Exam 3: protein organization Flashcards
(25 cards)
What are 3 functions of organelles in a cell?
- compartmentalization
- Organization
- Protection
What is included in the Endomembrane System? (7)
ER, Golgi, lysosomes, endosomes, peroxisomes, vesicles,
What is the function of lysosomes?
compartments in ES that digest fats, and unwanted material
What is the function of endosomes?
found in the ES, help with sorting of endocytosed molecules
What is the function of peroxisomes?
break down of toxic molecules
In regards to protein sorting, what determines where polypeptides end up?
determined by a sorting signal that is part of the protein sequence, also referred to as “tags”
Is there only ever one signal sequence in protein sorting?
No, sometimes more than one signal sequence is necessary
What happens of there is no signal sequence in protein sorting?
the protein will stay in the cytosol
What organelles have unique signals? (7)
mitochondria, nucleus, peroxisome, chloroplast, ER, Golgi, lysosome
What is a signal sequence and what is its function?
they are stretches of amino acids 4-60 Amino acids long that determine where a protein will end up
What happens to a Protein in an organelle that looses its signal sequence?
it will end up in the cytosol because it doesn’t have a signal
Where do proteins that are fully translated in the cytosol NOT end up in?
the plasma membrane
What is the last part of a polypeptide to leave the ribosome?
the C terminal end
What is the defining characteristic of an ER signal sequence?
containing primarily hydrophobic amino acids
Where does a protein with a unique nucleus, mitochondria, chloroplast, peroxisome tag go?
it is fully translated and folded in the cytosol, then moved to the appropriate organelle
Where does a protein with any tag for an endomembrane organelle OR any Plasma Membrane transmembrane proteins go?
the ribosome is sent to the ER mid-translation, and the protein is moved INTO the ER as translation occurs
What are the 3 ways proteins are transported into organelles?
- transport through nuclear pores
- transport across membranes
- transport by vesicles
What signal do proteins that will end up in the nucleus contain?
Nuclear Localization Signal (NLS)
What signal do proteins needing to come out of the nucleus contain?
contains a Nuclear Export Signal (NES)
What perceives the the Nuclear Localization Signal?
proteins that are cytosolic called nuclear import receptors
What does transport into mitochondria and chloroplasts require?
protein translocator proteins that are embedded in the membrane and help move cargo across dual membranes
What helps translocation?
chaperone proteins aid translocation by interacting with the protein inside the membrane and helping to pull it across the membrane
Where can proteins enter peroxisomes?
through both the cytosol and ER
Where do most proteins enter the peroxisome, and what signal aids in this?
most enter directly from the cytosol which is aided by a special peroxisome signal sequence
