Deck 8: Cytoplasmic Membrane Systems: Structure, Function, and Membrane Trafficking

Question 1

What is the name for a brief incubation of a tissue with radioactivity during which labeled amino acids are incorporated into protein?

A)chase
B)pulse
C)pulse-chase
D)labelation

Answer 1

B

Question 2

When cells are homogenized, the cytomembrane system is broken into fragments, which can fuse to form small membranous spheres called ________.

A)vacuoles
B)victuals
C)vesicles
D)nuclei
E)endosomes

Answer 2

C

Question 3

The correct order of passage of materials produced in a biosynthetic pathway is:

A)endoplasmic reticulum, Golgi complex, plasma membrane, secretory vesicle
B)endoplasmic reticulum, Golgi complex, secretory vesicle, plasma membrane
C)endoplasmic reticulum, lysosome, secretory vesicle, plasma membrane
D)endoplasmic reticulum, lysosome, Golgi complex, plasma membrane

Answer 3

B

Question 4

A cellular phenomenon called RNA interference (RNAi)is a process in which cells produce small RNAs called _________ bind to specific mRNAs and inhibit the translation of these mRNAs into proteins.

A)snRNAs
B)isRNAs
C)mRNAs
D)RNAsi
E)siRNAs

Question 5

What allows smooth and rough vesicles (microsomes)to be readily separated by density gradient centrifugation?

A)their size differences
B)their differences in lipid composition
C)their differences in color
D)their differences in density
E)their differences in water content

Question 6

When electron micrographs were first taken of the cell interior, what kinds of structures were seen?

A)membrane-bound vesicles of varying diameter, containing material of different electron density
B)long channels bounded by membranes and radiating through the cytoplasm
C)an interconnected network of canals
D)stacks of flattened, membrane-bound sacs called cisternae
E)all of these are correct

Question 7

The separation of organelles or vesicles derived from different organelles is called ______.

A)cell division
B)mitosis
C)meiosis
D)subcellular fractionation
E)cell ostentation

Question 8

Cells are infected with a virus carrying a temperature-sensitive mutant VSVG gene that encodes a protein that cannot leave the ER of infected cells grown at restrictive temperatures (40^oC). Thus, at higher temperatures:

A)VSVG protein heads immediately for the Golgi complex.
B)VSVG protein cannot leave the ER.
C)VSVG protein leaves the ER immediately.
D)all of the manufactured VSVG protein leaves the ER synchronously.
E)VSVG protein is degraded rapidly and never passes to the Golgi complex.

Question 9

Why are yeast cells often used to study eukaryotic gene mutations affecting secretion and other cytomembrane processes?

A)They have only a few genes.
B)They are small and single-celled and can be cultured easily.
C)They can be grown as haploid organisms so mutants are easily seen.
D)Deficiencies in yeast cells caused by mutants are easily detected.
E)All of these are correct.

Question 10

A scientist wishes to visualize movement of a protein in a living cell. Which procedure would work best?

A)pulse-chase
B)fusion of the green fluorescent protein gene to the protein that is to be tracked through the cell
C)fusion of the green fluorescent protein gene to the gene encoding the protein to be tracked through the cell
D)pulse-chase using fluorescent antibodies
E)all of these would work well

Question 11

A tissue has been briefly labeled with radiolabeled amino acids. It is then transferred to a medium containing unlabeled amino acids. This can be done several times with different tissue samples for varying periods of time. What is the entire procedure called?

A)chase
B)pulse
C)pulse-chase
D)labelard
E)statin

Question 12

Production and transport of materials in secretory vesicles which occurs continuously is known as:

A)regulated secretion
B)endogenous secretion
C)exogenous secretion
D)constitutive secretion

Question 13

What can be used to distinguish RER from SER?

A)the location of the ER
B)the proximity of the ER to the nucleus
C)the protein make-up of the ER
D)the shape of its component lipids

Question 14

Elevated temperatures at which temperature-sensitive mutants do not work are called ________ temperatures.

A)restrictive
B)permissive
C)temperature-sensitive
D)frame-shift
E)point

Question 15

When homogenized, the endomembrane system is broken up into vesicles, which are heterogeneous but similar in size. These vesicles can be purified and, after purification, often retain their biological activity. They are collectively referred to as _________.

A)endosomes
B)microsomes
C)ribosomes
D)minisomes
E)lysosomes

Question 16

What is the effect on a yeast cell of the presence of a mutant gene involved in vesicle fusion?

A)The ER shrinks.
B)The nucleus becomes swollen.
C)The Golgi complex expands greatly.
D)Cells accumulate expanded ER cisternae.
E)Cells amass an excess number of unfused vesicles.

Question 17

Cells are infected with a vesicular stomatitis virus (VSV)strain in which a viral gene (VSVG)is fused to the green fluorescent protein gene. When the chimeric protein is synthesized, what pathway does it follow from synthesis until it leaves the cell?

A)RER, Golgi complex, plasma membrane, viral envelopes
B)RER, Golgi complex, viral envelopes, plasma membrane
C)Golgi complex, RER, plasma membrane, viral envelopes
D)RER, Golgi complex, mitochondria, plasma membrane, viral envelopes
E)RER, mitochondria, Golgi complex, plasma membrane, viral envelopes

Question 18

Studies of cell physiology that occur in test tubes that do not contain whole cells are called:

A)in vivo systems
B)cell-free systems
C)test tube systems
D)onsite systems
E)cellonic systems

Question 19

A control cell that is synthesizing a GFP-labeled version of mannosidase II has fluorescence localized in the Golgi complexes of the cell. Normally, this enzyme is synthesized in the endoplasmic reticulum and moves via transport vesicles to the Golgi complex, where it takes up residence. If an experimental cell contains an siRNA that leads to the fluorescence being restricted to the endoplasmic reticulum, with what would the siRNA be likely to interfere?

A)an mRNA that codes for a protein involved in the transport of the enzyme from the ER to the Golgi complex
B)an rRNA that synthesizes the enzyme
C)the synthesis of mannosidase II from its mRNA
D)an mRNA that codes for a protein involved in the transport of the enzyme from the Golgi complex to the ER
E)an mRNA that codes for the enzyme

Question 20

In a pulse-chase procedure, if the chase is longer, which statement below correctly describes the location of the radioactively labeled proteins in the cell?

A)closer to the synthesis site
B)farther from the nucleus
C)farther from the synthesis site
D)closer to the nucleus
E)farther from the mitonchondria

Question 21

What are the two sites within a cell at which protein synthesisoccurs?

A)cytosolic surface of RER and cisternal surface of RER
B)cytosolic surface of RER and free ribosomes
C)cisternal surface of RER and free ribosomes
D)free ribosomes and cytosolic surface of SER
E)cytosolic surface of RER and cytosolic surface of SER

Question 22

Phospholipids are made by integral ER membrane enzymes whose active sites face the cytosol and they are inserted into the outer (cytoplasmic)leaflet of the ER membrane. How then do lipids destined for the luminal leaflet of the ER membrane get there?

A)They diffuse freely into the luminal leaflet.
B)There are enzymes called flippases that flip these lipids into the opposite leaflet later.
C)They are disassembled on the cytoplasmic side and reassembled on the luminal side.
D)They move to the cytoplasmic leaflet by osmosis.
E)There are enzymes called translocases that flip these lipids into the opposite leaflet later.

Question 23

What determines the function of a cell's smooth endoplasmic reticulum?

A)its lipid content
B)its polynucleotide content
C)its carbohydrate content
D)its protein content
E)its age

Question 24

What donates a sugar to the growing oligosaccharide chain of a glycoprotein?

A)a complex carbohydrate
B)a nucleotide peptide
C)a nucleotide sugar
D)a glycolipid

Question 25

What enzyme transfers a block of sugars to asparagine residues of a polypeptide as it enters the RER?

A)glycosyltransferase
B)acid phosphatase
C)oligosaccharyltransferase
D)cellulose
E)glycolase

Question 26

How do integral membrane proteins enter the lipid bilayer?

A)They insert into the membrane from the RER lumen after their synthesis is complete.
B)The aqueous translocon channel has a gate that continuously opens and closes, giving each nascent polypeptide segment a chance to partition itself into the lipid bilayer's hydrophobic core.
C)They insert into the membrane from the cytosol after their synthesis is complete.
D)The membrane is disrupted and proteins are incorporated during reassembly.

Question 27

What evidence suggests that the translocon, by itself, can properly orient transmembrane segments?

A)Purified components in cell-free systems show that the translocon, by itself, is capable of properly orienting transmembrane segments.
B)Reconstituted translocons properly oriented membrane proteins in a natural membrane.
C)Translocons orient proteins in red blood cells when exposed to them.
D)Translocons bind to proteins in vitro.
E)When translocons are missing, membrane proteins are not appropriately oriented.

Question 28

Blobel, Sabatini and Dobberstein proposed that the site of protein synthesis is determined by information contained in the N-terminal portion of the protein, the first part to emerge from the ribosome. What did they call their proposal?

A)the Chemiosmotic Hypothesis
B)the Posttranslational Hypothesis
C)the SRP Hypothesis
D)the Signal Hypothesis
E)the Co-translational Hypothesis

Question 29

How is the orientation of membrane proteins in the membrane thought to be accomplished?

A)After synthesis, an enzyme orients the protein properly.
B)During synthesis, the translocon inner lining orients the nascent polypeptide so the more positive end faces the cytosol.
C)During synthesis, the translocon inner lining orients the nascent polypeptide so the more negative end faces the cytosol.
D)During synthesis, the translocon inner lining orients the nascent polypeptide so the more positive end faces the mitochondrial intermembrane space.
E)After synthesis, the translocon inner lining orients the nascent polypeptide so the more positive end faces the cytosol.

Question 30

Which type of cells below is NOT known for its extensively developed SER?

A)skin cells
B)kidney tubule cells
C)skeletal muscle cells
D)steroid-producing endocrine cells
E)both skeletal muscle cells and kidney tubule cells

Question 31

Which of the following is a function associated with the smooth endoplasmic reticulum in at least some cells?

A)synthesis of steroid hormones
B)detoxification of many organic compounds, like barbiturates and ethanol
C)release of glucose into the bloodstream
D)sequestration of calcium Ca²⁺ ions within the cisternal space
E)all of these are correct

Question 32

Why is the ER ideal as a port of entry for secretory proteins?

A)The ER has a large surface area allowing for the attachment of many ribosomes.
B)The ER cisternae lumen favors unfolding and disassembly of proteins.
C)The RER can segregate secretory, lysosomal and cytoplasmic proteins from other newly made proteins, allowing their modification, and send them to their final destination.
D)The ER has a small surface area, allowing critical peptides to be concentrated into vesicles.

Question 33

When the SER detoxifies compounds, what is one known potential problem?

A)The detoxified compounds cause excessive weight gain.
B)The detoxified compounds cause excessive weight loss.
C)The detoxified compounds are carcinogeneic.
D)The detoxified compounds denature essential enzymes..
E)Detoxification leads to addiction.

Question 34

What appears to be the purpose of molecular chaperones like BiP?

A)They recognize and bind to unfolded or misfolded proteins and help them attain their native structure.
B)They recognize and bind to unfolded or misfolded DNAs and help them attain their native structure.
C)They recognize and bind to unfolded or misfolded RNAs and help them attain their native structure.
D)They recognize and bind unfolded or misfolded carbohydrates and help them attain their native shape.
E)They transport secretory proteins into secretory vesicles.

Question 35

When and where is the asymmetry of the phospholipid bilayers initially established?

A)in the Golgi complex during lipid and protein modification
B)in the ER during lipid and protein synthesis
C)in the secretory vesicles during lipid and protein modification
D)in the mitochondria by random insertion into the membranes
E)all of these are correct

Question 36

What is the arrangement of organelles in a secretory cell from the basal end to the apical end, an arrangement that reflects the flow of secretory products from synthesis to discharge?

A)nucleus and RER - SER - Golgi complex - secretory vesicles
B)Golgi complex - nucleus and RER - SER - secretory vesicles
C)nucleus and RER - Golgi complex - SER - secretory vesicles
D)SER - nucleus and RER - Golgi complex - secretory vesicles
E)secretory vesicles - nucleus and RER - SER - Golgi complex

Question 37

Which of the proteins below are NOT made on the membrane-bound ribosomes of the RER?

A)peripheral proteins of the inner surface of the plasma membrane
B)soluble lysosomal proteins
C)vacuolar enzymes
D)proteins of the extracellular matrix
E)all of these are correct

Question 38

RER has ribosomes, similarly to which structure that it is continuous with?

A)the inner membrane of the nuclear envelope
B)the outer membrane of the nuclear envelope
C)the outer mitochondrial membrane
D)the outer chloroplast membrane
E)the Golgi complex

Question 39

What cellular response is triggered by the regulated release of Ca²⁺ ions from the SER?

A)skeletal muscle cell contraction
B)secretory vesicle fusion with the plasma membrane
C)release of neurotransmitters from nerve cells
D)release of the contents of the acrosome from the head of a sperm

Question 40

What effect does the binding of the signal recognition particle (SRP)to the ribosome and the growing polypeptide chain have on protein synthesis?

A)Protein synthesis accelerates.
B)Protein synthesis ceases temporarily.
C)Protein synthesis ceases permanently.
D)Protein synthesis is terminated.

Question 41

What initially happens if misfolded proteins are generated in the ER at a faster rate than they can be exported to the cytoplasm?

A)They are degraded in the ER.
B)They are inserted into the ER membrane.
C)They are resynthesized in the ER.
D)They accumulate in the ER.
E)They accumulate in the Golgi complex.

Question 42

Which correctly describes the effects and treatment of CDG1b?

A)Mannose is unavailable for incorporation into oligosaccharides; oral supplements of mannose are the treatment.
B)Mannose is overproduced for incorporation into oligosaccharides; oral supplements of mannose are the treatment.
C)Mannose is unavailable for incorporation into oligosaccharides; a diet free of mannose is the treatment.
D)Mannose is overproduced for incorporation into oligosaccharides; a diet free of mannose is the treatment.
E)Fructose is unavailable for incorporation into oligosaccharides; oral supplements of fructose are the treatment.

Question 43

What happens to a newly synthesized glycoprotein after the binding of calnexin or calreticulin

A)When the glycoprotein's folding is correctly completed, the remaining glucose on its oligosaccharide chain is eventually reduced and the glycoprotein is released from the chaperone.
B)The oligosaccharide and amino acid chain are totally degraded.
C)Correct folding of the glycoprotein is prevented until the chaperone is removed.
D)When the glycoprotein's folding is correctly completed, the remaining glucose on its oligosaccharide chain is removed enzymatically and the glycoprotein is released from the chaperone.

Question 44

What is responsible for adding sugars to dolichol phosphate?

A)membrane-bound glycosyltransferases
B)membrane-bound oligosaccharyltransferase
C)membrane-bound gangliosidase
D)glycosylsynthetase
E)peptidyltransferase

Question 45

To what residue of a polypeptide are N-linked oligosaccharide chains attached as that poypeptide enters the RER lumen through the translocon?

A)arginine
B)asparagine
C)serine
D)threonine
E)ninhydrin

Question 46

Which of the following carbohydrates is NOT synthesized in the Golgi complex?

A)glycosaminoglycans in the animal extracellular matrix
B)plant cell wall polysaccharides like pectin and hemicellulose
C)the carbohydrates of glycolipids
D)the carbohydrates of glycoproteins
E)glycogen

Question 47

What happens if the UPR is unsuccessful in relieving the stressful conditions in the cell?

A)The cell grows.
B)The cell divides.
C)The cell-death pathway is triggered and the cell is destroyed.
D)The cell shrinks.
E)The cell's temperature is raised.

Question 48

What do studies suggest governs the "decision" to destroy a defective protein that has been unable to fold correctly and has been in the ER for an extended period of time?

A)a fast-acting ER enzyme that trims a mannose residue from an exposed end of the oligosaccharide of a protein
B)a slow-acting ER enzyme that trims a mannose residue from an exposed end of the oligosaccharide of a protein
C)a fast-acting cytoplasmic enzyme that trims a mannose residue from an exposed end of the oligosaccharide of a protein
D)a slow-acting nuclear enzyme that trims a mannose residue from an exposed end of the oligosaccharide of a protein
E)a slow-acting cytoplasmic enzyme that trims a mannose residue from an exposed end of the oligosaccharide of a protein

Question 49

Where are misfolded secretory proteins eventually destroyed?

A)in the RER
B)in the SER
C)in the Golgi complex
D)in the cytosol (cytoplasm)
E)in the nucleus

Question 50

The oligosaccharide block that is added to secretory proteins after they enter the ER lumen goes through a number of modifications after its attachment. What is the first modification that occurs?

A)addition of more sugars
B)addition of glucose
C)trimming of some sugars from the oligosaccharide block
D)chemical modification of the sugars on the oligosaccharide chain
E)both addition of more sugars and addition of glucose

Question 51

The accumulation of misfolded proteins in the ER is a potentially lethal situation and thus causes the triggering of what process?

A)the unfolded protein response (UPR)
B)the posttranscriptional response
C)the polysomal response
D)the proteasomal response
E)the intracellular protein response

Question 52

How does UGGT recognize incompletely folded or misfolded proteins that have been recently synthesized?

A)Such proteins display exposed hydrophilic residues that are absent from properly folded proteins.
B)Five histidine residues are exposed on the protein's surface when it is improperly folded.
C)Such proteins display exposed hydrophobic residues that are absent from properly folded proteins.
D)Six arginine residues are exposed on the protein's surface when it is improperly folded.
E)Such proteins display numerous carboxyl groups on their surfaces, which decreases their solubility.

Question 53

The ER reportedly contains sensors that monitor the concentration of unfolded or misfolded proteins in the lumen. One proposal suggests that the sensors are normally kept in an inactive state by ______, particularly ______.

A)molecular chaperones, ribosomes
B)proteasomes, BiP
C)molecular chaperones, BiP
D)enzymes, ER
E)molecular chaperones, Rubisco

Question 54

Which part of the Golgi complex distinguishes between proteins to be shipped back to the ER and those that are allowed to proceed to the next Golgi station?

A)the cis cisternae
B)the cis-Golgi network (CGN)
C)the medial cisternae
D)the trans cisternae
E)the trans-Golgi network (TGN)

Question 55

CDG1b results from a deficiency in what enzyme?

A)phosphomannose phosphatase
B)phosphotungstate isomerase
C)phosphomannose isomerase
D)phosphatase
E)phosphoenol pyruvate carboxylase

Question 56

What kind(s)of modifications are made in proteins as they move through the Golgi complex?

A)The protein's carbohydrates are modified by a series of stepwise enzymatic reactions.
B)Amino acids can be added to either end of the polypeptide chain.
C)Amino acids in the proteins may be chemically altered into nucleic acids.
D)Small segments of amino acids can be added into the center of an existing protein.
E)All of these are correct.

Question 57

Why does the cell use proteasomes to destroy misfolded proteins?

A)Destruction of misfolded proteins assures that aberrant proteins are not sent to other parts of the cell.
B)These proteins can be degraded into components that can be used to make polynucleotides.
C)These proteins are degraded into components that can be used to make polysaccharides.
D)These proteins are degraded into components that are used to make lipids.
E)Destruction of misfolded proteins prevents the dissolution of the plasma membrane.

Question 58

The movement of vesicular-tubular carriers (VTCs)farther away from the ER and toward the Golgi complex occurs along tracks composed of what material?

A)RNA
B)DNA
C)microtubules
D)microfilaments
E)intermediate filaments

Question 59

What is responsible for destroying misfolded proteins in the cytoplasm?

A)polysomes
B)polyribosomes
C)peroxisomes
D)proteasomes
E)spliceosome

Question 60

What does the conformation-sensing enzyme UGGT do if it binds to a misfolded or incompletely folded glycoprotein?

A)It degrades the oligosaccharide chain.
B)It adds a single mannose back to one of the glucose residues at the exposed end of the recently trimmed oligosaccharide.
C)It adds a single glucose back to one of the mannose residues at the exposed end of the recently trimmed oligosaccharide.
D)It degrades the protein.
E)It refolds the protein on its own.

Question 61

What sugar is usually removed from the N-linked core oligosaccharide chains on proteins in the Golgi complex as opposed to the glucose residues trimmed off in the ER?

A)glucose
B)galactose
C)mannose
D)sialic acid
E)fucose

Question 62

The coat of vesicles that transport materials around the cell interior ___________.

A)is composed of three distinct protein layers
B)is absent in vesicles moving in a retrograde direction
C)possesses adaptors that are able to select specific cargo molecules
D)possesses an outer layer of adaptors that serves primarily to bind the vesicle's cargo

Question 63

Which of the models below suggests that the Golgi cisternae are transient structures that form at the cis face of the stack by fusion of membranous carriers from the ER and ERGIC and that each cisterna travels through the Golgi complex from the cis to the trans end of the stack, changing in composition as it progresses?

A)the cisternal maturation model
B)the cargo carrying model
C)the vesicular transport model
D)the secretory transport model
E)the chemiosmotic model

Question 64

What determines the sequence of sugar addition to glycoproteins traveling through the Golgi complex?

A)Nothing - the sequence is random.
B)the spatial arrangement of specific glycosyltransferases that contact proteins as they pass through the Golgi complex
C)the concentration of sugars in the Golgi complex
D)the concentration of proteins in the Golgi complex
E)the sequence of nucleotides in the Golgi complex

Question 65

Sec23 and Sec24 bind together to form a "banana-shaped" dimer. What is the purpose of this dimer?

A)Because of its linear shape, it firms up the membrane.
B)Because of its curved shape, the dimer puts pressure on the membrane surface to help it further bend into a curved bud.
C)Because of its curved shape, the dimer puts pressure on the membrane surface to help it disintegrate.
D)The dimer stabilizes the Golgi complex membrane.
E)The dimer joins with other dimers to form a remarkably stable cage.

Question 66

What would happen if the enzyme that adds phosphate groups to the appropriate mannose residues on the carbohydrate chains of lysosomal enzymes were defective?

A)Lysosomal enzymes would be localized to lysosomes.
B)Lysosomal enzymes would be localized to peroxisomes.
C)Lysosomal enzymes would continue through the Golgi complex to secretory vesicles and would eventually be secreted.
D)Lysosomal enzymes would be degraded.
E)Lysosomal enzymes would be degraded.

Question 67

What enzymes are responsible for determining the sequence of sugars added to growing oligosaccharide chains of membrane proteins or secretory proteins as they travel through the Golgi complex?

A)glycosaminocosidases
B)peptidyltransferases
C)glycosyltransferases
D)amylases
E)Rubisco

Question 68

What is the primary adaptor protein of the COPII coat that interacts specifically with the ER export signals in the cytosolic tails of membrane proteins that are destined to traffic on to the Golgi complex?

A)ARF1
B)Sec23
C)Sec24
D)Sec31
E)Sec13

Question 69

Which GTP-binding protein plays a regulatory role by initiating vesicle formation and by regulating the assembly of the vesicle's COPII coat?

A)Sar1
B)Gar1
C)ARF1 (adenosylation ribose factor)
D)Ras
E)Src

Question 70

Most vesicles budding from the Golgi body have a fuzzy, electron-dense coat on their ______ surface. The coat appears to be made of _______.

A)luminal, protein
B)cytosolic, protein
C)luminal, lipid
D)cytosolic, carbohydrate
E)cytosolic, lipid

Question 71

Where in the Golgi complex does most protein sorting occur?

A)the medial cisternae
B)the TGN
C)the CGN
D)the cis network
E)the pre-Golgi network

Question 72

What happens to COPI-coated vesicles within the cell when the cell is treated with GTP analogues that can not be hydrolyzed?

A)They accumulate in the nucleus.
B)They accumulate in the cytoplasm.
C)They fuse into one giant vesicle in the cytoplasm.
D)They decrease substantially in number in the nucleus.
E)They decreasd substantially in number in the cytoplasm.

Question 73

What GTP-binding protein is associated with the formation of the COPI coat on COPI-coated vesicles?

A)Sar1
B)Arf Arf
C)Arf1 (adenosylation ribose factor)
D)Ras
E)Src

Question 74

What are the recognition signals for lysosomal enzymes that allow them to be localized correctly in lysosomes?

A)Lysosomal enzymes possess sulfated mannose residues on N-linked carbohydrate chains.
B)Lysosomal enzymes possess phosphorylated mannose residues on N-linked carbohydrate chains.
C)Lysosomal enzymes possess phosphorylated mannose residues on O-linked carbohydrate chains.
D)Lysosomal enzymes possess sulfated mannose residues on O-linked carbohydrate chains.
E)Lysosomal enzymes possess phosphorylated glucose residues on N-linked carbohydrate chains.

Question 75

Which components below are selected for transport by vesicles originating in the Golgi complex?

A)secretory proteins
B)lysosomal proteins
C)proteins required to dock the vesicle to an acceptor membrane
D)proteins required to target the vesicle to an acceptor membrane
E)all of these components

Question 76

How do protein coats select the cargo molecules to be carried by the vesicles they help to form?

A)They electromagnetically attract the correct cargo proteins.
B)The protein coats have a specific affinity for the cytosolic tails of integral membrane proteins that reside in the donor membrane.
C)The coats have a specific affinity for the luminal tails of integral membrane proteins that reside in the donor membrane.
D)The coat proteins directly attach to the cargo proteins in the lumen of the forming vesicles.
E)The coat proteins attach to the extracellular matrix.

Question 77

Which model of Golgi complex formation suggests that the cisternae of a Golgi stack remain in place as stable compartments held together by a protein scaffold, while the cargo is shuttled through the Golgi via vesicles that bud from one compartment and fuse with a neighboring one?

A)the cisternal maturation model
B)the cargo carrying model
C)the vesicular transport model
D)the secretory transport model
E)the chemiosmotic model

Question 78

Vesicles that move through the Golgi complex from a trans-donor to a cis-acceptor membrane are said to move in a(n)__________ direction.

A)astrograde
B)anterograde
C)retrograde
D)posterograde
E)vertigrade

Question 79

Which coated vesicles move materials in a retrograde direction from the ERGIC and Golgi stack backwards toward the ER?

A)COPII-coated vesicles
B)COPI-coated vesicles
C)clathrin-coated vesicles
D)cadmium-coated vesicles
E)both COPII-coated vesicles and COPI-coated vesicles

Question 80

What is usually the retrieval signal for escaped ER membrane proteins?

A)KKXX at the C-terminus of the protein
B)KDEL at the C-terminus of the protein
C)KDEL at the N-terminus of the protein
D)KKXX at the N-terminus of the protein
E)KXEL at the C-terminus of the protein