclear membrane
Explain how the nucleus biosynthesizes ribosomes
Nucleolus is membrane-less sub-organelle in the nucleus
Ribosomes are produced here
– Assembly of subunits - rRNA and protein
What subunits are ribosomes made in the nucleus? Where are they exported to
40S and 60S subunits are exported to cytoplasm where they are assembled as 80S ribosomes
What is the structure of the nuclear envelope
2 parallel phospholipid bilayers separated by 10-50 nm space
– Outer nuclear membrane
– Inner nuclear membrane
What is the importance of the nuclear envelope
Separation of interior and exterior nucleus separates processes of transcription and translation
Selective barrier allows limited movement of molecules between the nucleus and cytoplasm
What is the nuclear lamina?
A thin meshwork of filamentous proteins
- Nuclear lamina bound to inner membrane
What is the role of the nuclear lamina
Supports nuclear envelope
Attachment sites for chromatin
Do plants have a nuclear lamina?
Plants have nuclear lamina, but not made of lamin protein
The equivalent of lamin protein in plants is still being researched
What type of proteins is the nuclear lamina made of in animal cells
Lamins (intermediate filaments) - found in animal cells only
What is the nuclear pore?
Gateway between cytoplasm and nucleus
Where is the nuclear pore found, how large is it
Pores are found where inner and outer membrane fuses
- 3000 to 4000 pores
What is the shape and structure of the nuclear pore complex
Octagonal shape
Composed of nucleoporins (NUPs) - a large family of different proteins
What is the NPC
Nuclear pore complex
What can enter the nuclear pore, what can’t
Anything 40kDA or smaller can freely enter and exit the nucleus
Larger movement is regulated
How fast do small and large molecules enter the NPC
Small: About 1000 molecs/minute/pore
Large: 6 molecs/minute/pore
What is the NLS
Nuclear localization signal (NLS)
How do large molecules enter the NPC
Regulated movement of proteins into the nucleus require nuclear localization signal (NLS)
What is the NLS made of
NLS = several + charged AAs within protein sequence
What are the 3 steps of the NLS
- Recognition
- Transport
- Entry into nucleus
Explain the first step of the NLS: recognition
Recognition: Inside the cell, proteins containing an NLS are recognized by nuclear transport receptors. These receptors bind specifically to the NLS sequence.
Explain the second step of the NLS: transport
Transport: Once bound to the protein, the nuclear transport receptor guides the protein through the nuclear pore complexes, which are the gateways between the cytoplasm and the nucleus.
Why is Nucleocytoplasmic trafficking important
Import and outport critical for cell function:
Helps in transcription
DNA packaging
Proteins for DNA replication repair and transcription
Proteins for RNA processing (splicing) and export
Proteins for ribosomes synthesis and export
Explain the third step of the NLS: entry into the nucleus
Entry into the nucleus: The protein, along with the bound nuclear transport receptor, passes through the nuclear pore complex and enters the nucleus
What is Nucleocytoplasmic trafficking
The transportation of molecules to and from the nucleus, ensuring that the cell can carry out its functions effectively by regulating what enters and exits the nucleus.
What is the nucleolus
Largest structure within nucleus
Often multiple nucleolus within nucleus
