Unit 7 - Intracellular Transport Flashcards
1
Q
Protein Sorting
A
-the transfer of proteins into compartments where they are needed
2
Q
Signal Sequence
A
- stretch of amino acids that directs proteins to particular organelles
- usually removed after sorting
- if no sequence –> cytosol
3
Q
Nuclear Pore Complex``
A
- highly selective gate
- very high traffic through nuclear pore but flow is selective
- proteins imported have nuclear localization sequence
- small molecules freely pass through
- proteins pass through without unfolding
4
Q
Transport to Mitochondria & Chloroplasts
A
- proteins destined for mitochondria/chloroplasts made by free ribosomes in cytosol
- signal sequence at N terminus
- proteins must unfold to be imported, then refold before signal sequence is removed
- subsequent transport requires new signal sequence
5
Q
Transport to ER
A
- ER signal sequence & signal recognition particle (SRP) direct the free ribosome to the ER
- serves at entry point for proteins for ER, Golgi, lysosomes, endosomes, cell surface, & secretory proteins
- once in ER, proteins never re-enter cytosol
6
Q
Types of proteins transferred to ER include…
A
- Water soluble proteins translocated completely into ER lumen
- Transmembrane proteins translocated partially into ER lumen
7
Q
`Vesicular Transport
A
- Outwards from ER –> Golgi –> other organelles/plasma membrane
- Inward from plasma membrane –> lysosomes
8
Q
vesicle budding is driven by…
A
the formation of a protein coat
9
Q
Clathrin-Coated Vesicles
A
- receptor mediated endocytosis
- mediate transport from outward face to Golgi and inward from the plasma membrane
- clathrin forms ‘basket’ that gives vesicle shape
10
Q
Rab proteins
A
-family of monomeric GTPases, displayed on vesicle surface
11
Q
Tethering proteins
A
- displayed on cytosolic side of target membrane
- docking –> interaction between Rab & tethering protein
12
Q
SNAREs
A
-transmembrane proteins on vesicle (v-SNARE) and target membrane (t-SNARE) that consolidate docking and catalyze membrane fusion
13
Q
Glycosylation
A
- addition on sugar groups
- protects protein from degradation
- helps direct protein to proper organelle
- cell-cell recognition if on cell surface
14
Q
Unfolded Protein Response (UPR)
A
- if the protein produced exceeds capacity to keep up with folding, misfolded proteins accumulate
- signals lead to increased expression of chaperone proteins and expansion of the ER
- if cell can’t keep up (despite this) UPR will trigger cell death
15
Q
Golgi - Cis
A
-entry face/newly formed
