Chapter 12: Protein Sorting & Transport Flashcards
what are the components of the secretory pathway?
-RER
-SER
-Golgi
-lysosomes
what is the function of the RER
protein:
- folding
- modification
- processing
what is the function of the smooth ER
membrane & lipid synthesis
what is the function of the golgi
protein processing and sorting
the secretory pathway is connected by
vesicular transport
what experiments defines the secretory pathway?
labeling new proteins w/ radioactive amino acids
proteins synthesized from free ribosomes in the cytosol can be transported to
posttranslational import
- nucleus
- mitochondria
- chloroplasts
- peroxisomes
proteins synthesized from membrane-bound ribosomes can be transported to
cotranslational import
- Golgi
- endosomes
- plasma mem.
- lysosomes
- peroxisome membrane
- secretory vesicles
- nuclear mem.
protein sorting begins during
translation
which types of proteins retain their signal sequence?
cytosolic
proteins translated into _________ have their signal sequence cleaved
microsomes
signal sequences are removed by
proteolytic cleavage
what are the 2 mechanisms for targeting proteins to the ER
- cotranslational translocation
- posttranslational translocation
secreted proteins are AKA
lumenal proteins
are secreted proteins inserted into the ER membrane?
no they are released into the lumen of the ER
membrane proteins are…instead of…
inserted into the ER membrane instead of being released into the lumen
how are integral membrane proteins embedded into the ER mem.
by hydrophobic regions that span the phospholipid bilayer
the hydrophobic regions that embed integral membrane proteins are also known as
STS
stop-transfer-sequence
the STS are typically
α-helical
what are the 3 signal sequences
- ERSS
- STS
- ISS
the ERSS stands for
ER signal sequence
the STS stands for
stop transfer sequence
the ISS stands for
internal start sequence
list the characteristics of a type I protein
- ERSS @ N-terminus
- contains signal peptidase cleavage site
- STS
- N-terminus at ER lumen
- C-terminus at cytoplasm