Chapter 10 Flashcards by Mark Benning

The experiments of Palade and colleagues using incorporation of labeled amino acids, defined the pathway taken by secreted proteins as

a. rough ER, smooth ER, Golgi, secretory vesicles, cell exterior
b. rough ER, smooth ER, Golgi, endosomes, cell exterior
c. rough ER, Golgi, endosomes, cell exterior
d. rough ER, Golgi, secretory vesicles, cell exterior.

d. rough ER, Golgi, secretory vesicles, cell exterior

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A signal sequence on the polypeptide chain targets all but _________ proteins to the rough ER surface

a. secreted
b. plasma membrane
c. mitochondria
d. lysosomal

c. mitochondrial

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Most eukaryotic plasma membrane proteins are synthesized on

a. free ribosomes and inserted after translation into the plasma membrane
b. rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off
c. rough ER ribosomes and carried to the plasma membrane by vesicles that punch off from the rough ER
d. ribosomes associated with the plasma membrane and inserted into the membrane cotranslationally.

b. rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off

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When compared to ribosomes in free polyribosomes in the cytosol, rough ER-bound ribosomes have

a. different large and small subunits
b. the same large and small subunits
c. different large subunits but the same small subunits
d. different small subunits but the same large subunits

b. the same large and small subunits

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When compared to polypeptides synthesized in vitro on free ribosomes, the polypeptides synthesized from the same mRNA on microsomes-bound ribosomes are

a. the same size
b. larger
c. smaller
d. more hydrophobic

c. smaller

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The signal sequence that targets a polypeptide to the rough ER is rich in ______ amino acids

a. positively charged
b. negatively cahrged
c. hydrophilic
d. hydrophobic

d. hydrophobic

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As they emerge from the ribosome, signal sequences are recognized and bound by a

a. tRNA
b. signal peptidase
c. signal recognition particle
d. SRP receptor

c. signal recognition particle

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Which of the following is evidence for the signal hypothesis from targeting of a secretory protein in the rough ER?

a. The protein is larger when synthesized in vitro on free polysomes
b. The secretory protein ends up in the cytosol when a short sequence is deleted by genetic engineering
c. A normally cytosolic protein is secreted when a sequence is added to it by genetic engineering
d. All of the above

d. All of the above

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If you isolate the secretory protein from secretory vesicles and inject it into the cytosol, it will

a. be taken up into the rough ER and follow the secretory path
b. be taken up into secretory vesicles and secreted
c. be secreted through channels in the plasma membrane
d. remain in the cytosol until it is degraded

a. be taken up into the rough ER and follow the secretory path

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When the signal sequence emerges from the ribosome, it binds first to a

a. translocon
b. signal peptidase
c. signal recognition particle
d. SRP receptor

c. signal recognition particle

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Protein folding in the ER is assisted by a chaperone called

a. BiP
b. PiP
c. Hsp60
d. Hsp90

a. BiP

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Disulfide bonds within or between proteins form easily in which of the following?

a. Both cytosol and ER
b. Neither cytosol or ER
c. Cytosol but not ER
d. ER but not cytosol

d. ER but not cytosol

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GPI- anchored proteins are synthesized

a. on free ribosomes and attached to the GPI group on the outside of the ER
b. as transmembrane proteins, cleaved, and attacked to the GPI group on the inside surface of the ER
c. as transmembrance proteins, cleaved, and attached to the GPI group on the cytosolic surface of the ER
d. into the lumen of the ER and attached to the GPI group on the inside surface of the ER

c. as transmembrance proteins, cleaved, and attached to the GPI group on the cytosolic surface of the ER

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The unfolding response involves

a. general inhibition of protein synthesis
b. increased synthesis of chaperones
c. increased activity of proteosomes
d. All of the above

d. all of the above

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Most cellular lipids are synthesized in

a. fat droplets
b. mitochondria
c. the ER
d. Golgi apparatus

c. the ER

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Newly synthesized membrane lipids are found in both halves of membrane bilayers because they are

a. synthesized on both surfaces
b. removed and transported to these locations by lipid transport proteins
c. synthesized on one surface and flip spontaneously to the other surface
d. synthesized on one surface and flipped to the other surface by proteins called flippases

d. synthesized on one surface and flipped to the other surface by proteins called flippases

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The sequence Lys-Asp-Glu-Leu (KDEL) serves as an ER retention signal for proteins by binding to KDEL receptors that

a. hold the proteins in the rough ER
b. hold the proteins in the smooth ER
c. hold the proteins in both the smooth and rough ER and prevent their transport to the Golgi apparatus.
d. transport the proteins from the Golgi apparatus back to the ER

d. transport the proteins from the Golgi apparatus back to the ER

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Proteins attached to the outer layer of the plasma membrane bilayer are usually attached by a

a. farnesyl tail
b. GPI anchor
c. prenyl tail
d. geronyl tail

b. GPI anchor

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A signal sequence in ER does?

determines destination of proteins

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A signal recognition particle (SRP) in ER does?

recognizes a signal sequence of a protein and binds it to the ribosome

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A signal peptidase in ER does?

cleaves off the signal sequence

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a KDEL sequence does?

marks proteins which are suppose to remain in the ER lumen, if the proteins are exported, they are recognized and returned to the ER

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Protein disulfide isomerase does?

facilitates the disulfide bond formation

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What happens to a glycoprotein in the ER lumen if it fails to fold correctly?

the folding sensor will try to refold and if that fails, the misfolded protein is transfered to the cytosol where they are ubiquitinated.

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Vesicles initially enter the Golgi by fusing with a. the cis (convex) face. They exit from the trans (concave) face. b. the trans (concave) face. They exit from the cis (convex) face c. both faces. They exit from the sides of cisternac d. None of the above

a. the cis (convex) face. They exit from the trans (concave) face.

Which of the following proteins do not pass through the Golgi? a. Lysosomal enzymes b. Cell surface proteins c. Ribosomal proteins d. Proteins secreted by exocytosis

c. Ribosomal proteins

N-Linked oligosaccharides are added in the a. cis Golgi and modified in the medial Golgi b. ER and modified in the Golgi c. medial Golgi and modified in the trans Golgi d. cis Golgi and modified in the trans Golgi.

b. ER and modified in the Golgi

Lysosomal proteins are marked by adding a phosphate to a _____ group a. glucose b. serine c. GDP d. mannose

d. mannose

The plasma membrane of intestinal epithelial cells requires separate targeting of proteins to a. one continuous plasma membrane domain b. two plasma membrane domains: the apical and basolateral domains c. three plasma membrane domains: the apical, lateral, and basal domains d. four plasma membrane domains: one apical, two lateral, and a basal domain.

b. two plasma membrane domains: the apical and basolateral domains

Which of the following classes of lipids is synthesized in the Golgi apparatus? a. Phospholipids b. Glycolipids c. Cholesterol d. Ceramide

b. Glycolipids

Which of the following polysaccharides is synthesized in the Golgi apparatus? a. Pectin b. Cellulose c. Amylose d. Glycogen

a. Pectin

Which of the following does not bud directly from the trans Golgi network? a. Constitutive vesicles b. Regulated secretory vesicles c. Transport vesicles for lysosomal enzymes d. Lysosomes

d. Lysosomes

The enzyme that modified the mannose group on lysosomal proteins recognizes and binds to a(n) a. alpha helix b. signal sequence c. signal patch d. KDEL sequence

b. signal sequence

In plant cells, vesicles transport proteins from the Golgi to a. Lysosomes b. Vacuoles c. Chloroplasts d. Mitochondria

b. Vacuoles

Yeasts are advantageous for studying secretory pathways because a. they secret more proteins per cell than animal cells b. one can easily isolate Golgi c. they are amenable to genetic analysis d. they have only one simple pathway for secreted proteins

c. they are amenable to genetic analysis

Brain tissue is useful for studies of vesicular transport because a. many brain diseases involve mutant vesicular transport b. synaptic vesicles are abundant in the brain and can be isolated in large quantities for biochemical analysis c. the mechanisms of vesicle transport and fusion are unique to neurons d. All of the above

b. synaptic vesicles are abundant in the brain and can be isolated in large quantities for biochemical analysis

Vesicles that carry proteins from the rough ER to the Golgi bud off as _____ vesicles a. uncoated b. clathrim coated c. COPI coated d. COPII coated

d. COPII coated

Lysosomal proteins are initially incorporated into ________ vesicles a. uncoated b. clathrin coated c. COPI coated d. COPII coated

b. clathrin coated

ARF function on vesicles is regulated by a. phosphorylation of serine residues b. phosphorylation of mannose residues c. binding of GTP d. binding of ATP

d. binding of ATP

Clarthin coats are bound to specific receptors by a protein called a. adaptor protein b. ARF c. COPI d. NSF

a. adaptor protein

Clathrin molecules are composed of a. four protein molecules in the shape of a cross b. three protein chains in the shape of a triskelion c. six protein chains in the shape of a hexagon d. five protein chains in the shape of a pentagon

b. three protein chains in the shape of a triskelion

Rothman and colleagues proposed that the specificity of a vesicle fusing with its target membrane lies in the interaction of pairs of proteins called v=vesicles and t=target a. SNAPs b. SNAREs c. NSFs d. COPs

b. SNAREs

In vesicle fusion with a target membrane, ATP hydrolysis is required to a. bind t and v SNARES together b. bind SNAREs to Rabs c. bind NSF to SNAP d. serparate the bound t and v SNAREs

a. bind t and v SNARES together

Griscelli syndrome, a disease caused by mutations in the gene encoding Rab27a, is characterized by abnormal a. transport of melanosomes b. export of neruotransmitters c. export of vesicles in T lymphocytes d. Both a and c

d. Both a and c

The protein complexes where exocytosis occurs are called a. exocysts b. exocytocysts c. secretosites d. secretion sites

a. exocysts

What are the roles of SNAREs and SNAPs in the specific binding and fusion of these vessicles to a target compartment?

The v-SNARE carries the vesicle to the t-SNARE on the target. The SNAP disassembles the SNAREs, using the energy from the hydrolysis of ATP

What is Rab?

A family of small GTP binding proteins that play key roles in the vesicular transport

The pH inside lysosomes is about a. 7 b. 6 c. 5 d. 4

c. 5

Lysosomes digest a. proteins b. nucleic acid c. carbohydrates d. lipids e. All of the above

e. All of the above

The fate of mannose-6-phosphate receptors that bind and take up lysosomal hydrolasees into lysosomal transport vesicles is that they a. are transported to lysosomes and hold the lysosomal hydrolases there b. are transported to lysosomes and degraded there c. release the lysosomal hydrolases in the late endosomes and are recycled in vesicles back to the Golgi d. are degraded in late endosomes, allowing the relase of the lysosomal hydrolases

c. release the lysosomal hydrolases in the late endosomes and are recycled in vesicles back to the Golgi

Transport vesicles carrying acid hydrolases fuse with a. lysosomes b. endocytic vesicles c. early endosomes d. late endosomes

d. late endosomes

Gaucher disease is a failure of lysosomes of macrophages to hydrolaze a. proteins b. glucocerebrocide c. DNA d. polysaccharides

b. glucocerebrocide

The major function of the hydrophobic sequence at the amino terminals of proteins that are to be secreted from eukaryotic cells is to target those proteins to the RER

True

Polypeptides inside the ER are usually smaller than polypeptides synthesized from the same mRNA that have no entered the ER

True

The main method by which a cell gets rid of old, worn out organelles is exocytosis

False

The Golgi apparatus is the main site of intracellular drug detoxification

False

A newly synthesized polypeptide chain enters the ER through a protein chanel

True

Smooth ER is abundant in cells active in steroid hormone synthesis

True

The initial site of N-linked glycosylation is the Golgi apparatus

False

Phospholipids are synthesized in the cytosolic half of the ER membrane bilayer

True

Synaptic vesicles use a special mode of fusion that is completely different from regulated secretion in a typical secretory cell

False

Plasma membrane transmembrane proteins are synthesized on the RER

True

Vesicle formation is driven by the binding of clathrin or COP proteins

True

Gaucher's disease results from a mutation in an enzyme that does what?

In the gene that encodes a lysosomal enzyme required fro the breakdown of glycolipids

What is the cellular phenotype seen in patients with Gaucher's disease?

An increase of size and number of lysosomes within a cell leading to cellular malfunction

Type I Gaucher's disease can be treated by inhecting exogenous enzymes into the bloodstream. Why is this approach effective in replacing the mutant enzyme in the affect cells?

The exogenously administered enzymes might be taken up by endocytosis and transported to lysosomes

Hoe do hydrolytic enzymes get from teh Golgi apparatus to lysosomes?

through vesicle fusion

Describe the process of autophagy

The degradation of cytoplasmic proteins and organelles by their enclosures in cytoplasmic vesicles that fuse with lysosomes

What is phagocytosis?

the uptake of large aprticles, such as bacteria, by a cell

What is the function of the trans Golgi network?

To sort and package proteins in vesicles for transport

In polarized epitheial cells, proteins are specifically targeted to what two membrane domains?

Apical and basolateral domains

How do lysosomes become acidic?

A proton pump in the lysosomal membrane which actively transports protons into the lysosome from the cytosole

What is the deficiency that causes I-cell disease?

Gaucher disease

What pathway would you predict that lysosomal hydrolases would follow in patients with I-cell disease?

Because the mannose-6-phosphate never gets linked onto the protein, it never goes to the lysosome

What two families of small GTP bidning proteins are involved in formation of coated vesicles?

ARF1 and Sar1