Protein phosphatases
a. catalyze the addition of phosphate residues to proteins.
b. catalyze the removal of phosphate residues from proteins.
c. catalyze the addition of glycosylphosphatidylinositol to proteins.
d. are proteins that specifically bind phos
Correct Answer: b
Your Answer: b
Answer B Feedback: Correct! Phosphatases can remove phosphate residues from serine, threonine, and tyrosine residues.
Textbook Reference: Regulation of Protein Function
Which of the following statements regarding tRNAs is false?
a. tRNAS are approximately 70-80 bases long and form a cloverleaf structure.
b. All tRNAs have a CCA sequence at their 3? terminus.
c. tRNAs differ in sequence only at the anticodon.
d. There are
Correct Answer: c
Your Answer: c
Answer C Feedback: Correct! This is not true. While there are many regions of shared sequence identity between tRNAs, they are not identical.
Textbook Reference: Translation of mRNA
Antibiotics are powerful medications that inhibit the growth of bacteria. They work at a variety of levels, but many target the process of protein synthesis in the bacterial cell. In the developing of an antibiotic, which of the following would be an effe
Correct Answer: d
Your Answer: a
Answer A Feedback: Incorrect. This answer choice is correct, but the other answer choices are correct as well.
Textbook Reference: Translation of mRNA
A proteasome is a
a. vesicle containing proteolytic enzymes.
b. precursor to lysosomes.
c. complex of a proteolytic enzyme and the protein that is being degraded.
d. multisubunit protease complex that degrades proteins marked for destruction.
Correct Answer: d
Your Answer: c
Answer C Feedback: Incorrect. The proteasome contains more than one proteolytic enzyme.
Textbook Reference: Protein Degradation
Ferritin expression is stimulated by iron because iron
a. stimulates a protein to bind the ferritin mRNA and inhibit its degradation.
b. stimulates the dissociation of a translational inhibitor from the ferritin mRNA.
c. binding stabilizes the ferritin pr
Correct Answer: b
Your Answer: a
Answer A Feedback: Incorrect. This type of mechanism regulates transferrin-receptor expression.
Textbook Reference: Translation of mRNA
Which of the following statements about translational initiation is false?
a. Initiation codons in prokaryotic cells are preceded by Shine-Dalgarno sequences.
b. Viral mRNAs contain internal ribosome entry sites that allow ribosomes to bind to an internal
Correct Answer: c
Your Answer: b
Answer B Feedback: Incorrect. This is true, and these internal ribosome entry sites are often placed in front of genes when viruses are used as a vector in gene therapy.
Textbook Reference: Translation of mRNA
Which of the following processes does not require the assistance of chaperones?
a. Protein transport into the nucleus
b. Protein transport into the ER
c. Folding during protein synthesis
d. Assembly of proteins consisting of multiple polypeptide chains
Correct Answer: a
Your Answer: a
Answer A Feedback: Correct! Proteins do not need to be in an unfolded state to be transported into the nucleus, and hence do not require chaperones.
Textbook Reference: Protein Folding and Processing
Which of the following statements about translational regulation of ferritin is false?
a. The iron response element is a unique sequence of amino acids near the amino terminus of the growing polypeptide.
b. In the absence of iron, an iron regulatory prote
Correct Answer: a
Your Answer: a
Answer A Feedback: Correct! This is a false statement. The IRE is a unique sequence of bases located near the 5? cap of the mRNA.
Textbook Reference: Translation of mRNA
Which of the following is an example of posttranslational modification?
a. Glycosylation
b. Proteolysis
c. Palmitoylation
d. All of the above
Incorrect
Correct Answer: d
Your Answer: Did not answer
Textbook Reference: Protein Folding and Processing
Which of the following statements about the attachment of amino acids to tRNAs is false?
a. The amino acid is first joined to AMP, forming an aminoacyl AMP intermediate.
b. The amino acid is transferred to the 3? end of the tRNA.
c. Aminoacyl tRNA synthet
Correct Answer: d
Your Answer: b
Answer B Feedback: Incorrect. This is the second step in the process.
Textbook Reference: Translation of mRNA
The initiator codon in prokaryotes is
a. the first codon located at the 5? end of the mRNA.
b. recognized by scanning of the ribosome downstream of the 5? methylguanosine cap.
c. recognized via the Shine-Dalgarno sequence.
d. the first 5? AUG of the mRNA
Correct Answer: c
Your Answer: b
Answer B Feedback: Incorrect. This is the mechanism used in eukaryotes.
Textbook Reference: Translation of mRNA
The function of aminoacyl tRNA synthetases is to
a. covalently attach amino acids to their corresponding tRNA molecules.
b. synthesize tRNA molecules.
c. catalyze the formation of the aminoacyl-ATP intermediate during amino acid attachment to tRNAs.
d. ca
Correct Answer: a
Your Answer: c
Answer C Feedback: Incorrect. Aminoacyl tRNA synthetases catalyze the formation of an intermediate, but it is not aminoacyl-ATP.
Textbook Reference: Translation of mRNA
Which of the following is not a common lipid modification to proteins?
a. N-myristoylation
b. Prenylation
c. GPI anchor addition
d. Glycosylation
Correct Answer: d
Your Answer: d
Answer D Feedback: Correct! Glycosylation is the addition of an oligosaccharide, not a lipid, to a protein.
Textbook Reference: Protein Folding and Processing
The half-lives of proteins in the cell vary widely, ranging from
a. milliseconds to seconds.
b. three to seven minutes.
c. minutes to days.
d. days to weeks.
Correct Answer: c
Your Answer: d
Answer D Feedback: Incorrect. Few, if any, proteins would last as long as a few weeks.
Textbook Reference: Protein Degradation
Which of the following is not associated with translational regulation?
a. Dephosphorylation of 4E-BPs that bind eIF4E and prevent its interaction with eIF4G
b. Phosphorylation of eIF2, which inhibits GDP/GTP exchange
c. Cleavage of mRNA by miRNA/RISC com
Correct Answer: d
Your Answer: d
Answer D Feedback: Correct! This is not a form of translational regulation.
Textbook Reference: Translation of mRNA
The proteins shaped like a "double chamber" that are involved in protein folding are called
a. Hsp70 proteins.
b. protein disulfide isomerases.
c. chaperonin proteins.
d. peptidyl prolyl isomerases.
Correct Answer: c
Your Answer: b
Answer B Feedback: Incorrect. These enzymes promote correct protein folding by stimulating exchanges between paired disulfides in the ER, but they are not double-chamber shaped.
Textbook Reference: Protein Folding and Proc
Signal sequences are sequences of hydrophobic amino acids that target membrane translocation. Signal sequences are found
a. at the amino terminus of the secreted protein.
b. at the carboxy terminus of the secreted protein.
c. on the cytoplasmic side of th
Correct Answer: a
Your Answer: a
Answer A Feedback: Correct! These sequences are usually about 20 amino acids long.
Textbook Reference: Protein Folding and Processing
The first amino acid of eukaryotic polypeptides is
a. the amino acid encoded by the first 5? codon.
b. valine.
c. N-formylmethionine.
d. methionine.
Correct Answer: d
Your Answer: a
Answer A Feedback: Incorrect. In neither prokaryotic nor eukaryotic polypeptides is the first 5? codon the initiator codon.
Textbook Reference: Translation of mRNA
The primary function of rRNAs in the ribosome is
a. to serve as a scaffold for the ribosomal proteins.
b. to assist in the proper positioning of tRNAs along the mRNA template.
c. to catalyze peptide bond formation.
d. to assist in the proper folding of ri
Correct Answer: c
Your Answer: a
Answer A Feedback: Incorrect. This was once thought to be the case, but it is now considered inaccurate.
Textbook Reference: Translation of mRNA
cAMP activates cAMP-dependent protein kinase by
a. stimulating its phosphorylation.
b. stimulating the dimerization of kinase subunits.
c. stimulating the release of a translational inhibitory protein bound to its mRNA.
d. binding regulatory subunits and
Correct Answer: d
Your Answer: c
Answer C Feedback: Incorrect. This type of mechanism functions in the regulation of ferritin, but not for cAMP-dependent protein kinase.
Textbook Reference: Regulation of Protein Function