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Unformatted text preview: BCH 100, Spring 2010 Lecture 25, Translation (Dr. Ziegler) 1 BIOCHEMISTRY 100 Spring 2010 M. Ziegler Lecture 25 Translation Reading: Tymoczko et al., Chapters 38 and 39 (pp. 586-619) Learning Objectives 1. Terminology: initiation codon, stop codon, reading frame, wobble, amino acid activation, aminoacyl-tRNA, charging, Shine-Dalgarno sequence, prokaryotic initiation factors (especially IF2), prokaryotic elongation factors (especially EF-Tu and EF-G), A site, P site, E site, peptidyl transferase, prokaryotic release factors RF1, RF2, and RF3, polysome, eukaryotic miRNA and siRNA 2. Explain what is meant by describing the genetic code as a triplet code that is non-overlapping, comma-less, degenerate, and universal . 3. Given the genetic code, be able to translate a short mRNA sequence. 4. Discuss the directionality and specificity of base-pairing between the codon and the anticodon, including the wobble position. 5. Why do amino acids need to be activated in order to form peptide bonds? Explain the 2-step aminoacyl-tRNA synthetase reaction, including where and by what kind of linkage the activated amino acid is attached to the tRNA, and the energy cost of the reaction. Compare this 2-step activation reaction with activation of fatty acids, Lecture 14. 6. How is the amino acid (Met) activated and chemically modified for initiation in prokaryotes? 7. Describe the size of the subunits of a prokaryotic ribosome, and what kinds of molecules make up those subunits. BCH 100, Spring 2010 Lecture 25, Translation (Dr. Ziegler) 2 Learning Objectives, continued 8. Describe polypeptide chain initiation in prokaryotes: how is the AUG start codon identified, in what order do the ribosomal subunits assemble, and what protein factors are required? List the components of the 30S initiation complex, and explain how energy is expended in forming the 70S initiation complex. 9. Briefly outline the differences between eukaryotic and prokaryotic initiation of translation. 10. Explain the role of EF-Tu in the elongation steps of translation, including the energy cost for its role, and its role in proofreading codon-anticodon matching. 11. Explain the sequence of events/chemical reaction in the peptidyl transferase reaction. 12. Describe the ribosomal elongation cycle, including the steps requiring energy expenditure, and what protein factors catalyze that expenditure. 13. Briefly explain termination of translation in E. coli-- what signals the end of the polypeptide chain, what factor(s) read that signal, what energy expenditure is needed and what factor catalyzes that energy expenditure? Learning Objectives, continued 14. Summarize the energy-requiring steps in protein synthesis (translation). Calculate the number of high energy phosphate bonds required to make a polypeptide chain of any given length, showing how you obtained that number (component numbers for each step of protein synthesis)....
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