Lecture 12b

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Questions and Answers

During translation, which molecule is bound to IF2?

  • Pyrrolysine-tRNAprl
  • fMet-tRNAfmet (correct)
  • Met-tRNAmet
  • Sec-tRNA

Which molecule is introduced instead of methionine for the initiation codon?

  • Formyl methionine (fmet) (correct)
  • Sec
  • Leucine
  • Pyrrolysine

Which tRNA is formylated during translation?

  • tRNAmethionine
  • tRNAprl
  • tRNAfmet (correct)
  • tRNAsec

Which component of ribosomes in bacteria is responsible for catalyzing peptide bond formation?

<p>rRNA (B)</p> Signup and view all the answers

Which complex is formed by the 30S and 50S subunits in bacterial ribosomes?

<p>Functional 70S ribosomes (C)</p> Signup and view all the answers

Which molecule serves as a source of energy during the initiation of translation in bacteria?

<p>GTP (B)</p> Signup and view all the answers

What is the role of release factors (RF1, RF2, RF3) in the termination and ribosome recycling phase of translation?

<p>Release of the polypeptide chain (D)</p> Signup and view all the answers

In eukaryotic ribosomes, what is the size of the small subunit?

<p>40S (A)</p> Signup and view all the answers

What is the role of IF-3 during translation initiation in bacteria?

<p>Keeps the 30S and 50S ribosomal subunits apart (A)</p> Signup and view all the answers

What is the function of IF-2 during translation initiation?

<p>Recruits fMet-tRNA to the peptidyl site (B)</p> Signup and view all the answers

What is the significance of the Shine-Dalgarno sequence in translation initiation?

<p>Guides mRNA to its correct position on the ribosome (D)</p> Signup and view all the answers

Which molecule is responsible for binding to IF-1, IF-3, and mRNA during translation initiation?

<p>30S ribosomal subunit (C)</p> Signup and view all the answers

In what way is an internal met codon processed?

<p>Charged with met by met-tRNA synthetase (A)</p> Signup and view all the answers

What is the role of IF-2-GTP in the formation of the initiation complex in bacteria?

<p>Recruits fmet-tRNAfmet and hydrolyzes GTP (B)</p> Signup and view all the answers

What serves as a signal for the initiation of protein synthesis in bacteria?

<p>Shine-Dalgarno sequence on mRNA (D)</p> Signup and view all the answers

What happens to IF-2-GTP in the last step of initiation complex formation?

<p>It hydrolyzes to GDP and is released (A)</p> Signup and view all the answers

What is the function of Elongation Factor Tu (EF-Tu) in bacterial protein synthesis?

<p>Binds aminoacyl tRNA and GTP (D)</p> Signup and view all the answers

Where does the aminoacyl tRNA-EF-Tu-GTP complex bind in the 70S initiation complex?

<p>A site (A)</p> Signup and view all the answers

What occurs during the termination stage of protein synthesis?

<p>Release of mRNA and protein dissociation (C)</p> Signup and view all the answers

In the elongation phase of protein synthesis, what is the main function of the ribosome?

<p>Matching tRNAs to each codon (C)</p> Signup and view all the answers

What is the primary purpose of translocation during translation?

<p>Movement of ribosome along mRNA (D)</p> Signup and view all the answers

What happens when a STOP codon is reached during protein synthesis?

<p>Translation is terminated (C)</p> Signup and view all the answers

During protein synthesis, what role does ribosome recycling play?

<p>Prepares for another round of protein synthesis (C)</p> Signup and view all the answers

What catalyzes the reaction of transferring the fmet group from tRNA in the P site to the amino acid in the A site during elongation in bacterial protein synthesis?

<p>23S rRNA (ribozyme) (B)</p> Signup and view all the answers

What triggers the binding of termination factors (Release Factors) RF-1, RF-2, RF-3 in bacterial protein synthesis?

<p>Stop codons UAA, UAG, or UGA (B)</p> Signup and view all the answers

What role does Ribosome Recycling Factor (RRF) play in bacterial protein synthesis termination?

<p>Causes subunits of ribosome to dissociate (A)</p> Signup and view all the answers

What is the role of IF-3 during the formation of the initiation complex in bacterial translation?

<p>Keeps 30S and 50S subunits apart (D)</p> Signup and view all the answers

How many ATP equivalents are used in the aminoacetylation step?

<p>2 (B)</p> Signup and view all the answers

How many ATP equivalents are used in the elongation step?

<p>1 (A)</p> Signup and view all the answers

How many ATP equivalents are used in the translocation step?

<p>1 (A)</p> Signup and view all the answers

How many ATP equivalents are used in the initiation step?

<p>1 (A)</p> Signup and view all the answers

How many ATP equivalents are used in the termination step?

<p>1 (A)</p> Signup and view all the answers

How many ATP equivalents are used in proofreading?

<p>1 (A)</p> Signup and view all the answers

How many ATP equivalents are needed to synthesize a polypeptide of 150 amino acids that required proofreading for 2 of its amino acids?

<p>602 (B)</p> Signup and view all the answers

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