Question 1

Which of the following proteins involved in cotranslational translocation of proteins into the ER membrane is NOT a GTP-hydrolyzing protein?

Accepted Answer

A) α subunit of the SRP receptor 
B) elongation factors in ribosome-mediated mRNA translation 
C) P54 subunit of SRP 
D) Sec61 translocon 
A) α subunit of the SRP receptor 
B) elongation factors in ribosome-mediated mRNA translation 
C) P54 subunit of SRP 
D) Sec61 translocon D

Question 2

What is the meaning of "quality control in the ER?"

Accepted Answer

"Quality control within the ER" refers to the need for proteins to be properly modified and folded before they can exit from the ER and travel to the Golgi apparatus.Improperly modified and folded proteins are typically translocated into the cytosol for degradation.

Question 3

In the absence of targeting information,what is the default location of proteins synthesized on cytosolic ribosomes?

Accepted Answer

Proteins synthesized on cytosolic ribosomes that contain no information for targeting to organelles diffuse throughout the cytosol.

Question 4

Post-translational translocation of some secretory proteins in yeast is powered by:

Accepted Answer

A) ATP hydrolysis by BiP. 
B) cAMP hydrolysis by cAMP phosphodiesterase. 
C) GTP hydrolysis EF-Tu. 
D) phospholipid hydrolysis by phospholipase C. 
A) ATP hydrolysis by BiP. 
B) cAMP hydrolysis by cAMP phosphodiesterase. 
C) GTP hydrolysis EF-Tu. 
D) phospholipid hydrolysis by phospholipase C.

Question 5

In a cell-free protein synthesis system utilizing microsomes from fragmented ER,under which condition could you determine if the new protein was imported into the microsome?

Accepted Answer

A) Ribosomes and mRNA are incubated with microsomes,then a protease is added and the results are analyzed. 
B) Ribosomes and mRNA are incubated with microsomes,then a protease and detergent are added and the results are analyzed. 
C) Ribosomes and mRNA are incubated with protease,then microsomes are added and the results are analyzed. 
D) Ribosomes and mRNA are incubated with microsomes,then detergent is added and the results are analyzed. 
A) Ribosomes and mRNA are incubated with microsomes,then a protease is added and the results are analyzed. 
B) Ribosomes and mRNA are incubated with microsomes,then a protease and detergent are added and the results are analyzed. 
C) Ribosomes and mRNA are incubated with protease,then microsomes are added and the results are analyzed. 
D) Ribosomes and mRNA are incubated with microsomes,then detergent is added and the results are analyzed.

Question 6

Protein sequences for targeting to mitochondria or chloroplasts are located at:

Accepted Answer

A) the C-terminus of the precursor protein. 
B) amino acid position 173 in most mitochondrial and chloroplast proteins. 
C) the N-terminus of the precursor protein. 
D) the second and third answers are correct 
A) the C-terminus of the precursor protein. 
B) amino acid position 173 in most mitochondrial and chloroplast proteins. 
C) the N-terminus of the precursor protein. 
D) the second and third answers are correct

Question 7

To what extent do peroxisomal matrix protein import and peroxisomal membrane protein import share the same machinery?

Accepted Answer

The fact that mutated cells giving rise

Question 8

Type I membrane proteins have all of the following properties,except:

Accepted Answer

A) cleavable signal sequence. 
B) internal signal-anchor sequence. 
C) internal stop-transfer sequence. 
D) N-out,C-in topology. 
A) cleavable signal sequence. 
B) internal signal-anchor sequence. 
C) internal stop-transfer sequence. 
D) N-out,C-in topology.

Question 9

The topology of membrane proteins can often be predicted by computer programs that identify_____ topogenic segments.

Accepted Answer

A) glycosylation-specific 
B) hydrophilic 
C) hydrophobic 
D) cleavable signal sequence 
A) glycosylation-specific 
B) hydrophilic 
C) hydrophobic 
D) cleavable signal sequence

Question 10

Protein insertion into the mammalian ER membrane is typically:

Accepted Answer

A) cotranslational. 
B) post-translational. 
C) pretranslational. 
D) quasitranslational. 
A) cotranslational. 
B) post-translational. 
C) pretranslational. 
D) quasitranslational.

Question 11

Why are bacteria often a poor choice for the production of proteins for therapeutic purposes?

Accepted Answer

Typically,proteins used for therapeutic

Question 12

In a cell that lacks cytosolic Hsc70:

Accepted Answer

A) import of proteins into the mitochondrial matrix would be diminished. 
B) proteins in the ER would not fold properly. 
C) the peroxisome would contain more catalase. 
D) generation of ATP from the electron transport chain would happen at the plasma membrane. 
A) import of proteins into the mitochondrial matrix would be diminished. 
B) proteins in the ER would not fold properly. 
C) the peroxisome would contain more catalase. 
D) generation of ATP from the electron transport chain would happen at the plasma membrane.

Question 13

How does Ran·GTP participate in the nuclear export of the HIV Rev protein?

Accepted Answer

In the nucleus,Ran·GTP binds to the nucl

Question 14

During in vitro translation of mitochondrially targeted proteins,when must mitochondria be added for import of proteins synthesized on cytosolic ribosomes?

Accepted Answer

Proteins are imported into mitochondria

Question 15

Sorting of proteins to mitochondria and chloroplasts is:

Accepted Answer

A) cotranslational. 
B) post-translational. 
C) pretranslational. 
D) quasitranslational. 
A) cotranslational. 
B) post-translational. 
C) pretranslational. 
D) quasitranslational.

Question 16

Unassembled or misfolded proteins in the RER can be damaging to the physiology of a cell and therefore are transported to the cytosol where they are degraded.This transport process is referred to as:

Accepted Answer

A) polyubiquitination. 
B) disulfide isomerization. 
C) dislocation. 
D) O-linked glycosylation. 
A) polyubiquitination. 
B) disulfide isomerization. 
C) dislocation. 
D) O-linked glycosylation.

Question 17

How are proteins imported into the thylakoids of chloroplasts?

Accepted Answer

For cytosolically synthesized proteins t

Question 18

Having misfolded soluble or secretory proteins in the RER contributes to what investigators call the "traffic jam," a scenario associated with a number of human diseases where the normal transport of proteins is blocked by these abnormal proteins and the inability of protein complexes to arrive at their correct site and function properly.Briefly describe how the cell overcomes this particular traffic jam by exporting the misfolded proteins out of the RER into the cytosol,where they are degraded by the proteasome.

Accepted Answer

Essentially,the misfolded proteins have

Question 19

Which of the following components of mitochondrial import are NOT required for a sequence containing a matrix-targeting sequence and an intermembrane-space-targeting sequence?

Accepted Answer

A) Tom 
B) Tim 
C) Oxa1 
D) membrane-bound protease 
A) Tom 
B) Tim 
C) Oxa1 
D) membrane-bound protease

Question 20

During the import of proteins into the nucleus,the α importin subunit binds directly to:

Accepted Answer

A) FG nucleoporins. 
B) Ran·GDP 
C) basic nuclear localization signals in cargo proteins. 
D) all of the above 
A) FG nucleoporins. 
B) Ran·GDP 
C) basic nuclear localization signals in cargo proteins. 
D) all of the above

Exam 12: Moving Proteins Into Membranes and Organelles

Which of the following proteins involved in cotranslational translocation of proteins into the ER membrane is NOT a GTP-hydrolyzing protein?

What is the meaning of "quality control in the ER?"

In the absence of targeting information,what is the default location of proteins synthesized on cytosolic ribosomes?

Post-translational translocation of some secretory proteins in yeast is powered by:

In a cell-free protein synthesis system utilizing microsomes from fragmented ER,under which condition could you determine if the new protein was imported into the microsome?

Protein sequences for targeting to mitochondria or chloroplasts are located at:

To what extent do peroxisomal matrix protein import and peroxisomal membrane protein import share the same machinery?

Type I membrane proteins have all of the following properties,except:

The topology of membrane proteins can often be predicted by computer programs that identify_____ topogenic segments.

Protein insertion into the mammalian ER membrane is typically:

Why are bacteria often a poor choice for the production of proteins for therapeutic purposes?

In a cell that lacks cytosolic Hsc70:

How does Ran·GTP participate in the nuclear export of the HIV Rev protein?

During in vitro translation of mitochondrially targeted proteins,when must mitochondria be added for import of proteins synthesized on cytosolic ribosomes?

Sorting of proteins to mitochondria and chloroplasts is:

Unassembled or misfolded proteins in the RER can be damaging to the physiology of a cell and therefore are transported to the cytosol where they are degraded.This transport process is referred to as:

How are proteins imported into the thylakoids of chloroplasts?

Which of the following components of mitochondrial import are NOT required for a sequence containing a matrix-targeting sequence and an intermembrane-space-targeting sequence?

During the import of proteins into the nucleus,the α importin subunit binds directly to:

Chemical Foundations

Molecular Genetic Techniques

Protein Structure and Function

Culturing and Visualizing Cells

Fundamental Molecular Genetic Mechanisms

Bio-membrane Structure

Genes Genomics and Chromosomes

Transcriptional Control of Gene Expression

Post-Transcriptional Gene Control

Transmembrane Transport of Ions and Small Molecules

Cellular Energetics

Vesicular Traffic, Secretion, and Endocytosis

Signal Transduction and G-Protein Coupled Receptors

Signaling Pathways That Control Gene Activity

Cell Organization and Movement I: Microfilaments

Cell Organization and Movement II: Microtubules and Intermediate Filaments

Regulating the Eukaryotic Cell Cycle

Integrating Cells Into Tissues

Cell Birth, Lineage, and Death

Nerve Cells

Immunology

Cancer

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