The Nucleus Flashcards
(25 cards)
Prokaryotic Nucleus
Nucleoid
Free ribosomes
No endomembrane system
No mitochondria
Small
Eukaryotic Nucleus
Enclosed nucleus
Free ribosomes and rough ER
Vast interconnected endomembrane system
mitochondria/chloroplast
larger
Do Pro or eukaryotes have a membrane bound nucleus
- nuclear envelope
- nuclear pores
Eukaryotes
True or False the Nucleus is the smallest organelle
False it is the largest organelle
Nucleus Function
- Compartmentalization of the cellular genome and its activities
- site of DNA replication, transcription and RNA processing
- where translation components are synthesized
- coordination of cellular activities
- control of metabolism, protein synthesis, cell division
Outer membrane function of the nuclear envelope
binds ribosomes and is continuous with RER
Inner membrane function of the nuclear envelope
has a unique protein composition which connect to nuclear lamina
function of the nuclear envelope
separate nuclear contents from cytoplasm
separate genome from cytosol and transcription from translation
it is a selective barrier so it regulates passage of molecules between the nucleus and cytosol
regulates gene expression and composition of nucleus
what is the structure that is a thin meshwork of long filament like proteins
nuclear lamina
where is the nuclear lamina located
on the inner surface of the nuclear envelope (bound to it)
nuclear laminas function
scaffold for chromatin attachment
support structure of nuclear envelope
what are interchromosomal channels
regions between domains that serve as barriers to prevent unwanted DNA-DNA and or DNA-protein interactions
What are Transcription Factories
chromatin from different subdomains extending into interchromosomal channels
where transcription factors are concentrated
What are nuclear speckles
subdomains where mRNA splicing factors are concentrated
they can move quickly and grow/shrink depending on needs of the cell
where are nuclear speckles located
in interchromosomal channels next to transcription factories
What is the nucleolus structure
dense and granular in appearance
not membrane bound
size depends on metabolic activity of the cell
what does an increase in cellular activity have to do with protein synthesis, size and number
an increase in cellular activity = increase in protein synthesis = increase in size and number of nucleoli
What is the function of Ribosome Biogenesis
site of ribosomal DNA gene transcription and rRNA processing
Initial stage of rRNA and protein assembly (final assembly is in the cytosol)
What are nuclear pores
gateway between cytoplasm and nucleoplasm (3/4000 pores per nucleus)
Describe the structure of the Nuclear Pore Complex
It is the protein structure which fills the nuclear pore
extends into the cytoplasm and the nucleoplasm
FG nucleoporins (NUPs)
unusual amino acid composition - containing a large number of phenylalanine-glycine repeat sequences (FG domains)
FG domains structure
extended and flexible organization
extend into the central channel
form a hydrophobic mesh to limit diffusion of macromolecules larger than 40 kDa
where are NUPs
on the cytoplasmic and nuclear side of the nuclear pore complex
linked to the central scaffold and cytoplasmic filaments or basket
what are cytoplasmic fliaments
long protein filaments that extend into the cytosol (cytosolic side) and are involved in nuclear receptor cargo protein recognition and import of the nuclear basket
