CBU4

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104 Terms

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All vesicles use the same general mechanisms for

selection of cargo molecules,

budding,

and fusion with the appropriate target membranes

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cargo protein

Any protein that is carried within the vesicles of a cell's secretory system

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which complexes fill the space between a clathrin lattice and a vesicle membrane.

AP1 complexes

AP2 complexes

AP3 complexes

GGA

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The major function of lysosomes is to:

degrade extracellular materials taken up by the cell and intracellular components under certain conditions.

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In contrast to the secretory pathway, which allows proteins to be targeted to the cell surface, the _____ pathway is used to take up substances from the cell surface and move them to the interior of the cell.

endocycotic

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How are cargo proteins recruited to COPII vesicles?

through interaction of a diacidic sorting signal in the cargo protein's cytosolic domain with sec 24

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As part of the initial steps of anterograde transport, an uncoated COPII vesicle becomes tethered to the cis-Golgi membrane in a(n) _____-mediated process.

Rab

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Receptor-mediated endocytosis generally occurs via:

clathrin/AP2-coated pits and vesicles.

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Which vesicle transports proteins from the ER to the Golgi?

COPII

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The COPI coat is formed from large cytoplasmic complexes called:

coatomers

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coatomers

protein complex that coats membrane-bound transport vesicles

copi and copii

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In which process does a specific receptor on the cell surface bind tightly to an extracellular macromolecular ligand that it recognizes?

receptor mediated endocytosis

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The secretory pathway operates in two stages. The first stage takes place in:

Rough ER

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In pure form, these proteins can spontaneously assemble into a cage-like structure. Thus, it is thought that _____ form the scaffold for COPII vesicles.

sec 13 and sec 31

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Researchers initially identified five classes (A–E) of temperature sensitive yeast sec mutants. Double sec mutants were also analyzed—for example, yeast cells that contained mutations in both class B and class D functions. In what way were the double mutants particularly useful?

They revealed the order of the steps in the process.

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The KKXX signal that targets proteins to COPI vesicles must be located on:

the c terminus of the recruited protein

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Which organisms/organelles can fuse with lysosomes, releasing their contents into the lumen for degradation?

autophagosomes

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What is the FIRST step in the process of formation of a clathrin-coated vesicle?

AP2 complexes are recruited to the inner surface of the plasma membrane.

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Protein aggregation within the cis-Golgi network may play a role in sorting secreted proteins:

to storage vesicles in the regulated secretory pathway.

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What would happen if you incubated cultured human fibroblasts in a medium containing LDL particles at 4 °C?

The LDL particles would bind to their receptor but would not be internalized into the cell.

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How do proteins return to the ER from the Golgi?

through retrograde Golgi to ER transport

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The normal CFTR protein, which serves as a chloride channel in epithelial cell membranes, contains a di-acidic sorting signal that binds to the _____ subunit of _____ vesicle coats.

sec 24; COPII

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Which of these cell compartments has the LOWEST internal pH?

late endosome

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Proteins responsible for the eventual fusion of a vesicle with the target membrane are called:

v snares

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The plasma membrane of polarized epithelial cells is divided into two domains called:

apical and basolateral

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Which process is used to facilitate the mass transfer of lipids between cells?

lipoprotein carriers

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Which protein(s) regulate(s) docking of vesicles at the correct target membrane?

Rab proteins

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All vesicles whose coats contain AP1, AP2, AP3, or GGA complexes use _____ to initiate coat assembly on the donor membrane.

ARF

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The interior of an LDL lipoprotein is packed mainly with:

cholesterol esters

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This unifying principle governs all protein trafficking in the secretory and endocytic pathways.

Transport of membrane and soluble proteins is mediated by transport vesicles.

Cargo proteins are collected in buds arising from the membrane of one of the compartments involved in the transport.

Delivery of cargo proteins requires membrane fusion.

As transport vesicles bud from one membrane and fuse with the next, the same face of the membrane always faces the cytosol.

All of the answers are correct.

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Where does proteolytic maturation of proproteins such as proinsulin occur?

in vesicles carrying proteins from the trans-Golgi network to the cell surface, lysosomes, and late endosomes

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The LDL receptor makes a round trip in and out of the cell interior about every:

10-20 minutes

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Proteins bearing the signal sequence KDEL bind tightly to their receptor in the Golgi and are released from the receptor in the ER. How does this happen?

The binding affinity of the KDEL receptor is sensitive to pH, which is lower in the Golgi and higher in the ER.

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This is a flattened membrane compartment formed in the second stage of the secretory pathway when anterograde transport vesicles fuse with one another.

cis-Golgi cisterna

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Each clathrin triskelion contains:

three clathrin heavy chains and three clathrin light chains.

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Mature endosomes containing numerous vesicles in their interior are usually called:

multivesicular endosomes or bodies.

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Each of these transport processes utilizes ARF as its associated GTPase switch EXCEPT:

ER to cis-Golgi.

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Which transport method retrieves missorted ER-resident proteins from the cis-Golgi to correct sorting mistakes?

COPI-mediated retrograde transport

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Why are ER resident proteins such as BiP and disulfide isomerase often found in vesicles destined for the cis-Golgi?

Their sheer abundance causes them to be passively loaded into COPII vesicles.

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Which method combines receptor-mediated endocytosis and exocytosis to transport proteins to their final destination in the cell?

transcytosis

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Only some cells exhibit ____ secretion, while all cells exhibit ___ secretion.

regulated, constitutive

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In a classic experiment, researchers injected radioactive amino acids into the pancreas of hamsters. At different times after injection, the animals were sacrificed and the cellular locations of radioactive proteins were determined using autoradiography. Which of the following cell compartments would be radioactively labeled after the SHORTEST wait times after injection?

The ER

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As one of the initial steps in proteolytic processing of proproteins, the endopeptidase(s) _____ act(s) on constitutive proproteins to cleave the first two amino acids from the N-terminus.

furin

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Which part of the LDL-receptor protein interacts with apoB-100?

the N-terminal region containing seven cysteine-rich repeats

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The acidic pH of the _____ causes most receptor-ligand complexes to dissociate.

late endosome

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The MOST common mutation in the CFTR protein associated with cystic fibrosis prevents normal transport of CFTR to the plasma membrane by:

blocking the packaging of CFTR in COPII vesicles.

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Which vesicle fuses with the lysosome?

late endosome

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RabċGDP is tethered to the vesicle membrane via a(n):

isoprenoid anchor.

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The coat proteins associated with COPII vesicles include:

Sec 23/Sec24 and Sec 13/Sec31 complexes and Sec 16.

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What is the function of Rab GTPases?

They control the docking of vesicles on target membranes.

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Which protein pinches off vesicles and releases the specific cargo proteins it carries into the interior of the endosome? The electron micrograph labeled c shows a clump of buds with dark outlines. These are H I V buds attached to the plasma membrane, unable to leave the plasma membrane.">

ESCRT

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Which would you expect to see packaged in a COPII vesicle?

proteins destined for the cell surface

proteins destined for lysosomes

vesicle components such as v-SNAREs

All of the answers are correct.

all of the answers are correct

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_____ couple(s) a cycle of binding and hydrolysis to the formation and then dissociation of the COPII coat.

Sar1

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Place the cell structures into the correct order for the secretory protein synthesis and export from the cell

protein synthesis>protein modification > protein transport between organelles> protein modification and packaging for secretion >protein transport to plasma membrane>protein export from the cell

ribosome > rer> transport vesicle > golgi apparatus> transport vesicle > plasma membrane

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What are the differences between phagocytosis and autophagy?

Only one of the processes is a type of endocytosis ()

Phagocytosis is specific to a few cell types, while autophagy is a common cellular degradation method

autophagy degrades intracellular material, while phagocytosis degrades extracellular material

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