1. GPI anchored membrane proteins are membrane associated by
A) an ?-helical protein segment.
B) direct insertion of a glycine-proline-isoleucine sequence into the exoplasmic leaflet of the bilayer.
C) a covalently attached lipid.
D) an unusual sugar that
C
2. Glycosylation of proteins inside the endoplasmic reticulum does not involve:
A) a His residue on the protein.
B) an Asn residue on the protein.
C) dolichol phosphate.
D) glucose.
A
3. Protein import into the mitochondrial matrix is supported by energy input from
A) ATP hydrolysis by chaperone proteins in the cytosol.
B) ATP hydrolysis by chaperone proteins in the mitochondrial matrix.
C) the proton-motive force across the inner mito
D
4. All the following proteins interact with exposed amino acids during protein folding in the ER except
A) BiP.
B) calnexin.
C) PDI.
D) prolyl isomerase.
B
5. N-linked oligosaccharides are:
A) Added in the cis Golgi and modified in the trans Golgi
B) Added in the trans Golgi and modified in secretory vesicles
C) Added in the ER and modified in the Golgi
D) Added in the Golgi and modified in the ER
C
6. The targeting sequences directing proteins into chloroplasts, mitochondria and nuclei have the following feature in common.
A) They are located near the amino terminus of the precursor proteins
B) They are rich in hydrophobic amino acids
C) When added
C
7. Proteins that do not fold properly in the ER lumen are degraded in the cytosol by
A) the etiosome.
B) the microsome.
C) the proteasome.
D) the ribosome.
C
8. Type I membrane proteins have all of the following properties except
A) cleavable signal sequence.
B) internal signal-anchor sequence.
C) internal stop-transfer sequence.
D) Topology such that their N terminus is out of ER lumen and their C terminus in
D
9. Post-translational translocation of some secretory proteins in yeast is powered by
A) ATP hydrolysis by BiP.
B) cAMP hydrolysis by cAMP phosphodiesterase.
C) GTP hydrolysis EF-Tu.
D) phospholipid hydrolysis by phospholipase C.
A
10. The topology of membrane proteins can often be predicted by computer programs that identify ________________________________________ topogenic segments.
A) glycosylation-specific
B) phosphorylation-specific
C) hydrophobic
D) cleavable signal sequence
C
11. Which of the following is true about the sorting pathway for proteins destined for incorporation into lysosomes or the plasma membrane of eukaryotic cells?
A) Binding of SRP to the signal peptide and the ribosome temporarily accelerates protein synthe
D
12. During N-glycosylation of proteins, an oligosaccharide precursor is first synthesized (preformed) with _______sugar residue (s) and this preformed precursor is later transferred to the nascent polypeptide chain.
A) 1
B) 3
C) 7
D) 14
D
13. Protein insertion into the mammalian ER membrane is typically
A) cotranslational.
B) post-translational.
C) pretranslational.
D) quasitranslational.
A
14. During the import of proteins into the nucleus, the alpha importin subunit binds directly to
A) FG nucleoporins.
B) Ran�GDP
C) basic nuclear localization signals in cargo proteins.
D) all of the above
D
15. Tom/Tim protein complexes are involved in
A) post-receptor recognition events in the cytosolic folding of proteins prior to import into mitochondria.
B) pre-proteasomal steps in tagging aged proteins for degradation.
C) protein translocation into mito
C
16. Signal sequences that direct proteins to the ER membrane are:
A) Stretches of hydrophobic amino acids located generally located near the amino terminus of the protein
B) Stretches of hydrophilic amino acids generally located near the carboxyl terminus
A
17. Protein sequences for targeting to mitochondria are located at
A) the C-terminus of the precursor protein.
B) around amino acid position 173 in most mitochondrial proteins.
C) the N-terminus of the precursor protein.
D) the middle of the protein
C
18. Sorting of protein to mitochondria is
A) cotranslational.
B) post-translational.
C) pretranslational.
D) quasitranslational.
B
19. Many peroxisomal matrix proteins are imported as
A) folded proteins.
B) nascent chains in the process of completing their elongation.
C) protein fragments that are spliced together within the peroxisome.
D) unfolded proteins.
A
20. The nuclear pore complex allows for
A) passive diffusion of smaller molecules.
B) import of proteins.
C) active transport of very large molecules.
D) all of the above
D