Intracellular membrane traffic of proteins and other molecules

Question 1

Through the process of Blank, the secretory
pathway delivers newly synthesized proteins,
carbohydrates, and lipids either to the plasma
membrane or the extracellular space.

Answer 1

exocytosis

Question 2

In contrast, cells remove plasma membrane
components through endocytosis and deliver
them to internal compartments called

Answer 2

endosomes

Question 2

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.

Answer 2

lumen

Question 2

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

Answer 2

transport vesicles

Question 2

Within a eukaryotic cell, transport vesicles
continually bud off from one membrane and fuse
with another, carrying membrane components and
soluble lumenal molecules called

Answer 2

cargo

Question 2

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.

Answer 2

False: endoplasmic reticulum (ER), Golgi apparatus, lysosomes

Question 3

The best-characterized are Blank, which mediate transport from the plasma membrane
and the trans-Golgi network

Answer 3

clathrin-coated vesicles

Question 3

which mediate transport between Golgi cisternae and between the ER and the Golgi apparatus, respectively.

Answer 3

COPI- and COPII-coated vesicles

Question 4

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.

Answer 4

False: inner layer, outer layer

Question 5

Local synthesis of specific clathrin coat
creates binding sites that trigger phosphoinositides
assembly and vesicle budding.

Answer 5

False: phosphoinositides, clathrin coat

Question 6

Also, monomeric Blank help regulate
various steps in vesicle transport, including
both vesicle budding and docking.

Answer 6

GTPases

Question 7

The coat-recruitment GTPases, including Blank
and the Blank proteins, regulate coat assembly
and disassembly.

Answer 7

Sar1, ARF

Question 8

A large family of Blank functions as
vesicle-targeting GTPases.

Answer 8

Rab proteins

Question 9

The assembly and disassembly of Rab proteins and their effectors in specialized membrane domains are dynamically controlled by Blank and Blank

Answer 9

GTP binding and hydrolysis

Question 10

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.

Answer 10

False: Active Rab proteins, Rab effectors

Question 11

Complementary Blank proteins on transport vesicles

Answer 11

v-SNARE

Question 12

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.

Answer 12

False: t-SNARE proteins, trans-SNARE complexes

Question 13

Correctly folded and assembled proteins in the ER are
packaged into Blank that pinch off from the ER membrane.

Answer 13

COPII-coated transport vesicles

Question 14

In animal cells, the clusters then move on Golgi apparatus to the microtubule track, where they fuse to form the cis Golgi network.

Answer 14

False: microtubule tracks, Golgi apparatus

Question 15

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

Answer 15

COPI-coated vesicles.

Question 16

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.

Answer 16

glycosyltransferase

Question 17

The mannoses on the Blank that are added to the proteins in the ER are often initially removed, and further sugars are added.

Answer 17

N-linked oligosaccharides

Question 18

is the site where O-linked glycosylation occurs and where glycosaminoglycan chains are added to core proteins to form proteoglycans.

Answer 18

the Golgi apparatus

Question 19

Sulfation of the sugars in proteoglycans and of selected
tyrosines on proteins also occurs in a late Blank

Answer 19

Golgi compartment

Question 20

The Golgi apparatus is a polarized organelle, consisting of one or more stacks of disc-shaped Blank.

Answer 20

cisternae

Question 21

Each stack is organized as a series of at least three
functionally distinct compartments, termed Blank, blank and blank

Answer 21

cis, medial, and trans cisternae.

Question 22

The cis and trans cisternae are each connected to special sorting stations, called the Blank and the Blank, respectively.

Answer 22

cis-Golgi network, trans-Golgi network

Question 23

are specialized for the intracellular digestion of macromolecules.

Answer 23

Lysosomes

Question 24

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.

Answer 24

False: mannose 6-phosphate (M6P), M6P receptor

Question 25

The Blank shuttle back and forth between the trans-Golgi network and the endosomes.

Answer 25

M6P receptors

Question 26

Cells ingest fluid, molecules, and particles by
Blank, in which localized regions of the
plasma membrane invaginate and pinch off to
form endocytic vesicles.

Answer 26

endocytosis

Question 27

This large-scale endocytic-exocytic cycle is
mediated largely by Blank and Blank, but clathrin-independent endocytic
pathways also contribute.

Answer 27

clathrin-coated pits and vesicles

Question 28

guides activated receptors into clathrin-coated pits, they and their ligands are efficiently internalized and delivered to early
endosomes.

Answer 28

Ubiquitylation

Question 29

True or False
late endosomes, rapidly mature into Early endosomes.

Answer 29

False: Early endosomes, late endosomes

Question 30

This process is mediated by Blank and
sequesters the receptors away from the cytosol, which
terminates their signaling activity.

Answer 30

ESCRT complexes

Question 31

migrate along microtubules toward the interior of the cell where they fuse with one another and with lysosomes to form endolysosomes, where
degradation occurs

Answer 31

Late endosomes

Question 32

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.

Answer 32

transcytosis

Question 33

True or False
Cells can secrete molecules by endocytosis in
either a constitutive or a regulated fashion.

Answer 33

False: exocytosis