BIO test 2

The nuclear localization signal is recognized by and binds to which protein in the process of nuclear protein import?

*Importin Exportin The outer fibril protein Ran

Which of the following proteins do not pass through the Golgi apparatus?

*Ribosomal proteins Lysosomal enzymes Cell surface proteins Proteins secreted by exocytosis

The current model of vesicle fusion states that vesicle fusion into a target membrane is driven by interaction of pairs of proteins called:

*SNAREs. Rab proteins. COPs. tethers.

Clathrin coats are bound to specific receptors by a protein called:

*an adaptor protein. Arf. COP-I. Sar.

The nuclear lamina binds to:

*both the inner nuclear envelope membrane and the chromatin. the inner nuclear envelope membrane only. both the inner and outer nuclear envelope membranes. the chromatin only.

Transcription bodies are thought to represent sites of:

*coordinated transcription of multiple genes. small ribosomal subunit assembly. large ribosomal subunit assembly. DNA replication.

The lumen of a transport vesicle is equivalent topologically, and will eventually become part of the:

*extracellular space. liquid portion of the cytoplasm. cytoplasmic face of the plasma membrane. outer face of lysosomes.

In proteins being made on rough ER, short spans of hydrophobic amino acids that form a helices:

*induce a conformational change in the translocon, allowing them to exit into the ER membrane. are posttranslationally inserted into the ER membrane by BiP. are ubiquitinated and transferred into the cytosol for proteasomal degradation. cause premature termination of translation, leading to the unfolded protein response.

Lysosomal proteins are marked by the addition of a phosphate to a _______ group.

*mannose glucose serine asparagine

If secretory proteins are isolated from secretory vesicles and injected into the cytosol, they are most likely to:

*remain in the cytosol until they are degraded. be taken up into the rough ER and follow the secretory pathway. be secreted through channels in the plasma membrane. be taken up into secretory vesicles and secreted.

Most plasma membrane proteins in higher eukaryotic cells are synthesized on:

*rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off from the Golgi apparatus. rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off from the rough ER. free ribosomes and inserted after translation into the plasma membrane. ribosomes associated with the plasma membrane and inserted into the membrane co-translationally.

The nuclear envelope is continuous with the:

*rough endoplasmic reticulum. Golgi apparatus. plasma membrane. mitochondrial outer membrane.

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

*the cis (convex) face; trans (concave) face the trans (concave) face; cis (convex) face both the cis (convex) and the trans (concave) faces; sides of cisternae the sides of the cisternae; cis (convex) face

Eukaryotic ribosomes leave the nucleus as:

18S and 28S rRNAs. intact 80S ribosomes. intact 70S ribosomes. *40S and 60S ribosomal subunits.

The pH inside lysosomes is about:

7.0 6.0 *5.0 3.0

Which of the following is not a destination for vesicles leaving the Golgi apparatus?

Plasma membrane Exterior of the cell Lysosomes *Mitochondria

Which of the following does NOT contribute to transport of RNAs out of the nucleus?

Ran Exportins Expenditure of chemical energy *Passive diffusion

Which statement about transmembrane proteins is true?

They cross the membrane only once. The signal sequences are always cleaved off. *They usually have one or more helices spanning the membrane bilayer. They are always inserted with the amino terminus on the lumenal side and the carboxyl terminus in the cytosol.

What is the function of karyopherins?

They define the structure of polycomb bodies. They coat chromosomes. *They transport macromolecules into or out of the nucleus. They attach to chromosomes in order to activate heterochromatin.

Which of the following vesicle types does not bud directly from the trans-Golgi network?

Vesicles transporting plasma membrane receptors Vesicles that form regulated secretory vesicles Vesicles carrying lysosomal enzymes *Endosomes

Prior to N-linked glycosylation of a protein, a complex oligosaccharide is assembled in the endoplasmic reticulum on a lipid carrier called:

a prenyl group. myristic acid. *dolichol phosphate. phosphatidylinositol.

The ribosomes of the rough endoplasmic reticulum are targeted to the cytoplasmic side of the membrane via:

a signal sequence within the 28S ribosomal RNA. *a sequence within the protein being synthesized. the S6 ribosomal protein. the cap sequence at the 5′ end of the mRNA being translated.

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

a tRNA. *a signal recognition particle (SRP). a signal peptidase. an SRP receptor.

There are _____ Rab proteins used in vesicular transport to ______.

a. fewer than 10 a. about 25 *a. 60 or more b. ensure the proper COP/clathrin protein binds to the membrane *b. allow vesicles to identify many different membrane targets b. fuse the lipid bilayers of the vesicle to the target membrane

Chromosomes are distributed in the nucleus:

as condensed mitotic chromosomes. randomly. as cleavage fragments. *in differentially staining zones.

Proteins are translocated into the ER lumen:

by being pushed by translation through the lipid bilayer of the ER membrane. by being pulled by BiP across the lipid bilayer of the ER membrane. by flippases as they move lipids. *through an aqueous channel created by the Sec61 protein.

Coated pits are converted to coated vesicles by formation of rings of the protein:

caveolin. clathrin. COP-I. *dynamin.

The nucleolus is the site where _______ is(are) assembled.

chromatin nuclear pores the nuclear matrix *ribosomal subunits

Which coat protein directs retrograde vesicular transport from the ERGIC or Golgi to the endoplasmic reticulum?

clathrin COP-II *COP-I Both COP-I and COP-II

Which coat protein(s) would you expect to be recruited for vesicle formation by a KDEL receptor?

clathrin COP-II *COP-I Either COP-I or clathrin

The lumen of the ER is equivalent topologically to the:

cytoplasm. cytoplasmic face of the plasma membrane. *extracellular space. nucleoplasm.

The major site at which membrane lipids are synthesized is the:

cytosolic side of the ER membrane. cytosol. luminal side of the ER membrane. cytosolic side of the Golgi membrane.

Polycomb bodies act on _______ regions of chromatin, silencing gene expression.

distant very short *both adjacent and distant adjacent

The pinching off of budding clathrin-coated vesicles is driven by the action of:

dynamin and ATP hydrolysis. *dynamin and GTP hydrolysis. Arf bound to GTP. Sar bound to GTP.

Nuclear proteins that are stripped of their nuclear localization signal and injected into the cytoplasm of cultured cells will localize:

extracellularly. to the nucleus. in a ring around the outside of the nuclear envelope. *in the cytoplasm.

Most cellular lipids are synthesized in:

fat droplets. the Golgi apparatus. mitochondria. *the endoplasmic reticulum.

The ingestion of large particles by cells is a form of endocytosis known as:

fluid phase endocytosis. macropinocytosis. *phagocytosis. transcytosis.

Cargo proteins are transported through the Golgi apparatus by:

forward (anterograde) moving vesicles. backward (retrograde) moving vesicles. cisternal maturation in which the cisternae themselves are the carriers for cargo transport through the Golgi apparatus. *a combination of elements of both vesicular transport and cisternal maturation.

N-linked glycosylation attaches a complex carbohydrate onto the: Group of answer choices

free amino group at the amino terminal end of the polypeptide. *amino group of asparagine. amino group of lysine. carboxyl group of aspartic acid.

Most snoRNAs:

guide regions of rRNAs to modifying enzymes. splice cleaved mRNAs. *splice cleaved rRNAs. cleave the 45S rRNA.

The directionality of nuclear transport is determined by _______ in the nucleus and _______ in the cytosol.

high Ran/GDP; high Ran/GTP low Ran; high Ran *high Ran/GTP; high Ran/GDP high Ran; low Ran

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

hold the proteins in the rough ER. hold the proteins in the smooth ER. hold the proteins in both the smooth ER and rough ER and prevent their transport to the Golgi apparatus. *transport the proteins from the Golgi apparatus back to the ER.

The trans-Golgi network is the:

intermediate compartment between the ER and the Golgi. part of the Golgi where fusion of vesicles from the ER occurs. *exit part of the Golgi where sorting of proteins to the lysosomes, plasma membrane, and cell exterior occurs. network of vesicles that transport resident Golgi proteins between cisternae.

The fibrous nuclear lamina is built of proteins called:

keratins. nucleoplasmins. *lamins. collagens.

Lamins are associated with the inner nuclear envelope membrane via:

lamin-binding proteins. *lipid tails on lamins and lamin-binding proteins both. GPI anchors on lamins. lipid tails on lamins.

The enzyme protein disulfide isomerase, which facilitates breakage and reformation of disulfide bonds, is located primarily in the:

matrix of mitochondria. lumen of lysosomes. cytosol. *lumen of the endoplasmic reticulum.

N-linked oligosaccharides are added in the _______ and modified in the _______.

medial Golgi; trans Golgi cis Golgi; trans Golgi *ER; Golgi cis Golgi; medial Golgi

The filaments of the nuclear lamina are composed of a type of:

microtubule. microfilament. *intermediate filament. thick filament.

Heterochromatin is normally associated with:

mutated chromosomes. only a few specific human chromosomes. ribosomes. *the nuclear lamina.

The region of chromosomes that codes for most of the rRNAs is found in the:

nucleolus. *nucleolar organizing region. ribosomal assembly region. ribosomal organizer region.

Small polar molecules (< 20 kd) enter nuclei by way of:

passive diffusion across the nuclear envelope membranes. selective transport through nuclear pore complexes. active transport across the nuclear envelope membranes. *passive diffusion through nuclear pore complexes.

Cholesterol is taken up into most cells of the body by:

phagocytosis. *receptor-mediated endocytosis. simple diffusion. caveolae formation.

Arf and Sar activity on vesicles is regulated by:

phosphorylation of serine residues. phosphorylation of mannose residues. *binding of GTP. hydrolysis of ATP.

The major pathway for molecules to pass into and out of the nucleus is through:

porin channels in the nuclear envelope membranes. gap junctions between the nuclear envelope membranes. diffusion through the membrane bilayers of the nuclear envelope. *nuclear pore complexes.

The signal sequence that targets a nascent polypeptide and its mRNA to the rough ER is rich in _______ amino acids.

positively charged negatively charged hydrophilic *hydrophobic

The sequence Lys-Asp-Glu-Leu (KDEL) serves to retain proteins in the ER by:

preventing their packaging into vesicles destined for the Golgi. *binding to receptors within the membranes of the ERGIC and Golgi, which retain them or return them to the ER. binding the SRP receptor in the ER membrane. associating with the lipids in the ER membrane.

Lysosomes digest:

proteins only. *proteins, nucleic acids, and carbohydrates. nucleic acids and proteins only. carbohydrates only.

Export of RNAs from the nucleus occurs primarily by:

release from the nucleus when it breaks down at mitosis. *selective transport through nuclear pore complexes. passive diffusion through nuclear pore complexes. cotranscriptional insertion through protein pores of the nuclear envelope membrane.

In polarized epithelial cells, membrane proteins containing a dileucine (LL) motif in their cytoplasmic domain are:

retained in the Golgi apparatus. *targeted to the basolateral plasma membrane. targeted to lysosomes. targeted to the apical plasma membrane.

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

secreted plasma membrane *mitochondrial lysosomal

The nuclear localization signal is typically a(n) _______, rich in the amino acids _______.

short sequence; Pro, Leu, and Gly α helix; Leu, Phe, and Gly α helix; Pro, Lys, and Arg *short sequence; Lys and Arg

The genes encoding 5.8S, 18S, and 28S ribosome RNA are clustered together in:

tandem arrays located on all chromosomes. *tandem arrays located on five chromosomes. tandem arrays interspersed with tandem arrays of genes encoding 5S ribosomal RNA. tandem arrays located on one chromosome.

mRNA molecules are exported from the nucleus to the cytoplasm via:

the 7-methylguanosine cap structure. *a recruited protein complex. importin. a consensus sequence located at the 3ʹ terminus.

The directionality of nuclear protein import is determined by:

the nuclear lamina. *an unequal distribution of Ran/GTP. an ion gradient. importin.

The difference between free ribosomes in cytosol and ribosomes bound to ER membrane is:

the sizes of large and small subunits used. *whether a protein is synthesized continuously, or with pauses in the process. the sequence of mRNAs to which they bind. which codons are used as the start site for translation.

By restricting the traffic of proteins and RNA across the nuclear envelope, eukaryotic cells can regulate _______ in unique ways that prokaryotes cannot.

translation only endocytosis transcription only *translation and transcription

Lysosomal proteins are initially incorporated into _______ vesicles.

uncoated *clathrin-coated COPI-coated COPII-coated

Vesicles that carry proteins forward through the Golgi apparatus bud off as _______ vesicles.

uncoated clathrin-coated COP-I-coated *COP-II-coated

In polarized epithelial cells, proteins anchored in the membrane by a GPI anchor are:

used to hold vesicles near the surface before secretion. sent to the basal membrane. targeted to cell-cell connection domains. targeted to the apical plasma membrane.