Unit 5 - Intracellular Compartments Flashcards
(31 cards)
Describe the origin of mitochondria.
- mitochondria originated as bacteria with an outer and plasma membrane
- was engulfed by the cell
- mitochondria becomes a double-membrane organelle
Describe the origin of endomebrane system.
Ribosomes caused the plasma membrane of entire cell to invaginate
What are the 3 ways that proteins are into organelles?
- Nuclear Pores (nucleus)
- Across membrane (mitochondria)
- Vesicles (ER)
What is a signal sequence?
- section of amino acids on protein
- indicates protein destination
- can be transferred between proteins
Describe nuclear pores.
- very selective basket-shaped gate on nuclear envelope (2 membranes)
- proteins do not unfold to pass
- large proteins require active transport
Describe nuclear active transport.
- nuclear import receptor binds to protein
- receport recognizes nuclear localization signal
- protein moves through basket/pore
- protein is delivered to nuclear and receptor breaks off
Describe mitochondrial import
- a signal sequence is recognized by import receptor on outer membrane
- protein moves into membrane and into protein transloactor on inner membrane
- as protein moves through, it unfolds
- when protein is fully in matrix, it fold back into shape
How many membranes do chloroplasts have?
3
Which organelle is the entry point of proteins in the endomembrane system?
ER
Describe translation for ER-bound proteins.
- ER signal sequence hooks onto growing polypeptide chain
- signal sequence is recognized by SRP on ER membrane
- particle hooks onto receptor, hooks onto translocation channel
- protein continues to translate into ER membrane
What are the two types of ER proteins?
Soluble and transmembrane
Describe solube proteins
A type of ER protein that has one signal sequence and fully translates into ER lumen, could eventually be secreted
Describe integral/transmembrane proteins
- Has multiple signal sequences
- has a stop transfer sequence where translation stops and a portion of the protein remains outside of the ER
Describe temporary vesicles.
- facilitates movement of material in and out of cells in the endomembrane
What is exocytosis?
when a vesicle moves outward toward plasma membrane to be secreted
What is endocytosis?
when a secicle moves inward from plasma membrane to cysotol of cell
Where do vesicles go outward from ER?
Golgi apparatus, plasma membrane or other organelles
Where do vesicles go when entering the endomembrane?
plasma membrane, endosomes, lysosomes
Describe vesicle budding.
- budding forms a vesicle for transport between ER and golgi, golgi and plasma membrane
Describe the budding process in clathrin-coated vesicles.
- receptors bind to target molecules on membrane
- adaptin traps receptor
- clathrin attatches to adaption and forms a the bud, removing entire structure from membrane
Describe vesicle docking.
- Rab and v-snares bind to vesicle
- Tethering protein binds to Rab and pulls vesicle
- V-snare binds to T-snare on membrane and twist to fuse with membrane
What post-translational processing to proteins occurs in the ER?
- disulfide bonds form
- glycosylation: sugars are added
- misfolded proteins are re-folded
Describe the ER’s role in fixing misfolded proteins.
- sensors for misfolded proteins are activated with phosphate
- increased chaperone proteins
- ER expands to allow more folding capacity
Describe the role of disulfide bonds formed in the ER
provides stabilility to proteins that will be secreted out of cell to a more hostile environemnt
