ER Flashcards
where are most proteins begin synthesis?
on ribisomes in the cytosol
where (and how) do new proteins go?
to the organelle where it functions, by sorting signals in amino acid sequence
what are the main steps of the secretory pathway?
1 - translates from mRNA in ribisomes to cytoplasm
2 - enters ER lumen
3 - goes from the Er to the golgi in a vesicle
4 - transits the golgi
5 - exits golgi in vesicle
6 - vesicle fuses cell membrane
7 - its outside!!!!!!
what are the types of mutants?
1 - fail ER import
2 - fail to produce ER vesicles
3 - vesicles dont fuse to golgi
4 - fail to leave golgi (golgi vesicles dont form)
5 - vesicles dont fuse with cell membrane
where were the main proteins in protein trafficking discovered?
in yeast
how is the ER organized?
into a netlike labyrinth of branching tubules and flattened sacs that extend throughout the cytosol
what is the difference between the rough and smooth ER?
rough has ribisomes bound to membrane surface, smooth doesn’t and is used in biosynthesis and metabolism of lipids
what is cotranslational import into the ER?
the first step in protein secretion
how is the ER signal sequence guided to the ER membrane?
signal reception particle (SRP) that binds to a signal sequence
SRP receptor in ER membrane
what happens when signal sequence binds?
SRP exposes a binding site for SRP receptor (transmembrane protein complex in the rough ER membrane)
what do membrane-bound ER ribisomes do?
make proteins that are co-translocated across the ER membrane
what is a translocator (or translocon)?
has a signal sequence gated aqueous channel that polypeptide chain passes throgh
where to translocated polypeptide chains fold and assemble?
in the rough ER lumen
what are disulfide bonds?
post-translational modifications (occur in the ER)
part of tertiary structure
what are oligosaccharides used for?
as tags to mark the state of protein folding (folded properly - remove last glucose, folded improperly - add a glucose)
