Molecular Bio Test #4 Flashcards _ Quizlet

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12/20/23, 1:24 AM Molecular Bio Test #4 Flashcards | Quizlet https://quizlet.com/132047546/molecular-bio-test-4-flash-cards/ 1/6 Molecular Bio Test #4 8 studiers in 3 days Leave the first rating Students also viewed Terms in this set (19) Try Magic Notes and save time Upload notes Molecular Biology - Das - Chapter 1 ... 27 terms shelby_rauh Preview Pre-Lecture 14A Reading Quiz 6 terms ngriswel Preview Chapter 20 - Mo Bio 35 terms eursiriwan Preview Molecular E 24 terms so_stall 1. Which of the following statements about the bacterial ribosome is not true? A. The 70S ribosome is a complex of 50S and 30S subunits. B. The entire protein component of the 30S subunit is a single polypeptide chain. C. Each ribosomal subunit contains at least one RNA molecule. D. An rRNA molecule, rather than protein, catalyzes peptide bond formation. B. The entire protein component of the 30S subunit is a single polypeptide chain. 2. Which of the following describes an accurate order of events in translation? A. Ribosomal translocation occurs before the first aminoacyl-tRNA molecule binds to the small subunit. B. Initiation of translation occurs only after the small subunit dissociates from the mRNA. C. The large subunit of the ribosome binds the mRNA before the small subunit. D. The first aminoacyl-tRNA molecule binds to the small subunit before the large subunit binds. D. The first aminoacyl-tRNA molecule binds to the small subunit before the large subunit binds.

12/20/23, 1:24 AM Molecular Bio Test #4 Flashcards | Quizlet https://quizlet.com/132047546/molecular-bio-test-4-flash-cards/ 2/6 3. Which of the following statements is true of bacterial polysomes? A. Translation can initiate with an mRNA before transcription of that mRNA is complete. B. A single ribosome can translate multiple mRNA molecules at the same time. C. Polysome formation ensures that only one polypeptide is translated per mRNA molecule. D. Polysomes are membrane-bound compartments where translation occurs. A. Translation can initiate with an mRNA before transcription of that mRNA is complete. 4. Which one of the following experimental results does not support the hypothesis that the ribosome is a ribozyme? A. There are no proteins observed within 18 Å of the peptidyl transferase active site in the crystal structure. B. Peptidyl transferase activity is not inactivated by treating the ribosome with detergent. C. Peptidyl transferase activity can be inactivated by base changes in the rRNA. D. Ribosomes from thermophilic organisms are more stable than those from Escherichia coli. D. Ribosomes from thermophilic organisms are more stable than those from Escherichia coli. 1. Which of the following best describes the tRNA binding sites of the ribosome? A. Only one of the three sites can be occupied by a tRNA molecule at any given time. B. Each tRNA that associates with the ribosome must first bind in the P site and then move to the A site. C. The P site contains the tRNA molecule covalently bound to the growing chain of amino acids. D. All tRNAs leave the ribosome through the A site. C. The P site contains the tRNA molecule covalently bound to the growing chain of amino acids. 6. Which site on the ribosome is never occupied by a tRNA linked to a nascent polypeptide chain? A. the A site B. the P site C. the E site C. the E site Learn

12/20/23, 1:24 AM Molecular Bio Test #4 Flashcards | Quizlet https://quizlet.com/132047546/molecular-bio-test-4-flash-cards/ 3/6 See an expert-written answer! 7. The "charging" or activation of a tRNA molecule includes: A. the covalent attachment of an amino acid to the 3'-terminal cytosine of the tRNA. B. the covalent attachment of the amino group of an amino acid to the tRNA. C. the covalent attachment of the carboxyl group of an amino acid to the tRNA. D. the covalent attachment of an amino acid to the 5'-terminal adenosine of the tRNA. C. the covalent attachment of the carboxyl group of an amino acid to the tRNA. 8. The enzyme that catalyzes the activation of tRNA molecules is: A. the ribosome. B. RNA polymerase. C. tRNA isomerse. D. aminoacyl-tRNA synthetase. D. aminoacyl-tRNA synthetase. 9. The difference between a Class I and a Class II tRNA synthetase is: A. the Class I synthetase requires ATP cofactor and the Class II does not. B. the Class I synthetase uses the 2'-OH of 3' end of the tRNA as a nucleophile and the Class II uses the 3'-OH. C. the Class II synthetase reaction requires a transesterification reaction not necessary in the Class I reaction. D. the Class II synthetases are typically monomeric, whereas the Class I enzymes frequently function as multimeric protein complexes. B. the Class I synthetase uses the 2'-OH of 3' end of the tRNA as a nucleophile and the Class II uses the 3'-OH. 10. Which of the following best explains why not all individual aminoacyl-tRNA synthetase enzymes recognize the correct tRNA molecules through the anticodon sequence? A. All tRNA molecules have the same anticodon sequence. B. Synthetases only contact the tRNA molecules at the 3'-terminal hydroxyl. C. More than one codon may code for one amino acid. D. There are 61 different aminoacyl-tRNA synthetase enzymes. C. More than one codon may code for one amino acid. Learn

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12/20/23, 1:24 AM Molecular Bio Test #4 Flashcards | Quizlet https://quizlet.com/132047546/molecular-bio-test-4-flash-cards/ 4/6 11. Which of the following is an intermediate in the reaction that forms Ala-tRNA? A. Alanyl-ATP B. Alanyl-ADP C. Alanyl-PPi D. Alanyl-AMP D. Alanyl-AMP 12. Kinetic proofreading allows an enzyme to discriminate between two substrates by: A. using a binding pocket of a specific size. B. using a multistep reaction and energy to reverse reactions. C. using a binding pocket of a specific shape. D. increasing the rate of the single chemical step of the reaction. B. using a multistep reaction and energy to reverse reactions. 13. The amino acids valine and threonine differ only by the presence of a hydroxyl group or a methyl group. The aminoacyl-tRNA synthetases for tRNAVal and tRNAThr must discriminate between using these two very structurally similar amino acids as substrate for creating charged tRNAs. The discrimination by the Valyl-tRNA synthetase is by differential binding of valine and/or threonine to a first site on the synthetase and, then, differential binding to a second site on the synthetase. This is an example of what known process in the specificity of tRNA synthetases? A. adenylation B. kinetic proofreading C. wobble D. premature termination E. accommodation B. kinetic proofreading 14. Different aminoacyl-tRNA synthetases: A. may bind the same amino acid. B. may bind the same tRNA. C. do not appear to recognize the same features of tRNAs. D. will always recognize both the acceptor stem and anticodon sequences of tRNAs. E. will always recognize the complete tRNA anticodon sequence. C. do not appear to recognize the same features of tRNAs. Learn

12/20/23, 1:24 AM Molecular Bio Test #4 Flashcards | Quizlet https://quizlet.com/132047546/molecular-bio-test-4-flash-cards/ 5/6 15. Which of the following is not true of the formation of a bacterial translation initiation complex? A. The 30S ribosome associates with the mRNA before the 50S ribosome. B. N-formylmethionyl-tRNAfMet binds in the P site. C. IF-3 binding to GTP is required for the charged tRNA to associate with the first mRNA codon. D. IF-1, IF-2, and IF-3 dissociate upon the 50S subunit binding. C. IF-3 binding to GTP is required for the charged tRNA to associate with the first mRNA codon. 16. The bacterial Shine-Dalgarno mRNA sequence is: A. a translation termination signal. B. the ribosomal binding site. C. a translational elongation factor. D. a protein coding region. B. the ribosomal binding site. 17. Which of the following is not an essential component of the bacterial initiation stage of translation? A. mRNA B. IF-2 C. ATP D. N-formylmethionyl-tRNAfMet C. ATP 18. Which of the following is not an essential component of the eukaryotic initiation stage of translation? A. 40S ribosome B. eIF2 C. GTP D. N-formylmethionyl-tRNAfMet D. N-formylmethionyl-tRNAfMet Learn

12/20/23, 1:24 AM Molecular Bio Test #4 Flashcards | Quizlet https://quizlet.com/132047546/molecular-bio-test-4-flash-cards/ 6/6 13. The amino acids valine and threonine differ only by the presence of a hydroxyl group or a methyl group. The aminoacyl-tRNA synthetases for tRNAVal and tRNAThr must discriminate between using these two very structurally similar amino acids as substrate for creating charged tRNAs. The discrimination by the Valyl-tRNA synthetase is by differential binding of valine and/or threonine to a first site on the synthetase and, then, differential binding to a second site on the synthetase. This is an example of what known process in the specificity of tRNA synthetases? A. adenylation B. kinetic proofreading C. wobble D. premature termination E. accommodation B. kinetic proofreading Learn

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Molecular Bio Test #4 Flashcards _ Quizlet

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