Nucleus Flashcards
What does the nuclear pore complex regulate?
It regulates movement in and out of the nucleus.
It is selective
What is the nuclear envelope also known as?
Nuclear membrane
What is the inner and outer layer of the nuclear envelope?
lipid bilayer
inner membrane is a binding site for chromosomes
outer membrane is continuous w/ ER and studded w. ribosomes
Describe the shape of the NPC?
How many nucleoporins are there?
Octagonal Symmetry
20 NPC proteins
How many NPC are there per cell?
3k-4k NPC per cell
How many macromolecules does the npc transport per second?
500 macromolecules
There is bidirectional movement in the NPC
How large are proteins that cannot pass via passive diffusion?
60k Daltons
What happens to the nuclear membrane during mitosis?
It breaks down during prophase
The NPC and nuclear lamina dissemble and the envelop fragments
What can move in the nuclear pore?
Name 3 things
Building blocks for DNA+RNA synthesis
Molecules used to provide energy
Ribosomal proteins made in cytoplasm then go back into nucleus
What can move out of the nuclear pore?
Name one thing
Ribosomal subunits synthesized by the nucleolus
Why is the function of the NPC important?
Allows nucleus and cytoplasm to maintain distinct populations if proteins
What size of molecules can move through the nuclear membrane?
Small molecules <5 Kda rapidly move freely in/out
Larger move more slowly
>60Kda can barely pass freely
What is the Nuclear Location Signal?
Amino Acid sequence that tags a protein anywhere on its surface for entry into the nucleus
What is the Nuclear Export Signal?
Amino Acid sequence that tags a proteins for exit from the nucleus
The ER constitutes for how much of the cellular membrane in an animal cell?
50%
Name 3 functions of the ER
ER has key role in protein and cell synthesises
Contains Ca2+ stored which is important to signalling process
sit of synthesise of transmembrane proteins and lipids for cell organisation
Where do most proteins destined for secretion or the ER lumen golgi or lysosome are initially delivered where?
Initially delivered to the ER
What are the 2 types of endoplasmic reticuculm?
Smooth and Rough
What is transitional ER?
Areas of smooth ER where proteins and lipid move to the Golgi.
Describe co-translational protein import into the ER
Import of proteins into ER before its complete synthesise of the polypeptide chain
Describe the signal hypothesis
Translocator is closed until ribosome binds
N-terminal signal peptide intimates passage of protein through the translocator
Signal peptide cleaved by signal peptidase
Mature protein located in the ER Lumen
Ribosome released and translocator close so permeability is retained
When synthesised where is the protein imported for?
Imported from the cytosol
What is a polysome ?
a cluster of ribosomes held together by a strand of messenger RNA which each is translating.
What is protein glycosylation ?
Attaching carbohydrates to proteins
N-linked glycosylation to asparagine residues
Precursors oligosaccharide transferred from a dolichol lipid anchor catalysed by a transmembrane oligosaccharyl transferase enzyme
Trimming of the oligosaccharide occurs in the golgi
