Intracellular membrane traffic of proteins and other molecules Flashcards
Through the process of Blank, the secretory
pathway delivers newly synthesized proteins,
carbohydrates, and lipids either to the plasma
membrane or the extracellular space.
exocytosis
In contrast, cells remove plasma membrane
components through endocytosis and deliver
them to internal compartments called
endosomes
The interior space, called the Blank , of each
membrane-enclosed compartment along the secretory
and endocytic pathways, is equivalent to the lumen of
most other membrane-enclosed compartments and the
cell exterior.
lumen
These containers are formed from the donor
compartment and are either small, spherical vesicles,
larger irregular vesicles, or tubules.
● All these forms of containers are called
transport vesicles
Within a eukaryotic cell, transport vesicles
continually bud off from one membrane and fuse
with another, carrying membrane components and
soluble lumenal molecules called
cargo
True or False
The secretory pathway leads outward from the
Golgi apparatus toward the endoplasmic reticulum (ER)
and cell surface, with a side route leading to peroxisomes, while the endocytic pathway
leads inward from the plasma membrane.
False: endoplasmic reticulum (ER), Golgi apparatus, lysosomes
The best-characterized are Blank, which mediate transport from the plasma membrane
and the trans-Golgi network
clathrin-coated vesicles
which mediate transport between Golgi cisternae and between the ER and the Golgi apparatus, respectively.
COPI- and COPII-coated vesicles
True or False
Coats have a common two-layered structure: an outer layer formed of adaptor proteins links the inner layer (or cage) to the vesicle membrane and also traps specific cargo molecules for packaging into the vesicle.
False: inner layer, outer layer
Local synthesis of specific clathrin coat
creates binding sites that trigger phosphoinositides
assembly and vesicle budding.
False: phosphoinositides, clathrin coat
Also, monomeric Blank help regulate
various steps in vesicle transport, including
both vesicle budding and docking.
GTPases
The coat-recruitment GTPases, including Blank
and the Blank proteins, regulate coat assembly
and disassembly.
Sar1, ARF
A large family of Blank functions as
vesicle-targeting GTPases.
Rab proteins
The assembly and disassembly of Rab proteins and their effectors in specialized membrane domains are dynamically controlled by Blank and Blank
GTP binding and hydrolysis
Rab effectors recruit Active Rab proteins, such as motor proteins, which transport vesicles along actin filaments or microtubules, and filamentous tethering proteins, which help ensure that the vesicles deliver their contents only to the appropriate target membrane.
False: Active Rab proteins, Rab effectors
Complementary Blank proteins on transport vesicles
v-SNARE
True and False
trans-SNARE complexes on the target membrane form stable t-SNARE proteins, which force the two membranes into close apposition so that their lipid bilayer can fuse.
False: t-SNARE proteins, trans-SNARE complexes
Correctly folded and assembled proteins in the ER are
packaged into Blank that pinch off from the ER membrane.
COPII-coated transport vesicles
In animal cells, the clusters then move on Golgi apparatus to the microtubule track, where they fuse to form the cis Golgi network.
False: microtubule tracks, Golgi apparatus
Any resident ER proteins that escape from the ER are
returned there from the vesicular tubular clusters and
Golgi apparatus by retrograde transport in Blank
COPI-coated vesicles.
The Golgi apparatus, unlike the ER, contains many sugar nucleotides, which Blank enzymes use to glycosylate lipid and protein molecules as they pass through the Golgi apparatus.
glycosyltransferase
The mannoses on the Blank that are added to the proteins in the ER are often initially removed, and further sugars are added.
N-linked oligosaccharides
is the site where O-linked glycosylation occurs and where glycosaminoglycan chains are added to core proteins to form proteoglycans.
the Golgi apparatus
Sulfation of the sugars in proteoglycans and of selected
tyrosines on proteins also occurs in a late Blank
Golgi compartment
The Golgi apparatus is a polarized organelle, consisting of one or more stacks of disc-shaped Blank.
cisternae
Each stack is organized as a series of at least three
functionally distinct compartments, termed Blank, blank and blank
cis, medial, and trans cisternae.
The cis and trans cisternae are each connected to special sorting stations, called the Blank and the Blank, respectively.
cis-Golgi network, trans-Golgi network
are specialized for the intracellular digestion of macromolecules.
Lysosomes
These M6P receptor groups are recognized by an mannose 6-phosphate (M6P) protein in the trans-Golgi network that segregates the hydrolases and helps package them into budding transport vesicles that deliver their contents to endosomes.
False: mannose 6-phosphate (M6P), M6P receptor
The Blank shuttle back and forth between the trans-Golgi network and the endosomes.
M6P receptors
Cells ingest fluid, molecules, and particles by
Blank, in which localized regions of the
plasma membrane invaginate and pinch off to
form endocytic vesicles.
endocytosis
This large-scale endocytic-exocytic cycle is
mediated largely by Blank and Blank, but clathrin-independent endocytic
pathways also contribute.
clathrin-coated pits and vesicles
guides activated receptors into clathrin-coated pits, they and their ligands are efficiently internalized and delivered to early
endosomes.
Ubiquitylation
True or False
late endosomes, rapidly mature into Early endosomes.
False: Early endosomes, late endosomes
This process is mediated by Blank and
sequesters the receptors away from the cytosol, which
terminates their signaling activity.
ESCRT complexes
migrate along microtubules toward the interior of the cell where they fuse with one another and with lysosomes to form endolysosomes, where
degradation occurs
Late endosomes
In some cases, both receptor and ligand are transferred
to a different plasma membrane domain, causing the
ligand to be released at a different surface from where it originated, a process called Blank.
transcytosis
True or False
Cells can secrete molecules by endocytosis in
either a constitutive or a regulated fashion.
False: exocytosis
