Trans Flashcards
How do proteins get to where they need to go?
- Gated transport
- transmembrane transport
- Vesicular transport
Gated transport
between the cytosol and nucleus Via nuclear pores
transmembrane transport
Via transmembrane proteins
Vesicular transport
via vesicle “ferries”
Ran in GTP bound form:
Binds importins to release NLS cargos
Order thefollowing molecules from the most membrane permeable to the least:
Large uncharged polar, hydrophobic, small uncharged polar, ions
- Hydrophobic
- small uncharged polar
- large uncharged polar
- ions
why a specialized form of transport is needed for entry into the secretory pathway for proper localization in certain organelles, display on the cell surface or secretion from the cell?
because of the lipid bilayer
Lumen
- The inside of an organelle
- spatially equivalent to the extracellularspace
- Contains Resident Enzymes and soluble protein cargos
When are Channels and transporters required?
for transport of some molecules across a membrane
Endoplasmic
reticulum
Site of lipid and protein synthesis and modification
Rough
ER
- pancreatic exocrine cell
- The outer (cytosolic) face of the rough endoplasmic reticulum is studded with ribosomes that are the sites of protein synthesis.
Smooth
ER
- testosterone-‐secreting human testis cell
- the smooth endoplasmic reticulum lacks ribosomes and functions in lipid manufacture and metabolism, the production of steroid hormones, and detoxification.
What does transport into the ER require?
an ER signal (sorting) sequence and the signal recognition particle (SRP)
The signal recognition particle(SRP)
- represses translational elongation on mRNAs encoding secreted proteins
- binds the ER signal sequence as it emerges and blocks EF binding
