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Cell Biology Practice Test Q&As

What types of substances would move retrograde to the rough ER?

A: proteins with the amino acid sequence R-X-R
B: rough ER retention tags
C: amino acids from the lysosomes to be used in protein synthesis
D: proteins with a KDEL retrieval tag

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proteins with a KDEL retrieval tag

Which of the following statements best describes the difference between pinocytosis and receptor-mediated endocytosis?

ANSWER: The difference between pinocytosis and receptor-mediated endocytosis is that pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity.

True or False:Transmembrane proteins in the plasma membrane are synthesized on the rough ER.

A: TRUE
B: FALSE

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TRUE

Which statement about transmembrane proteins is true?

Which of the following statements about transmembrane proteins is true?
A: They cross the membrane only once.
B: The signal sequences are always cleaved off.
C: They usually have one or more α helices spanning the membrane bilayer.
D: They are always inserted with the amino terminus on the lumenal side and the carboxyl terminus in the cytosol.

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They usually have one or more α helices spanning the membrane bilayer.

The transmembrane portions are usually α helices of approximately 20‒25 amino acids. α helices are especially stable in the nonpolar environment of the lipid bilayer.

Ribosomes that are free in the cytosol and those that are bound to the ER membrane have

Free ribosomes in the cytosol and ribosomes bound to the er membrane have
A: different types of large and small subunits.
B: the same types of large and small subunits.
C: different types of large subunits but the same small subunits.
D: different types of small subunits but the same large subunits.

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different types of small subunits but the same large subunits.

Plasma membrane proteins of intestinal epithelial cells requires separate targeting to

A: one continuous plasma membrane domain.
B: two plasma membrane domains: the apical and basolateral.
C: three plasma membrane domains: the apical, lateral, and basal.
D: four plasma membrane domains: one apical, two lateral, and a basal.

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four plasma membrane domains: one apical, two lateral, and a basal.

Yeasts are advantageous for studying secretory pathways because

A: they secrete more proteins per cell than animal cells do.
B: Golgi apparatuses are easily isolated in yeasts.
C: they are amenable to genetic analysis.
D: they have only one simple pathway for secreted proteins.

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they are amenable to genetic analysis.

A signal sequence in the polypeptide chain targets all but _______ proteins to the rough ER surface.

A signal sequence in a polypeptide chain targets all but _______ proteins to the rough er surface.
A: secreted
B: plasma membrane
C: mitochondrial
D: lysosomal

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mitochondrial

Vesicles enter the Golgi apparatus by fusing with _______ and they exit _______.

Vesicles enter the golgi apparatus by fusing with and they exit from the
A: the cis (convex) face; the trans (concave) face
B: the trans (concave) face; the cis (convex) face
C: both the cis (convex) and the trans (concave) faces; the sides of cisternae
D: the sides of the cisternae; the cis (convex) face

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the cis (convex) face; the trans (concave) face

Question: Vesicles initially enter the Golgi apparatus 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 cisternae.
D: None of the above

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

Question: Which of the following is NOT processed in the Golgi apparatus?
A: integral membrane proteins of the plasma membrane
B: proteins that are secreted from the cell
C: enzymes required for DNA synthesis
D: proteins that will be used to break down macromolecules in the lysosome

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enzymes required for DNA synthesis

Question: What does the Golgi apparatus do?
A: Cell brain
B: Cell manufacturing center
C: Packaging and distribution
D: Energy storage

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Packaging and distribution

The Golgi apparatus is a membrane-bound structure with a single membrane. The Golgi apparatus is an organelle inside eukaryotic cells that packages proteins into membrane-bound vesicles that are important in packaging macromolecules for transport elsewhere in the cell. * Receives proteins from ER and modifies them
* Adds sugar
* Puts protein into vesicle
* Modifies, packages and sorts protein from the RER produces lysomes
* Packages and transports within the cell through vesicles; produce lysosomes
* Transported to cell surface membrane OR secreted out of cell

Question: What happens to proteins as they pass through the Golgi apparatus?
A: Proteins are unfolded and refolded into new conformations
B: Proteins are modified by having sugars attached or removed
C: Proteins are degraded into smaller polypeptide chains
D: Proteins are assembled into large multi-protein complexes

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Proteins are modified by having sugars attached or removed

Question: Some proteins that are on the surface of mammalian cells contain carbohydrates. These proteins are synthesized by _______ and the carbohydrates are added in the _______.
A: mitochondrial ribosomes; smooth endoplasmic reticulum
B: cytoplasmic ribosomes; cell membrane
C: the rough endoplasmic reticulum; Golgi apparatus
D: Golgi apparatus; rough endoplasmic reticulum
E: Cytoplasmic ribosomes; smooth endoplasmic reticulum

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The rough endoplasmic reticulum; Golgi apparatus

Question: Besides the proteins being processed for distribution, what other components could be expected to be found inside the Golgi apparatus?
A: DNA
B: Enzymes
C: Ribosomes
D: Cytoskeleton

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Enzymes

Question: Cargo proteins are transported through the Golgi apparatus by
ANS: remains controversial and may include elements of both vesicular transport and cisternal maturation
ANS: cisternal maturation in which the cisternae themselves are the carriers for cargo transport through the Golgi apparatus

Question: Most cellular lipids are synthesized in
A: fat droplets.
B: mitochondria.
C: the endoplasmic reticulum.
D: the Golgi apparatus.

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the endoplasmic reticulum.

Question: In proteins being made on rough er, short spans of hydrophobic amino acids that form α helices
In proteins being made on rough ER, short spans of hydrophobic amino acids that form a helices
In proteins being made on rough ER, short spans of hydrophobic amino acids that form alpha helices
A: induce a conformational change in the translocon, allowing them to exit into the ER membrane.
B: are posttranslationally inserted into the ER membrane by BiP.
C: are ubiquitinated and transferred into the cytosol for proteasomal degradation.
D: cause premature termination of translation, leading to the unfolded protein response

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induce a conformational change in the translocon, allowing them to exit into the ER membrane.

Question: Newly synthesized membrane lipids are found in both halves of a membrane bilayer because they are
A: synthesized on one surface and flipped to the other surface by proteins called flippases.
B: removed and transported to these locations by lipid transport proteins.
C: synthesized on one surface and flipped spontaneously to the other surface.
D: synthesized on both surfaces.

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

Question: Most plasma membrane proteins in higher eukaryotic cells are synthesized on
A: rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off from the Golgi apparatus.
B: free ribosomes and inserted after translation into the plasma membrane.
C: ribosomes associated with the plasma membrane and inserted into the membrane cotranslationally.
D: rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off from the rough ER.

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rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off from the Golgi apparatus.

Question: Eukaryotic cells manufacture cytoskeletal proteins, which help to maintain cell shapes and functions. What would you predict about these proteins?
A: They initially contain signal sequences that allow their entrance into the endoplasmic reticulum
B: They are manufactured on free ribosomes in the cytoplasm.
C: They travel to the nucleus in a transport vesicle with a specific signal
D: They are glycosylated in the Golgi apparatus

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They are manufactured on free ribosomes in the cytoplasm.

Question: Protein insertion into the ER membrane is typically:
A: Pretranslational
B: Posttranslational
C: Cotranslational
D: Quasitranslational
E: All of the above

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Cotranslational

Question: The lumen of the ER is equivalent topologically to the
A: cytoplasm
B: cytoplasmic face of the plasma membrane
C: extracellular space
D: nucleoplasm

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extracellular space

Question: Proteins are translocated into the ER lumen
A: by flippases.
B: by being pushed by translation through the lipid bilayer of the ER membrane.
C: through an aqueous channel created by the Sec61 protein.
D: by being pulled by BiP across the lipid bilayer of the ER membrane.

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through an aqueous channel created by the Sec61 protein.

Question: The major site at which membrane lipids are synthesized is the _____.
A: cytosolic side of the ER membrane.
B: cytosol.
C: cytosolic side of the Golgi membrane.
D: lumenal side of the ER membrane.

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cytosolic side of the ER membrane.

Question: All of the following are part of the core oligosaccharide side chain in the ER, except
A: N-acetyl glucosamine.
B: erythrose.
C: mannose.
D: glucose.

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Erythrose

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